networking/tls.c

   1 /*
   2  * Copyright (C) 2017 Denys Vlasenko
   3  *
   4  * Licensed under GPLv2, see file LICENSE in this source tree.
   5  */
   6 //config:config TLS
   7 //config:       bool #No description makes it a hidden option
   8 //config:       default n
   9
  10 //kbuild:lib-$(CONFIG_TLS) += tls.o
  11 //kbuild:lib-$(CONFIG_TLS) += tls_pstm.o
  12 //kbuild:lib-$(CONFIG_TLS) += tls_pstm_montgomery_reduce.o
  13 //kbuild:lib-$(CONFIG_TLS) += tls_pstm_mul_comba.o
  14 //kbuild:lib-$(CONFIG_TLS) += tls_pstm_sqr_comba.o
  15 //kbuild:lib-$(CONFIG_TLS) += tls_rsa.o
  16 //kbuild:lib-$(CONFIG_TLS) += tls_aes.o
  17 ////kbuild:lib-$(CONFIG_TLS) += tls_aes_gcm.o
  18
  19 #include "tls.h"
  20
  21 //Tested against kernel.org:
  22 //TLS 1.2
  23 #define TLS_MAJ 3
  24 #define TLS_MIN 3
  25 //#define CIPHER_ID TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA // ok, recvs SERVER_KEY_EXCHANGE *** matrixssl uses this on my box
  26 //#define CIPHER_ID TLS_RSA_WITH_AES_256_CBC_SHA256 // ok, no SERVER_KEY_EXCHANGE
  27 //#define CIPHER_ID TLS_DH_anon_WITH_AES_256_CBC_SHA // SSL_ALERT_HANDSHAKE_FAILURE
  28 //^^^^^^^^^^^^^^^^^^^^^^^ (tested b/c this one doesn't req server certs... no luck, server refuses it)
  29 //#define CIPHER_ID TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 // SSL_ALERT_HANDSHAKE_FAILURE
  30 //#define CIPHER_ID TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 // SSL_ALERT_HANDSHAKE_FAILURE
  31 //#define CIPHER_ID TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 // ok, recvs SERVER_KEY_EXCHANGE
  32 //#define CIPHER_ID TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
  33 //#define CIPHER_ID TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384
  34 //#define CIPHER_ID TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256 // SSL_ALERT_HANDSHAKE_FAILURE
  35 //#define CIPHER_ID TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384
  36 //#define CIPHER_ID TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256 // SSL_ALERT_HANDSHAKE_FAILURE
  37 //#define CIPHER_ID TLS_RSA_WITH_AES_256_GCM_SHA384 // ok, no SERVER_KEY_EXCHANGE
  38 //#define CIPHER_ID TLS_RSA_WITH_AES_128_GCM_SHA256 // ok, no SERVER_KEY_EXCHANGE *** select this?
  39
  40 // works against "openssl s_server -cipher NULL"
  41 // and against wolfssl-3.9.10-stable/examples/server/server.c:
  42 //#define CIPHER_ID TLS_RSA_WITH_NULL_SHA256 // for testing (does everything except encrypting)
  43
  44 // works against wolfssl-3.9.10-stable/examples/server/server.c
  45 // works for kernel.org
  46 // does not work for cdn.kernel.org (e.g. downloading an actual tarball, not a web page)
  47 //  getting alert 40 "handshake failure" at once
  48 //  with GNU Wget 1.18, they agree on TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (0xC02F) cipher
  49 //  fail: openssl s_client -connect cdn.kernel.org:443 -debug -tls1_2 -no_tls1 -no_tls1_1 -cipher AES256-SHA256
  50 //  fail: openssl s_client -connect cdn.kernel.org:443 -debug -tls1_2 -no_tls1 -no_tls1_1 -cipher AES256-GCM-SHA384
  51 //  fail: openssl s_client -connect cdn.kernel.org:443 -debug -tls1_2 -no_tls1 -no_tls1_1 -cipher AES128-SHA256
  52 //  ok:   openssl s_client -connect cdn.kernel.org:443 -debug -tls1_2 -no_tls1 -no_tls1_1 -cipher AES128-GCM-SHA256
  53 //  ok:   openssl s_client -connect cdn.kernel.org:443 -debug -tls1_2 -no_tls1 -no_tls1_1 -cipher AES128-SHA
  54 //        (TLS_RSA_WITH_AES_128_CBC_SHA - in TLS 1.2 it's mandated to be always supported)
  55 #define CIPHER_ID1  TLS_RSA_WITH_AES_256_CBC_SHA256 // no SERVER_KEY_EXCHANGE from peer
  56 // Does not work yet:
  57 //#define CIPHER_ID2  TLS_RSA_WITH_AES_128_CBC_SHA
  58 #define CIPHER_ID2  0
  59
  60
  61 #define TLS_DEBUG      1
  62 #define TLS_DEBUG_HASH 1
  63 #define TLS_DEBUG_DER  1
  64 #define TLS_DEBUG_FIXED_SECRETS 1
  65 #if 0
  66 # define dump_raw_out(...) dump_hex(__VA_ARGS__)
  67 #else
  68 # define dump_raw_out(...) ((void)0)
  69 #endif
  70 #if 0
  71 # define dump_raw_in(...) dump_hex(__VA_ARGS__)
  72 #else
  73 # define dump_raw_in(...) ((void)0)
  74 #endif
  75
  76 #if TLS_DEBUG
  77 # define dbg(...) fprintf(stderr, __VA_ARGS__)
  78 #else
  79 # define dbg(...) ((void)0)
  80 #endif
  81
  82 #if TLS_DEBUG_DER
  83 # define dbg_der(...) fprintf(stderr, __VA_ARGS__)
  84 #else
  85 # define dbg_der(...) ((void)0)
  86 #endif
  87
  88 #define RECORD_TYPE_CHANGE_CIPHER_SPEC  20
  89 #define RECORD_TYPE_ALERT               21
  90 #define RECORD_TYPE_HANDSHAKE           22
  91 #define RECORD_TYPE_APPLICATION_DATA    23
  92
  93 #define HANDSHAKE_HELLO_REQUEST         0
  94 #define HANDSHAKE_CLIENT_HELLO          1
  95 #define HANDSHAKE_SERVER_HELLO          2
  96 #define HANDSHAKE_HELLO_VERIFY_REQUEST  3
  97 #define HANDSHAKE_NEW_SESSION_TICKET    4
  98 #define HANDSHAKE_CERTIFICATE           11
  99 #define HANDSHAKE_SERVER_KEY_EXCHANGE   12
 100 #define HANDSHAKE_CERTIFICATE_REQUEST   13
 101 #define HANDSHAKE_SERVER_HELLO_DONE     14
 102 #define HANDSHAKE_CERTIFICATE_VERIFY    15
 103 #define HANDSHAKE_CLIENT_KEY_EXCHANGE   16
 104 #define HANDSHAKE_FINISHED              20
 105
 106 #define SSL_NULL_WITH_NULL_NULL                 0x0000
 107 #define SSL_RSA_WITH_NULL_MD5                   0x0001
 108 #define SSL_RSA_WITH_NULL_SHA                   0x0002
 109 #define SSL_RSA_WITH_RC4_128_MD5                0x0004
 110 #define SSL_RSA_WITH_RC4_128_SHA                0x0005
 111 #define SSL_RSA_WITH_3DES_EDE_CBC_SHA           0x000A  /* 10 */
 112 #define TLS_RSA_WITH_AES_128_CBC_SHA            0x002F  /* 47 */
 113 #define TLS_RSA_WITH_AES_256_CBC_SHA            0x0035  /* 53 */
 114 #define TLS_RSA_WITH_NULL_SHA256                0x003B  /* 59 */
 115
 116 #define TLS_EMPTY_RENEGOTIATION_INFO_SCSV       0x00FF
 117
 118 #define TLS_RSA_WITH_IDEA_CBC_SHA               0x0007  /* 7 */
 119 #define SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA       0x0016  /* 22 */
 120 #define SSL_DH_anon_WITH_RC4_128_MD5            0x0018  /* 24 */
 121 #define SSL_DH_anon_WITH_3DES_EDE_CBC_SHA       0x001B  /* 27 */
 122 #define TLS_DHE_RSA_WITH_AES_128_CBC_SHA        0x0033  /* 51 */
 123 #define TLS_DHE_RSA_WITH_AES_256_CBC_SHA        0x0039  /* 57 */
 124 #define TLS_DHE_RSA_WITH_AES_128_CBC_SHA256     0x0067  /* 103 */
 125 #define TLS_DHE_RSA_WITH_AES_256_CBC_SHA256     0x006B  /* 107 */
 126 #define TLS_DH_anon_WITH_AES_128_CBC_SHA        0x0034  /* 52 */
 127 #define TLS_DH_anon_WITH_AES_256_CBC_SHA        0x003A  /* 58 */
 128 #define TLS_RSA_WITH_AES_128_CBC_SHA256         0x003C  /* 60 */
 129 #define TLS_RSA_WITH_AES_256_CBC_SHA256         0x003D  /* 61 */
 130 #define TLS_RSA_WITH_SEED_CBC_SHA               0x0096  /* 150 */
 131 #define TLS_PSK_WITH_AES_128_CBC_SHA            0x008C  /* 140 */
 132 #define TLS_PSK_WITH_AES_128_CBC_SHA256         0x00AE  /* 174 */
 133 #define TLS_PSK_WITH_AES_256_CBC_SHA384         0x00AF  /* 175 */
 134 #define TLS_PSK_WITH_AES_256_CBC_SHA            0x008D  /* 141 */
 135 #define TLS_DHE_PSK_WITH_AES_128_CBC_SHA        0x0090  /* 144 */
 136 #define TLS_DHE_PSK_WITH_AES_256_CBC_SHA        0x0091  /* 145 */
 137 #define TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA     0xC004  /* 49156 */
 138 #define TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA     0xC005  /* 49157 */
 139 #define TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA    0xC009  /* 49161 */
 140 #define TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA    0xC00A  /* 49162 */
 141 #define TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA     0xC012  /* 49170 */
 142 #define TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA      0xC013  /* 49171 */
 143 #define TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA      0xC014  /* 49172 */
 144 #define TLS_ECDH_RSA_WITH_AES_128_CBC_SHA       0xC00E  /* 49166 */
 145 #define TLS_ECDH_RSA_WITH_AES_256_CBC_SHA       0xC00F  /* 49167 */
 146 #define TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 0xC023  /* 49187 */
 147 #define TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 0xC024  /* 49188 */
 148 #define TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256  0xC025  /* 49189 */
 149 #define TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384  0xC026  /* 49190 */
 150 #define TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256   0xC027  /* 49191 */
 151 #define TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384   0xC028  /* 49192 */
 152 #define TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256    0xC029  /* 49193 */
 153 #define TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384    0xC02A  /* 49194 */
 154
 155 /* RFC 5288 "AES Galois Counter Mode (GCM) Cipher Suites for TLS" */
 156 #define TLS_RSA_WITH_AES_128_GCM_SHA256         0x009C  /* 156 */
 157 #define TLS_RSA_WITH_AES_256_GCM_SHA384         0x009D  /* 157 */
 158 #define TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 0xC02B  /* 49195 */
 159 #define TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 0xC02C  /* 49196 */
 160 #define TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256  0xC02D  /* 49197 */
 161 #define TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384  0xC02E  /* 49198 */
 162 #define TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256   0xC02F  /* 49199 */
 163 #define TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384   0xC030  /* 49200 */
 164 #define TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256    0xC031  /* 49201 */
 165 #define TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384    0xC032  /* 49202 */
 166
 167 /* Might go to libbb.h */
 168 #define TLS_MAX_CRYPTBLOCK_SIZE 16
 169 #define TLS_MAX_OUTBUF          (1 << 14)
 170
 171 enum {
 172         SHA_INSIZE     = 64,
 173         SHA1_OUTSIZE   = 20,
 174         SHA256_OUTSIZE = 32,
 175
 176         AES_BLOCKSIZE  = 16,
 177         AES128_KEYSIZE = 16,
 178         AES256_KEYSIZE = 32,
 179
 180         RSA_PREMASTER_SIZE = 48,
 181
 182         RECHDR_LEN = 5,
 183
 184         /* 8 = 3+5. 3 extra bytes result in record data being 32-bit aligned */
 185         OUTBUF_PFX = 8 + AES_BLOCKSIZE, /* header + IV */
 186         OUTBUF_SFX = TLS_MAX_MAC_SIZE + TLS_MAX_CRYPTBLOCK_SIZE, /* MAC + padding */
 187
 188         // RFC 5246
 189         // | 6.2.1. Fragmentation
 190         // |  The record layer fragments information blocks into TLSPlaintext
 191         // |  records carrying data in chunks of 2^14 bytes or less.  Client
 192         // |  message boundaries are not preserved in the record layer (i.e.,
 193         // |  multiple client messages of the same ContentType MAY be coalesced
 194         // |  into a single TLSPlaintext record, or a single message MAY be
 195         // |  fragmented across several records)
 196         // |...
 197         // |  length
 198         // |    The length (in bytes) of the following TLSPlaintext.fragment.
 199         // |    The length MUST NOT exceed 2^14.
 200         // |...
 201         // | 6.2.2. Record Compression and Decompression
 202         // |...
 203         // |  Compression must be lossless and may not increase the content length
 204         // |  by more than 1024 bytes.  If the decompression function encounters a
 205         // |  TLSCompressed.fragment that would decompress to a length in excess of
 206         // |  2^14 bytes, it MUST report a fatal decompression failure error.
 207         // |...
 208         // |  length
 209         // |    The length (in bytes) of the following TLSCompressed.fragment.
 210         // |    The length MUST NOT exceed 2^14 + 1024.
 211         // |...
 212         // | 6.2.3.  Record Payload Protection
 213         // |  The encryption and MAC functions translate a TLSCompressed
 214         // |  structure into a TLSCiphertext.  The decryption functions reverse
 215         // |  the process.  The MAC of the record also includes a sequence
 216         // |  number so that missing, extra, or repeated messages are
 217         // |  detectable.
 218         // |...
 219         // |  length
 220         // |    The length (in bytes) of the following TLSCiphertext.fragment.
 221         // |    The length MUST NOT exceed 2^14 + 2048.
 222         MAX_INBUF = RECHDR_LEN + (1 << 14) + 2048,
 223 };
 224
 225 struct record_hdr {
 226         uint8_t type;
 227         uint8_t proto_maj, proto_min;
 228         uint8_t len16_hi, len16_lo;
 229 };
 230
 231 struct tls_handshake_data {
 232         /* In bbox, md5/sha1/sha256 ctx's are the same structure */
 233         md5sha_ctx_t handshake_hash_ctx;
 234
 235         uint8_t client_and_server_rand32[2 * 32];
 236         uint8_t master_secret[48];
 237 //TODO: store just the DER key here, parse/use/delete it when sending client key
 238 //this way it will stay key type agnostic here.
 239         psRsaKey_t server_rsa_pub_key;
 240
 241         unsigned saved_client_hello_size;
 242         uint8_t saved_client_hello[1];
 243 };
 244
 245
 246 static unsigned get24be(const uint8_t *p)
 247 {
 248         return 0x100*(0x100*p[0] + p[1]) + p[2];
 249 }
 250
 251 #if TLS_DEBUG
 252 static void dump_hex(const char *fmt, const void *vp, int len)
 253 {
 254         char hexbuf[32 * 1024 + 4];
 255         const uint8_t *p = vp;
 256
 257         bin2hex(hexbuf, (void*)p, len)[0] = '\0';
 258         dbg(fmt, hexbuf);
 259 }
 260
 261 static void dump_tls_record(const void *vp, int len)
 262 {
 263         const uint8_t *p = vp;
 264
 265         while (len > 0) {
 266                 unsigned xhdr_len;
 267                 if (len < RECHDR_LEN) {
 268                         dump_hex("< |%s|\n", p, len);
 269                         return;
 270                 }
 271                 xhdr_len = 0x100*p[3] + p[4];
 272                 dbg("< hdr_type:%u ver:%u.%u len:%u", p[0], p[1], p[2], xhdr_len);
 273                 p += RECHDR_LEN;
 274                 len -= RECHDR_LEN;
 275                 if (len >= 4 && p[-RECHDR_LEN] == RECORD_TYPE_HANDSHAKE) {
 276                         unsigned len24 = get24be(p + 1);
 277                         dbg(" type:%u len24:%u", p[0], len24);
 278                 }
 279                 if (xhdr_len > len)
 280                         xhdr_len = len;
 281                 dump_hex(" |%s|\n", p, xhdr_len);
 282                 p += xhdr_len;
 283                 len -= xhdr_len;
 284         }
 285 }
 286 #else
 287 # define dump_hex(...) ((void)0)
 288 # define dump_tls_record(...) ((void)0)
 289 #endif
 290
 291 void tls_get_random(void *buf, unsigned len)
 292 {
 293         if (len != open_read_close("/dev/urandom", buf, len))
 294                 xfunc_die();
 295 }
 296
 297 /* Nondestructively see the current hash value */
 298 static unsigned sha_peek(md5sha_ctx_t *ctx, void *buffer)
 299 {
 300         md5sha_ctx_t ctx_copy = *ctx; /* struct copy */
 301         return sha_end(&ctx_copy, buffer);
 302 }
 303
 304 static ALWAYS_INLINE unsigned get_handshake_hash(tls_state_t *tls, void *buffer)
 305 {
 306         return sha_peek(&tls->hsd->handshake_hash_ctx, buffer);
 307 }
 308
 309 #if !TLS_DEBUG_HASH
 310 # define hash_handshake(tls, fmt, buffer, len) \
 311          hash_handshake(tls, buffer, len)
 312 #endif
 313 static void hash_handshake(tls_state_t *tls, const char *fmt, const void *buffer, unsigned len)
 314 {
 315         md5sha_hash(&tls->hsd->handshake_hash_ctx, buffer, len);
 316 #if TLS_DEBUG_HASH
 317         {
 318                 uint8_t h[TLS_MAX_MAC_SIZE];
 319                 dump_hex(fmt, buffer, len);
 320                 dbg(" (%u bytes) ", (int)len);
 321                 len = sha_peek(&tls->hsd->handshake_hash_ctx, h);
 322                 if (len == SHA1_OUTSIZE)
 323                         dump_hex("sha1:%s\n", h, len);
 324                 else
 325                 if (len == SHA256_OUTSIZE)
 326                         dump_hex("sha256:%s\n", h, len);
 327                 else
 328                         dump_hex("sha???:%s\n", h, len);
 329         }
 330 #endif
 331 }
 332
 333 // RFC 2104
 334 // HMAC(key, text) based on a hash H (say, sha256) is:
 335 // ipad = [0x36 x INSIZE]
 336 // opad = [0x5c x INSIZE]
 337 // HMAC(key, text) = H((key XOR opad) + H((key XOR ipad) + text))
 338 //
 339 // H(key XOR opad) and H(key XOR ipad) can be precomputed
 340 // if we often need HMAC hmac with the same key.
 341 //
 342 // text is often given in disjoint pieces.
 343 static unsigned hmac_sha_precomputed_v(uint8_t *out,
 344                 md5sha_ctx_t *hashed_key_xor_ipad,
 345                 md5sha_ctx_t *hashed_key_xor_opad,
 346                 va_list va)
 347 {
 348         uint8_t *text;
 349         unsigned len;
 350
 351         /* hashed_key_xor_ipad contains unclosed "H((key XOR ipad) +" state */
 352         /* hashed_key_xor_opad contains unclosed "H((key XOR opad) +" state */
 353
 354         /* calculate out = H((key XOR ipad) + text) */
 355         while ((text = va_arg(va, uint8_t*)) != NULL) {
 356                 unsigned text_size = va_arg(va, unsigned);
 357                 md5sha_hash(hashed_key_xor_ipad, text, text_size);
 358         }
 359         len = sha_end(hashed_key_xor_ipad, out);
 360
 361         /* out = H((key XOR opad) + out) */
 362         md5sha_hash(hashed_key_xor_opad, out, len);
 363         return sha_end(hashed_key_xor_opad, out);
 364 }
 365
 366 static unsigned hmac(tls_state_t *tls, uint8_t *out, uint8_t *key, unsigned key_size, ...)
 367 {
 368         md5sha_ctx_t hashed_key_xor_ipad;
 369         md5sha_ctx_t hashed_key_xor_opad;
 370         uint8_t key_xor_ipad[SHA_INSIZE];
 371         uint8_t key_xor_opad[SHA_INSIZE];
 372         uint8_t tempkey[SHA256_OUTSIZE];
 373         va_list va;
 374         unsigned i;
 375
 376         va_start(va, key_size);
 377
 378         // "The authentication key can be of any length up to INSIZE, the
 379         // block length of the hash function.  Applications that use keys longer
 380         // than INSIZE bytes will first hash the key using H and then use the
 381         // resultant OUTSIZE byte string as the actual key to HMAC."
 382         if (key_size > SHA_INSIZE) {
 383                 md5sha_ctx_t ctx;
 384                 if (tls->MAC_size == SHA256_OUTSIZE)
 385                         sha256_begin(&ctx);
 386                 else
 387                         sha1_begin(&ctx);
 388                 md5sha_hash(&ctx, key, key_size);
 389                 key_size = sha_end(&ctx, tempkey);
 390         }
 391
 392         for (i = 0; i < key_size; i++) {
 393                 key_xor_ipad[i] = key[i] ^ 0x36;
 394                 key_xor_opad[i] = key[i] ^ 0x5c;
 395         }
 396         for (; i < SHA_INSIZE; i++) {
 397                 key_xor_ipad[i] = 0x36;
 398                 key_xor_opad[i] = 0x5c;
 399         }
 400
 401         if (tls->MAC_size == SHA256_OUTSIZE) {
 402                 sha256_begin(&hashed_key_xor_ipad);
 403                 sha256_begin(&hashed_key_xor_opad);
 404         } else {
 405                 sha1_begin(&hashed_key_xor_ipad);
 406                 sha1_begin(&hashed_key_xor_opad);
 407         }
 408         md5sha_hash(&hashed_key_xor_ipad, key_xor_ipad, SHA_INSIZE);
 409         md5sha_hash(&hashed_key_xor_opad, key_xor_opad, SHA_INSIZE);
 410
 411         i = hmac_sha_precomputed_v(out, &hashed_key_xor_ipad, &hashed_key_xor_opad, va);
 412         va_end(va);
 413         return i;
 414 }
 415
 416 // RFC 5246:
 417 // 5.  HMAC and the Pseudorandom Function
 418 //...
 419 // In this section, we define one PRF, based on HMAC.  This PRF with the
 420 // SHA-256 hash function is used for all cipher suites defined in this
 421 // document and in TLS documents published prior to this document when
 422 // TLS 1.2 is negotiated.
 423 //...
 424 //    P_hash(secret, seed) = HMAC_hash(secret, A(1) + seed) +
 425 //                           HMAC_hash(secret, A(2) + seed) +
 426 //                           HMAC_hash(secret, A(3) + seed) + ...
 427 // where + indicates concatenation.
 428 // A() is defined as:
 429 //    A(0) = seed
 430 //    A(1) = HMAC_hash(secret, A(0)) = HMAC_hash(secret, seed)
 431 //    A(i) = HMAC_hash(secret, A(i-1))
 432 // P_hash can be iterated as many times as necessary to produce the
 433 // required quantity of data.  For example, if P_SHA256 is being used to
 434 // create 80 bytes of data, it will have to be iterated three times
 435 // (through A(3)), creating 96 bytes of output data; the last 16 bytes
 436 // of the final iteration will then be discarded, leaving 80 bytes of
 437 // output data.
 438 //
 439 // TLS's PRF is created by applying P_hash to the secret as:
 440 //
 441 //    PRF(secret, label, seed) = P_<hash>(secret, label + seed)
 442 //
 443 // The label is an ASCII string.
 444 static void prf_hmac(tls_state_t *tls,
 445                 uint8_t *outbuf, unsigned outbuf_size,
 446                 uint8_t *secret, unsigned secret_size,
 447                 const char *label,
 448                 uint8_t *seed, unsigned seed_size)
 449 {
 450         uint8_t a[TLS_MAX_MAC_SIZE];
 451         uint8_t *out_p = outbuf;
 452         unsigned label_size = strlen(label);
 453         unsigned MAC_size = tls->MAC_size;
 454
 455         /* In P_hash() calculation, "seed" is "label + seed": */
 456 #define SEED   label, label_size, seed, seed_size
 457 #define SECRET secret, secret_size
 458 #define A      a, MAC_size
 459
 460         /* A(1) = HMAC_hash(secret, seed) */
 461         hmac(tls, a, SECRET, SEED, NULL);
 462 //TODO: convert hmac to precomputed
 463
 464         for(;;) {
 465                 /* HMAC_hash(secret, A(1) + seed) */
 466                 if (outbuf_size <= MAC_size) {
 467                         /* Last, possibly incomplete, block */
 468                         /* (use a[] as temp buffer) */
 469                         hmac(tls, a, SECRET, A, SEED, NULL);
 470                         memcpy(out_p, a, outbuf_size);
 471                         return;
 472                 }
 473                 /* Not last block. Store directly to result buffer */
 474                 hmac(tls, out_p, SECRET, A, SEED, NULL);
 475                 out_p += MAC_size;
 476                 outbuf_size -= MAC_size;
 477                 /* A(2) = HMAC_hash(secret, A(1)) */
 478                 hmac(tls, a, SECRET, A, NULL);
 479         }
 480 #undef A
 481 #undef SECRET
 482 #undef SEED
 483 }
 484
 485 static void bad_record_die(tls_state_t *tls, const char *expected, int len)
 486 {
 487         bb_error_msg_and_die("got bad TLS record (len:%d) while expecting %s", len, expected);
 488         if (len > 0) {
 489                 uint8_t *p = tls->inbuf;
 490                 while (len > 0)
 491                         fprintf(stderr, " %02x", *p++);
 492                 fputc('\n', stderr);
 493         }
 494         xfunc_die();
 495 }
 496
 497 static void tls_error_die(tls_state_t *tls)
 498 {
 499         dump_tls_record(tls->inbuf, tls->ofs_to_buffered + tls->buffered_size);
 500         bb_error_msg_and_die("TODO: useful diagnostic about %p", tls);
 501 }
 502
 503 #if 0 //UNUSED
 504 static void tls_free_inbuf(tls_state_t *tls)
 505 {
 506         if (tls->buffered_size == 0) {
 507                 free(tls->inbuf);
 508                 tls->inbuf_size = 0;
 509                 tls->inbuf = NULL;
 510         }
 511 }
 512 #endif
 513
 514 static void tls_free_outbuf(tls_state_t *tls)
 515 {
 516         free(tls->outbuf);
 517         tls->outbuf_size = 0;
 518         tls->outbuf = NULL;
 519 }
 520
 521 static void *tls_get_outbuf(tls_state_t *tls, int len)
 522 {
 523         if (len > TLS_MAX_OUTBUF)
 524                 xfunc_die();
 525         len += OUTBUF_PFX + OUTBUF_SFX;
 526         if (tls->outbuf_size < len) {
 527                 tls->outbuf_size = len;
 528                 tls->outbuf = xrealloc(tls->outbuf, len);
 529         }
 530         return tls->outbuf + OUTBUF_PFX;
 531 }
 532
 533 static void xwrite_encrypted(tls_state_t *tls, unsigned size, unsigned type)
 534 {
 535         uint8_t *buf = tls->outbuf + OUTBUF_PFX;
 536         struct record_hdr *xhdr;
 537         uint8_t padding_length;
 538
 539         xhdr = (void*)(buf - RECHDR_LEN);
 540         if (tls->cipher_id != TLS_RSA_WITH_NULL_SHA256)
 541                 xhdr = (void*)(buf - RECHDR_LEN - AES_BLOCKSIZE); /* place for IV */
 542
 543         xhdr->type = type;
 544         xhdr->proto_maj = TLS_MAJ;
 545         xhdr->proto_min = TLS_MIN;
 546         /* fake unencrypted record len for MAC calculation */
 547         xhdr->len16_hi = size >> 8;
 548         xhdr->len16_lo = size & 0xff;
 549
 550         /* Calculate MAC signature */
 551         hmac(tls, buf + size, /* result */
 552                 tls->client_write_MAC_key, tls->MAC_size,
 553                 &tls->write_seq64_be, sizeof(tls->write_seq64_be),
 554                 xhdr, RECHDR_LEN,
 555                 buf, size,
 556                 NULL
 557         );
 558         tls->write_seq64_be = SWAP_BE64(1 + SWAP_BE64(tls->write_seq64_be));
 559
 560         size += tls->MAC_size;
 561
 562         // RFC 5246
 563         // 6.2.3.1.  Null or Standard Stream Cipher
 564         //
 565         // Stream ciphers (including BulkCipherAlgorithm.null; see Appendix A.6)
 566         // convert TLSCompressed.fragment structures to and from stream
 567         // TLSCiphertext.fragment structures.
 568         //
 569         //    stream-ciphered struct {
 570         //        opaque content[TLSCompressed.length];
 571         //        opaque MAC[SecurityParameters.mac_length];
 572         //    } GenericStreamCipher;
 573         //
 574         // The MAC is generated as:
 575         //    MAC(MAC_write_key, seq_num +
 576         //                          TLSCompressed.type +
 577         //                          TLSCompressed.version +
 578         //                          TLSCompressed.length +
 579         //                          TLSCompressed.fragment);
 580         // where "+" denotes concatenation.
 581         // seq_num
 582         //    The sequence number for this record.
 583         // MAC
 584         //    The MAC algorithm specified by SecurityParameters.mac_algorithm.
 585         //
 586         // Note that the MAC is computed before encryption.  The stream cipher
 587         // encrypts the entire block, including the MAC.
 588         //...
 589         // Appendix C.  Cipher Suite Definitions
 590         //...
 591         // MAC       Algorithm    mac_length  mac_key_length
 592         // --------  -----------  ----------  --------------
 593         // SHA       HMAC-SHA1       20            20
 594         // SHA256    HMAC-SHA256     32            32
 595         if (tls->cipher_id == TLS_RSA_WITH_NULL_SHA256) {
 596                 /* No encryption, only signing */
 597                 xhdr->len16_hi = size >> 8;
 598                 xhdr->len16_lo = size & 0xff;
 599                 dump_raw_out(">> %s\n", xhdr, RECHDR_LEN + size);
 600                 xwrite(tls->ofd, xhdr, RECHDR_LEN + size);
 601                 dbg("wrote %u bytes (NULL crypt, SHA256 hash)\n", size);
 602                 return;
 603         }
 604
 605         // 6.2.3.2.  CBC Block Cipher
 606         // For block ciphers (such as 3DES or AES), the encryption and MAC
 607         // functions convert TLSCompressed.fragment structures to and from block
 608         // TLSCiphertext.fragment structures.
 609         //    struct {
 610         //        opaque IV[SecurityParameters.record_iv_length];
 611         //        block-ciphered struct {
 612         //            opaque content[TLSCompressed.length];
 613         //            opaque MAC[SecurityParameters.mac_length];
 614         //            uint8 padding[GenericBlockCipher.padding_length];
 615         //            uint8 padding_length;
 616         //        };
 617         //    } GenericBlockCipher;
 618         //...
 619         // IV
 620         //    The Initialization Vector (IV) SHOULD be chosen at random, and
 621         //    MUST be unpredictable.  Note that in versions of TLS prior to 1.1,
 622         //    there was no IV field (...).  For block ciphers, the IV length is
 623         //    of length SecurityParameters.record_iv_length, which is equal to the
 624         //    SecurityParameters.block_size.
 625         // padding
 626         //    Padding that is added to force the length of the plaintext to be
 627         //    an integral multiple of the block cipher's block length.
 628         // padding_length
 629         //    The padding length MUST be such that the total size of the
 630         //    GenericBlockCipher structure is a multiple of the cipher's block
 631         //    length.  Legal values range from zero to 255, inclusive.
 632         //...
 633         // Appendix C.  Cipher Suite Definitions
 634         //...
 635         //                         Key      IV   Block
 636         // Cipher        Type    Material  Size  Size
 637         // ------------  ------  --------  ----  -----
 638         // AES_128_CBC   Block      16      16     16
 639         // AES_256_CBC   Block      32      16     16
 640
 641         /* Fill IV and padding in outbuf */
 642         tls_get_random(buf - AES_BLOCKSIZE, AES_BLOCKSIZE); /* IV */
 643         dbg("before crypt: 5 hdr + %u data + %u hash bytes\n", size, tls->MAC_size);
 644         // RFC is talking nonsense:
 645         //    "Padding that is added to force the length of the plaintext to be
 646         //    an integral multiple of the block cipher's block length."
 647         // WRONG. _padding+padding_length_, not just _padding_,
 648         // pads the data.
 649         // IOW: padding_length is the last byte of padding[] array,
 650         // contrary to what RFC depicts.
 651         //
 652         // What actually happens is that there is always padding.
 653         // If you need one byte to reach BLOCKSIZE, this byte is 0x00.
 654         // If you need two bytes, they are both 0x01.
 655         // If you need three, they are 0x02,0x02,0x02. And so on.
 656         // If you need no bytes to reach BLOCKSIZE, you have to pad a full
 657         // BLOCKSIZE with bytes of value (BLOCKSIZE-1).
 658         // It's ok to have more than minimum padding, but we do minimum.
 659         padding_length = (~size) & (AES_BLOCKSIZE - 1);
 660         do {
 661                 buf[size++] = padding_length; /* padding */
 662         } while ((size & (AES_BLOCKSIZE - 1)) != 0);
 663
 664         /* Encrypt content+MAC+padding in place */
 665         {
 666                 psCipherContext_t ctx;
 667                 psAesInit(&ctx, buf - AES_BLOCKSIZE, /* IV */
 668                         tls->client_write_key, tls->key_size /* selects 128/256 */
 669                 );
 670                 psAesEncrypt(&ctx,
 671                         buf, /* plaintext */
 672                         buf, /* ciphertext */
 673                         size
 674                 );
 675         }
 676
 677         /* Write out */
 678         dbg("writing 5 + %u IV + %u encrypted bytes, padding_length:0x%02x\n",
 679                         AES_BLOCKSIZE, size, padding_length);
 680         size += AES_BLOCKSIZE;     /* + IV */
 681         xhdr->len16_hi = size >> 8;
 682         xhdr->len16_lo = size & 0xff;
 683         dump_raw_out(">> %s\n", xhdr, RECHDR_LEN + size);
 684         xwrite(tls->ofd, xhdr, RECHDR_LEN + size);
 685         dbg("wrote %u bytes\n", (int)RECHDR_LEN + size);
 686 }
 687
 688 static void xwrite_handshake_record(tls_state_t *tls, unsigned size)
 689 {
 690         //if (!tls->encrypt_on_write) {
 691                 uint8_t *buf = tls->outbuf + OUTBUF_PFX;
 692                 struct record_hdr *xhdr = (void*)(buf - RECHDR_LEN);
 693
 694                 xhdr->type = RECORD_TYPE_HANDSHAKE;
 695                 xhdr->proto_maj = TLS_MAJ;
 696                 xhdr->proto_min = TLS_MIN;
 697                 xhdr->len16_hi = size >> 8;
 698                 xhdr->len16_lo = size & 0xff;
 699                 dump_raw_out(">> %s\n", xhdr, RECHDR_LEN + size);
 700                 xwrite(tls->ofd, xhdr, RECHDR_LEN + size);
 701                 dbg("wrote %u bytes\n", (int)RECHDR_LEN + size);
 702         //      return;
 703         //}
 704         //xwrite_encrypted(tls, size, RECORD_TYPE_HANDSHAKE);
 705 }
 706
 707 static void xwrite_and_update_handshake_hash(tls_state_t *tls, unsigned size)
 708 {
 709         if (!tls->encrypt_on_write) {
 710                 uint8_t *buf;
 711
 712                 xwrite_handshake_record(tls, size);
 713                 /* Handshake hash does not include record headers */
 714                 buf = tls->outbuf + OUTBUF_PFX;
 715                 hash_handshake(tls, ">> hash:%s", buf, size);
 716                 return;
 717         }
 718         xwrite_encrypted(tls, size, RECORD_TYPE_HANDSHAKE);
 719 }
 720
 721 static int tls_has_buffered_record(tls_state_t *tls)
 722 {
 723         int buffered = tls->buffered_size;
 724         struct record_hdr *xhdr;
 725         int rec_size;
 726
 727         if (buffered < RECHDR_LEN)
 728                 return 0;
 729         xhdr = (void*)(tls->inbuf + tls->ofs_to_buffered);
 730         rec_size = RECHDR_LEN + (0x100 * xhdr->len16_hi + xhdr->len16_lo);
 731         if (buffered < rec_size)
 732                 return 0;
 733         return rec_size;
 734 }
 735
 736 static const char *alert_text(int code)
 737 {
 738         switch (code) {
 739         case 20:  return "bad MAC";
 740         case 50:  return "decode error";
 741         case 51:  return "decrypt error";
 742         case 40:  return "handshake failure";
 743         case 112: return "unrecognized name";
 744         }
 745         return itoa(code);
 746 }
 747
 748 static int tls_xread_record(tls_state_t *tls)
 749 {
 750         struct record_hdr *xhdr;
 751         int sz;
 752         int total;
 753         int target;
 754
 755  again:
 756         dbg("ofs_to_buffered:%u buffered_size:%u\n", tls->ofs_to_buffered, tls->buffered_size);
 757         total = tls->buffered_size;
 758         if (total != 0) {
 759                 memmove(tls->inbuf, tls->inbuf + tls->ofs_to_buffered, total);
 760                 //dbg("<< remaining at %d [%d] ", tls->ofs_to_buffered, total);
 761                 //dump_raw_in("<< %s\n", tls->inbuf, total);
 762         }
 763         errno = 0;
 764         target = MAX_INBUF;
 765         for (;;) {
 766                 int rem;
 767
 768                 if (total >= RECHDR_LEN && target == MAX_INBUF) {
 769                         xhdr = (void*)tls->inbuf;
 770                         target = RECHDR_LEN + (0x100 * xhdr->len16_hi + xhdr->len16_lo);
 771                         if (target > MAX_INBUF) {
 772                                 /* malformed input (too long): yell and die */
 773                                 tls->buffered_size = 0;
 774                                 tls->ofs_to_buffered = total;
 775                                 tls_error_die(tls);
 776                         }
 777                         /* can also check type/proto_maj/proto_min here */
 778                         dbg("xhdr type:%d ver:%d.%d len:%d\n",
 779                                 xhdr->type, xhdr->proto_maj, xhdr->proto_min,
 780                                 0x100 * xhdr->len16_hi + xhdr->len16_lo
 781                         );
 782                 }
 783                 /* if total >= target, we have a full packet (and possibly more)... */
 784                 if (total - target >= 0)
 785                         break;
 786                 /* input buffer is grown only as needed */
 787                 rem = tls->inbuf_size - total;
 788                 if (rem == 0) {
 789                         tls->inbuf_size += MAX_INBUF / 8;
 790                         if (tls->inbuf_size > MAX_INBUF)
 791                                 tls->inbuf_size = MAX_INBUF;
 792                         dbg("inbuf_size:%d\n", tls->inbuf_size);
 793                         rem = tls->inbuf_size - total;
 794                         tls->inbuf = xrealloc(tls->inbuf, tls->inbuf_size);
 795                 }
 796                 sz = safe_read(tls->ifd, tls->inbuf + total, rem);
 797                 if (sz <= 0) {
 798                         if (sz == 0 && total == 0) {
 799                                 /* "Abrupt" EOF, no TLS shutdown (seen from kernel.org) */
 800                                 dbg("EOF (without TLS shutdown) from peer\n");
 801                                 tls->buffered_size = 0;
 802                                 goto end;
 803                         }
 804                         bb_perror_msg_and_die("short read, have only %d", total);
 805                 }
 806                 dump_raw_in("<< %s\n", tls->inbuf + total, sz);
 807                 total += sz;
 808         }
 809         tls->buffered_size = total - target;
 810         tls->ofs_to_buffered = target;
 811         //dbg("<< stashing at %d [%d] ", tls->ofs_to_buffered, tls->buffered_size);
 812         //dump_hex("<< %s\n", tls->inbuf + tls->ofs_to_buffered, tls->buffered_size);
 813
 814         sz = target - RECHDR_LEN;
 815
 816         /* Needs to be decrypted? */
 817         if (tls->min_encrypted_len_on_read > tls->MAC_size) {
 818                 psCipherContext_t ctx;
 819                 uint8_t *p = tls->inbuf + RECHDR_LEN;
 820                 int padding_len;
 821
 822                 if (sz & (AES_BLOCKSIZE-1)
 823                  || sz < tls->min_encrypted_len_on_read
 824                 ) {
 825                         bb_error_msg_and_die("bad encrypted len:%u", sz);
 826                 }
 827                 /* Decrypt content+MAC+padding, moving it over IV in the process */
 828                 psAesInit(&ctx, p, /* IV */
 829                         tls->server_write_key, tls->key_size /* selects 128/256 */
 830                 );
 831                 sz -= AES_BLOCKSIZE; /* we will overwrite IV now */
 832                 psAesDecrypt(&ctx,
 833                         p + AES_BLOCKSIZE, /* ciphertext */
 834                         p,                 /* plaintext */
 835                         sz
 836                 );
 837                 padding_len = p[sz - 1];
 838                 dbg("encrypted size:%u type:0x%02x padding_length:0x%02x\n", sz, p[0], padding_len);
 839                 padding_len++;
 840                 sz -= tls->MAC_size + padding_len; /* drop MAC and padding */
 841                 //if (sz < 0)
 842                 //      bb_error_msg_and_die("bad padding size:%u", padding_len);
 843         } else {
 844                 /* if nonzero, then it's TLS_RSA_WITH_NULL_SHA256: drop MAC */
 845                 /* else: no encryption yet on input, subtract zero = NOP */
 846                 sz -= tls->min_encrypted_len_on_read;
 847         }
 848         if (sz < 0)
 849                 bb_error_msg_and_die("encrypted data too short");
 850
 851         //dump_hex("<< %s\n", tls->inbuf, RECHDR_LEN + sz);
 852
 853         xhdr = (void*)tls->inbuf;
 854         if (xhdr->type == RECORD_TYPE_ALERT && sz >= 2) {
 855                 uint8_t *p = tls->inbuf + RECHDR_LEN;
 856                 dbg("ALERT size:%d level:%d description:%d\n", sz, p[0], p[1]);
 857                 if (p[0] == 2) { /* fatal */
 858                         bb_error_msg_and_die("TLS %s from peer (alert code %d): %s",
 859                                 "error",
 860                                 p[1], alert_text(p[1])
 861                         );
 862                 }
 863                 if (p[0] == 1) { /* warning */
 864                         if (p[1] == 0) { /* "close_notify" warning: it's EOF */
 865                                 dbg("EOF (TLS encoded) from peer\n");
 866                                 sz = 0;
 867                                 goto end;
 868                         }
 869 //This possibly needs to be cached and shown only if
 870 //a fatal alert follows
 871 //                      bb_error_msg("TLS %s from peer (alert code %d): %s",
 872 //                              "warning",
 873 //                              p[1], alert_text(p[1])
 874 //                      );
 875                         /* discard it, get next record */
 876                         goto again;
 877                 }
 878                 /* p[0] not 1 or 2: not defined in protocol */
 879                 sz = 0;
 880                 goto end;
 881         }
 882
 883         /* RFC 5246 is not saying it explicitly, but sha256 hash
 884          * in our FINISHED record must include data of incoming packets too!
 885          */
 886         if (tls->inbuf[0] == RECORD_TYPE_HANDSHAKE
 887          && tls->MAC_size != 0 /* do we know which hash to use? (server_hello() does not!) */
 888         ) {
 889                 hash_handshake(tls, "<< hash:%s", tls->inbuf + RECHDR_LEN, sz);
 890         }
 891  end:
 892         dbg("got block len:%u\n", sz);
 893         return sz;
 894 }
 895
 896 /*
 897  * DER parsing routines
 898  */
 899 static unsigned get_der_len(uint8_t **bodyp, uint8_t *der, uint8_t *end)
 900 {
 901         unsigned len, len1;
 902
 903         if (end - der < 2)
 904                 xfunc_die();
 905 //      if ((der[0] & 0x1f) == 0x1f) /* not single-byte item code? */
 906 //              xfunc_die();
 907
 908         len = der[1]; /* maybe it's short len */
 909         if (len >= 0x80) {
 910                 /* no, it's long */
 911
 912                 if (len == 0x80 || end - der < (int)(len - 0x7e)) {
 913                         /* 0x80 is "0 bytes of len", invalid DER: must use short len if can */
 914                         /* need 3 or 4 bytes for 81, 82 */
 915                         xfunc_die();
 916                 }
 917
 918                 len1 = der[2]; /* if (len == 0x81) it's "ii 81 xx", fetch xx */
 919                 if (len > 0x82) {
 920                         /* >0x82 is "3+ bytes of len", should not happen realistically */
 921                         xfunc_die();
 922                 }
 923                 if (len == 0x82) { /* it's "ii 82 xx yy" */
 924                         len1 = 0x100*len1 + der[3];
 925                         der += 1; /* skip [yy] */
 926                 }
 927                 der += 1; /* skip [xx] */
 928                 len = len1;
 929 //              if (len < 0x80)
 930 //                      xfunc_die(); /* invalid DER: must use short len if can */
 931         }
 932         der += 2; /* skip [code]+[1byte] */
 933
 934         if (end - der < (int)len)
 935                 xfunc_die();
 936         *bodyp = der;
 937
 938         return len;
 939 }
 940
 941 static uint8_t *enter_der_item(uint8_t *der, uint8_t **endp)
 942 {
 943         uint8_t *new_der;
 944         unsigned len = get_der_len(&new_der, der, *endp);
 945         dbg_der("entered der @%p:0x%02x len:%u inner_byte @%p:0x%02x\n", der, der[0], len, new_der, new_der[0]);
 946         /* Move "end" position to cover only this item */
 947         *endp = new_der + len;
 948         return new_der;
 949 }
 950
 951 static uint8_t *skip_der_item(uint8_t *der, uint8_t *end)
 952 {
 953         uint8_t *new_der;
 954         unsigned len = get_der_len(&new_der, der, end);
 955         /* Skip body */
 956         new_der += len;
 957         dbg_der("skipped der 0x%02x, next byte 0x%02x\n", der[0], new_der[0]);
 958         return new_der;
 959 }
 960
 961 static void der_binary_to_pstm(pstm_int *pstm_n, uint8_t *der, uint8_t *end)
 962 {
 963         uint8_t *bin_ptr;
 964         unsigned len = get_der_len(&bin_ptr, der, end);
 965
 966         dbg_der("binary bytes:%u, first:0x%02x\n", len, bin_ptr[0]);
 967         pstm_init_for_read_unsigned_bin(/*pool:*/ NULL, pstm_n, len);
 968         pstm_read_unsigned_bin(pstm_n, bin_ptr, len);
 969         //return bin + len;
 970 }
 971
 972 static void find_key_in_der_cert(tls_state_t *tls, uint8_t *der, int len)
 973 {
 974 /* Certificate is a DER-encoded data structure. Each DER element has a length,
 975  * which makes it easy to skip over large compound elements of any complexity
 976  * without parsing them. Example: partial decode of kernel.org certificate:
 977  *  SEQ 0x05ac/1452 bytes (Certificate): 308205ac
 978  *    SEQ 0x0494/1172 bytes (tbsCertificate): 30820494
 979  *      [ASN_CONTEXT_SPECIFIC | ASN_CONSTRUCTED | 0] 3 bytes: a003
 980  *        INTEGER (version): 0201 02
 981  *      INTEGER 0x11 bytes (serialNumber): 0211 00 9f85bf664b0cddafca508679501b2be4
 982  *      //^^^^^^note: matrixSSL also allows [ASN_CONTEXT_SPECIFIC | ASN_PRIMITIVE | 2] = 0x82 type
 983  *      SEQ 0x0d bytes (signatureAlgo): 300d
 984  *        OID 9 bytes: 0609 2a864886f70d01010b (OID_SHA256_RSA_SIG 42.134.72.134.247.13.1.1.11)
 985  *        NULL: 0500
 986  *      SEQ 0x5f bytes (issuer): 305f
 987  *        SET 11 bytes: 310b
 988  *          SEQ 9 bytes: 3009
 989  *            OID 3 bytes: 0603 550406
 990  *            Printable string "FR": 1302 4652
 991  *        SET 14 bytes: 310e
 992  *          SEQ 12 bytes: 300c
 993  *            OID 3 bytes: 0603 550408
 994  *            Printable string "Paris": 1305 5061726973
 995  *        SET 14 bytes: 310e
 996  *          SEQ 12 bytes: 300c
 997  *            OID 3 bytes: 0603 550407
 998  *            Printable string "Paris": 1305 5061726973
 999  *        SET 14 bytes: 310e
1000  *          SEQ 12 bytes: 300c
1001  *            OID 3 bytes: 0603 55040a
1002  *            Printable string "Gandi": 1305 47616e6469
1003  *        SET 32 bytes: 3120
1004  *          SEQ 30 bytes: 301e
1005  *            OID 3 bytes: 0603 550403
1006  *            Printable string "Gandi Standard SSL CA 2": 1317 47616e6469205374616e646172642053534c2043412032
1007  *      SEQ 30 bytes (validity): 301e
1008  *        TIME "161011000000Z": 170d 3136313031313030303030305a
1009  *        TIME "191011235959Z": 170d 3139313031313233353935395a
1010  *      SEQ 0x5b/91 bytes (subject): 305b //I did not decode this
1011  *          3121301f060355040b1318446f6d61696e20436f
1012  *          6e74726f6c2056616c6964617465643121301f06
1013  *          0355040b1318506f73697469766553534c204d75
1014  *          6c74692d446f6d61696e31133011060355040313
1015  *          0a6b65726e656c2e6f7267
1016  *      SEQ 0x01a2/418 bytes (subjectPublicKeyInfo): 308201a2
1017  *        SEQ 13 bytes (algorithm): 300d
1018  *          OID 9 bytes: 0609 2a864886f70d010101 (OID_RSA_KEY_ALG 42.134.72.134.247.13.1.1.1)
1019  *          NULL: 0500
1020  *        BITSTRING 0x018f/399 bytes (publicKey): 0382018f
1021  *          ????: 00
1022  *          //after the zero byte, it appears key itself uses DER encoding:
1023  *          SEQ 0x018a/394 bytes: 3082018a
1024  *            INTEGER 0x0181/385 bytes (modulus): 02820181
1025  *                  00b1ab2fc727a3bef76780c9349bf3
1026  *                  ...24 more blocks of 15 bytes each...
1027  *                  90e895291c6bc8693b65
1028  *            INTEGER 3 bytes (exponent): 0203 010001
1029  *      [ASN_CONTEXT_SPECIFIC | ASN_CONSTRUCTED | 0x3] 0x01e5 bytes (X509v3 extensions): a38201e5
1030  *        SEQ 0x01e1 bytes: 308201e1
1031  *        ...
1032  * Certificate is a sequence of three elements:
1033  *      tbsCertificate (SEQ)
1034  *      signatureAlgorithm (AlgorithmIdentifier)
1035  *      signatureValue (BIT STRING)
1036  *
1037  * In turn, tbsCertificate is a sequence of:
1038  *      version
1039  *      serialNumber
1040  *      signatureAlgo (AlgorithmIdentifier)
1041  *      issuer (Name, has complex structure)
1042  *      validity (Validity, SEQ of two Times)
1043  *      subject (Name)
1044  *      subjectPublicKeyInfo (SEQ)
1045  *      ...
1046  *
1047  * subjectPublicKeyInfo is a sequence of:
1048  *      algorithm (AlgorithmIdentifier)
1049  *      publicKey (BIT STRING)
1050  *
1051  * We need Certificate.tbsCertificate.subjectPublicKeyInfo.publicKey
1052  */
1053         uint8_t *end = der + len;
1054
1055         /* enter "Certificate" item: [der, end) will be only Cert */
1056         der = enter_der_item(der, &end);
1057
1058         /* enter "tbsCertificate" item: [der, end) will be only tbsCert */
1059         der = enter_der_item(der, &end);
1060
1061         /* skip up to subjectPublicKeyInfo */
1062         der = skip_der_item(der, end); /* version */
1063         der = skip_der_item(der, end); /* serialNumber */
1064         der = skip_der_item(der, end); /* signatureAlgo */
1065         der = skip_der_item(der, end); /* issuer */
1066         der = skip_der_item(der, end); /* validity */
1067         der = skip_der_item(der, end); /* subject */
1068
1069         /* enter subjectPublicKeyInfo */
1070         der = enter_der_item(der, &end);
1071         { /* check subjectPublicKeyInfo.algorithm */
1072                 static const uint8_t expected[] = {
1073                         0x30,0x0d, // SEQ 13 bytes
1074                         0x06,0x09, 0x2a,0x86,0x48,0x86,0xf7,0x0d,0x01,0x01,0x01, // OID RSA_KEY_ALG 42.134.72.134.247.13.1.1.1
1075                         //0x05,0x00, // NULL
1076                 };
1077                 if (memcmp(der, expected, sizeof(expected)) != 0)
1078                         bb_error_msg_and_die("not RSA key");
1079         }
1080         /* skip subjectPublicKeyInfo.algorithm */
1081         der = skip_der_item(der, end);
1082         /* enter subjectPublicKeyInfo.publicKey */
1083 //      die_if_not_this_der_type(der, end, 0x03); /* must be BITSTRING */
1084         der = enter_der_item(der, &end);
1085
1086         /* parse RSA key: */
1087 //based on getAsnRsaPubKey(), pkcs1ParsePrivBin() is also of note
1088         dbg("key bytes:%u, first:0x%02x\n", (int)(end - der), der[0]);
1089         if (end - der < 14) xfunc_die();
1090         /* example format:
1091          * ignore bits: 00
1092          * SEQ 0x018a/394 bytes: 3082018a
1093          *   INTEGER 0x0181/385 bytes (modulus): 02820181 XX...XXX
1094          *   INTEGER 3 bytes (exponent): 0203 010001
1095          */
1096         if (*der != 0) /* "ignore bits", should be 0 */
1097                 xfunc_die();
1098         der++;
1099         der = enter_der_item(der, &end); /* enter SEQ */
1100         /* memset(tls->hsd->server_rsa_pub_key, 0, sizeof(tls->hsd->server_rsa_pub_key)); - already is */
1101         der_binary_to_pstm(&tls->hsd->server_rsa_pub_key.N, der, end); /* modulus */
1102         der = skip_der_item(der, end);
1103         der_binary_to_pstm(&tls->hsd->server_rsa_pub_key.e, der, end); /* exponent */
1104         tls->hsd->server_rsa_pub_key.size = pstm_unsigned_bin_size(&tls->hsd->server_rsa_pub_key.N);
1105         dbg("server_rsa_pub_key.size:%d\n", tls->hsd->server_rsa_pub_key.size);
1106 }
1107
1108 /*
1109  * TLS Handshake routines
1110  */
1111 static int tls_xread_handshake_block(tls_state_t *tls, int min_len)
1112 {
1113         struct record_hdr *xhdr;
1114         int len = tls_xread_record(tls);
1115
1116         xhdr = (void*)tls->inbuf;
1117         if (len < min_len
1118          || xhdr->type != RECORD_TYPE_HANDSHAKE
1119          || xhdr->proto_maj != TLS_MAJ
1120          || xhdr->proto_min != TLS_MIN
1121         ) {
1122                 bad_record_die(tls, "handshake record", len);
1123         }
1124         dbg("got HANDSHAKE\n");
1125         return len;
1126 }
1127
1128 static ALWAYS_INLINE void fill_handshake_record_hdr(void *buf, unsigned type, unsigned len)
1129 {
1130         struct handshake_hdr {
1131                 uint8_t type;
1132                 uint8_t len24_hi, len24_mid, len24_lo;
1133         } *h = buf;
1134
1135         len -= 4;
1136         h->type = type;
1137         h->len24_hi  = len >> 16;
1138         h->len24_mid = len >> 8;
1139         h->len24_lo  = len & 0xff;
1140 }
1141
1142 static void send_client_hello_and_alloc_hsd(tls_state_t *tls, const char *sni)
1143 {
1144         struct client_hello {
1145                 uint8_t type;
1146                 uint8_t len24_hi, len24_mid, len24_lo;
1147                 uint8_t proto_maj, proto_min;
1148                 uint8_t rand32[32];
1149                 uint8_t session_id_len;
1150                 /* uint8_t session_id[]; */
1151                 uint8_t cipherid_len16_hi, cipherid_len16_lo;
1152                 uint8_t cipherid[2 * (2 + !!CIPHER_ID2)]; /* actually variable */
1153                 uint8_t comprtypes_len;
1154                 uint8_t comprtypes[1]; /* actually variable */
1155                 /* Extensions (SNI shown):
1156                  * hi,lo // len of all extensions
1157                  *   00,00 // extension_type: "Server Name"
1158                  *   00,0e // list len (there can be more than one SNI)
1159                  *     00,0c // len of 1st Server Name Indication
1160                  *       00    // name type: host_name
1161                  *       00,09   // name len
1162                  *       "localhost" // name
1163                  */
1164 // GNU Wget 1.18 to cdn.kernel.org sends these extensions:
1165 // 0055
1166 //   0005 0005 0100000000 - status_request
1167 //   0000 0013 0011 00 000e 63646e 2e 6b65726e656c 2e 6f7267 - server_name
1168 //   ff01 0001 00 - renegotiation_info
1169 //   0023 0000 - session_ticket
1170 //   000a 0008 0006001700180019 - supported_groups
1171 //   000b 0002 0100 - ec_point_formats
1172 //   000d 0016 00140401040305010503060106030301030302010203 - signature_algorithms
1173         };
1174         struct client_hello *record;
1175         int len;
1176         int sni_len = sni ? strnlen(sni, 127) : 0;
1177
1178         len = sizeof(*record);
1179         if (sni_len)
1180                 len += 11 + strlen(sni);
1181         record = tls_get_outbuf(tls, len);
1182         memset(record, 0, len);
1183
1184         fill_handshake_record_hdr(record, HANDSHAKE_CLIENT_HELLO, len);
1185         record->proto_maj = TLS_MAJ;    /* the "requested" version of the protocol, */
1186         record->proto_min = TLS_MIN;    /* can be higher than one in record headers */
1187         tls_get_random(record->rand32, sizeof(record->rand32));
1188         if (TLS_DEBUG_FIXED_SECRETS)
1189                 memset(record->rand32, 0x11, sizeof(record->rand32));
1190         /* record->session_id_len = 0; - already is */
1191
1192         /* record->cipherid_len16_hi = 0; */
1193         record->cipherid_len16_lo = sizeof(record->cipherid);
1194         /* RFC 5746 Renegotiation Indication Extension - some servers will refuse to work with us otherwise */
1195         /*record->cipherid[0] = TLS_EMPTY_RENEGOTIATION_INFO_SCSV >> 8; - zero */
1196         record->cipherid[1] = TLS_EMPTY_RENEGOTIATION_INFO_SCSV & 0xff;
1197         if ((CIPHER_ID1 >> 8) != 0) record->cipherid[2] = CIPHER_ID1 >> 8;
1198         /*************************/ record->cipherid[3] = CIPHER_ID1 & 0xff;
1199 #if CIPHER_ID2
1200         if ((CIPHER_ID2 >> 8) != 0) record->cipherid[4] = CIPHER_ID2 >> 8;
1201         /*************************/ record->cipherid[5] = CIPHER_ID2 & 0xff;
1202 #endif
1203
1204         record->comprtypes_len = 1;
1205         /* record->comprtypes[0] = 0; */
1206
1207         if (sni_len) {
1208                 uint8_t *p = (void*)(record + 1);
1209                 //p[0] = 0;         //
1210                 p[1] = sni_len + 9; //ext_len
1211                 //p[2] = 0;             //
1212                 //p[3] = 0;             //extension_type
1213                 //p[4] = 0;         //
1214                 p[5] = sni_len + 5; //list len
1215                 //p[6] = 0;             //
1216                 p[7] = sni_len + 3;     //len of 1st SNI
1217                 //p[8] = 0;         //name type
1218                 //p[9] = 0;             //
1219                 p[10] = sni_len;        //name len
1220                 memcpy(&p[11], sni, sni_len);
1221         }
1222
1223         dbg(">> CLIENT_HELLO\n");
1224         /* Can hash it only when we know which MAC hash to use */
1225         /*xwrite_and_update_handshake_hash(tls, len); - WRONG! */
1226         xwrite_handshake_record(tls, len);
1227
1228         tls->hsd = xzalloc(sizeof(*tls->hsd) + len);
1229         tls->hsd->saved_client_hello_size = len;
1230         memcpy(tls->hsd->saved_client_hello, record, len);
1231         memcpy(tls->hsd->client_and_server_rand32, record->rand32, sizeof(record->rand32));
1232 }
1233
1234 static void get_server_hello(tls_state_t *tls)
1235 {
1236         struct server_hello {
1237                 struct record_hdr xhdr;
1238                 uint8_t type;
1239                 uint8_t len24_hi, len24_mid, len24_lo;
1240                 uint8_t proto_maj, proto_min;
1241                 uint8_t rand32[32]; /* first 4 bytes are unix time in BE format */
1242                 uint8_t session_id_len;
1243                 uint8_t session_id[32];
1244                 uint8_t cipherid_hi, cipherid_lo;
1245                 uint8_t comprtype;
1246                 /* extensions may follow, but only those which client offered in its Hello */
1247         };
1248
1249         struct server_hello *hp;
1250         uint8_t *cipherid;
1251         unsigned cipher;
1252         int len, len24;
1253
1254         len = tls_xread_handshake_block(tls, 74);
1255
1256         hp = (void*)tls->inbuf;
1257         // 74 bytes:
1258         // 02  000046 03|03   58|78|cf|c1 50|a5|49|ee|7e|29|48|71|fe|97|fa|e8|2d|19|87|72|90|84|9d|37|a3|f0|cb|6f|5f|e3|3c|2f |20  |d8|1a|78|96|52|d6|91|01|24|b3|d6|5b|b7|d0|6c|b3|e1|78|4e|3c|95|de|74|a0|ba|eb|a7|3a|ff|bd|a2|bf |00|9c |00|
1259         //SvHl len=70 maj.min unixtime^^^ 28randbytes^^^^^^^^^^^^^^^^^^^^^^^^^^^^_^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^_^^^ slen sid32bytes^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cipSel comprSel
1260         if (hp->type != HANDSHAKE_SERVER_HELLO
1261          || hp->len24_hi  != 0
1262          || hp->len24_mid != 0
1263          /* hp->len24_lo checked later */
1264          || hp->proto_maj != TLS_MAJ
1265          || hp->proto_min != TLS_MIN
1266         ) {
1267                 bad_record_die(tls, "'server hello'", len);
1268         }
1269
1270         cipherid = &hp->cipherid_hi;
1271         len24 = hp->len24_lo;
1272         if (hp->session_id_len != 32) {
1273                 if (hp->session_id_len != 0)
1274                         tls_error_die(tls);
1275
1276                 // session_id_len == 0: no session id
1277                 // "The server
1278                 // may return an empty session_id to indicate that the session will
1279                 // not be cached and therefore cannot be resumed."
1280                 cipherid -= 32;
1281                 len24 += 32; /* what len would be if session id would be present */
1282         }
1283
1284         if (len24 < 70
1285 //       || cipherid[0]  != (CIPHER_ID >> 8)
1286 //       || cipherid[1]  != (CIPHER_ID & 0xff)
1287 //       || cipherid[2]  != 0 /* comprtype */
1288         ) {
1289                 tls_error_die(tls);
1290         }
1291         dbg("<< SERVER_HELLO\n");
1292
1293         memcpy(tls->hsd->client_and_server_rand32 + 32, hp->rand32, sizeof(hp->rand32));
1294
1295         tls->cipher_id = cipher = 0x100 * cipherid[0] + cipherid[1];
1296         dbg("server chose cipher %04x\n", cipher);
1297
1298         if (cipher == TLS_RSA_WITH_AES_128_CBC_SHA) {
1299                 tls->key_size = AES128_KEYSIZE;
1300                 tls->MAC_size = SHA1_OUTSIZE;
1301                 sha1_begin(&tls->hsd->handshake_hash_ctx);
1302         }
1303         else { /* TLS_RSA_WITH_AES_256_CBC_SHA256 */
1304                 tls->key_size = AES256_KEYSIZE;
1305                 tls->MAC_size = SHA256_OUTSIZE;
1306                 sha256_begin(&tls->hsd->handshake_hash_ctx);
1307         }
1308         hash_handshake(tls, ">> client hello hash:%s",
1309                 tls->hsd->saved_client_hello, tls->hsd->saved_client_hello_size
1310         );
1311         hash_handshake(tls, "<< server hello hash:%s",
1312                 tls->inbuf + RECHDR_LEN, len
1313         );
1314 }
1315
1316 static void get_server_cert(tls_state_t *tls)
1317 {
1318         struct record_hdr *xhdr;
1319         uint8_t *certbuf;
1320         int len, len1;
1321
1322         len = tls_xread_handshake_block(tls, 10);
1323
1324         xhdr = (void*)tls->inbuf;
1325         certbuf = (void*)(xhdr + 1);
1326         if (certbuf[0] != HANDSHAKE_CERTIFICATE)
1327                 tls_error_die(tls);
1328         dbg("<< CERTIFICATE\n");
1329         // 4392 bytes:
1330         // 0b  00|11|24 00|11|21 00|05|b0 30|82|05|ac|30|82|04|94|a0|03|02|01|02|02|11|00|9f|85|bf|66|4b|0c|dd|af|ca|50|86|79|50|1b|2b|e4|30|0d...
1331         //Cert len=4388 ChainLen CertLen^ DER encoded X509 starts here. openssl x509 -in FILE -inform DER -noout -text
1332         len1 = get24be(certbuf + 1);
1333         if (len1 > len - 4) tls_error_die(tls);
1334         len = len1;
1335         len1 = get24be(certbuf + 4);
1336         if (len1 > len - 3) tls_error_die(tls);
1337         len = len1;
1338         len1 = get24be(certbuf + 7);
1339         if (len1 > len - 3) tls_error_die(tls);
1340         len = len1;
1341
1342         if (len)
1343                 find_key_in_der_cert(tls, certbuf + 10, len);
1344 }
1345
1346 static void send_client_key_exchange(tls_state_t *tls)
1347 {
1348         struct client_key_exchange {
1349                 uint8_t type;
1350                 uint8_t len24_hi, len24_mid, len24_lo;
1351                 /* keylen16 exists for RSA (in TLS, not in SSL), but not for some other key types */
1352                 uint8_t keylen16_hi, keylen16_lo;
1353                 uint8_t key[4 * 1024]; // size??
1354         };
1355 //FIXME: better size estimate
1356         struct client_key_exchange *record = tls_get_outbuf(tls, sizeof(*record));
1357         uint8_t rsa_premaster[RSA_PREMASTER_SIZE];
1358         int len;
1359
1360         tls_get_random(rsa_premaster, sizeof(rsa_premaster));
1361         if (TLS_DEBUG_FIXED_SECRETS)
1362                 memset(rsa_premaster, 0x44, sizeof(rsa_premaster));
1363         // RFC 5246
1364         // "Note: The version number in the PreMasterSecret is the version
1365         // offered by the client in the ClientHello.client_version, not the
1366         // version negotiated for the connection."
1367         rsa_premaster[0] = TLS_MAJ;
1368         rsa_premaster[1] = TLS_MIN;
1369         len = psRsaEncryptPub(/*pool:*/ NULL,
1370                 /* psRsaKey_t* */ &tls->hsd->server_rsa_pub_key,
1371                 rsa_premaster, /*inlen:*/ sizeof(rsa_premaster),
1372                 record->key, sizeof(record->key),
1373                 data_param_ignored
1374         );
1375         record->keylen16_hi = len >> 8;
1376         record->keylen16_lo = len & 0xff;
1377         len += 2;
1378         record->type = HANDSHAKE_CLIENT_KEY_EXCHANGE;
1379         record->len24_hi  = 0;
1380         record->len24_mid = len >> 8;
1381         record->len24_lo  = len & 0xff;
1382         len += 4;
1383
1384         dbg(">> CLIENT_KEY_EXCHANGE\n");
1385         xwrite_and_update_handshake_hash(tls, len);
1386
1387         // RFC 5246
1388         // For all key exchange methods, the same algorithm is used to convert
1389         // the pre_master_secret into the master_secret.  The pre_master_secret
1390         // should be deleted from memory once the master_secret has been
1391         // computed.
1392         //      master_secret = PRF(pre_master_secret, "master secret",
1393         //                          ClientHello.random + ServerHello.random)
1394         //                          [0..47];
1395         // The master secret is always exactly 48 bytes in length.  The length
1396         // of the premaster secret will vary depending on key exchange method.
1397         prf_hmac(tls,
1398                 tls->hsd->master_secret, sizeof(tls->hsd->master_secret),
1399                 rsa_premaster, sizeof(rsa_premaster),
1400                 "master secret",
1401                 tls->hsd->client_and_server_rand32, sizeof(tls->hsd->client_and_server_rand32)
1402         );
1403         dump_hex("master secret:%s\n", tls->hsd->master_secret, sizeof(tls->hsd->master_secret));
1404
1405         // RFC 5246
1406         // 6.3.  Key Calculation
1407         //
1408         // The Record Protocol requires an algorithm to generate keys required
1409         // by the current connection state (see Appendix A.6) from the security
1410         // parameters provided by the handshake protocol.
1411         //
1412         // The master secret is expanded into a sequence of secure bytes, which
1413         // is then split to a client write MAC key, a server write MAC key, a
1414         // client write encryption key, and a server write encryption key.  Each
1415         // of these is generated from the byte sequence in that order.  Unused
1416         // values are empty.  Some AEAD ciphers may additionally require a
1417         // client write IV and a server write IV (see Section 6.2.3.3).
1418         //
1419         // When keys and MAC keys are generated, the master secret is used as an
1420         // entropy source.
1421         //
1422         // To generate the key material, compute
1423         //
1424         //    key_block = PRF(SecurityParameters.master_secret,
1425         //                    "key expansion",
1426         //                    SecurityParameters.server_random +
1427         //                    SecurityParameters.client_random);
1428         //
1429         // until enough output has been generated.  Then, the key_block is
1430         // partitioned as follows:
1431         //
1432         //    client_write_MAC_key[SecurityParameters.mac_key_length]
1433         //    server_write_MAC_key[SecurityParameters.mac_key_length]
1434         //    client_write_key[SecurityParameters.enc_key_length]
1435         //    server_write_key[SecurityParameters.enc_key_length]
1436         //    client_write_IV[SecurityParameters.fixed_iv_length]
1437         //    server_write_IV[SecurityParameters.fixed_iv_length]
1438         {
1439                 uint8_t tmp64[64];
1440
1441                 /* make "server_rand32 + client_rand32" */
1442                 memcpy(&tmp64[0] , &tls->hsd->client_and_server_rand32[32], 32);
1443                 memcpy(&tmp64[32], &tls->hsd->client_and_server_rand32[0] , 32);
1444
1445                 prf_hmac(tls,
1446                         tls->client_write_MAC_key, 2 * (tls->MAC_size + tls->key_size),
1447                         // also fills:
1448                         // server_write_MAC_key[]
1449                         // client_write_key[]
1450                         // server_write_key[]
1451                         tls->hsd->master_secret, sizeof(tls->hsd->master_secret),
1452                         "key expansion",
1453                         tmp64, 64
1454                 );
1455                 tls->client_write_key = tls->client_write_MAC_key + (2 * tls->MAC_size);
1456                 tls->server_write_key = tls->client_write_key + tls->key_size;
1457                 dump_hex("client_write_MAC_key:%s\n",
1458                         tls->client_write_MAC_key, tls->MAC_size
1459                 );
1460                 dump_hex("client_write_key:%s\n",
1461                         tls->client_write_key, tls->key_size
1462                 );
1463         }
1464 }
1465
1466 static const uint8_t rec_CHANGE_CIPHER_SPEC[] = {
1467         RECORD_TYPE_CHANGE_CIPHER_SPEC, TLS_MAJ, TLS_MIN, 00, 01,
1468         01
1469 };
1470
1471 static void send_change_cipher_spec(tls_state_t *tls)
1472 {
1473         dbg(">> CHANGE_CIPHER_SPEC\n");
1474         xwrite(tls->ofd, rec_CHANGE_CIPHER_SPEC, sizeof(rec_CHANGE_CIPHER_SPEC));
1475 }
1476
1477 // 7.4.9.  Finished
1478 // A Finished message is always sent immediately after a change
1479 // cipher spec message to verify that the key exchange and
1480 // authentication processes were successful.  It is essential that a
1481 // change cipher spec message be received between the other handshake
1482 // messages and the Finished message.
1483 //...
1484 // The Finished message is the first one protected with the just
1485 // negotiated algorithms, keys, and secrets.  Recipients of Finished
1486 // messages MUST verify that the contents are correct.  Once a side
1487 // has sent its Finished message and received and validated the
1488 // Finished message from its peer, it may begin to send and receive
1489 // application data over the connection.
1490 //...
1491 // struct {
1492 //     opaque verify_data[verify_data_length];
1493 // } Finished;
1494 //
1495 // verify_data
1496 //    PRF(master_secret, finished_label, Hash(handshake_messages))
1497 //       [0..verify_data_length-1];
1498 //
1499 // finished_label
1500 //    For Finished messages sent by the client, the string
1501 //    "client finished".  For Finished messages sent by the server,
1502 //    the string "server finished".
1503 //
1504 // Hash denotes a Hash of the handshake messages.  For the PRF
1505 // defined in Section 5, the Hash MUST be the Hash used as the basis
1506 // for the PRF.  Any cipher suite which defines a different PRF MUST
1507 // also define the Hash to use in the Finished computation.
1508 //
1509 // In previous versions of TLS, the verify_data was always 12 octets
1510 // long.  In the current version of TLS, it depends on the cipher
1511 // suite.  Any cipher suite which does not explicitly specify
1512 // verify_data_length has a verify_data_length equal to 12.  This
1513 // includes all existing cipher suites.
1514 static void send_client_finished(tls_state_t *tls)
1515 {
1516         struct finished {
1517                 uint8_t type;
1518                 uint8_t len24_hi, len24_mid, len24_lo;
1519                 uint8_t prf_result[12];
1520         };
1521         struct finished *record = tls_get_outbuf(tls, sizeof(*record));
1522         uint8_t handshake_hash[TLS_MAX_MAC_SIZE];
1523         unsigned len;
1524
1525         fill_handshake_record_hdr(record, HANDSHAKE_FINISHED, sizeof(*record));
1526
1527         len = get_handshake_hash(tls, handshake_hash);
1528         prf_hmac(tls,
1529                 record->prf_result, sizeof(record->prf_result),
1530                 tls->hsd->master_secret, sizeof(tls->hsd->master_secret),
1531                 "client finished",
1532                 handshake_hash, len
1533         );
1534         dump_hex("from secret: %s\n", tls->hsd->master_secret, sizeof(tls->hsd->master_secret));
1535         dump_hex("from labelSeed: %s", "client finished", sizeof("client finished")-1);
1536         dump_hex("%s\n", handshake_hash, sizeof(handshake_hash));
1537         dump_hex("=> digest: %s\n", record->prf_result, sizeof(record->prf_result));
1538
1539         dbg(">> FINISHED\n");
1540         xwrite_encrypted(tls, sizeof(*record), RECORD_TYPE_HANDSHAKE);
1541 }
1542
1543 void FAST_FUNC tls_handshake(tls_state_t *tls, const char *sni)
1544 {
1545         // Client              RFC 5246                Server
1546         // (*) - optional messages, not always sent
1547         //
1548         // ClientHello          ------->
1549         //                                        ServerHello
1550         //                                       Certificate*
1551         //                                 ServerKeyExchange*
1552         //                                CertificateRequest*
1553         //                      <-------      ServerHelloDone
1554         // Certificate*
1555         // ClientKeyExchange
1556         // CertificateVerify*
1557         // [ChangeCipherSpec]
1558         // Finished             ------->
1559         //                                 [ChangeCipherSpec]
1560         //                      <-------             Finished
1561         // Application Data     <------>     Application Data
1562         int len;
1563
1564         send_client_hello_and_alloc_hsd(tls, sni);
1565         get_server_hello(tls);
1566
1567         // RFC 5246
1568         // The server MUST send a Certificate message whenever the agreed-
1569         // upon key exchange method uses certificates for authentication
1570         // (this includes all key exchange methods defined in this document
1571         // except DH_anon).  This message will always immediately follow the
1572         // ServerHello message.
1573         //
1574         // IOW: in practice, Certificate *always* follows.
1575         // (for example, kernel.org does not even accept DH_anon cipher id)
1576         get_server_cert(tls);
1577
1578         len = tls_xread_handshake_block(tls, 4);
1579         if (tls->inbuf[RECHDR_LEN] == HANDSHAKE_SERVER_KEY_EXCHANGE) {
1580                 // 459 bytes:
1581                 // 0c   00|01|c7 03|00|17|41|04|87|94|2e|2f|68|d0|c9|f4|97|a8|2d|ef|ed|67|ea|c6|f3|b3|56|47|5d|27|b6|bd|ee|70|25|30|5e|b0|8e|f6|21|5a...
1582                 //SvKey len=455^
1583                 // with TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA: 461 bytes:
1584                 // 0c   00|01|c9 03|00|17|41|04|cd|9b|b4|29|1f|f6|b0|c2|84|82|7f|29|6a|47|4e|ec|87|0b|c1|9c|69|e1|f8|c6|d0|53|e9|27|90|a5|c8|02|15|75...
1585                 dbg("<< SERVER_KEY_EXCHANGE len:%u\n", len);
1586 //probably need to save it
1587                 tls_xread_handshake_block(tls, 4);
1588         }
1589
1590 //      if (tls->inbuf[RECHDR_LEN] == HANDSHAKE_CERTIFICATE_REQUEST) {
1591 //              dbg("<< CERTIFICATE_REQUEST\n");
1592 // RFC 5246: (in response to this,) "If no suitable certificate is available,
1593 // the client MUST send a certificate message containing no
1594 // certificates.  That is, the certificate_list structure has a
1595 // length of zero. ...
1596 // Client certificates are sent using the Certificate structure
1597 // defined in Section 7.4.2."
1598 // (i.e. the same format as server certs)
1599 //              tls_xread_handshake_block(tls, 4);
1600 //      }
1601
1602         if (tls->inbuf[RECHDR_LEN] != HANDSHAKE_SERVER_HELLO_DONE)
1603                 tls_error_die(tls);
1604         // 0e 000000 (len:0)
1605         dbg("<< SERVER_HELLO_DONE\n");
1606
1607         send_client_key_exchange(tls);
1608
1609         send_change_cipher_spec(tls);
1610         /* from now on we should send encrypted */
1611         /* tls->write_seq64_be = 0; - already is */
1612         tls->encrypt_on_write = 1;
1613
1614         send_client_finished(tls);
1615
1616         /* Get CHANGE_CIPHER_SPEC */
1617         len = tls_xread_record(tls);
1618         if (len != 1 || memcmp(tls->inbuf, rec_CHANGE_CIPHER_SPEC, 6) != 0)
1619                 tls_error_die(tls);
1620         dbg("<< CHANGE_CIPHER_SPEC\n");
1621         if (tls->cipher_id == TLS_RSA_WITH_NULL_SHA256)
1622                 tls->min_encrypted_len_on_read = tls->MAC_size;
1623         else
1624                 /* all incoming packets now should be encrypted and have IV + MAC + padding */
1625                 tls->min_encrypted_len_on_read = AES_BLOCKSIZE + tls->MAC_size + AES_BLOCKSIZE;
1626
1627         /* Get (encrypted) FINISHED from the server */
1628         len = tls_xread_record(tls);
1629         if (len < 4 || tls->inbuf[RECHDR_LEN] != HANDSHAKE_FINISHED)
1630                 tls_error_die(tls);
1631         dbg("<< FINISHED\n");
1632         /* application data can be sent/received */
1633
1634         /* free handshake data */
1635 //      if (PARANOIA)
1636 //              memset(tls->hsd, 0, tls->hsd->hsd_size);
1637         free(tls->hsd);
1638         tls->hsd = NULL;
1639 }
1640
1641 static void tls_xwrite(tls_state_t *tls, int len)
1642 {
1643         dbg(">> DATA\n");
1644         xwrite_encrypted(tls, len, RECORD_TYPE_APPLICATION_DATA);
1645 }
1646
1647 // To run a test server using openssl:
1648 // openssl req -x509 -newkey rsa:$((4096/4*3)) -keyout key.pem -out server.pem -nodes -days 99999 -subj '/CN=localhost'
1649 // openssl s_server -key key.pem -cert server.pem -debug -tls1_2 -no_tls1 -no_tls1_1
1650 //
1651 // Unencryped SHA256 example:
1652 // openssl req -x509 -newkey rsa:$((4096/4*3)) -keyout key.pem -out server.pem -nodes -days 99999 -subj '/CN=localhost'
1653 // openssl s_server -key key.pem -cert server.pem -debug -tls1_2 -no_tls1 -no_tls1_1 -cipher NULL
1654 // openssl s_client -connect 127.0.0.1:4433 -debug -tls1_2 -no_tls1 -no_tls1_1 -cipher NULL-SHA256
1655
1656 void FAST_FUNC tls_run_copy_loop(tls_state_t *tls)
1657 {
1658         fd_set readfds;
1659         int inbuf_size;
1660         const int INBUF_STEP = 4 * 1024;
1661
1662 //TODO: convert to poll
1663         /* Select loop copying stdin to ofd, and ifd to stdout */
1664         FD_ZERO(&readfds);
1665         FD_SET(tls->ifd, &readfds);
1666         FD_SET(STDIN_FILENO, &readfds);
1667
1668         inbuf_size = INBUF_STEP;
1669         for (;;) {
1670                 fd_set testfds;
1671                 int nread;
1672
1673                 testfds = readfds;
1674                 if (select(tls->ifd + 1, &testfds, NULL, NULL, NULL) < 0)
1675                         bb_perror_msg_and_die("select");
1676
1677                 if (FD_ISSET(STDIN_FILENO, &testfds)) {
1678                         void *buf;
1679
1680                         dbg("STDIN HAS DATA\n");
1681                         buf = tls_get_outbuf(tls, inbuf_size);
1682                         nread = safe_read(STDIN_FILENO, buf, inbuf_size);
1683                         if (nread < 1) {
1684                                 /* We'd want to do this: */
1685                                 /* Close outgoing half-connection so they get EOF,
1686                                  * but leave incoming alone so we can see response
1687                                  */
1688                                 //shutdown(tls->ofd, SHUT_WR);
1689                                 /* But TLS has no way to encode this,
1690                                  * doubt it's ok to do it "raw"
1691                                  */
1692                                 FD_CLR(STDIN_FILENO, &readfds);
1693                                 tls_free_outbuf(tls); /* mem usage optimization */
1694                         } else {
1695                                 if (nread == inbuf_size) {
1696                                         /* TLS has per record overhead, if input comes fast,
1697                                          * read, encrypt and send bigger chunks
1698                                          */
1699                                         inbuf_size += INBUF_STEP;
1700                                         if (inbuf_size > TLS_MAX_OUTBUF)
1701                                                 inbuf_size = TLS_MAX_OUTBUF;
1702                                 }
1703                                 tls_xwrite(tls, nread);
1704                         }
1705                 }
1706                 if (FD_ISSET(tls->ifd, &testfds)) {
1707                         dbg("NETWORK HAS DATA\n");
1708  read_record:
1709                         nread = tls_xread_record(tls);
1710                         if (nread < 1) {
1711                                 /* TLS protocol has no real concept of one-sided shutdowns:
1712                                  * if we get "TLS EOF" from the peer, writes will fail too
1713                                  */
1714                                 //FD_CLR(tls->ifd, &readfds);
1715                                 //close(STDOUT_FILENO);
1716                                 //tls_free_inbuf(tls); /* mem usage optimization */
1717                                 //continue;
1718                                 break;
1719                         }
1720                         if (tls->inbuf[0] != RECORD_TYPE_APPLICATION_DATA)
1721                                 bb_error_msg_and_die("unexpected record type %d", tls->inbuf[0]);
1722                         xwrite(STDOUT_FILENO, tls->inbuf + RECHDR_LEN, nread);
1723                         /* We may already have a complete next record buffered,
1724                          * can process it without network reads (and possible blocking)
1725                          */
1726                         if (tls_has_buffered_record(tls))
1727                                 goto read_record;
1728                 }
1729         }
1730 }