networking/tls.c

   1 /*
   2  * Licensed under GPLv2, see file LICENSE in this source tree.
   3  *
   4  * Copyright (C) 2017 Denys Vlasenko
   5  */
   6 //config:config TLS
   7 //config:       bool "tls (debugging)"
   8 //config:       default n
   9
  10 //applet:IF_TLS(APPLET(tls, BB_DIR_USR_BIN, BB_SUID_DROP))
  11
  12 //kbuild:lib-$(CONFIG_TLS) += tls.o
  13 ////kbuild:lib-$(CONFIG_TLS) += tls_ciphers.o
  14 ////kbuild:lib-$(CONFIG_TLS) += tls_aes.o
  15 ////kbuild:lib-$(CONFIG_TLS) += tls_aes_gcm.o
  16
  17 //usage:#define tls_trivial_usage
  18 //usage:       "HOST[:PORT]"
  19 //usage:#define tls_full_usage "\n\n"
  20
  21 #include "libbb.h"
  22 //#include "tls_cryptoapi.h"
  23 //#include "tls_ciphers.h"
  24
  25 #if 1
  26 # define dbg(...) fprintf(stderr, __VA_ARGS__)
  27 #else
  28 # define dbg(...) ((void)0)
  29 #endif
  30
  31 #define RECORD_TYPE_CHANGE_CIPHER_SPEC 20
  32 #define RECORD_TYPE_ALERT              21
  33 #define RECORD_TYPE_HANDSHAKE          22
  34 #define RECORD_TYPE_APPLICATION_DATA   23
  35
  36 #define HANDSHAKE_HELLO_REQUEST        0
  37 #define HANDSHAKE_CLIENT_HELLO         1
  38 #define HANDSHAKE_SERVER_HELLO         2
  39 #define HANDSHAKE_HELLO_VERIFY_REQUEST 3
  40 #define HANDSHAKE_NEW_SESSION_TICKET   4
  41 #define HANDSHAKE_CERTIFICATE          11
  42 #define HANDSHAKE_SERVER_KEY_EXCHANGE  12
  43 #define HANDSHAKE_CERTIFICATE_REQUEST  13
  44 #define HANDSHAKE_SERVER_HELLO_DONE    14
  45 #define HANDSHAKE_CERTIFICATE_VERIFY   15
  46 #define HANDSHAKE_CLIENT_KEY_EXCHANGE  16
  47 #define HANDSHAKE_FINISHED             20
  48
  49 #define SSL_NULL_WITH_NULL_NULL                 0x0000
  50 #define SSL_RSA_WITH_NULL_MD5                   0x0001
  51 #define SSL_RSA_WITH_NULL_SHA                   0x0002
  52 #define SSL_RSA_WITH_RC4_128_MD5                0x0004
  53 #define SSL_RSA_WITH_RC4_128_SHA                0x0005
  54 #define SSL_RSA_WITH_3DES_EDE_CBC_SHA           0x000A  /* 10 */
  55 #define TLS_RSA_WITH_AES_128_CBC_SHA            0x002F  /* 47 */
  56 #define TLS_RSA_WITH_AES_256_CBC_SHA            0x0035  /* 53 */
  57 #define TLS_EMPTY_RENEGOTIATION_INFO_SCSV       0x00FF
  58
  59 #define TLS_RSA_WITH_IDEA_CBC_SHA               0x0007  /* 7 */
  60 #define SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA       0x0016  /* 22 */
  61 #define SSL_DH_anon_WITH_RC4_128_MD5            0x0018  /* 24 */
  62 #define SSL_DH_anon_WITH_3DES_EDE_CBC_SHA       0x001B  /* 27 */
  63 #define TLS_DHE_RSA_WITH_AES_128_CBC_SHA        0x0033  /* 51 */
  64 #define TLS_DHE_RSA_WITH_AES_256_CBC_SHA        0x0039  /* 57 */
  65 #define TLS_DHE_RSA_WITH_AES_128_CBC_SHA256     0x0067  /* 103 */
  66 #define TLS_DHE_RSA_WITH_AES_256_CBC_SHA256     0x006B  /* 107 */
  67 #define TLS_DH_anon_WITH_AES_128_CBC_SHA        0x0034  /* 52 */
  68 #define TLS_DH_anon_WITH_AES_256_CBC_SHA        0x003A  /* 58 */
  69 #define TLS_RSA_WITH_AES_128_CBC_SHA256         0x003C  /* 60 */
  70 #define TLS_RSA_WITH_AES_256_CBC_SHA256         0x003D  /* 61 */
  71 #define TLS_RSA_WITH_SEED_CBC_SHA               0x0096  /* 150 */
  72 #define TLS_PSK_WITH_AES_128_CBC_SHA            0x008C  /* 140 */
  73 #define TLS_PSK_WITH_AES_128_CBC_SHA256         0x00AE  /* 174 */
  74 #define TLS_PSK_WITH_AES_256_CBC_SHA384         0x00AF  /* 175 */
  75 #define TLS_PSK_WITH_AES_256_CBC_SHA            0x008D  /* 141 */
  76 #define TLS_DHE_PSK_WITH_AES_128_CBC_SHA        0x0090  /* 144 */
  77 #define TLS_DHE_PSK_WITH_AES_256_CBC_SHA        0x0091  /* 145 */
  78 #define TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA     0xC004  /* 49156 */
  79 #define TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA     0xC005  /* 49157 */
  80 #define TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA    0xC009  /* 49161 */
  81 #define TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA    0xC00A  /* 49162 */
  82 #define TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA     0xC012  /* 49170 */
  83 #define TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA      0xC013  /* 49171 */
  84 #define TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA      0xC014  /* 49172 */
  85 #define TLS_ECDH_RSA_WITH_AES_128_CBC_SHA       0xC00E  /* 49166 */
  86 #define TLS_ECDH_RSA_WITH_AES_256_CBC_SHA       0xC00F  /* 49167 */
  87 #define TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 0xC023  /* 49187 */
  88 #define TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384 0xC024  /* 49188 */
  89 #define TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256  0xC025  /* 49189 */
  90 #define TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384  0xC026  /* 49190 */
  91 #define TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256   0xC027  /* 49191 */
  92 #define TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384   0xC028  /* 49192 */
  93 #define TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256    0xC029  /* 49193 */
  94 #define TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384    0xC02A  /* 49194 */
  95
  96 #define TLS_RSA_WITH_AES_128_GCM_SHA256         0x009C  /* 156 */
  97 #define TLS_RSA_WITH_AES_256_GCM_SHA384         0x009D  /* 157 */
  98 #define TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 0xC02B  /* 49195 */
  99 #define TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 0xC02C  /* 49196 */
 100 #define TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256  0xC02D  /* 49197 */
 101 #define TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384  0xC02E  /* 49198 */
 102 #define TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256   0xC02F  /* 49199 */
 103 #define TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384   0xC030  /* 49200 */
 104 #define TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256    0xC031  /* 49201 */
 105 #define TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384    0xC032  /* 49202 */
 106
 107 //Tested against kernel.org:
 108 //TLS 1.1
 109 //#define TLS_MAJ 3
 110 //#define TLS_MIN 2
 111 //#define CIPHER_ID TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA // ok, recvs SERVER_KEY_EXCHANGE
 112 //TLS 1.2
 113 #define TLS_MAJ 3
 114 #define TLS_MIN 3
 115 //#define CIPHER_ID TLS_RSA_WITH_AES_256_CBC_SHA256 // ok, no SERVER_KEY_EXCHANGE
 116 // All GCMs:
 117 //#define CIPHER_ID TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384 // SSL_ALERT_HANDSHAKE_FAILURE
 118 //#define CIPHER_ID TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 // SSL_ALERT_HANDSHAKE_FAILURE
 119 //#define CIPHER_ID TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 // ok, recvs SERVER_KEY_EXCHANGE
 120 //#define CIPHER_ID TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
 121 //#define CIPHER_ID TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384
 122 //#define CIPHER_ID TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256 // SSL_ALERT_HANDSHAKE_FAILURE
 123 //#define CIPHER_ID TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384
 124 //#define CIPHER_ID TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256 // SSL_ALERT_HANDSHAKE_FAILURE
 125 //#define CIPHER_ID TLS_RSA_WITH_AES_256_GCM_SHA384 // ok, no SERVER_KEY_EXCHANGE
 126 #define CIPHER_ID TLS_RSA_WITH_AES_128_GCM_SHA256 // ok, no SERVER_KEY_EXCHANGE
 127 //#define CIPHER_ID TLS_DH_anon_WITH_AES_256_CBC_SHA // SSL_ALERT_HANDSHAKE_FAILURE
 128 // (tested b/c this one doesn't req server certs... no luck)
 129 //test TLS_RSA_WITH_AES_128_CBC_SHA, in tls 1.2 it's mandated to be always supported
 130
 131 struct transport_hdr {
 132         uint8_t type;
 133         uint8_t proto_maj, proto_min;
 134         uint8_t len16_hi, len16_lo;
 135 };
 136
 137 typedef struct tls_state {
 138         int fd;
 139
 140         uint8_t *pubkey;
 141         int pubkey_len;
 142
 143         int insize;
 144         int tail;
 145         // RFC 5246
 146         // |6.2.1. Fragmentation
 147         // |  The record layer fragments information blocks into TLSPlaintext
 148         // |  records carrying data in chunks of 2^14 bytes or less.  Client
 149         // |  message boundaries are not preserved in the record layer (i.e.,
 150         // |  multiple client messages of the same ContentType MAY be coalesced
 151         // |  into a single TLSPlaintext record, or a single message MAY be
 152         // |  fragmented across several records)
 153         // |...
 154         // |  length
 155         // |    The length (in bytes) of the following TLSPlaintext.fragment.
 156         // |    The length MUST NOT exceed 2^14.
 157         // |...
 158         // | 6.2.2. Record Compression and Decompression
 159         // |...
 160         // |  Compression must be lossless and may not increase the content length
 161         // |  by more than 1024 bytes.  If the decompression function encounters a
 162         // |  TLSCompressed.fragment that would decompress to a length in excess of
 163         // |  2^14 bytes, it MUST report a fatal decompression failure error.
 164         // |...
 165         // |  length
 166         // |    The length (in bytes) of the following TLSCompressed.fragment.
 167         // |    The length MUST NOT exceed 2^14 + 1024.
 168         //
 169         // Since our buffer also contains 5-byte headers, make it a bit bigger:
 170         uint8_t inbuf[18*1024];
 171 } tls_state_t;
 172
 173 static
 174 tls_state_t *new_tls_state(void)
 175 {
 176         tls_state_t *tls = xzalloc(sizeof(*tls));
 177         tls->fd = -1;
 178         return tls;
 179 }
 180
 181 static unsigned get24be(const uint8_t *p)
 182 {
 183         return 0x100*(0x100*p[0] + p[1]) + p[2];
 184 }
 185
 186 static void dump(const void *vp, int len)
 187 {
 188         char hexbuf[32 * 1024 + 4];
 189         const uint8_t *p = vp;
 190
 191         while (len > 0) {
 192                 unsigned xhdr_len;
 193                 if (len < 5) {
 194                         bin2hex(hexbuf, (void*)p, len)[0] = '\0';
 195                         dbg("< |%s|\n", hexbuf);
 196                         return;
 197                 }
 198                 xhdr_len = 0x100*p[3] + p[4];
 199                 dbg("< hdr_type:%u ver:%u.%u len:%u", p[0], p[1], p[2], xhdr_len);
 200                 p += 5;
 201                 len -= 5;
 202                 if (len >= 4 && p[-5] == RECORD_TYPE_HANDSHAKE) {
 203                         unsigned len24 = get24be(p + 1);
 204                         dbg(" type:%u len24:%u", p[0], len24);
 205                 }
 206                 if (xhdr_len > len)
 207                         xhdr_len = len;
 208                 bin2hex(hexbuf, (void*)p, xhdr_len)[0] = '\0';
 209                 dbg(" |%s|\n", hexbuf);
 210                 p += xhdr_len;
 211                 len -= xhdr_len;
 212         }
 213 }
 214
 215 static void tls_error_die(tls_state_t *tls)
 216 {
 217         dump(tls->inbuf, tls->insize + tls->tail);
 218         xfunc_die();
 219 }
 220
 221 static int xread_tls_block(tls_state_t *tls)
 222 {
 223         int len;
 224         int total;
 225         int target;
 226
 227         dbg("insize:%u tail:%u\n", tls->insize, tls->tail);
 228         memmove(tls->inbuf, tls->inbuf + tls->insize, tls->tail);
 229         errno = 0;
 230         total = tls->tail;
 231         target = sizeof(tls->inbuf);
 232         for (;;) {
 233                 if (total >= sizeof(struct transport_hdr) && target == sizeof(tls->inbuf)) {
 234                         struct transport_hdr *xhdr = (void*)tls->inbuf;
 235                         target = sizeof(*xhdr) + (0x100 * xhdr->len16_hi + xhdr->len16_lo);
 236                 }
 237                 /* if total >= target, we have a full packet (and possibly more)... */
 238                 if (target - total <= 0)
 239                         break;
 240                 len = safe_read(tls->fd, tls->inbuf + total, sizeof(tls->inbuf) - total);
 241                 if (len <= 0)
 242                         bb_perror_msg_and_die("short read");
 243                 total += len;
 244         }
 245         tls->tail = -(target - total);
 246         tls->insize = target;
 247         target -= sizeof(struct transport_hdr);
 248         dbg("got block len:%u\n", target);
 249         return target;
 250 }
 251
 252 static void send_client_hello(tls_state_t *tls)
 253 {
 254         struct client_hello {
 255                 struct transport_hdr xhdr;
 256                 uint8_t type;
 257                 uint8_t len24_hi, len24_mid, len24_lo;
 258                 uint8_t proto_maj, proto_min;
 259                 uint8_t rand32[32];
 260                 uint8_t session_id_len;
 261                 /* uint8_t session_id[]; */
 262                 uint8_t cipherid_len16_hi, cipherid_len16_lo;
 263                 uint8_t cipherid[2 * 1]; /* actually variable */
 264                 uint8_t comprtypes_len;
 265                 uint8_t comprtypes[1]; /* actually variable */
 266         };
 267         struct client_hello hello;
 268
 269         memset(&hello, 0, sizeof(hello));
 270         hello.xhdr.type = RECORD_TYPE_HANDSHAKE;
 271         hello.xhdr.proto_maj = TLS_MAJ;
 272         hello.xhdr.proto_min = TLS_MIN;
 273         hello.xhdr.len16_hi = (sizeof(hello) - sizeof(hello.xhdr)) >> 8;
 274         hello.xhdr.len16_lo = (sizeof(hello) - sizeof(hello.xhdr));
 275         hello.type = HANDSHAKE_CLIENT_HELLO;
 276         hello.len24_mid = (sizeof(hello) - sizeof(hello.xhdr) - 4) >> 8;
 277         hello.len24_lo  = (sizeof(hello) - sizeof(hello.xhdr) - 4);
 278         hello.proto_maj = TLS_MAJ;
 279         hello.proto_min = TLS_MIN;
 280         //fillrand(hello.rand32, sizeof(hello.rand32));
 281         open_read_close("/dev/urandom", hello.rand32, sizeof(hello.rand32));
 282         //hello.session_id_len = 0;
 283         //hello.cipherid_len16_hi = 0;
 284         hello.cipherid_len16_lo = 2;
 285         hello.cipherid[0] = CIPHER_ID >> 8;
 286         hello.cipherid[1] = CIPHER_ID & 0xff;
 287         hello.comprtypes_len = 1;
 288         //hello.comprtypes[0] = 0;
 289
 290         xwrite(tls->fd, &hello, sizeof(hello));
 291 }
 292
 293 static void get_server_hello_or_die(tls_state_t *tls)
 294 {
 295         struct server_hello {
 296                 struct transport_hdr xhdr;
 297                 uint8_t type;
 298                 uint8_t len24_hi, len24_mid, len24_lo;
 299                 uint8_t proto_maj, proto_min;
 300                 uint8_t rand32[32]; /* first 4 bytes are unix time in BE format */
 301                 uint8_t session_id_len;
 302                 uint8_t session_id[32];
 303                 uint8_t cipherid_hi, cipherid_lo;
 304                 uint8_t comprtype;
 305                 /* extensions may follow, but only those which client offered in its Hello */
 306         };
 307         struct server_hello *hp;
 308         int len;
 309
 310         len = xread_tls_block(tls);
 311
 312         hp = (void*)tls->inbuf;
 313         if (len != 74 /* TODO: if we accept extensions, should be < instead of != */
 314          || hp->xhdr.type != RECORD_TYPE_HANDSHAKE
 315          || hp->xhdr.proto_maj != TLS_MAJ
 316          || hp->xhdr.proto_min != TLS_MIN
 317         ) {
 318                 /* example: RECORD_TYPE_ALERT if server can't support our ciphers */
 319                 tls_error_die(tls);
 320         }
 321         dbg("got HANDSHAKE\n");
 322         // 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|
 323         // SvHl len=70 maj.min unixtime^^^ 28randbytes^^^^^^^^^^^^^^^^^^^^^^^^^^^^_^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^_^^^ slen sid32bytes^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ cipSel comprSel
 324         if (hp->type != HANDSHAKE_SERVER_HELLO
 325          || hp->len24_hi  != 0
 326          || hp->len24_mid != 0
 327          || hp->len24_lo  != 70
 328          || hp->proto_maj != TLS_MAJ
 329          || hp->proto_min != TLS_MIN
 330          || hp->session_id_len != 32
 331          || hp->cipherid_hi != (CIPHER_ID >> 8)
 332          || hp->cipherid_lo != (CIPHER_ID & 0xff)
 333          || hp->comprtype != 0
 334         ) {
 335                 tls_error_die(tls);
 336         }
 337         dbg("got SERVER_HELLO\n");
 338 }
 339
 340 static unsigned get_der_len(uint8_t **bodyp, uint8_t *der, uint8_t *end)
 341 {
 342         unsigned len;
 343
 344         if (end - der < 2)
 345                 xfunc_die();
 346 //      if ((der[0] & 0x1f) == 0x1f) /* not single-byte item code? */
 347 //              xfunc_die();
 348
 349         len = der[1]; /* maybe it's short len */
 350         if (len >= 0x80) {
 351                 /* no */
 352                 if (len != 0x82) {
 353                         /* 0x80 is "0 bytes of len", invalid DER: must use short len if can */
 354                         /* 0x81 is "1 byte of len", invalid DER */
 355                         /* >0x82 is "3+ bytes of len", should not happen realistically */
 356                         xfunc_die();
 357                 }
 358                 if (end - der < 4)
 359                         xfunc_die();
 360                 /* it's "ii 82 xx yy" */
 361                 len = 0x100*der[2] + der[3];
 362                 if (len < 0x80)
 363                         xfunc_die(); /* invalid DER: must use short len if can */
 364
 365                 der += 2; /* skip [code]+[82]+[2byte_len] */
 366         }
 367         der += 2; /* skip [code]+[1byte_len] */
 368
 369         if (end - der < len)
 370                 xfunc_die();
 371         *bodyp = der;
 372
 373         return len;
 374 }
 375
 376 static uint8_t *enter_der_item(uint8_t *der, uint8_t **endp)
 377 {
 378         uint8_t *new_der;
 379         unsigned len = get_der_len(&new_der, der, *endp);
 380         dbg("entered der @%p:0x%02x len:%u inner_byte @%p:0x%02x\n", der, der[0], len, new_der, new_der[0]);
 381         /* Move "end" position to cover only this item */
 382         *endp = new_der + len;
 383         return new_der;
 384 }
 385
 386 static uint8_t *skip_der_item(uint8_t *der, uint8_t *end)
 387 {
 388         uint8_t *new_der;
 389         unsigned len = get_der_len(&new_der, der, end);
 390         /* Skip body */
 391         new_der += len;
 392         dbg("skipped der 0x%02x, next byte 0x%02x\n", der[0], new_der[0]);
 393         return new_der;
 394 }
 395
 396 static void *find_key_in_der_cert(int *key_len, uint8_t *der, int len)
 397 {
 398 /* Example: partial decode of kernel.org certificate in DER format.
 399  *  SEQ 0x05ac/1452 bytes (Certificate): 308205ac
 400  *    SEQ 0x0494/1172 bytes (tbsCertificate): 30820494
 401  *      [ASN_CONTEXT_SPECIFIC | ASN_CONSTRUCTED | 0] 3 bytes: a003
 402  *        INTEGER (version): 0201 02
 403  *      INTEGER 0x11 bytes (serialNumber): 0211 00 9f85bf664b0cddafca508679501b2be4
 404  *      //^^^^^^note: matrixSSL also allows [ASN_CONTEXT_SPECIFIC | ASN_PRIMITIVE | 2] = 0x82 type
 405  *      SEQ 0x0d bytes (signatureAlgo): 300d
 406  *        OID 9 bytes: 0609 2a864886f70d01010b (OID_SHA256_RSA_SIG 42.134.72.134.247.13.1.1.11)
 407  *        NULL: 0500
 408  *      SEQ 0x5f bytes (issuer): 305f
 409  *        SET 11 bytes: 310b
 410  *          SEQ 9 bytes: 3009
 411  *            OID 3 bytes: 0603 550406
 412  *            Printable string "FR": 1302 4652
 413  *        SET 14 bytes: 310e
 414  *          SEQ 12 bytes: 300c
 415  *            OID 3 bytes: 0603 550408
 416  *            Printable string "Paris": 1305 5061726973
 417  *        SET 14 bytes: 310e
 418  *          SEQ 12 bytes: 300c
 419  *            OID 3 bytes: 0603 550407
 420  *            Printable string "Paris": 1305 5061726973
 421  *        SET 14 bytes: 310e
 422  *          SEQ 12 bytes: 300c
 423  *            OID 3 bytes: 0603 55040a
 424  *            Printable string "Gandi": 1305 47616e6469
 425  *        SET 32 bytes: 3120
 426  *          SEQ 30 bytes: 301e
 427  *            OID 3 bytes: 0603 550403
 428  *            Printable string "Gandi Standard SSL CA 2": 1317
 429  *                              47616e6469205374616e646172642053534c2043412032
 430  *      SEQ 30 bytes (validity): 301e
 431  *        TIME "161011000000Z": 170d 3136313031313030303030305a
 432  *        TIME "191011235959Z": 170d 3139313031313233353935395a
 433  *      SEQ 0x5b/91 bytes (subject): 305b //I did not decode this
 434  *          3121301f060355040b1318446f6d61696e20436f
 435  *          6e74726f6c2056616c6964617465643121301f06
 436  *          0355040b1318506f73697469766553534c204d75
 437  *          6c74692d446f6d61696e31133011060355040313
 438  *          0a6b65726e656c2e6f7267
 439  *      SEQ 0x01a2/418 bytes (subjectPublicKeyInfo): 308201a2
 440  *        SEQ 13 bytes (algorithm): 300d
 441  *          OID 9 bytes: 0609 2a864886f70d010101 (OID_RSA_KEY_ALG 42.134.72.134.247.13.1.1.1)
 442  *          NULL: 0500
 443  *        BITSTRING 0x018f/399 bytes (publicKey): 0382018f
 444  *          ????: 00
 445  *          //after the zero byte, it appears key itself uses DER encoding:
 446  *          SEQ 0x018a/394 bytes: 3082018a
 447  *            INTEGER 0x0181/385 bytes (modulus): 02820181
 448  *                  00b1ab2fc727a3bef76780c9349bf3
 449  *                  ...24 more blocks of 15 bytes each...
 450  *                  90e895291c6bc8693b65
 451  *            INTEGER 3 bytes (exponent): 0203 010001
 452  *      [ASN_CONTEXT_SPECIFIC | ASN_CONSTRUCTED | 0x3] 0x01e5 bytes (X509v3 extensions): a38201e5
 453  *        SEQ 0x01e1 bytes: 308201e1
 454  *        ...
 455  * Certificate is a DER-encoded data structure. Each DER element has a length,
 456  * which makes it easy to skip over large compound elements of any complexity
 457  * without parsing them.
 458  *
 459  * Certificate is a sequence of three elements:
 460  *      tbsCertificate (SEQ)
 461  *      signatureAlgorithm (AlgorithmIdentifier)
 462  *      signatureValue (BIT STRING)
 463  *
 464  * In turn, tbsCertificate is a sequence of:
 465  *      version
 466  *      serialNumber
 467  *      signatureAlgo (AlgorithmIdentifier)
 468  *      issuer (Name, has complex structure)
 469  *      validity (Validity, SEQ of two Times)
 470  *      subject (Name)
 471  *      subjectPublicKeyInfo (SEQ)
 472  *      ...
 473  *
 474  * subjectPublicKeyInfo is a sequence of:
 475  *      algorithm (AlgorithmIdentifier)
 476  *      publicKey (BIT STRING)
 477  *
 478  * Essentially, we want subjectPublicKeyInfo.publicKey
 479  */
 480         uint8_t *end = der + len;
 481
 482         /* enter "Certificate" item: [der, end) will be only Cert */
 483         der = enter_der_item(der, &end);
 484
 485         /* enter "tbsCertificate" item: [der, end) will be only tbsCert */
 486         der = enter_der_item(der, &end);
 487
 488         /* skip up to subjectPublicKeyInfo */
 489         der = skip_der_item(der, end); /* version */
 490         der = skip_der_item(der, end); /* serialNumber */
 491         der = skip_der_item(der, end); /* signatureAlgo */
 492         der = skip_der_item(der, end); /* issuer */
 493         der = skip_der_item(der, end); /* validity */
 494         der = skip_der_item(der, end); /* subject */
 495
 496         /* enter "subjectPublicKeyInfo" */
 497         der = enter_der_item(der, &end);
 498
 499         /* skip "subjectPublicKeyInfo.algorithm" */
 500         der = skip_der_item(der, end);
 501         /* enter "subjectPublicKeyInfo.publicKey" */
 502 //      die_if_not_this_der_type(der, end, 0x03); /* must be BITSTRING */
 503         der = enter_der_item(der, &end);
 504
 505         /* return a copy */
 506         *key_len = end - der;
 507         dbg("copying key bytes:%u, first:0x%02x\n", *key_len, der[0]);
 508         return xmemdup(der, *key_len);
 509 }
 510
 511 static void get_server_cert_or_die(tls_state_t *tls)
 512 {
 513         struct transport_hdr *xhdr;
 514         uint8_t *certbuf;
 515         int len, len1;
 516
 517         len = xread_tls_block(tls);
 518         xhdr = (void*)tls->inbuf;
 519         if (len < sizeof(*xhdr) + 10
 520          || xhdr->type != RECORD_TYPE_HANDSHAKE
 521          || xhdr->proto_maj != TLS_MAJ
 522          || xhdr->proto_min != TLS_MIN
 523         ) {
 524                 tls_error_die(tls);
 525         }
 526         dbg("got HANDSHAKE\n");
 527         certbuf = (void*)(xhdr + 1);
 528         if (certbuf[0] != HANDSHAKE_CERTIFICATE)
 529                 tls_error_die(tls);
 530         dbg("got CERTIFICATE\n");
 531         // 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... (4392 bytes)
 532         // Cert len=4388 ChainLen CertLen^ DER encoded X509 starts here. openssl x509 -in FILE -inform DER -noout -text
 533         len1 = get24be(certbuf + 1);
 534         if (len1 > len - 4) tls_error_die(tls);
 535         len = len1;
 536
 537         len1 = get24be(certbuf + 4);
 538         if (len1 > len - 3) tls_error_die(tls);
 539         len = len1;
 540
 541         len1 = get24be(certbuf + 7);
 542         if (len1 > len - 3) tls_error_die(tls);
 543         len = len1;
 544
 545         if (len)
 546                 tls->pubkey = find_key_in_der_cert(&tls->pubkey_len, certbuf + 10, len);
 547 }
 548
 549 static void tls_handshake(tls_state_t *tls)
 550 {
 551         // Client              RFC 5246                Server
 552         // (*) - optional messages, not always sent
 553         //
 554         // ClientHello          ------->
 555         //                                        ServerHello
 556         //                                       Certificate*
 557         //                                 ServerKeyExchange*
 558         //                                CertificateRequest*
 559         //                      <-------      ServerHelloDone
 560         // Certificate*
 561         // ClientKeyExchange
 562         // CertificateVerify*
 563         // [ChangeCipherSpec]
 564         // Finished             ------->
 565         //                                 [ChangeCipherSpec]
 566         //                      <-------             Finished
 567         // Application Data     <------>     Application Data
 568         int len;
 569
 570         send_client_hello(tls);
 571 #if 0 /* dump */
 572         for (;;) {
 573                 uint8_t buf[16*1024];
 574                 sleep(2);
 575                 len = recv(tls->fd, buf, sizeof(buf), 0); //MSG_DONTWAIT);
 576                 if (len < 0) {
 577                         if (errno == EAGAIN)
 578                                 continue;
 579                         bb_perror_msg_and_die("recv");
 580                 }
 581                 if (len == 0)
 582                         break;
 583                 dump(buf, len);
 584         }
 585 #endif
 586
 587         get_server_hello_or_die(tls);
 588
 589         //RFC 5246
 590         // The server MUST send a Certificate message whenever the agreed-
 591         // upon key exchange method uses certificates for authentication
 592         // (this includes all key exchange methods defined in this document
 593         // except DH_anon).  This message will always immediately follow the
 594         // ServerHello message.
 595         //
 596         // IOW: in practice, Certificate *always* follows.
 597         // (for example, kernel.org does not even accept DH_anon cipher id)
 598         get_server_cert_or_die(tls);
 599
 600         len = xread_tls_block(tls);
 601         /* Next handshake type is not predetermined */
 602         switch (tls->inbuf[5]) {
 603         case HANDSHAKE_SERVER_KEY_EXCHANGE:
 604                 //0c    0001c7 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... 459 bytes
 605                 //SvKey len^^^
 606                 dbg("got SERVER_KEY_EXCHANGE\n");
 607                 len = xread_tls_block(tls);
 608                 break;
 609         case HANDSHAKE_CERTIFICATE_REQUEST:
 610                 dbg("got CERTIFICATE_REQUEST\n");
 611                 len = xread_tls_block(tls);
 612                 break;
 613         case HANDSHAKE_SERVER_HELLO_DONE:
 614                 // 0e 000000 (len:0)
 615                 dbg("got SERVER_HELLO_DONE\n");
 616                 break;
 617         default:
 618                 tls_error_die(tls);
 619         }
 620 }
 621
 622 int tls_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 623 int tls_main(int argc UNUSED_PARAM, char **argv)
 624 {
 625         tls_state_t *tls;
 626         len_and_sockaddr *lsa;
 627         int fd;
 628
 629         // INIT_G();
 630         // getopt32(argv, "myopts")
 631
 632         if (!argv[1])
 633                 bb_show_usage();
 634
 635         lsa = xhost2sockaddr(argv[1], 443);
 636         fd = xconnect_stream(lsa);
 637
 638         tls = new_tls_state();
 639         tls->fd = fd;
 640         tls_handshake(tls);
 641
 642         return EXIT_SUCCESS;
 643 }