//kbuild:lib-$(CONFIG_TLS) += tls_pstm_montgomery_reduce.o
//kbuild:lib-$(CONFIG_TLS) += tls_pstm_mul_comba.o
//kbuild:lib-$(CONFIG_TLS) += tls_pstm_sqr_comba.o
-//kbuild:lib-$(CONFIG_TLS) += tls_rsa.o
//kbuild:lib-$(CONFIG_TLS) += tls_aes.o
+//kbuild:lib-$(CONFIG_TLS) += tls_rsa.o
+//kbuild:lib-$(CONFIG_TLS) += tls_fe.o
////kbuild:lib-$(CONFIG_TLS) += tls_aes_gcm.o
#include "tls.h"
#define CIPHER_ID2 TLS_RSA_WITH_AES_128_CBC_SHA
// bug #11456: host is.gd accepts only ECDHE-ECDSA-foo (the simplest which works: ECDHE-ECDSA-AES128-SHA 0xC009)
+#define CIPHER_ID3 TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
#define TLS_DEBUG 0
uint8_t len16_hi, len16_lo;
};
+enum {
+ KEY_ALG_RSA,
+ KEY_ALG_ECDSA,
+};
struct tls_handshake_data {
/* In bbox, md5/sha1/sha256 ctx's are the same structure */
md5sha_ctx_t handshake_hash_ctx;
uint8_t client_and_server_rand32[2 * 32];
uint8_t master_secret[48];
+
+ smallint key_alg;
//TODO: store just the DER key here, parse/use/delete it when sending client key
//this way it will stay key type agnostic here.
psRsaKey_t server_rsa_pub_key;
+ uint8_t ecc_pub_key32[32];
unsigned saved_client_hello_size;
uint8_t saved_client_hello[1];
return new_der;
}
+//
+static void binary_to_pstm(pstm_int *pstm_n, uint8_t *bin_ptr, unsigned len)
+{
+ pstm_init_for_read_unsigned_bin(/*pool:*/ NULL, pstm_n, len);
+ pstm_read_unsigned_bin(pstm_n, bin_ptr, len);
+ //return bin_ptr + len;
+}
+//
+
static void der_binary_to_pstm(pstm_int *pstm_n, uint8_t *der, uint8_t *end)
{
uint8_t *bin_ptr;
unsigned len = get_der_len(&bin_ptr, der, end);
dbg_der("binary bytes:%u, first:0x%02x\n", len, bin_ptr[0]);
- pstm_init_for_read_unsigned_bin(/*pool:*/ NULL, pstm_n, len);
- pstm_read_unsigned_bin(pstm_n, bin_ptr, len);
- //return bin + len;
+ binary_to_pstm(pstm_n, bin_ptr, len);
+ //pstm_init_for_read_unsigned_bin(/*pool:*/ NULL, pstm_n, len);
+ //pstm_read_unsigned_bin(pstm_n, bin_ptr, len);
+ ////return bin_ptr + len;
}
static void find_key_in_der_cert(tls_state_t *tls, uint8_t *der, int len)
* publicKey (BIT STRING)
*
* We need Certificate.tbsCertificate.subjectPublicKeyInfo.publicKey
+ *
+ * Example of an ECDSA key:
+ * SEQ 0x59 bytes (subjectPublicKeyInfo): 3059
+ * SEQ 0x13 bytes (algorithm): 3013
+ * OID 7 bytes: 0607 2a8648ce3d0201 (OID_ECDSA_KEY_ALG 42.134.72.206.61.2.1)
+ * OID 8 bytes: 0608 2a8648ce3d030107 (OID_EC_prime256v1 42.134.72.206.61.3.1.7)
+ * BITSTRING 0x42 bytes (publicKey): 0342
+ * 0004 53af f65e 50cc 7959 7e29 0171 c75c
+ * 7335 e07d f45b 9750 b797 3a38 aebb 2ac6
+ * 8329 2748 e77e 41cb d482 2ce6 05ec a058
+ * f3ab d561 2f4c d845 9ad3 7252 e3de bd3b
+ * 9012
*/
uint8_t *end = der + len;
/* enter subjectPublicKeyInfo */
der = enter_der_item(der, &end);
{ /* check subjectPublicKeyInfo.algorithm */
- static const uint8_t expected[] = {
+ static const uint8_t OID_RSA_KEY_ALG[] = {
0x30,0x0d, // SEQ 13 bytes
0x06,0x09, 0x2a,0x86,0x48,0x86,0xf7,0x0d,0x01,0x01,0x01, // OID RSA_KEY_ALG 42.134.72.134.247.13.1.1.1
//0x05,0x00, // NULL
};
- if (memcmp(der, expected, sizeof(expected)) != 0)
- bb_error_msg_and_die("not RSA key");
+ static const uint8_t OID_ECDSA_KEY_ALG[] = {
+ 0x30,0x13, // SEQ 0x13 bytes
+ 0x06,0x07, 0x2a,0x86,0x48,0xce,0x3d,0x02,0x01, //OID_ECDSA_KEY_ALG 42.134.72.206.61.2.1
+ 0x06,0x08, 0x2a,0x86,0x48,0xce,0x3d,0x03,0x01,0x07, //OID_EC_prime256v1 42.134.72.206.61.3.1.7
+ //rfc3279:
+ //42.134.72.206.61.3 is ellipticCurve
+ //42.134.72.206.61.3.0 is c-TwoCurve
+ //42.134.72.206.61.3.1 is primeCurve
+ //42.134.72.206.61.3.1.7 is prime256v1
+ };
+ if (memcmp(der, OID_RSA_KEY_ALG, sizeof(OID_RSA_KEY_ALG)) == 0) {
+ dbg("RSA key\n");
+ tls->hsd->key_alg = KEY_ALG_RSA;
+ } else
+ if (memcmp(der, OID_ECDSA_KEY_ALG, sizeof(OID_ECDSA_KEY_ALG)) == 0) {
+ dbg("ECDSA key\n");
+ tls->hsd->key_alg = KEY_ALG_ECDSA;
+ } else
+ bb_error_msg_and_die("not RSA or ECDSA key");
}
- /* skip subjectPublicKeyInfo.algorithm */
- der = skip_der_item(der, end);
- /* enter subjectPublicKeyInfo.publicKey */
-// die_if_not_this_der_type(der, end, 0x03); /* must be BITSTRING */
- der = enter_der_item(der, &end);
- /* parse RSA key: */
-//based on getAsnRsaPubKey(), pkcs1ParsePrivBin() is also of note
- dbg("key bytes:%u, first:0x%02x\n", (int)(end - der), der[0]);
- if (end - der < 14) xfunc_die();
- /* example format:
- * ignore bits: 00
- * SEQ 0x018a/394 bytes: 3082018a
- * INTEGER 0x0181/385 bytes (modulus): 02820181 XX...XXX
- * INTEGER 3 bytes (exponent): 0203 010001
- */
- if (*der != 0) /* "ignore bits", should be 0 */
- xfunc_die();
- der++;
- der = enter_der_item(der, &end); /* enter SEQ */
- /* memset(tls->hsd->server_rsa_pub_key, 0, sizeof(tls->hsd->server_rsa_pub_key)); - already is */
- der_binary_to_pstm(&tls->hsd->server_rsa_pub_key.N, der, end); /* modulus */
- der = skip_der_item(der, end);
- der_binary_to_pstm(&tls->hsd->server_rsa_pub_key.e, der, end); /* exponent */
- tls->hsd->server_rsa_pub_key.size = pstm_unsigned_bin_size(&tls->hsd->server_rsa_pub_key.N);
- dbg("server_rsa_pub_key.size:%d\n", tls->hsd->server_rsa_pub_key.size);
+ if (tls->hsd->key_alg == KEY_ALG_RSA) {
+ /* parse RSA key: */
+ //based on getAsnRsaPubKey(), pkcs1ParsePrivBin() is also of note
+ /* skip subjectPublicKeyInfo.algorithm */
+ der = skip_der_item(der, end);
+ /* enter subjectPublicKeyInfo.publicKey */
+// die_if_not_this_der_type(der, end, 0x03); /* must be BITSTRING */
+ der = enter_der_item(der, &end);
+
+ dbg("key bytes:%u, first:0x%02x\n", (int)(end - der), der[0]);
+ if (end - der < 14)
+ xfunc_die();
+ /* example format:
+ * ignore bits: 00
+ * SEQ 0x018a/394 bytes: 3082018a
+ * INTEGER 0x0181/385 bytes (modulus): 02820181 XX...XXX
+ * INTEGER 3 bytes (exponent): 0203 010001
+ */
+ if (*der != 0) /* "ignore bits", should be 0 */
+ xfunc_die();
+ der++;
+ der = enter_der_item(der, &end); /* enter SEQ */
+ /* memset(tls->hsd->server_rsa_pub_key, 0, sizeof(tls->hsd->server_rsa_pub_key)); - already is */
+ der_binary_to_pstm(&tls->hsd->server_rsa_pub_key.N, der, end); /* modulus */
+ der = skip_der_item(der, end);
+ der_binary_to_pstm(&tls->hsd->server_rsa_pub_key.e, der, end); /* exponent */
+ tls->hsd->server_rsa_pub_key.size = pstm_unsigned_bin_size(&tls->hsd->server_rsa_pub_key.N);
+ dbg("server_rsa_pub_key.size:%d\n", tls->hsd->server_rsa_pub_key.size);
+ }
}
/*
static void send_client_hello_and_alloc_hsd(tls_state_t *tls, const char *sni)
{
+ static const uint8_t supported_groups[] = {
+ 0x00,0x0a, //extension_type: "supported_groups"
+ 0x00,0x04, //ext len
+ 0x00,0x02, //list len
+ 0x00,0x1d, //curve_x25519 (rfc7748)
+ //0x00,0x17, //curve_secp256r1
+ //0x00,0x18, //curve_secp384r1
+ //0x00,0x19, //curve_secp521r1
+ };
+ //static const uint8_t signature_algorithms[] = {
+ // 000d
+ // 0020
+ // 001e
+ // 0601 0602 0603 0501 0502 0503 0401 0402 0403 0301 0302 0303 0201 0202 0203
+ //};
+
struct client_hello {
uint8_t type;
uint8_t len24_hi, len24_mid, len24_lo;
uint8_t session_id_len;
/* uint8_t session_id[]; */
uint8_t cipherid_len16_hi, cipherid_len16_lo;
- uint8_t cipherid[2 * (2 + !!CIPHER_ID2)]; /* actually variable */
+ uint8_t cipherid[2 * (2 + !!CIPHER_ID2 + !!CIPHER_ID3)]; /* actually variable */
uint8_t comprtypes_len;
uint8_t comprtypes[1]; /* actually variable */
/* Extensions (SNI shown):
// 0017 0000 - extended master secret
};
struct client_hello *record;
+ uint8_t *ptr;
int len;
- int sni_len = sni ? strnlen(sni, 127 - 9) : 0;
+ int ext_len;
+ int sni_len = sni ? strnlen(sni, 127 - 5) : 0;
- len = sizeof(*record);
+ ext_len = 0;
+ /* is.gd responds with "handshake failure" to our hello if there's no supported_groups element */
+ ext_len += sizeof(supported_groups);
if (sni_len)
- len += 11 + sni_len;
+ ext_len += 9 + sni_len;
+
+ /* +2 is for "len of all extensions" 2-byte field */
+ len = sizeof(*record) + 2 + ext_len;
record = tls_get_outbuf(tls, len);
memset(record, 0, len);
if ((CIPHER_ID2 >> 8) != 0) record->cipherid[4] = CIPHER_ID2 >> 8;
/*************************/ record->cipherid[5] = CIPHER_ID2 & 0xff;
#endif
+#if CIPHER_ID3
+ if ((CIPHER_ID3 >> 8) != 0) record->cipherid[6] = CIPHER_ID3 >> 8;
+ /*************************/ record->cipherid[7] = CIPHER_ID3 & 0xff;
+#endif
record->comprtypes_len = 1;
/* record->comprtypes[0] = 0; */
+ ptr = (void*)(record + 1);
+ *ptr++ = ext_len >> 8;
+ *ptr++ = ext_len;
if (sni_len) {
- uint8_t *p = (void*)(record + 1);
- //p[0] = 0; //
- p[1] = sni_len + 9; //ext_len
- //p[2] = 0; //
- //p[3] = 0; //extension_type
- //p[4] = 0; //
- p[5] = sni_len + 5; //list len
- //p[6] = 0; //
- p[7] = sni_len + 3; //len of 1st SNI
- //p[8] = 0; //name type
- //p[9] = 0; //
- p[10] = sni_len; //name len
- memcpy(&p[11], sni, sni_len);
+ //ptr[0] = 0; //
+ //ptr[1] = 0; //extension_type
+ //ptr[2] = 0; //
+ ptr[3] = sni_len + 5; //list len
+ //ptr[4] = 0; //
+ ptr[5] = sni_len + 3; //len of 1st SNI
+ //ptr[6] = 0; //name type
+ //ptr[7] = 0; //
+ ptr[8] = sni_len; //name len
+ ptr = mempcpy(&ptr[9], sni, sni_len);
}
+ mempcpy(ptr, supported_groups, sizeof(supported_groups));
dbg(">> CLIENT_HELLO\n");
/* Can hash it only when we know which MAC hash to use */
tls->cipher_id = cipher = 0x100 * cipherid[0] + cipherid[1];
dbg("server chose cipher %04x\n", cipher);
- if (cipher == TLS_RSA_WITH_AES_128_CBC_SHA) {
+ if (cipher == TLS_RSA_WITH_AES_128_CBC_SHA
+ || cipher == TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
+ ) {
tls->key_size = AES128_KEYSIZE;
tls->MAC_size = SHA1_OUTSIZE;
}
find_key_in_der_cert(tls, certbuf + 10, len);
}
+/* On input, len is known to be >= 4.
+ * The record is known to be SERVER_KEY_EXCHANGE.
+ */
+static void process_server_key(tls_state_t *tls, int len)
+{
+ struct record_hdr *xhdr;
+ uint8_t *keybuf;
+ int len1;
+ uint32_t t32;
+
+ xhdr = (void*)tls->inbuf;
+ keybuf = (void*)(xhdr + 1);
+//seen from is.gd: it selects curve_x25519:
+// 0c 00006e //SERVER_KEY_EXCHANGE
+// 03 //curve_type: named curve
+// 001d //curve_x25519
+//server-chosen EC point, and then signed_params
+// (rfc8422: "A hash of the params, with the signature
+// appropriate to that hash applied. The private key corresponding
+// to the certified public key in the server's Certificate message is
+// used for signing.")
+//follow. Format unclear/guessed:
+// 20 //eccPubKeyLen
+// 25511923d73b70dd2f60e66ba2f3fda31a9c25170963c7a3a972e481dbb2835d //eccPubKey (32bytes)
+// 0203 //hashSigAlg: 2:SHA1 (4:SHA256 5:SHA384 6:SHA512), 3:ECDSA (1:RSA)
+// 0046 //len (16bit)
+// 30 44 //SEQ, len
+// 02 20 //INTEGER, len
+// 2e18e7c2a9badd0a70cd3059a6ab114539b9f5163568911147386cd77ed7c412 //32bytes
+//this item ^^^^^ is sometimes 33 bytes (with all container sizes also +1)
+// 02 20 //INTEGER, len
+// 64523d6216cb94c43c9b20e377d8c52c55be6703fd6730a155930c705eaf3af6 //32bytes
+//same about this item ^^^^^
+ /* Get and verify length */
+ len1 = get24be(keybuf + 1);
+ if (len1 > len - 4) tls_error_die(tls);
+ len = len1;
+ if (len < (1+2+1+32)) tls_error_die(tls);
+ keybuf += 4;
+
+ /* So far we only support curve_x25519 */
+ move_from_unaligned32(t32, keybuf);
+ if (t32 != htonl(0x03001d20))
+ tls_error_die(tls);
+
+ memcpy(tls->hsd->ecc_pub_key32, keybuf + 4, 32);
+ dbg("got eccPubKey\n");
+}
+
static void send_empty_client_cert(tls_state_t *tls)
{
struct client_empty_cert {
uint8_t cert_chain_len24_hi, cert_chain_len24_mid, cert_chain_len24_lo;
};
struct client_empty_cert *record;
+ static const uint8_t empty_client_cert[] = {
+ HANDSHAKE_CERTIFICATE,
+ 0, 0, 3, //len24
+ 0, 0, 0, //cert_chain_len24
+ };
record = tls_get_outbuf(tls, sizeof(*record));
-//FIXME: can just memcpy a ready-made one.
- fill_handshake_record_hdr(record, HANDSHAKE_CERTIFICATE, sizeof(*record));
- record->cert_chain_len24_hi = 0;
- record->cert_chain_len24_mid = 0;
- record->cert_chain_len24_lo = 0;
+ //fill_handshake_record_hdr(record, HANDSHAKE_CERTIFICATE, sizeof(*record));
+ //record->cert_chain_len24_hi = 0;
+ //record->cert_chain_len24_mid = 0;
+ //record->cert_chain_len24_lo = 0;
+ memcpy(record, empty_client_cert, sizeof(empty_client_cert));
dbg(">> CERTIFICATE\n");
xwrite_and_update_handshake_hash(tls, sizeof(*record));
struct client_key_exchange {
uint8_t type;
uint8_t len24_hi, len24_mid, len24_lo;
- /* keylen16 exists for RSA (in TLS, not in SSL), but not for some other key types */
- uint8_t keylen16_hi, keylen16_lo;
- uint8_t key[4 * 1024]; // size??
+ uint8_t key[2 + 4 * 1024]; // size??
};
//FIXME: better size estimate
struct client_key_exchange *record = tls_get_outbuf(tls, sizeof(*record));
uint8_t rsa_premaster[RSA_PREMASTER_SIZE];
+ uint8_t x25519_premaster[CURVE25519_KEYSIZE];
+ uint8_t *premaster;
+ int premaster_size;
int len;
- tls_get_random(rsa_premaster, sizeof(rsa_premaster));
- if (TLS_DEBUG_FIXED_SECRETS)
- memset(rsa_premaster, 0x44, sizeof(rsa_premaster));
- // RFC 5246
- // "Note: The version number in the PreMasterSecret is the version
- // offered by the client in the ClientHello.client_version, not the
- // version negotiated for the connection."
- rsa_premaster[0] = TLS_MAJ;
- rsa_premaster[1] = TLS_MIN;
- dump_hex("premaster:%s\n", rsa_premaster, sizeof(rsa_premaster));
- len = psRsaEncryptPub(/*pool:*/ NULL,
- /* psRsaKey_t* */ &tls->hsd->server_rsa_pub_key,
- rsa_premaster, /*inlen:*/ sizeof(rsa_premaster),
- record->key, sizeof(record->key),
- data_param_ignored
- );
- record->keylen16_hi = len >> 8;
- record->keylen16_lo = len & 0xff;
- len += 2;
+ if (tls->hsd->key_alg == KEY_ALG_RSA) {
+ tls_get_random(rsa_premaster, sizeof(rsa_premaster));
+ if (TLS_DEBUG_FIXED_SECRETS)
+ memset(rsa_premaster, 0x44, sizeof(rsa_premaster));
+ // RFC 5246
+ // "Note: The version number in the PreMasterSecret is the version
+ // offered by the client in the ClientHello.client_version, not the
+ // version negotiated for the connection."
+ rsa_premaster[0] = TLS_MAJ;
+ rsa_premaster[1] = TLS_MIN;
+ dump_hex("premaster:%s\n", rsa_premaster, sizeof(rsa_premaster));
+ len = psRsaEncryptPub(/*pool:*/ NULL,
+ /* psRsaKey_t* */ &tls->hsd->server_rsa_pub_key,
+ rsa_premaster, /*inlen:*/ sizeof(rsa_premaster),
+ record->key + 2, sizeof(record->key) - 2,
+ data_param_ignored
+ );
+ /* keylen16 exists for RSA (in TLS, not in SSL), but not for some other key types */
+ record->key[0] = len >> 8;
+ record->key[1] = len & 0xff;
+ len += 2;
+ premaster = rsa_premaster;
+ premaster_size = sizeof(rsa_premaster);
+ } else {
+ /* KEY_ALG_ECDSA */
+ static const uint8_t basepoint9[CURVE25519_KEYSIZE] = {9};
+ uint8_t privkey[CURVE25519_KEYSIZE]; //[32]
+
+ /* Generate random private key, see RFC 7748 */
+ tls_get_random(privkey, sizeof(privkey));
+ privkey[0] &= 0xf8;
+ privkey[CURVE25519_KEYSIZE-1] = ((privkey[CURVE25519_KEYSIZE-1] & 0x7f) | 0x40);
+
+ /* Compute public key */
+ curve25519(record->key + 1, privkey, basepoint9);
+
+ /* Compute premaster using peer's public key */
+ dbg("computing x25519_premaster\n");
+ curve25519(x25519_premaster, privkey, tls->hsd->ecc_pub_key32);
+
+ len = CURVE25519_KEYSIZE;
+ record->key[0] = len;
+ len++;
+ premaster = x25519_premaster;
+ premaster_size = sizeof(x25519_premaster);
+ }
+
record->type = HANDSHAKE_CLIENT_KEY_EXCHANGE;
record->len24_hi = 0;
record->len24_mid = len >> 8;
// of the premaster secret will vary depending on key exchange method.
prf_hmac_sha256(/*tls,*/
tls->hsd->master_secret, sizeof(tls->hsd->master_secret),
- rsa_premaster, sizeof(rsa_premaster),
+ premaster, premaster_size,
"master secret",
tls->hsd->client_and_server_rand32, sizeof(tls->hsd->client_and_server_rand32)
);
//SvKey len=455^
// with TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA: 461 bytes:
// 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...
+ //
+ // RFC 8422 5.4. Server Key Exchange
+ // This message is sent when using the ECDHE_ECDSA, ECDHE_RSA, and
+ // ECDH_anon key exchange algorithms.
+ // This message is used to convey the server's ephemeral ECDH public key
+ // (and the corresponding elliptic curve domain parameters) to the
+ // client.
dbg("<< SERVER_KEY_EXCHANGE len:%u\n", len);
-//probably need to save it
+ dump_raw_in("<< %s\n", tls->inbuf, RECHDR_LEN + len);
+ if (tls->hsd->key_alg == KEY_ALG_ECDSA)
+ process_server_key(tls, len);
+
+ // read next handshake block
len = tls_xread_handshake_block(tls, 4);
}
--- /dev/null
+/*
+ * Copyright (C) 2018 Denys Vlasenko
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+#include "tls.h"
+
+typedef uint8_t byte;
+typedef uint16_t word16;
+typedef uint32_t word32;
+#define XMEMSET memset
+
+#define F25519_SIZE CURVE25519_KEYSIZE
+
+/* The code below is taken from wolfssl-3.15.3/wolfcrypt/src/fe_low_mem.c
+ * Header comment is kept intact:
+ */
+
+/* fe_low_mem.c
+ *
+ * Copyright (C) 2006-2017 wolfSSL Inc.
+ *
+ * This file is part of wolfSSL.
+ *
+ * wolfSSL is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * wolfSSL is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335, USA
+ */
+
+
+/* Based from Daniel Beer's public domain work. */
+
+#if 0 //UNUSED
+static void fprime_copy(byte *x, const byte *a)
+{
+ int i;
+ for (i = 0; i < F25519_SIZE; i++)
+ x[i] = a[i];
+}
+#endif
+
+static void lm_copy(byte* x, const byte* a)
+{
+ int i;
+ for (i = 0; i < F25519_SIZE; i++)
+ x[i] = a[i];
+}
+
+#if 0 //UNUSED
+static void fprime_select(byte *dst, const byte *zero, const byte *one, byte condition)
+{
+ const byte mask = -condition;
+ int i;
+
+ for (i = 0; i < F25519_SIZE; i++)
+ dst[i] = zero[i] ^ (mask & (one[i] ^ zero[i]));
+}
+#endif
+
+static void fe_select(byte *dst,
+ const byte *zero, const byte *one,
+ byte condition)
+{
+ const byte mask = -condition;
+ int i;
+
+ for (i = 0; i < F25519_SIZE; i++)
+ dst[i] = zero[i] ^ (mask & (one[i] ^ zero[i]));
+}
+
+#if 0 //UNUSED
+static void raw_add(byte *x, const byte *p)
+{
+ word16 c = 0;
+ int i;
+
+ for (i = 0; i < F25519_SIZE; i++) {
+ c += ((word16)x[i]) + ((word16)p[i]);
+ x[i] = (byte)c;
+ c >>= 8;
+ }
+}
+#endif
+
+#if 0 //UNUSED
+static void raw_try_sub(byte *x, const byte *p)
+{
+ byte minusp[F25519_SIZE];
+ word16 c = 0;
+ int i;
+
+ for (i = 0; i < F25519_SIZE; i++) {
+ c = ((word16)x[i]) - ((word16)p[i]) - c;
+ minusp[i] = (byte)c;
+ c = (c >> 8) & 1;
+ }
+
+ fprime_select(x, minusp, x, (byte)c);
+}
+#endif
+
+#if 0 //UNUSED
+static int prime_msb(const byte *p)
+{
+ int i;
+ byte x;
+ int shift = 1;
+ int z = F25519_SIZE - 1;
+
+ /*
+ Test for any hot bits.
+ As soon as one instance is encountered set shift to 0.
+ */
+ for (i = F25519_SIZE - 1; i >= 0; i--) {
+ shift &= ((shift ^ ((-p[i] | p[i]) >> 7)) & 1);
+ z -= shift;
+ }
+ x = p[z];
+ z <<= 3;
+ shift = 1;
+ for (i = 0; i < 8; i++) {
+ shift &= ((-(x >> i) | (x >> i)) >> (7 - i) & 1);
+ z += shift;
+ }
+
+ return z - 1;
+}
+#endif
+
+#if 0 //UNUSED
+static void fprime_add(byte *r, const byte *a, const byte *modulus)
+{
+ raw_add(r, a);
+ raw_try_sub(r, modulus);
+}
+#endif
+
+#if 0 //UNUSED
+static void fprime_sub(byte *r, const byte *a, const byte *modulus)
+{
+ raw_add(r, modulus);
+ raw_try_sub(r, a);
+ raw_try_sub(r, modulus);
+}
+#endif
+
+#if 0 //UNUSED
+static void fprime_mul(byte *r, const byte *a, const byte *b,
+ const byte *modulus)
+{
+ word16 c = 0;
+ int i,j;
+
+ XMEMSET(r, 0, F25519_SIZE);
+
+ for (i = prime_msb(modulus); i >= 0; i--) {
+ const byte bit = (b[i >> 3] >> (i & 7)) & 1;
+ byte plusa[F25519_SIZE];
+
+ for (j = 0; j < F25519_SIZE; j++) {
+ c |= ((word16)r[j]) << 1;
+ r[j] = (byte)c;
+ c >>= 8;
+ }
+ raw_try_sub(r, modulus);
+
+ fprime_copy(plusa, r);
+ fprime_add(plusa, a, modulus);
+
+ fprime_select(r, r, plusa, bit);
+ }
+}
+#endif
+
+#if 0 //UNUSED
+static void fe_load(byte *x, word32 c)
+{
+ word32 i;
+
+ for (i = 0; i < sizeof(c); i++) {
+ x[i] = c;
+ c >>= 8;
+ }
+
+ for (; i < F25519_SIZE; i++)
+ x[i] = 0;
+}
+#endif
+
+static void fe_normalize(byte *x)
+{
+ byte minusp[F25519_SIZE];
+ word16 c;
+ int i;
+
+ /* Reduce using 2^255 = 19 mod p */
+ c = (x[31] >> 7) * 19;
+ x[31] &= 127;
+
+ for (i = 0; i < F25519_SIZE; i++) {
+ c += x[i];
+ x[i] = (byte)c;
+ c >>= 8;
+ }
+
+ /* The number is now less than 2^255 + 18, and therefore less than
+ * 2p. Try subtracting p, and conditionally load the subtracted
+ * value if underflow did not occur.
+ */
+ c = 19;
+
+ for (i = 0; i + 1 < F25519_SIZE; i++) {
+ c += x[i];
+ minusp[i] = (byte)c;
+ c >>= 8;
+ }
+
+ c += ((word16)x[i]) - 128;
+ minusp[31] = (byte)c;
+
+ /* Load x-p if no underflow */
+ fe_select(x, minusp, x, (c >> 15) & 1);
+}
+
+static void lm_add(byte* r, const byte* a, const byte* b)
+{
+ word16 c = 0;
+ int i;
+
+ /* Add */
+ for (i = 0; i < F25519_SIZE; i++) {
+ c >>= 8;
+ c += ((word16)a[i]) + ((word16)b[i]);
+ r[i] = (byte)c;
+ }
+
+ /* Reduce with 2^255 = 19 mod p */
+ r[31] &= 127;
+ c = (c >> 7) * 19;
+
+ for (i = 0; i < F25519_SIZE; i++) {
+ c += r[i];
+ r[i] = (byte)c;
+ c >>= 8;
+ }
+}
+
+static void lm_sub(byte* r, const byte* a, const byte* b)
+{
+ word32 c = 0;
+ int i;
+
+ /* Calculate a + 2p - b, to avoid underflow */
+ c = 218;
+ for (i = 0; i + 1 < F25519_SIZE; i++) {
+ c += 65280 + ((word32)a[i]) - ((word32)b[i]);
+ r[i] = c;
+ c >>= 8;
+ }
+
+ c += ((word32)a[31]) - ((word32)b[31]);
+ r[31] = c & 127;
+ c = (c >> 7) * 19;
+
+ for (i = 0; i < F25519_SIZE; i++) {
+ c += r[i];
+ r[i] = c;
+ c >>= 8;
+ }
+}
+
+#if 0 //UNUSED
+static void lm_neg(byte* r, const byte* a)
+{
+ word32 c = 0;
+ int i;
+
+ /* Calculate 2p - a, to avoid underflow */
+ c = 218;
+ for (i = 0; i + 1 < F25519_SIZE; i++) {
+ c += 65280 - ((word32)a[i]);
+ r[i] = c;
+ c >>= 8;
+ }
+
+ c -= ((word32)a[31]);
+ r[31] = c & 127;
+ c = (c >> 7) * 19;
+
+ for (i = 0; i < F25519_SIZE; i++) {
+ c += r[i];
+ r[i] = c;
+ c >>= 8;
+ }
+}
+#endif
+
+static void fe_mul__distinct(byte *r, const byte *a, const byte *b)
+{
+ word32 c = 0;
+ int i;
+
+ for (i = 0; i < F25519_SIZE; i++) {
+ int j;
+
+ c >>= 8;
+ for (j = 0; j <= i; j++)
+ c += ((word32)a[j]) * ((word32)b[i - j]);
+
+ for (; j < F25519_SIZE; j++)
+ c += ((word32)a[j]) *
+ ((word32)b[i + F25519_SIZE - j]) * 38;
+
+ r[i] = c;
+ }
+
+ r[31] &= 127;
+ c = (c >> 7) * 19;
+
+ for (i = 0; i < F25519_SIZE; i++) {
+ c += r[i];
+ r[i] = c;
+ c >>= 8;
+ }
+}
+
+#if 0 //UNUSED
+static void lm_mul(byte *r, const byte* a, const byte *b)
+{
+ byte tmp[F25519_SIZE];
+
+ fe_mul__distinct(tmp, a, b);
+ lm_copy(r, tmp);
+}
+#endif
+
+static void fe_mul_c(byte *r, const byte *a, word32 b)
+{
+ word32 c = 0;
+ int i;
+
+ for (i = 0; i < F25519_SIZE; i++) {
+ c >>= 8;
+ c += b * ((word32)a[i]);
+ r[i] = c;
+ }
+
+ r[31] &= 127;
+ c >>= 7;
+ c *= 19;
+
+ for (i = 0; i < F25519_SIZE; i++) {
+ c += r[i];
+ r[i] = c;
+ c >>= 8;
+ }
+}
+
+static void fe_inv__distinct(byte *r, const byte *x)
+{
+ byte s[F25519_SIZE];
+ int i;
+
+ /* This is a prime field, so by Fermat's little theorem:
+ *
+ * x^(p-1) = 1 mod p
+ *
+ * Therefore, raise to (p-2) = 2^255-21 to get a multiplicative
+ * inverse.
+ *
+ * This is a 255-bit binary number with the digits:
+ *
+ * 11111111... 01011
+ *
+ * We compute the result by the usual binary chain, but
+ * alternate between keeping the accumulator in r and s, so as
+ * to avoid copying temporaries.
+ */
+
+ /* 1 1 */
+ fe_mul__distinct(s, x, x);
+ fe_mul__distinct(r, s, x);
+
+ /* 1 x 248 */
+ for (i = 0; i < 248; i++) {
+ fe_mul__distinct(s, r, r);
+ fe_mul__distinct(r, s, x);
+ }
+
+ /* 0 */
+ fe_mul__distinct(s, r, r);
+
+ /* 1 */
+ fe_mul__distinct(r, s, s);
+ fe_mul__distinct(s, r, x);
+
+ /* 0 */
+ fe_mul__distinct(r, s, s);
+
+ /* 1 */
+ fe_mul__distinct(s, r, r);
+ fe_mul__distinct(r, s, x);
+
+ /* 1 */
+ fe_mul__distinct(s, r, r);
+ fe_mul__distinct(r, s, x);
+}
+
+#if 0 //UNUSED
+static void lm_invert(byte *r, const byte *x)
+{
+ byte tmp[F25519_SIZE];
+
+ fe_inv__distinct(tmp, x);
+ lm_copy(r, tmp);
+}
+#endif
+
+#if 0 //UNUSED
+/* Raise x to the power of (p-5)/8 = 2^252-3, using s for temporary
+ * storage.
+ */
+static void exp2523(byte *r, const byte *x, byte *s)
+{
+ int i;
+
+ /* This number is a 252-bit number with the binary expansion:
+ *
+ * 111111... 01
+ */
+
+ /* 1 1 */
+ fe_mul__distinct(r, x, x);
+ fe_mul__distinct(s, r, x);
+
+ /* 1 x 248 */
+ for (i = 0; i < 248; i++) {
+ fe_mul__distinct(r, s, s);
+ fe_mul__distinct(s, r, x);
+ }
+
+ /* 0 */
+ fe_mul__distinct(r, s, s);
+
+ /* 1 */
+ fe_mul__distinct(s, r, r);
+ fe_mul__distinct(r, s, x);
+}
+#endif
+
+#if 0 //UNUSED
+static void fe_sqrt(byte *r, const byte *a)
+{
+ byte v[F25519_SIZE];
+ byte i[F25519_SIZE];
+ byte x[F25519_SIZE];
+ byte y[F25519_SIZE];
+
+ /* v = (2a)^((p-5)/8) [x = 2a] */
+ fe_mul_c(x, a, 2);
+ exp2523(v, x, y);
+
+ /* i = 2av^2 - 1 */
+ fe_mul__distinct(y, v, v);
+ fe_mul__distinct(i, x, y);
+ fe_load(y, 1);
+ lm_sub(i, i, y);
+
+ /* r = avi */
+ fe_mul__distinct(x, v, a);
+ fe_mul__distinct(r, x, i);
+}
+#endif
+
+/* Differential addition */
+static void xc_diffadd(byte *x5, byte *z5,
+ const byte *x1, const byte *z1,
+ const byte *x2, const byte *z2,
+ const byte *x3, const byte *z3)
+{
+ /* Explicit formulas database: dbl-1987-m3
+ *
+ * source 1987 Montgomery "Speeding the Pollard and elliptic curve
+ * methods of factorization", page 261, fifth display, plus
+ * common-subexpression elimination
+ * compute A = X2+Z2
+ * compute B = X2-Z2
+ * compute C = X3+Z3
+ * compute D = X3-Z3
+ * compute DA = D A
+ * compute CB = C B
+ * compute X5 = Z1(DA+CB)^2
+ * compute Z5 = X1(DA-CB)^2
+ */
+ byte da[F25519_SIZE];
+ byte cb[F25519_SIZE];
+ byte a[F25519_SIZE];
+ byte b[F25519_SIZE];
+
+ lm_add(a, x2, z2);
+ lm_sub(b, x3, z3); /* D */
+ fe_mul__distinct(da, a, b);
+
+ lm_sub(b, x2, z2);
+ lm_add(a, x3, z3); /* C */
+ fe_mul__distinct(cb, a, b);
+
+ lm_add(a, da, cb);
+ fe_mul__distinct(b, a, a);
+ fe_mul__distinct(x5, z1, b);
+
+ lm_sub(a, da, cb);
+ fe_mul__distinct(b, a, a);
+ fe_mul__distinct(z5, x1, b);
+}
+
+/* Double an X-coordinate */
+static void xc_double(byte *x3, byte *z3,
+ const byte *x1, const byte *z1)
+{
+ /* Explicit formulas database: dbl-1987-m
+ *
+ * source 1987 Montgomery "Speeding the Pollard and elliptic
+ * curve methods of factorization", page 261, fourth display
+ * compute X3 = (X1^2-Z1^2)^2
+ * compute Z3 = 4 X1 Z1 (X1^2 + a X1 Z1 + Z1^2)
+ */
+ byte x1sq[F25519_SIZE];
+ byte z1sq[F25519_SIZE];
+ byte x1z1[F25519_SIZE];
+ byte a[F25519_SIZE];
+
+ fe_mul__distinct(x1sq, x1, x1);
+ fe_mul__distinct(z1sq, z1, z1);
+ fe_mul__distinct(x1z1, x1, z1);
+
+ lm_sub(a, x1sq, z1sq);
+ fe_mul__distinct(x3, a, a);
+
+ fe_mul_c(a, x1z1, 486662);
+ lm_add(a, x1sq, a);
+ lm_add(a, z1sq, a);
+ fe_mul__distinct(x1sq, x1z1, a);
+ fe_mul_c(z3, x1sq, 4);
+}
+
+void curve25519(byte *result, const byte *e, const byte *q)
+{
+ /* from wolfssl-3.15.3/wolfssl/wolfcrypt/fe_operations.h */
+ static const byte f25519_one[F25519_SIZE] = {1};
+
+ /* Current point: P_m */
+ byte xm[F25519_SIZE];
+ byte zm[F25519_SIZE] = {1};
+
+ /* Predecessor: P_(m-1) */
+ byte xm1[F25519_SIZE] = {1};
+ byte zm1[F25519_SIZE] = {0};
+
+ int i;
+
+ /* Note: bit 254 is assumed to be 1 */
+ lm_copy(xm, q);
+
+ for (i = 253; i >= 0; i--) {
+ const int bit = (e[i >> 3] >> (i & 7)) & 1;
+ byte xms[F25519_SIZE];
+ byte zms[F25519_SIZE];
+
+ /* From P_m and P_(m-1), compute P_(2m) and P_(2m-1) */
+ xc_diffadd(xm1, zm1, q, f25519_one, xm, zm, xm1, zm1);
+ xc_double(xm, zm, xm, zm);
+
+ /* Compute P_(2m+1) */
+ xc_diffadd(xms, zms, xm1, zm1, xm, zm, q, f25519_one);
+
+ /* Select:
+ * bit = 1 --> (P_(2m+1), P_(2m))
+ * bit = 0 --> (P_(2m), P_(2m-1))
+ */
+ fe_select(xm1, xm1, xm, bit);
+ fe_select(zm1, zm1, zm, bit);
+ fe_select(xm, xm, xms, bit);
+ fe_select(zm, zm, zms, bit);
+ }
+
+ /* Freeze out of projective coordinates */
+ fe_inv__distinct(zm1, zm);
+ fe_mul__distinct(result, zm1, xm);
+ fe_normalize(result);
+}
projects / oweals / busybox.git / commitdiff