Loading ssl/s3_srvr.c +89 −45 Original line number Diff line number Diff line Loading @@ -2195,6 +2195,10 @@ int ssl3_get_client_key_exchange(SSL *s) #ifndef OPENSSL_NO_RSA if (alg_k & SSL_kRSA) { unsigned char rand_premaster_secret[SSL_MAX_MASTER_KEY_LENGTH]; int decrypt_len, decrypt_good_mask; unsigned char version_good; /* FIX THIS UP EAY EAY EAY EAY */ if (s->s3->tmp.use_rsa_tmp) { Loading Loading @@ -2242,52 +2246,92 @@ int ssl3_get_client_key_exchange(SSL *s) n=i; } i=RSA_private_decrypt((int)n,p,p,rsa,RSA_PKCS1_PADDING); /* We must not leak whether a decryption failure occurs because * of Bleichenbacher's attack on PKCS #1 v1.5 RSA padding (see * RFC 2246, section 7.4.7.1). The code follows that advice of * the TLS RFC and generates a random premaster secret for the * case that the decrypt fails. See * https://tools.ietf.org/html/rfc5246#section-7.4.7.1 */ al = -1; /* should be RAND_bytes, but we cannot work around a failure. */ if (RAND_pseudo_bytes(rand_premaster_secret, sizeof(rand_premaster_secret)) <= 0) goto err; decrypt_len = RSA_private_decrypt((int)n,p,p,rsa,RSA_PKCS1_PADDING); ERR_clear_error(); if (i != SSL_MAX_MASTER_KEY_LENGTH) { al=SSL_AD_DECODE_ERROR; /* SSLerr(SSL_F_SSL3_GET_CLIENT_KEY_EXCHANGE,SSL_R_BAD_RSA_DECRYPT); */ } /* decrypt_len should be SSL_MAX_MASTER_KEY_LENGTH. * decrypt_good_mask will be zero if so and non-zero otherwise. */ decrypt_good_mask = decrypt_len ^ SSL_MAX_MASTER_KEY_LENGTH; if ((al == -1) && !((p[0] == (s->client_version>>8)) && (p[1] == (s->client_version & 0xff)))) { /* The premaster secret must contain the same version number as the * ClientHello to detect version rollback attacks (strangely, the * protocol does not offer such protection for DH ciphersuites). * However, buggy clients exist that send the negotiated protocol * version instead if the server does not support the requested * protocol version. * If SSL_OP_TLS_ROLLBACK_BUG is set, tolerate such clients. */ if (!((s->options & SSL_OP_TLS_ROLLBACK_BUG) && (p[0] == (s->version>>8)) && (p[1] == (s->version & 0xff)))) { al=SSL_AD_DECODE_ERROR; /* SSLerr(SSL_F_SSL3_GET_CLIENT_KEY_EXCHANGE,SSL_R_BAD_PROTOCOL_VERSION_NUMBER); */ /* The Klima-Pokorny-Rosa extension of Bleichenbacher's attack /* If the version in the decrypted pre-master secret is correct * then version_good will be zero. The Klima-Pokorny-Rosa * extension of Bleichenbacher's attack * (http://eprint.iacr.org/2003/052/) exploits the version * number check as a "bad version oracle" -- an alert would * reveal that the plaintext corresponding to some ciphertext * made up by the adversary is properly formatted except * that the version number is wrong. To avoid such attacks, * we should treat this just like any other decryption error. */ } } if (al != -1) { /* Some decryption failure -- use random value instead as countermeasure * against Bleichenbacher's attack on PKCS #1 v1.5 RSA padding * (see RFC 2246, section 7.4.7.1). */ ERR_clear_error(); i = SSL_MAX_MASTER_KEY_LENGTH; p[0] = s->client_version >> 8; p[1] = s->client_version & 0xff; if (RAND_pseudo_bytes(p+2, i-2) <= 0) /* should be RAND_bytes, but we cannot work around a failure */ goto err; * number check as a "bad version oracle". Thus version checks * are done in constant time and are treated like any other * decryption error. */ version_good = p[0] ^ (s->client_version>>8); version_good |= p[1] ^ (s->client_version&0xff); /* The premaster secret must contain the same version number as * the ClientHello to detect version rollback attacks * (strangely, the protocol does not offer such protection for * DH ciphersuites). However, buggy clients exist that send the * negotiated protocol version instead if the server does not * support the requested protocol version. If * SSL_OP_TLS_ROLLBACK_BUG is set, tolerate such clients. */ if (s->options & SSL_OP_TLS_ROLLBACK_BUG) { unsigned char workaround_mask = version_good; unsigned char workaround; /* workaround_mask will be 0xff if version_good is * non-zero (i.e. the version match failed). Otherwise * it'll be 0x00. */ workaround_mask |= workaround_mask >> 4; workaround_mask |= workaround_mask >> 2; workaround_mask |= workaround_mask >> 1; workaround_mask = ~((workaround_mask & 1) - 1); workaround = p[0] ^ (s->version>>8); workaround |= p[1] ^ (s->version&0xff); /* If workaround_mask is 0xff (i.e. there was a version * mismatch) then we copy the value of workaround over * version_good. */ version_good = (workaround & workaround_mask) | (version_good & ~workaround_mask); } /* If any bits in version_good are set then they'll poision * decrypt_good_mask and cause rand_premaster_secret to be * used. */ decrypt_good_mask |= version_good; /* decrypt_good_mask will be zero iff decrypt_len == * SSL_MAX_MASTER_KEY_LENGTH and the version check passed. We * fold the bottom 32 bits of it with an OR so that the LSB * will be zero iff everything is good. This assumes that we'll * never decrypt a value > 2**31 bytes, which seems safe. */ decrypt_good_mask |= decrypt_good_mask >> 16; decrypt_good_mask |= decrypt_good_mask >> 8; decrypt_good_mask |= decrypt_good_mask >> 4; decrypt_good_mask |= decrypt_good_mask >> 2; decrypt_good_mask |= decrypt_good_mask >> 1; /* Now select only the LSB and subtract one. If decrypt_len == * SSL_MAX_MASTER_KEY_LENGTH and the version check passed then * decrypt_good_mask will be all ones. Otherwise it'll be all * zeros. */ decrypt_good_mask &= 1; decrypt_good_mask--; /* Now copy rand_premaster_secret over p using * decrypt_good_mask. */ for (i = 0; i < (int) sizeof(rand_premaster_secret); i++) { p[i] = (p[i] & decrypt_good_mask) | (rand_premaster_secret[i] & ~decrypt_good_mask); } s->session->master_key_length= Loading Loading
ssl/s3_srvr.c +89 −45 Original line number Diff line number Diff line Loading @@ -2195,6 +2195,10 @@ int ssl3_get_client_key_exchange(SSL *s) #ifndef OPENSSL_NO_RSA if (alg_k & SSL_kRSA) { unsigned char rand_premaster_secret[SSL_MAX_MASTER_KEY_LENGTH]; int decrypt_len, decrypt_good_mask; unsigned char version_good; /* FIX THIS UP EAY EAY EAY EAY */ if (s->s3->tmp.use_rsa_tmp) { Loading Loading @@ -2242,52 +2246,92 @@ int ssl3_get_client_key_exchange(SSL *s) n=i; } i=RSA_private_decrypt((int)n,p,p,rsa,RSA_PKCS1_PADDING); /* We must not leak whether a decryption failure occurs because * of Bleichenbacher's attack on PKCS #1 v1.5 RSA padding (see * RFC 2246, section 7.4.7.1). The code follows that advice of * the TLS RFC and generates a random premaster secret for the * case that the decrypt fails. See * https://tools.ietf.org/html/rfc5246#section-7.4.7.1 */ al = -1; /* should be RAND_bytes, but we cannot work around a failure. */ if (RAND_pseudo_bytes(rand_premaster_secret, sizeof(rand_premaster_secret)) <= 0) goto err; decrypt_len = RSA_private_decrypt((int)n,p,p,rsa,RSA_PKCS1_PADDING); ERR_clear_error(); if (i != SSL_MAX_MASTER_KEY_LENGTH) { al=SSL_AD_DECODE_ERROR; /* SSLerr(SSL_F_SSL3_GET_CLIENT_KEY_EXCHANGE,SSL_R_BAD_RSA_DECRYPT); */ } /* decrypt_len should be SSL_MAX_MASTER_KEY_LENGTH. * decrypt_good_mask will be zero if so and non-zero otherwise. */ decrypt_good_mask = decrypt_len ^ SSL_MAX_MASTER_KEY_LENGTH; if ((al == -1) && !((p[0] == (s->client_version>>8)) && (p[1] == (s->client_version & 0xff)))) { /* The premaster secret must contain the same version number as the * ClientHello to detect version rollback attacks (strangely, the * protocol does not offer such protection for DH ciphersuites). * However, buggy clients exist that send the negotiated protocol * version instead if the server does not support the requested * protocol version. * If SSL_OP_TLS_ROLLBACK_BUG is set, tolerate such clients. */ if (!((s->options & SSL_OP_TLS_ROLLBACK_BUG) && (p[0] == (s->version>>8)) && (p[1] == (s->version & 0xff)))) { al=SSL_AD_DECODE_ERROR; /* SSLerr(SSL_F_SSL3_GET_CLIENT_KEY_EXCHANGE,SSL_R_BAD_PROTOCOL_VERSION_NUMBER); */ /* The Klima-Pokorny-Rosa extension of Bleichenbacher's attack /* If the version in the decrypted pre-master secret is correct * then version_good will be zero. The Klima-Pokorny-Rosa * extension of Bleichenbacher's attack * (http://eprint.iacr.org/2003/052/) exploits the version * number check as a "bad version oracle" -- an alert would * reveal that the plaintext corresponding to some ciphertext * made up by the adversary is properly formatted except * that the version number is wrong. To avoid such attacks, * we should treat this just like any other decryption error. */ } } if (al != -1) { /* Some decryption failure -- use random value instead as countermeasure * against Bleichenbacher's attack on PKCS #1 v1.5 RSA padding * (see RFC 2246, section 7.4.7.1). */ ERR_clear_error(); i = SSL_MAX_MASTER_KEY_LENGTH; p[0] = s->client_version >> 8; p[1] = s->client_version & 0xff; if (RAND_pseudo_bytes(p+2, i-2) <= 0) /* should be RAND_bytes, but we cannot work around a failure */ goto err; * number check as a "bad version oracle". Thus version checks * are done in constant time and are treated like any other * decryption error. */ version_good = p[0] ^ (s->client_version>>8); version_good |= p[1] ^ (s->client_version&0xff); /* The premaster secret must contain the same version number as * the ClientHello to detect version rollback attacks * (strangely, the protocol does not offer such protection for * DH ciphersuites). However, buggy clients exist that send the * negotiated protocol version instead if the server does not * support the requested protocol version. If * SSL_OP_TLS_ROLLBACK_BUG is set, tolerate such clients. */ if (s->options & SSL_OP_TLS_ROLLBACK_BUG) { unsigned char workaround_mask = version_good; unsigned char workaround; /* workaround_mask will be 0xff if version_good is * non-zero (i.e. the version match failed). Otherwise * it'll be 0x00. */ workaround_mask |= workaround_mask >> 4; workaround_mask |= workaround_mask >> 2; workaround_mask |= workaround_mask >> 1; workaround_mask = ~((workaround_mask & 1) - 1); workaround = p[0] ^ (s->version>>8); workaround |= p[1] ^ (s->version&0xff); /* If workaround_mask is 0xff (i.e. there was a version * mismatch) then we copy the value of workaround over * version_good. */ version_good = (workaround & workaround_mask) | (version_good & ~workaround_mask); } /* If any bits in version_good are set then they'll poision * decrypt_good_mask and cause rand_premaster_secret to be * used. */ decrypt_good_mask |= version_good; /* decrypt_good_mask will be zero iff decrypt_len == * SSL_MAX_MASTER_KEY_LENGTH and the version check passed. We * fold the bottom 32 bits of it with an OR so that the LSB * will be zero iff everything is good. This assumes that we'll * never decrypt a value > 2**31 bytes, which seems safe. */ decrypt_good_mask |= decrypt_good_mask >> 16; decrypt_good_mask |= decrypt_good_mask >> 8; decrypt_good_mask |= decrypt_good_mask >> 4; decrypt_good_mask |= decrypt_good_mask >> 2; decrypt_good_mask |= decrypt_good_mask >> 1; /* Now select only the LSB and subtract one. If decrypt_len == * SSL_MAX_MASTER_KEY_LENGTH and the version check passed then * decrypt_good_mask will be all ones. Otherwise it'll be all * zeros. */ decrypt_good_mask &= 1; decrypt_good_mask--; /* Now copy rand_premaster_secret over p using * decrypt_good_mask. */ for (i = 0; i < (int) sizeof(rand_premaster_secret); i++) { p[i] = (p[i] & decrypt_good_mask) | (rand_premaster_secret[i] & ~decrypt_good_mask); } s->session->master_key_length= Loading
