/* * dh.c - Diffie-Helman algorithm code against SSH 2 * * This file is part of the SSH Library * * Copyright (c) 2003-2013 by Aris Adamantiadis * Copyright (c) 2009-2013 by Andreas Schneider * Copyright (c) 2012 by Dmitriy Kuznetsov * * The SSH Library is free software; you can redistribute it and/or modify * it under the terms of the GNU Lesser General Public License as published by * the Free Software Foundation; either version 2.1 of the License, or (at your * option) any later version. * * The SSH Library 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 Lesser General Public * License for more details. * * You should have received a copy of the GNU Lesser General Public License * along with the SSH Library; see the file COPYING. If not, write to * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, * MA 02111-1307, USA. */ /* * Let us resume the dh protocol. * Each side computes a private prime number, x at client side, y at server * side. * g and n are two numbers common to every ssh software. * client's public key (e) is calculated by doing: * e = g^x mod p * client sends e to the server. * the server computes his own public key, f * f = g^y mod p * it sends it to the client * the common key K is calculated by the client by doing * k = f^x mod p * the server does the same with the client public key e * k' = e^y mod p * if everything went correctly, k and k' are equal */ #include "config.h" #include #include #include #include #ifndef _WIN32 #include #include #endif #include "libssh/priv.h" #include "libssh/crypto.h" #include "libssh/buffer.h" #include "libssh/session.h" #include "libssh/misc.h" #include "libssh/dh.h" #include "libssh/ssh2.h" #include "libssh/pki.h" /* todo: remove it */ #include "libssh/string.h" #ifdef HAVE_LIBCRYPTO #include #include #include #endif static unsigned char p_group1_value[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2, 0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1, 0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6, 0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD, 0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D, 0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45, 0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9, 0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED, 0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11, 0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE6, 0x53, 0x81, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}; #define P_GROUP1_LEN 128 /* Size in bytes of the p number */ static unsigned char p_group14_value[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2, 0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1, 0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6, 0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD, 0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D, 0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45, 0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9, 0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED, 0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11, 0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE4, 0x5B, 0x3D, 0xC2, 0x00, 0x7C, 0xB8, 0xA1, 0x63, 0xBF, 0x05, 0x98, 0xDA, 0x48, 0x36, 0x1C, 0x55, 0xD3, 0x9A, 0x69, 0x16, 0x3F, 0xA8, 0xFD, 0x24, 0xCF, 0x5F, 0x83, 0x65, 0x5D, 0x23, 0xDC, 0xA3, 0xAD, 0x96, 0x1C, 0x62, 0xF3, 0x56, 0x20, 0x85, 0x52, 0xBB, 0x9E, 0xD5, 0x29, 0x07, 0x70, 0x96, 0x96, 0x6D, 0x67, 0x0C, 0x35, 0x4E, 0x4A, 0xBC, 0x98, 0x04, 0xF1, 0x74, 0x6C, 0x08, 0xCA, 0x18, 0x21, 0x7C, 0x32, 0x90, 0x5E, 0x46, 0x2E, 0x36, 0xCE, 0x3B, 0xE3, 0x9E, 0x77, 0x2C, 0x18, 0x0E, 0x86, 0x03, 0x9B, 0x27, 0x83, 0xA2, 0xEC, 0x07, 0xA2, 0x8F, 0xB5, 0xC5, 0x5D, 0xF0, 0x6F, 0x4C, 0x52, 0xC9, 0xDE, 0x2B, 0xCB, 0xF6, 0x95, 0x58, 0x17, 0x18, 0x39, 0x95, 0x49, 0x7C, 0xEA, 0x95, 0x6A, 0xE5, 0x15, 0xD2, 0x26, 0x18, 0x98, 0xFA, 0x05, 0x10, 0x15, 0x72, 0x8E, 0x5A, 0x8A, 0xAC, 0xAA, 0x68, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF}; #define P_GROUP14_LEN 256 /* Size in bytes of the p number for group 14 */ static unsigned long g_int = 2 ; /* G is defined as 2 by the ssh2 standards */ static bignum g; static bignum p_group1; static bignum p_group14; static int ssh_crypto_initialized; static bignum select_p(enum ssh_key_exchange_e type) { return type == SSH_KEX_DH_GROUP14_SHA1 ? p_group14 : p_group1; } int ssh_get_random(void *where, int len, int strong){ #ifdef HAVE_LIBGCRYPT /* variable not used in gcrypt */ (void) strong; /* not using GCRY_VERY_STRONG_RANDOM which is a bit overkill */ gcry_randomize(where,len,GCRY_STRONG_RANDOM); return 1; #elif defined HAVE_LIBCRYPTO if (strong) { return RAND_bytes(where,len); } else { return RAND_pseudo_bytes(where,len); } #endif /* never reached */ return 1; } /* * This inits the values g and p which are used for DH key agreement * FIXME: Make the function thread safe by adding a semaphore or mutex. */ int ssh_crypto_init(void) { if (ssh_crypto_initialized == 0) { #ifdef HAVE_LIBGCRYPT gcry_check_version(NULL); if (!gcry_control(GCRYCTL_INITIALIZATION_FINISHED_P,0)) { gcry_control(GCRYCTL_INIT_SECMEM, 4096); gcry_control(GCRYCTL_INITIALIZATION_FINISHED,0); } #endif g = bignum_new(); if (g == NULL) { return -1; } bignum_set_word(g,g_int); #ifdef HAVE_LIBGCRYPT bignum_bin2bn(p_group1_value, P_GROUP1_LEN, &p_group1); if (p_group1 == NULL) { bignum_free(g); g = NULL; return -1; } bignum_bin2bn(p_group14_value, P_GROUP14_LEN, &p_group14); if (p_group14 == NULL) { bignum_free(g); bignum_free(p_group1); g = NULL; p_group1 = NULL; return -1; } #elif defined HAVE_LIBCRYPTO p_group1 = bignum_new(); if (p_group1 == NULL) { bignum_free(g); g = NULL; return -1; } bignum_bin2bn(p_group1_value, P_GROUP1_LEN, p_group1); p_group14 = bignum_new(); if (p_group14 == NULL) { bignum_free(g); bignum_free(p_group1); g = NULL; p_group1 = NULL; return -1; } bignum_bin2bn(p_group14_value, P_GROUP14_LEN, p_group14); OpenSSL_add_all_algorithms(); #endif ssh_crypto_initialized = 1; } return 0; } void ssh_crypto_finalize(void) { if (ssh_crypto_initialized) { bignum_free(g); g = NULL; bignum_free(p_group1); p_group1 = NULL; bignum_free(p_group14); p_group14 = NULL; #ifdef HAVE_LIBGCRYPT gcry_control(GCRYCTL_TERM_SECMEM); #elif defined HAVE_LIBCRYPTO EVP_cleanup(); CRYPTO_cleanup_all_ex_data(); #endif ssh_crypto_initialized=0; } } /* prints the bignum on stderr */ void ssh_print_bignum(const char *which, bignum num) { #ifdef HAVE_LIBGCRYPT unsigned char *hex = NULL; bignum_bn2hex(num, &hex); #elif defined HAVE_LIBCRYPTO char *hex = NULL; hex = bignum_bn2hex(num); #endif fprintf(stderr, "%s value: ", which); fprintf(stderr, "%s\n", (hex == NULL) ? "(null)" : (char *) hex); SAFE_FREE(hex); } int dh_generate_x(ssh_session session) { session->next_crypto->x = bignum_new(); if (session->next_crypto->x == NULL) { return -1; } #ifdef HAVE_LIBGCRYPT bignum_rand(session->next_crypto->x, 128); #elif defined HAVE_LIBCRYPTO bignum_rand(session->next_crypto->x, 128, 0, -1); #endif /* not harder than this */ #ifdef DEBUG_CRYPTO ssh_print_bignum("x", session->next_crypto->x); #endif return 0; } /* used by server */ int dh_generate_y(ssh_session session) { session->next_crypto->y = bignum_new(); if (session->next_crypto->y == NULL) { return -1; } #ifdef HAVE_LIBGCRYPT bignum_rand(session->next_crypto->y, 128); #elif defined HAVE_LIBCRYPTO bignum_rand(session->next_crypto->y, 128, 0, -1); #endif /* not harder than this */ #ifdef DEBUG_CRYPTO ssh_print_bignum("y", session->next_crypto->y); #endif return 0; } /* used by server */ int dh_generate_e(ssh_session session) { #ifdef HAVE_LIBCRYPTO bignum_CTX ctx = bignum_ctx_new(); if (ctx == NULL) { return -1; } #endif session->next_crypto->e = bignum_new(); if (session->next_crypto->e == NULL) { #ifdef HAVE_LIBCRYPTO bignum_ctx_free(ctx); #endif return -1; } #ifdef HAVE_LIBGCRYPT bignum_mod_exp(session->next_crypto->e, g, session->next_crypto->x, select_p(session->next_crypto->kex_type)); #elif defined HAVE_LIBCRYPTO bignum_mod_exp(session->next_crypto->e, g, session->next_crypto->x, select_p(session->next_crypto->kex_type), ctx); #endif #ifdef DEBUG_CRYPTO ssh_print_bignum("e", session->next_crypto->e); #endif #ifdef HAVE_LIBCRYPTO bignum_ctx_free(ctx); #endif return 0; } int dh_generate_f(ssh_session session) { #ifdef HAVE_LIBCRYPTO bignum_CTX ctx = bignum_ctx_new(); if (ctx == NULL) { return -1; } #endif session->next_crypto->f = bignum_new(); if (session->next_crypto->f == NULL) { #ifdef HAVE_LIBCRYPTO bignum_ctx_free(ctx); #endif return -1; } #ifdef HAVE_LIBGCRYPT bignum_mod_exp(session->next_crypto->f, g, session->next_crypto->y, select_p(session->next_crypto->kex_type)); #elif defined HAVE_LIBCRYPTO bignum_mod_exp(session->next_crypto->f, g, session->next_crypto->y, select_p(session->next_crypto->kex_type), ctx); #endif #ifdef DEBUG_CRYPTO ssh_print_bignum("f", session->next_crypto->f); #endif #ifdef HAVE_LIBCRYPTO bignum_ctx_free(ctx); #endif return 0; } ssh_string make_bignum_string(bignum num) { ssh_string ptr = NULL; int pad = 0; unsigned int len = bignum_num_bytes(num); unsigned int bits = bignum_num_bits(num); if (len == 0) { return NULL; } /* If the first bit is set we have a negative number */ if (!(bits % 8) && bignum_is_bit_set(num, bits - 1)) { pad++; } #ifdef DEBUG_CRYPTO fprintf(stderr, "%d bits, %d bytes, %d padding\n", bits, len, pad); #endif /* DEBUG_CRYPTO */ ptr = ssh_string_new(len + pad); if (ptr == NULL) { return NULL; } /* We have a negative number so we need a leading zero */ if (pad) { ptr->data[0] = 0; } #ifdef HAVE_LIBGCRYPT bignum_bn2bin(num, len, ptr->data + pad); #elif HAVE_LIBCRYPTO bignum_bn2bin(num, ptr->data + pad); #endif return ptr; } bignum make_string_bn(ssh_string string){ bignum bn = NULL; unsigned int len = ssh_string_len(string); #ifdef DEBUG_CRYPTO fprintf(stderr, "Importing a %d bits, %d bytes object ...\n", len * 8, len); #endif /* DEBUG_CRYPTO */ #ifdef HAVE_LIBGCRYPT bignum_bin2bn(string->data, len, &bn); #elif defined HAVE_LIBCRYPTO bn = bignum_bin2bn(string->data, len, NULL); #endif return bn; } void make_string_bn_inplace(ssh_string string, bignum bnout) { unsigned int len = ssh_string_len(string); #ifdef HAVE_LIBGCRYPT #error "unsupported" #elif defined HAVE_LIBCRYPTO bignum_bin2bn(string->data, len, bnout); #endif } ssh_string dh_get_e(ssh_session session) { return make_bignum_string(session->next_crypto->e); } /* used by server */ ssh_string dh_get_f(ssh_session session) { return make_bignum_string(session->next_crypto->f); } void dh_import_pubkey(ssh_session session, ssh_string pubkey_string) { session->next_crypto->server_pubkey = pubkey_string; } int dh_import_f(ssh_session session, ssh_string f_string) { session->next_crypto->f = make_string_bn(f_string); if (session->next_crypto->f == NULL) { return -1; } #ifdef DEBUG_CRYPTO ssh_print_bignum("f",session->next_crypto->f); #endif return 0; } /* used by the server implementation */ int dh_import_e(ssh_session session, ssh_string e_string) { session->next_crypto->e = make_string_bn(e_string); if (session->next_crypto->e == NULL) { return -1; } #ifdef DEBUG_CRYPTO ssh_print_bignum("e",session->next_crypto->e); #endif return 0; } int dh_build_k(ssh_session session) { #ifdef HAVE_LIBCRYPTO bignum_CTX ctx = bignum_ctx_new(); if (ctx == NULL) { return -1; } #endif session->next_crypto->k = bignum_new(); if (session->next_crypto->k == NULL) { #ifdef HAVE_LIBCRYPTO bignum_ctx_free(ctx); #endif return -1; } /* the server and clients don't use the same numbers */ #ifdef HAVE_LIBGCRYPT if(session->client) { bignum_mod_exp(session->next_crypto->k, session->next_crypto->f, session->next_crypto->x, select_p(session->next_crypto->kex_type)); } else { bignum_mod_exp(session->next_crypto->k, session->next_crypto->e, session->next_crypto->y, select_p(session->next_crypto->kex_type)); } #elif defined HAVE_LIBCRYPTO if (session->client) { bignum_mod_exp(session->next_crypto->k, session->next_crypto->f, session->next_crypto->x, select_p(session->next_crypto->kex_type), ctx); } else { bignum_mod_exp(session->next_crypto->k, session->next_crypto->e, session->next_crypto->y, select_p(session->next_crypto->kex_type), ctx); } #endif #ifdef DEBUG_CRYPTO ssh_print_hexa("Session server cookie", session->next_crypto->server_kex.cookie, 16); ssh_print_hexa("Session client cookie", session->next_crypto->client_kex.cookie, 16); ssh_print_bignum("Shared secret key", session->next_crypto->k); #endif #ifdef HAVE_LIBCRYPTO bignum_ctx_free(ctx); #endif return 0; } /** @internal * @brief Starts diffie-hellman-group1 key exchange */ int ssh_client_dh_init(ssh_session session){ ssh_string e = NULL; int rc; if (buffer_add_u8(session->out_buffer, SSH2_MSG_KEXDH_INIT) < 0) { goto error; } if (dh_generate_x(session) < 0) { goto error; } if (dh_generate_e(session) < 0) { goto error; } e = dh_get_e(session); if (e == NULL) { goto error; } if (buffer_add_ssh_string(session->out_buffer, e) < 0) { goto error; } ssh_string_burn(e); ssh_string_free(e); e=NULL; rc = packet_send(session); return rc; error: if(e != NULL){ ssh_string_burn(e); ssh_string_free(e); } return SSH_ERROR; } int ssh_client_dh_reply(ssh_session session, ssh_buffer packet){ ssh_string f; ssh_string pubkey = NULL; ssh_string signature = NULL; int rc; pubkey = buffer_get_ssh_string(packet); if (pubkey == NULL){ ssh_set_error(session,SSH_FATAL, "No public key in packet"); goto error; } dh_import_pubkey(session, pubkey); f = buffer_get_ssh_string(packet); if (f == NULL) { ssh_set_error(session,SSH_FATAL, "No F number in packet"); goto error; } rc = dh_import_f(session, f); ssh_string_burn(f); ssh_string_free(f); if (rc < 0) { ssh_set_error(session, SSH_FATAL, "Cannot import f number"); goto error; } signature = buffer_get_ssh_string(packet); if (signature == NULL) { ssh_set_error(session, SSH_FATAL, "No signature in packet"); goto error; } session->next_crypto->dh_server_signature = signature; signature=NULL; /* ownership changed */ if (dh_build_k(session) < 0) { ssh_set_error(session, SSH_FATAL, "Cannot build k number"); goto error; } /* Send the MSG_NEWKEYS */ if (buffer_add_u8(session->out_buffer, SSH2_MSG_NEWKEYS) < 0) { goto error; } rc=packet_send(session); SSH_LOG(SSH_LOG_PROTOCOL, "SSH_MSG_NEWKEYS sent"); return rc; error: return SSH_ERROR; } /* static void sha_add(ssh_string str,SHACTX ctx){ sha1_update(ctx,str,string_len(str)+4); #ifdef DEBUG_CRYPTO ssh_print_hexa("partial hashed sessionid",str,string_len(str)+4); #endif } */ int make_sessionid(ssh_session session) { ssh_string num = NULL; ssh_string str = NULL; ssh_buffer server_hash = NULL; ssh_buffer client_hash = NULL; ssh_buffer buf = NULL; uint32_t len; int rc = SSH_ERROR; buf = ssh_buffer_new(); if (buf == NULL) { return rc; } str = ssh_string_from_char(session->clientbanner); if (str == NULL) { goto error; } if (buffer_add_ssh_string(buf, str) < 0) { goto error; } ssh_string_free(str); str = ssh_string_from_char(session->serverbanner); if (str == NULL) { goto error; } if (buffer_add_ssh_string(buf, str) < 0) { goto error; } if (session->client) { server_hash = session->in_hashbuf; client_hash = session->out_hashbuf; } else { server_hash = session->out_hashbuf; client_hash = session->in_hashbuf; } if (buffer_add_u32(server_hash, 0) < 0) { goto error; } if (buffer_add_u8(server_hash, 0) < 0) { goto error; } if (buffer_add_u32(client_hash, 0) < 0) { goto error; } if (buffer_add_u8(client_hash, 0) < 0) { goto error; } len = ntohl(buffer_get_rest_len(client_hash)); if (buffer_add_u32(buf,len) < 0) { goto error; } if (buffer_add_data(buf, buffer_get_rest(client_hash), buffer_get_rest_len(client_hash)) < 0) { goto error; } len = ntohl(buffer_get_rest_len(server_hash)); if (buffer_add_u32(buf, len) < 0) { goto error; } if (buffer_add_data(buf, buffer_get_rest(server_hash), buffer_get_rest_len(server_hash)) < 0) { goto error; } len = ssh_string_len(session->next_crypto->server_pubkey) + 4; if (buffer_add_data(buf, session->next_crypto->server_pubkey, len) < 0) { goto error; } if(session->next_crypto->kex_type == SSH_KEX_DH_GROUP1_SHA1 || session->next_crypto->kex_type == SSH_KEX_DH_GROUP14_SHA1) { num = make_bignum_string(session->next_crypto->e); if (num == NULL) { goto error; } len = ssh_string_len(num) + 4; if (buffer_add_data(buf, num, len) < 0) { goto error; } ssh_string_free(num); num = make_bignum_string(session->next_crypto->f); if (num == NULL) { goto error; } len = ssh_string_len(num) + 4; if (buffer_add_data(buf, num, len) < 0) { goto error; } ssh_string_free(num); #ifdef HAVE_ECDH } else if (session->next_crypto->kex_type == SSH_KEX_ECDH_SHA2_NISTP256){ if(session->next_crypto->ecdh_client_pubkey == NULL || session->next_crypto->ecdh_server_pubkey == NULL){ SSH_LOG(SSH_LOG_WARNING, "ECDH parameted missing"); goto error; } rc = buffer_add_ssh_string(buf,session->next_crypto->ecdh_client_pubkey); if (rc < 0) { goto error; } rc = buffer_add_ssh_string(buf,session->next_crypto->ecdh_server_pubkey); if (rc < 0) { goto error; } #endif #ifdef HAVE_CURVE25519 } else if(session->next_crypto->kex_type == SSH_KEX_CURVE25519_SHA256_LIBSSH_ORG){ rc = buffer_add_u32(buf, htonl(CURVE25519_PUBKEY_SIZE)); rc += buffer_add_data(buf, session->next_crypto->curve25519_client_pubkey, CURVE25519_PUBKEY_SIZE); rc += buffer_add_u32(buf, htonl(CURVE25519_PUBKEY_SIZE)); rc += buffer_add_data(buf, session->next_crypto->curve25519_server_pubkey, CURVE25519_PUBKEY_SIZE); if (rc != SSH_OK) { goto error; } #endif } num = make_bignum_string(session->next_crypto->k); if (num == NULL) { goto error; } len = ssh_string_len(num) + 4; if (buffer_add_data(buf, num, len) < 0) { goto error; } #ifdef DEBUG_CRYPTO ssh_print_hexa("hash buffer", ssh_buffer_get_begin(buf), ssh_buffer_get_len(buf)); #endif switch(session->next_crypto->kex_type){ case SSH_KEX_DH_GROUP1_SHA1: case SSH_KEX_DH_GROUP14_SHA1: session->next_crypto->digest_len = SHA_DIGEST_LENGTH; session->next_crypto->mac_type = SSH_MAC_SHA1; session->next_crypto->secret_hash = malloc(session->next_crypto->digest_len); if(session->next_crypto->secret_hash == NULL){ ssh_set_error_oom(session); goto error; } sha1(buffer_get_rest(buf), buffer_get_rest_len(buf), session->next_crypto->secret_hash); break; case SSH_KEX_ECDH_SHA2_NISTP256: case SSH_KEX_CURVE25519_SHA256_LIBSSH_ORG: session->next_crypto->digest_len = SHA256_DIGEST_LENGTH; session->next_crypto->mac_type = SSH_MAC_SHA256; session->next_crypto->secret_hash = malloc(session->next_crypto->digest_len); if(session->next_crypto->secret_hash == NULL){ ssh_set_error_oom(session); goto error; } sha256(buffer_get_rest(buf), buffer_get_rest_len(buf), session->next_crypto->secret_hash); break; } /* During the first kex, secret hash and session ID are equal. However, after * a key re-exchange, a new secret hash is calculated. This hash will not replace * but complement existing session id. */ if (!session->next_crypto->session_id){ session->next_crypto->session_id = malloc(session->next_crypto->digest_len); if (session->next_crypto->session_id == NULL){ ssh_set_error_oom(session); goto error; } memcpy(session->next_crypto->session_id, session->next_crypto->secret_hash, session->next_crypto->digest_len); } #ifdef DEBUG_CRYPTO printf("Session hash: \n"); ssh_print_hexa("secret hash", session->next_crypto->secret_hash, session->next_crypto->digest_len); ssh_print_hexa("session id", session->next_crypto->session_id, session->next_crypto->digest_len); #endif rc = SSH_OK; error: ssh_buffer_free(buf); ssh_buffer_free(client_hash); ssh_buffer_free(server_hash); session->in_hashbuf = NULL; session->out_hashbuf = NULL; ssh_string_free(str); ssh_string_free(num); return rc; } int hashbufout_add_cookie(ssh_session session) { session->out_hashbuf = ssh_buffer_new(); if (session->out_hashbuf == NULL) { return -1; } if (buffer_add_u8(session->out_hashbuf, 20) < 0) { buffer_reinit(session->out_hashbuf); return -1; } if (session->server) { if (buffer_add_data(session->out_hashbuf, session->next_crypto->server_kex.cookie, 16) < 0) { buffer_reinit(session->out_hashbuf); return -1; } } else { if (buffer_add_data(session->out_hashbuf, session->next_crypto->client_kex.cookie, 16) < 0) { buffer_reinit(session->out_hashbuf); return -1; } } return 0; } int hashbufin_add_cookie(ssh_session session, unsigned char *cookie) { session->in_hashbuf = ssh_buffer_new(); if (session->in_hashbuf == NULL) { return -1; } if (buffer_add_u8(session->in_hashbuf, 20) < 0) { buffer_reinit(session->in_hashbuf); return -1; } if (buffer_add_data(session->in_hashbuf,cookie, 16) < 0) { buffer_reinit(session->in_hashbuf); return -1; } return 0; } static int generate_one_key(ssh_string k, struct ssh_crypto_struct *crypto, unsigned char *output, char letter) { ssh_mac_ctx ctx; ctx=ssh_mac_ctx_init(crypto->mac_type); if (ctx == NULL) { return -1; } ssh_mac_update(ctx, k, ssh_string_len(k) + 4); ssh_mac_update(ctx, crypto->secret_hash, crypto->digest_len); ssh_mac_update(ctx, &letter, 1); ssh_mac_update(ctx, crypto->session_id, crypto->digest_len); ssh_mac_final(output, ctx); return 0; } int generate_session_keys(ssh_session session) { ssh_string k_string = NULL; ssh_mac_ctx ctx = NULL; struct ssh_crypto_struct *crypto = session->next_crypto; unsigned char *tmp; int rc = -1; k_string = make_bignum_string(crypto->k); if (k_string == NULL) { ssh_set_error_oom(session); goto error; } crypto->encryptIV = malloc(crypto->digest_len); crypto->decryptIV = malloc(crypto->digest_len); crypto->encryptkey = malloc(crypto->digest_len); crypto->decryptkey = malloc(crypto->digest_len); crypto->encryptMAC = malloc(crypto->digest_len); crypto->decryptMAC = malloc(crypto->digest_len); if(crypto->encryptIV == NULL || crypto->decryptIV == NULL || crypto->encryptkey == NULL || crypto->decryptkey == NULL || crypto->encryptMAC == NULL || crypto->decryptMAC == NULL){ ssh_set_error_oom(session); goto error; } /* IV */ if (session->client) { if (generate_one_key(k_string, crypto, crypto->encryptIV, 'A') < 0) { goto error; } if (generate_one_key(k_string, crypto, crypto->decryptIV, 'B') < 0) { goto error; } } else { if (generate_one_key(k_string, crypto, crypto->decryptIV, 'A') < 0) { goto error; } if (generate_one_key(k_string, crypto, crypto->encryptIV, 'B') < 0) { goto error; } } if (session->client) { if (generate_one_key(k_string, crypto, crypto->encryptkey, 'C') < 0) { goto error; } if (generate_one_key(k_string, crypto, crypto->decryptkey, 'D') < 0) { goto error; } } else { if (generate_one_key(k_string, crypto, crypto->decryptkey, 'C') < 0) { goto error; } if (generate_one_key(k_string, crypto, crypto->encryptkey, 'D') < 0) { goto error; } } /* some ciphers need more than DIGEST_LEN bytes of input key */ if (crypto->out_cipher->keysize > crypto->digest_len * 8) { tmp = realloc(crypto->encryptkey, crypto->digest_len * 2); if (tmp == NULL) { goto error; } crypto->encryptkey = tmp; ctx = ssh_mac_ctx_init(crypto->mac_type); if (ctx == NULL) { goto error; } ssh_mac_update(ctx, k_string, ssh_string_len(k_string) + 4); ssh_mac_update(ctx, crypto->secret_hash, crypto->digest_len); ssh_mac_update(ctx, crypto->encryptkey, crypto->digest_len); ssh_mac_final(crypto->encryptkey + crypto->digest_len, ctx); } if (crypto->in_cipher->keysize > crypto->digest_len * 8) { tmp = realloc(crypto->decryptkey, crypto->digest_len *2); if (tmp == NULL) { goto error; } crypto->decryptkey = tmp; if(crypto->decryptkey == NULL) goto error; ctx = ssh_mac_ctx_init(crypto->mac_type); ssh_mac_update(ctx, k_string, ssh_string_len(k_string) + 4); ssh_mac_update(ctx, crypto->secret_hash, crypto->digest_len); ssh_mac_update(ctx, crypto->decryptkey, crypto->digest_len); ssh_mac_final(crypto->decryptkey + crypto->digest_len, ctx); } if(session->client) { if (generate_one_key(k_string, crypto, crypto->encryptMAC, 'E') < 0) { goto error; } if (generate_one_key(k_string, crypto, crypto->decryptMAC, 'F') < 0) { goto error; } } else { if (generate_one_key(k_string, crypto, crypto->decryptMAC, 'E') < 0) { goto error; } if (generate_one_key(k_string, crypto, crypto->encryptMAC, 'F') < 0) { goto error; } } #ifdef DEBUG_CRYPTO ssh_print_hexa("Encrypt IV", crypto->encryptIV, SHA_DIGEST_LEN); ssh_print_hexa("Decrypt IV", crypto->decryptIV, SHA_DIGEST_LEN); ssh_print_hexa("Encryption key", crypto->encryptkey, crypto->out_cipher->keysize); ssh_print_hexa("Decryption key", crypto->decryptkey, crypto->in_cipher->keysize); ssh_print_hexa("Encryption MAC", crypto->encryptMAC, SHA_DIGEST_LEN); ssh_print_hexa("Decryption MAC", crypto->decryptMAC, 20); #endif rc = 0; error: ssh_string_free(k_string); return rc; } /** * @addtogroup libssh_session * * @{ */ /** * @deprecated Use ssh_get_publickey_hash() */ int ssh_get_pubkey_hash(ssh_session session, unsigned char **hash) { ssh_string pubkey; MD5CTX ctx; unsigned char *h; if (session == NULL || hash == NULL) { return SSH_ERROR; } *hash = NULL; if (session->current_crypto == NULL || session->current_crypto->server_pubkey == NULL){ ssh_set_error(session,SSH_FATAL,"No current cryptographic context"); return SSH_ERROR; } h = malloc(sizeof(unsigned char) * MD5_DIGEST_LEN); if (h == NULL) { return SSH_ERROR; } ctx = md5_init(); if (ctx == NULL) { SAFE_FREE(h); return SSH_ERROR; } pubkey = session->current_crypto->server_pubkey; md5_update(ctx, ssh_string_data(pubkey), ssh_string_len(pubkey)); md5_final(h, ctx); *hash = h; return MD5_DIGEST_LEN; } /** * @brief Deallocate the hash obtained by ssh_get_pubkey_hash. * * This is required under Microsoft platform as this library might use a * different C library than your software, hence a different heap. * * @param[in] hash The buffer to deallocate. * * @see ssh_get_pubkey_hash() */ void ssh_clean_pubkey_hash(unsigned char **hash) { SAFE_FREE(*hash); *hash = NULL; } /** * @brief Get the server public key from a session. * * @param[in] session The session to get the key from. * * @param[out] key A pointer to store the allocated key. You need to free * the key. * * @return SSH_OK on success, SSH_ERROR on errror. * * @see ssh_key_free() */ int ssh_get_publickey(ssh_session session, ssh_key *key) { if (session==NULL || session->current_crypto ==NULL || session->current_crypto->server_pubkey == NULL) { return SSH_ERROR; } return ssh_pki_import_pubkey_blob(session->current_crypto->server_pubkey, key); } /** * @brief Allocates a buffer with the hash of the public key. * * This function allows you to get a hash of the public key. You can then * print this hash in a human-readable form to the user so that he is able to * verify it. Use ssh_get_hexa() or ssh_print_hexa() to display it. * * @param[in] key The public key to create the hash for. * * @param[in] type The type of the hash you want. * * @param[in] hash A pointer to store the allocated buffer. It can be * freed using ssh_clean_pubkey_hash(). * * @param[in] hlen The length of the hash. * * @return 0 on success, -1 if an error occured. * * @warning It is very important that you verify at some moment that the hash * matches a known server. If you don't do it, cryptography wont help * you at making things secure. * OpenSSH uses SHA1 to print public key digests. * * @see ssh_is_server_known() * @see ssh_get_hexa() * @see ssh_print_hexa() * @see ssh_clean_pubkey_hash() */ int ssh_get_publickey_hash(const ssh_key key, enum ssh_publickey_hash_type type, unsigned char **hash, size_t *hlen) { ssh_string blob; unsigned char *h; int rc; rc = ssh_pki_export_pubkey_blob(key, &blob); if (rc < 0) { return rc; } switch (type) { case SSH_PUBLICKEY_HASH_SHA1: { SHACTX ctx; h = malloc(SHA_DIGEST_LEN); if (h == NULL) { rc = -1; goto out; } ctx = sha1_init(); if (ctx == NULL) { free(h); rc = -1; goto out; } sha1_update(ctx, ssh_string_data(blob), ssh_string_len(blob)); sha1_final(h, ctx); *hlen = SHA_DIGEST_LEN; } break; case SSH_PUBLICKEY_HASH_MD5: { MD5CTX ctx; h = malloc(MD5_DIGEST_LEN); if (h == NULL) { rc = -1; goto out; } ctx = md5_init(); if (ctx == NULL) { free(h); rc = -1; goto out; } md5_update(ctx, ssh_string_data(blob), ssh_string_len(blob)); md5_final(h, ctx); *hlen = MD5_DIGEST_LEN; } break; default: rc = -1; goto out; } *hash = h; rc = 0; out: ssh_string_free(blob); return rc; } /** * @brief Convert a buffer into a colon separated hex string. * The caller has to free the memory. * * @param what What should be converted to a hex string. * * @param len Length of the buffer to convert. * * @return The hex string or NULL on error. * * @see ssh_string_free_char() */ char *ssh_get_hexa(const unsigned char *what, size_t len) { const char h[] = "0123456789abcdef"; char *hexa; size_t i; size_t hlen = len * 3; if (len > (UINT_MAX - 1) / 3) { return NULL; } hexa = malloc(hlen + 1); if (hexa == NULL) { return NULL; } for (i = 0; i < len; i++) { hexa[i * 3] = h[(what[i] >> 4) & 0xF]; hexa[i * 3 + 1] = h[what[i] & 0xF]; hexa[i * 3 + 2] = ':'; } hexa[hlen - 1] = '\0'; return hexa; } /** * @brief Print a buffer as colon separated hex string. * * @param descr Description printed in front of the hex string. * * @param what What should be converted to a hex string. * * @param len Length of the buffer to convert. */ void ssh_print_hexa(const char *descr, const unsigned char *what, size_t len) { char *hexa = ssh_get_hexa(what, len); if (hexa == NULL) { return; } printf("%s: %s\n", descr, hexa); free(hexa); } /** @} */ /* vim: set ts=4 sw=4 et cindent: */