/* * Dropbear SSH * * Copyright (c) 2002,2003 Matt Johnston * Copyright (c) 2004 by Mihnea Stoenescu * All rights reserved. * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. */ #include "includes.h" #include "algo.h" #include "session.h" #include "dbutil.h" #include "dh_groups.h" #include "ltc_prng.h" #include "ecc.h" /* This file (algo.c) organises the ciphers which can be used, and is used to * decide which ciphers/hashes/compression/signing to use during key exchange*/ static int void_cipher(const unsigned char* in, unsigned char* out, unsigned long len, void* UNUSED(cipher_state)) { if (in != out) { memmove(out, in, len); } return CRYPT_OK; } static int void_start(int UNUSED(cipher), const unsigned char* UNUSED(IV), const unsigned char* UNUSED(key), int UNUSED(keylen), int UNUSED(num_rounds), void* UNUSED(cipher_state)) { return CRYPT_OK; } /* Mappings for ciphers, parameters are {&cipher_desc, keysize, blocksize} */ /* Remember to add new ciphers/hashes to regciphers/reghashes too */ #if DROPBEAR_AES256 static const struct dropbear_cipher dropbear_aes256 = {&aes_desc, 32, 16}; #endif #if DROPBEAR_AES128 static const struct dropbear_cipher dropbear_aes128 = {&aes_desc, 16, 16}; #endif #if DROPBEAR_BLOWFISH static const struct dropbear_cipher dropbear_blowfish = {&blowfish_desc, 16, 8}; #endif #if DROPBEAR_TWOFISH256 static const struct dropbear_cipher dropbear_twofish256 = {&twofish_desc, 32, 16}; #endif #if DROPBEAR_TWOFISH128 static const struct dropbear_cipher dropbear_twofish128 = {&twofish_desc, 16, 16}; #endif #if DROPBEAR_3DES static const struct dropbear_cipher dropbear_3des = {&des3_desc, 24, 8}; #endif /* used to indicate no encryption, as defined in rfc2410 */ const struct dropbear_cipher dropbear_nocipher = {NULL, 16, 8}; /* A few void* s are required to silence warnings * about the symmetric_CBC vs symmetric_CTR cipher_state pointer */ #if DROPBEAR_ENABLE_CBC_MODE const struct dropbear_cipher_mode dropbear_mode_cbc = {(void*)cbc_start, (void*)cbc_encrypt, (void*)cbc_decrypt}; #endif /* DROPBEAR_ENABLE_CBC_MODE */ const struct dropbear_cipher_mode dropbear_mode_none = {void_start, void_cipher, void_cipher}; #if DROPBEAR_ENABLE_CTR_MODE /* a wrapper to make ctr_start and cbc_start look the same */ static int dropbear_big_endian_ctr_start(int cipher, const unsigned char *IV, const unsigned char *key, int keylen, int num_rounds, symmetric_CTR *ctr) { return ctr_start(cipher, IV, key, keylen, num_rounds, CTR_COUNTER_BIG_ENDIAN, ctr); } const struct dropbear_cipher_mode dropbear_mode_ctr = {(void*)dropbear_big_endian_ctr_start, (void*)ctr_encrypt, (void*)ctr_decrypt}; #endif /* DROPBEAR_ENABLE_CTR_MODE */ /* Mapping of ssh hashes to libtomcrypt hashes, including keysize etc. {&hash_desc, keysize, hashsize} */ #if DROPBEAR_SHA1_HMAC static const struct dropbear_hash dropbear_sha1 = {&sha1_desc, 20, 20}; #endif #if DROPBEAR_SHA1_96_HMAC static const struct dropbear_hash dropbear_sha1_96 = {&sha1_desc, 20, 12}; #endif #if DROPBEAR_SHA2_256_HMAC static const struct dropbear_hash dropbear_sha2_256 = {&sha256_desc, 32, 32}; #endif #if DROPBEAR_SHA2_512_HMAC static const struct dropbear_hash dropbear_sha2_512 = {&sha512_desc, 64, 64}; #endif #if DROPBEAR_MD5_HMAC static const struct dropbear_hash dropbear_md5 = {&md5_desc, 16, 16}; #endif const struct dropbear_hash dropbear_nohash = {NULL, 16, 0}; /* used initially */ /* The following map ssh names to internal values. * The ordering here is important for the client - the first mode * that is also supported by the server will get used. */ algo_type sshciphers[] = { #if DROPBEAR_ENABLE_CTR_MODE #if DROPBEAR_AES128 {"aes128-ctr", 0, &dropbear_aes128, 1, &dropbear_mode_ctr}, #endif #if DROPBEAR_AES256 {"aes256-ctr", 0, &dropbear_aes256, 1, &dropbear_mode_ctr}, #endif #if DROPBEAR_TWOFISH_CTR /* twofish ctr is conditional as it hasn't been tested for interoperability, see options.h */ #if DROPBEAR_TWOFISH256 {"twofish256-ctr", 0, &dropbear_twofish256, 1, &dropbear_mode_ctr}, #endif #if DROPBEAR_TWOFISH128 {"twofish128-ctr", 0, &dropbear_twofish128, 1, &dropbear_mode_ctr}, #endif #endif /* DROPBEAR_TWOFISH_CTR */ #endif /* DROPBEAR_ENABLE_CTR_MODE */ #if DROPBEAR_ENABLE_CBC_MODE #if DROPBEAR_AES128 {"aes128-cbc", 0, &dropbear_aes128, 1, &dropbear_mode_cbc}, #endif #if DROPBEAR_AES256 {"aes256-cbc", 0, &dropbear_aes256, 1, &dropbear_mode_cbc}, #endif #if DROPBEAR_TWOFISH256 {"twofish256-cbc", 0, &dropbear_twofish256, 1, &dropbear_mode_cbc}, {"twofish-cbc", 0, &dropbear_twofish256, 1, &dropbear_mode_cbc}, #endif #if DROPBEAR_TWOFISH128 {"twofish128-cbc", 0, &dropbear_twofish128, 1, &dropbear_mode_cbc}, #endif #if DROPBEAR_3DES {"3des-ctr", 0, &dropbear_3des, 1, &dropbear_mode_ctr}, #endif #if DROPBEAR_3DES {"3des-cbc", 0, &dropbear_3des, 1, &dropbear_mode_cbc}, #endif #if DROPBEAR_BLOWFISH {"blowfish-cbc", 0, &dropbear_blowfish, 1, &dropbear_mode_cbc}, #endif #endif /* DROPBEAR_ENABLE_CBC_MODE */ {NULL, 0, NULL, 0, NULL} }; algo_type sshhashes[] = { #if DROPBEAR_SHA1_96_HMAC {"hmac-sha1-96", 0, &dropbear_sha1_96, 1, NULL}, #endif #if DROPBEAR_SHA1_HMAC {"hmac-sha1", 0, &dropbear_sha1, 1, NULL}, #endif #if DROPBEAR_SHA2_256_HMAC {"hmac-sha2-256", 0, &dropbear_sha2_256, 1, NULL}, #endif #if DROPBEAR_SHA2_512_HMAC {"hmac-sha2-512", 0, &dropbear_sha2_512, 1, NULL}, #endif #if DROPBEAR_MD5_HMAC {"hmac-md5", 0, (void*)&dropbear_md5, 1, NULL}, #endif {NULL, 0, NULL, 0, NULL} }; #ifndef DISABLE_ZLIB algo_type ssh_compress[] = { {"zlib@openssh.com", DROPBEAR_COMP_ZLIB_DELAY, NULL, 1, NULL}, {"zlib", DROPBEAR_COMP_ZLIB, NULL, 1, NULL}, {"none", DROPBEAR_COMP_NONE, NULL, 1, NULL}, {NULL, 0, NULL, 0, NULL} }; algo_type ssh_delaycompress[] = { {"zlib@openssh.com", DROPBEAR_COMP_ZLIB_DELAY, NULL, 1, NULL}, {"none", DROPBEAR_COMP_NONE, NULL, 1, NULL}, {NULL, 0, NULL, 0, NULL} }; #endif algo_type ssh_nocompress[] = { {"none", DROPBEAR_COMP_NONE, NULL, 1, NULL}, {NULL, 0, NULL, 0, NULL} }; algo_type sshhostkey[] = { #if DROPBEAR_ECDSA #if DROPBEAR_ECC_256 {"ecdsa-sha2-nistp256", DROPBEAR_SIGNKEY_ECDSA_NISTP256, NULL, 1, NULL}, #endif #if DROPBEAR_ECC_384 {"ecdsa-sha2-nistp384", DROPBEAR_SIGNKEY_ECDSA_NISTP384, NULL, 1, NULL}, #endif #if DROPBEAR_ECC_521 {"ecdsa-sha2-nistp521", DROPBEAR_SIGNKEY_ECDSA_NISTP521, NULL, 1, NULL}, #endif #endif #if DROPBEAR_RSA {"ssh-rsa", DROPBEAR_SIGNKEY_RSA, NULL, 1, NULL}, #endif #if DROPBEAR_DSS {"ssh-dss", DROPBEAR_SIGNKEY_DSS, NULL, 1, NULL}, #endif {NULL, 0, NULL, 0, NULL} }; #if DROPBEAR_DH_GROUP1 static const struct dropbear_kex kex_dh_group1 = {DROPBEAR_KEX_NORMAL_DH, dh_p_1, DH_P_1_LEN, NULL, &sha1_desc }; #endif #if DROPBEAR_DH_GROUP14_SHA1 static const struct dropbear_kex kex_dh_group14_sha1 = {DROPBEAR_KEX_NORMAL_DH, dh_p_14, DH_P_14_LEN, NULL, &sha1_desc }; #endif #if DROPBEAR_DH_GROUP14_SHA256 static const struct dropbear_kex kex_dh_group14_sha256 = {DROPBEAR_KEX_NORMAL_DH, dh_p_14, DH_P_14_LEN, NULL, &sha256_desc }; #endif #if DROPBEAR_DH_GROUP16 static const struct dropbear_kex kex_dh_group16_sha512 = {DROPBEAR_KEX_NORMAL_DH, dh_p_16, DH_P_16_LEN, NULL, &sha512_desc }; #endif /* These can't be const since dropbear_ecc_fill_dp() fills out ecc_curve at runtime */ #if DROPBEAR_ECDH #if DROPBEAR_ECC_256 static const struct dropbear_kex kex_ecdh_nistp256 = {DROPBEAR_KEX_ECDH, NULL, 0, &ecc_curve_nistp256, &sha256_desc }; #endif #if DROPBEAR_ECC_384 static const struct dropbear_kex kex_ecdh_nistp384 = {DROPBEAR_KEX_ECDH, NULL, 0, &ecc_curve_nistp384, &sha384_desc }; #endif #if DROPBEAR_ECC_521 static const struct dropbear_kex kex_ecdh_nistp521 = {DROPBEAR_KEX_ECDH, NULL, 0, &ecc_curve_nistp521, &sha512_desc }; #endif #endif /* DROPBEAR_ECDH */ #if DROPBEAR_CURVE25519 /* Referred to directly */ static const struct dropbear_kex kex_curve25519 = {DROPBEAR_KEX_CURVE25519, NULL, 0, NULL, &sha256_desc }; #endif algo_type sshkex[] = { #if DROPBEAR_CURVE25519 {"curve25519-sha256", 0, &kex_curve25519, 1, NULL}, {"curve25519-sha256@libssh.org", 0, &kex_curve25519, 1, NULL}, #endif #if DROPBEAR_ECDH #if DROPBEAR_ECC_521 {"ecdh-sha2-nistp521", 0, &kex_ecdh_nistp521, 1, NULL}, #endif #if DROPBEAR_ECC_384 {"ecdh-sha2-nistp384", 0, &kex_ecdh_nistp384, 1, NULL}, #endif #if DROPBEAR_ECC_256 {"ecdh-sha2-nistp256", 0, &kex_ecdh_nistp256, 1, NULL}, #endif #endif #if DROPBEAR_DH_GROUP14_SHA256 {"diffie-hellman-group14-sha256", 0, &kex_dh_group14_sha256, 1, NULL}, #endif #if DROPBEAR_DH_GROUP14_SHA1 {"diffie-hellman-group14-sha1", 0, &kex_dh_group14_sha1, 1, NULL}, #endif #if DROPBEAR_DH_GROUP1 {"diffie-hellman-group1-sha1", 0, &kex_dh_group1, 1, NULL}, #endif #if DROPBEAR_DH_GROUP16 {"diffie-hellman-group16-sha512", 0, &kex_dh_group16_sha512, 1, NULL}, #endif #if DROPBEAR_KEXGUESS2 {KEXGUESS2_ALGO_NAME, KEXGUESS2_ALGO_ID, NULL, 1, NULL}, #endif {NULL, 0, NULL, 0, NULL} }; /* algolen specifies the length of algo, algos is our local list to match * against. * Returns DROPBEAR_SUCCESS if we have a match for algo, DROPBEAR_FAILURE * otherwise */ int have_algo(const char* algo, size_t algolen, const algo_type algos[]) { int i; for (i = 0; algos[i].name != NULL; i++) { if (strlen(algos[i].name) == algolen && (strncmp(algos[i].name, algo, algolen) == 0)) { return DROPBEAR_SUCCESS; } } return DROPBEAR_FAILURE; } /* Output a comma separated list of algorithms to a buffer */ void buf_put_algolist(buffer * buf, const algo_type localalgos[]) { unsigned int i, len; unsigned int donefirst = 0; buffer *algolist = NULL; algolist = buf_new(300); for (i = 0; localalgos[i].name != NULL; i++) { if (localalgos[i].usable) { if (donefirst) buf_putbyte(algolist, ','); donefirst = 1; len = strlen(localalgos[i].name); buf_putbytes(algolist, (const unsigned char *) localalgos[i].name, len); } } buf_putstring(buf, (const char*)algolist->data, algolist->len); TRACE(("algolist add '%*s'", algolist->len, algolist->data)) buf_free(algolist); } /* match the first algorithm in the comma-separated list in buf which is * also in localalgos[], or return NULL on failure. * (*goodguess) is set to 1 if the preferred client/server algos match, * 0 otherwise. This is used for checking if the kexalgo/hostkeyalgos are * guessed correctly */ algo_type * buf_match_algo(buffer* buf, algo_type localalgos[], enum kexguess2_used *kexguess2, int *goodguess) { char * algolist = NULL; const char *remotenames[MAX_PROPOSED_ALGO], *localnames[MAX_PROPOSED_ALGO]; unsigned int len; unsigned int remotecount, localcount, clicount, servcount, i, j; algo_type * ret = NULL; const char **clinames, **servnames; if (goodguess) { *goodguess = 0; } /* get the comma-separated list from the buffer ie "algo1,algo2,algo3" */ algolist = buf_getstring(buf, &len); TRACE(("buf_match_algo: %s", algolist)) if (len > MAX_PROPOSED_ALGO*(MAX_NAME_LEN+1)) { goto out; } /* remotenames will contain a list of the strings parsed out */ /* We will have at least one string (even if it's just "") */ remotenames[0] = algolist; remotecount = 1; for (i = 0; i < len; i++) { if (algolist[i] == '\0') { /* someone is trying something strange */ goto out; } if (algolist[i] == ',') { algolist[i] = '\0'; remotenames[remotecount] = &algolist[i+1]; remotecount++; } if (remotecount >= MAX_PROPOSED_ALGO) { break; } } if (kexguess2 && *kexguess2 == KEXGUESS2_LOOK) { for (i = 0; i < remotecount; i++) { if (strcmp(remotenames[i], KEXGUESS2_ALGO_NAME) == 0) { *kexguess2 = KEXGUESS2_YES; break; } } if (*kexguess2 == KEXGUESS2_LOOK) { *kexguess2 = KEXGUESS2_NO; } } for (i = 0; localalgos[i].name != NULL; i++) { if (localalgos[i].usable) { localnames[i] = localalgos[i].name; } else { localnames[i] = NULL; } } localcount = i; if (IS_DROPBEAR_SERVER) { clinames = remotenames; clicount = remotecount; servnames = localnames; servcount = localcount; } else { clinames = localnames; clicount = localcount; servnames = remotenames; servcount = remotecount; } /* iterate and find the first match */ for (i = 0; i < clicount; i++) { for (j = 0; j < servcount; j++) { if (!(servnames[j] && clinames[i])) { /* unusable algos are NULL */ continue; } if (strcmp(servnames[j], clinames[i]) == 0) { /* set if it was a good guess */ if (goodguess && kexguess2) { if (*kexguess2 == KEXGUESS2_YES) { if (i == 0) { *goodguess = 1; } } else { if (i == 0 && j == 0) { *goodguess = 1; } } } /* set the algo to return */ if (IS_DROPBEAR_SERVER) { ret = &localalgos[j]; } else { ret = &localalgos[i]; } goto out; } } } out: m_free(algolist); return ret; } #if DROPBEAR_USER_ALGO_LIST char * algolist_string(const algo_type algos[]) { char *ret_list; buffer *b = buf_new(200); buf_put_algolist(b, algos); buf_setpos(b, b->len); buf_putbyte(b, '\0'); buf_setpos(b, 4); ret_list = m_strdup((const char *) buf_getptr(b, b->len - b->pos)); buf_free(b); return ret_list; } static algo_type* check_algo(const char* algo_name, algo_type *algos) { algo_type *a; for (a = algos; a->name != NULL; a++) { if (strcmp(a->name, algo_name) == 0) { return a; } } return NULL; } /* Checks a user provided comma-separated algorithm list for available * options. Any that are not acceptable are removed in-place. Returns the * number of valid algorithms. */ int check_user_algos(const char* user_algo_list, algo_type * algos, const char *algo_desc) { algo_type new_algos[MAX_PROPOSED_ALGO+1]; char *work_list = m_strdup(user_algo_list); char *start = work_list; char *c; int n; /* So we can iterate and look for null terminator */ memset(new_algos, 0x0, sizeof(new_algos)); for (c = work_list, n = 0; ; c++) { char oc = *c; if (n >= MAX_PROPOSED_ALGO) { dropbear_exit("Too many algorithms '%s'", user_algo_list); } if (*c == ',' || *c == '\0') { algo_type *match_algo = NULL; *c = '\0'; match_algo = check_algo(start, algos); if (match_algo) { if (check_algo(start, new_algos)) { TRACE(("Skip repeated algorithm '%s'", start)) } else { new_algos[n] = *match_algo; n++; } } else { dropbear_log(LOG_WARNING, "This Dropbear program does not support '%s' %s algorithm", start, algo_desc); } c++; start = c; } if (oc == '\0') { break; } } m_free(work_list); /* n+1 to include a null terminator */ memcpy(algos, new_algos, sizeof(*new_algos) * (n+1)); return n; } #endif /* DROPBEAR_USER_ALGO_LIST */