/* $NetBSD: ssh-dss.c,v 1.17.6.1 2023/08/11 15:36:40 martin Exp $ */ /* $OpenBSD: ssh-dss.c,v 1.49 2023/03/05 05:34:09 dtucker Exp $ */ /* * Copyright (c) 2000 Markus Friedl. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ #include "includes.h" __RCSID("$NetBSD: ssh-dss.c,v 1.17.6.1 2023/08/11 15:36:40 martin Exp $"); #include #include #include #include #include "sshbuf.h" #include "ssherr.h" #include "digest.h" #define SSHKEY_INTERNAL #include "sshkey.h" #define INTBLOB_LEN 20 #define SIGBLOB_LEN (2*INTBLOB_LEN) static u_int ssh_dss_size(const struct sshkey *key) { const BIGNUM *dsa_p; if (key->dsa == NULL) return 0; DSA_get0_pqg(key->dsa, &dsa_p, NULL, NULL); return BN_num_bits(dsa_p); } static int ssh_dss_alloc(struct sshkey *k) { if ((k->dsa = DSA_new()) == NULL) return SSH_ERR_ALLOC_FAIL; return 0; } static void ssh_dss_cleanup(struct sshkey *k) { DSA_free(k->dsa); k->dsa = NULL; } static int ssh_dss_equal(const struct sshkey *a, const struct sshkey *b) { const BIGNUM *dsa_p_a, *dsa_q_a, *dsa_g_a, *dsa_pub_key_a; const BIGNUM *dsa_p_b, *dsa_q_b, *dsa_g_b, *dsa_pub_key_b; if (a->dsa == NULL || b->dsa == NULL) return 0; DSA_get0_pqg(a->dsa, &dsa_p_a, &dsa_q_a, &dsa_g_a); DSA_get0_pqg(b->dsa, &dsa_p_b, &dsa_q_b, &dsa_g_b); DSA_get0_key(a->dsa, &dsa_pub_key_a, NULL); DSA_get0_key(b->dsa, &dsa_pub_key_b, NULL); if (dsa_p_a == NULL || dsa_p_b == NULL || dsa_q_a == NULL || dsa_q_b == NULL || dsa_g_a == NULL || dsa_g_b == NULL || dsa_pub_key_a == NULL || dsa_pub_key_b == NULL) return 0; if (BN_cmp(dsa_p_a, dsa_p_b) != 0) return 0; if (BN_cmp(dsa_q_a, dsa_q_b) != 0) return 0; if (BN_cmp(dsa_g_a, dsa_g_b) != 0) return 0; if (BN_cmp(dsa_pub_key_a, dsa_pub_key_b) != 0) return 0; return 1; } static int ssh_dss_serialize_public(const struct sshkey *key, struct sshbuf *b, enum sshkey_serialize_rep opts) { int r; const BIGNUM *dsa_p, *dsa_q, *dsa_g, *dsa_pub_key; if (key->dsa == NULL) return SSH_ERR_INVALID_ARGUMENT; DSA_get0_pqg(key->dsa, &dsa_p, &dsa_q, &dsa_g); DSA_get0_key(key->dsa, &dsa_pub_key, NULL); if (dsa_p == NULL || dsa_q == NULL || dsa_g == NULL || dsa_pub_key == NULL) return SSH_ERR_INTERNAL_ERROR; if ((r = sshbuf_put_bignum2(b, dsa_p)) != 0 || (r = sshbuf_put_bignum2(b, dsa_q)) != 0 || (r = sshbuf_put_bignum2(b, dsa_g)) != 0 || (r = sshbuf_put_bignum2(b, dsa_pub_key)) != 0) return r; return 0; } static int ssh_dss_serialize_private(const struct sshkey *key, struct sshbuf *b, enum sshkey_serialize_rep opts) { int r; const BIGNUM *dsa_priv_key; DSA_get0_key(key->dsa, NULL, &dsa_priv_key); if (!sshkey_is_cert(key)) { if ((r = ssh_dss_serialize_public(key, b, opts)) != 0) return r; } if ((r = sshbuf_put_bignum2(b, dsa_priv_key)) != 0) return r; return 0; } static int ssh_dss_generate(struct sshkey *k, int bits) { DSA *private; if (bits != 1024) return SSH_ERR_KEY_LENGTH; if ((private = DSA_new()) == NULL) return SSH_ERR_ALLOC_FAIL; if (!DSA_generate_parameters_ex(private, bits, NULL, 0, NULL, NULL, NULL) || !DSA_generate_key(private)) { DSA_free(private); return SSH_ERR_LIBCRYPTO_ERROR; } k->dsa = private; return 0; } static int ssh_dss_copy_public(const struct sshkey *from, struct sshkey *to) { const BIGNUM *dsa_p, *dsa_q, *dsa_g, *dsa_pub_key; BIGNUM *dsa_p_dup = NULL, *dsa_q_dup = NULL, *dsa_g_dup = NULL; BIGNUM *dsa_pub_key_dup = NULL; int r = SSH_ERR_INTERNAL_ERROR; DSA_get0_pqg(from->dsa, &dsa_p, &dsa_q, &dsa_g); DSA_get0_key(from->dsa, &dsa_pub_key, NULL); if ((dsa_p_dup = BN_dup(dsa_p)) == NULL || (dsa_q_dup = BN_dup(dsa_q)) == NULL || (dsa_g_dup = BN_dup(dsa_g)) == NULL || (dsa_pub_key_dup = BN_dup(dsa_pub_key)) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } if (!DSA_set0_pqg(to->dsa, dsa_p_dup, dsa_q_dup, dsa_g_dup)) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } dsa_p_dup = dsa_q_dup = dsa_g_dup = NULL; /* transferred */ if (!DSA_set0_key(to->dsa, dsa_pub_key_dup, NULL)) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } dsa_pub_key_dup = NULL; /* transferred */ /* success */ r = 0; out: BN_clear_free(dsa_p_dup); BN_clear_free(dsa_q_dup); BN_clear_free(dsa_g_dup); BN_clear_free(dsa_pub_key_dup); return r; } static int ssh_dss_deserialize_public(const char *ktype, struct sshbuf *b, struct sshkey *key) { int ret = SSH_ERR_INTERNAL_ERROR; BIGNUM *dsa_p = NULL, *dsa_q = NULL, *dsa_g = NULL, *dsa_pub_key = NULL; if (sshbuf_get_bignum2(b, &dsa_p) != 0 || sshbuf_get_bignum2(b, &dsa_q) != 0 || sshbuf_get_bignum2(b, &dsa_g) != 0 || sshbuf_get_bignum2(b, &dsa_pub_key) != 0) { ret = SSH_ERR_INVALID_FORMAT; goto out; } if (!DSA_set0_pqg(key->dsa, dsa_p, dsa_q, dsa_g)) { ret = SSH_ERR_LIBCRYPTO_ERROR; goto out; } dsa_p = dsa_q = dsa_g = NULL; /* transferred */ if (!DSA_set0_key(key->dsa, dsa_pub_key, NULL)) { ret = SSH_ERR_LIBCRYPTO_ERROR; goto out; } dsa_pub_key = NULL; /* transferred */ #ifdef DEBUG_PK DSA_print_fp(stderr, key->dsa, 8); #endif /* success */ ret = 0; out: BN_clear_free(dsa_p); BN_clear_free(dsa_q); BN_clear_free(dsa_g); BN_clear_free(dsa_pub_key); return ret; } static int ssh_dss_deserialize_private(const char *ktype, struct sshbuf *b, struct sshkey *key) { int r; BIGNUM *dsa_priv_key = NULL; if (!sshkey_is_cert(key)) { if ((r = ssh_dss_deserialize_public(ktype, b, key)) != 0) return r; } if ((r = sshbuf_get_bignum2(b, &dsa_priv_key)) != 0) return r; if (!DSA_set0_key(key->dsa, NULL, dsa_priv_key)) { BN_clear_free(dsa_priv_key); return SSH_ERR_LIBCRYPTO_ERROR; } return 0; } static int ssh_dss_sign(struct sshkey *key, u_char **sigp, size_t *lenp, const u_char *data, size_t datalen, const char *alg, const char *sk_provider, const char *sk_pin, u_int compat) { DSA_SIG *sig = NULL; const BIGNUM *sig_r, *sig_s; u_char digest[SSH_DIGEST_MAX_LENGTH], sigblob[SIGBLOB_LEN]; size_t rlen, slen, len, dlen = ssh_digest_bytes(SSH_DIGEST_SHA1); struct sshbuf *b = NULL; int ret = SSH_ERR_INVALID_ARGUMENT; if (lenp != NULL) *lenp = 0; if (sigp != NULL) *sigp = NULL; if (key == NULL || key->dsa == NULL || sshkey_type_plain(key->type) != KEY_DSA) return SSH_ERR_INVALID_ARGUMENT; if (dlen == 0) return SSH_ERR_INTERNAL_ERROR; if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, datalen, digest, sizeof(digest))) != 0) goto out; if ((sig = DSA_do_sign(digest, dlen, key->dsa)) == NULL) { ret = SSH_ERR_LIBCRYPTO_ERROR; goto out; } DSA_SIG_get0(sig, &sig_r, &sig_s); rlen = BN_num_bytes(sig_r); slen = BN_num_bytes(sig_s); if (rlen > INTBLOB_LEN || slen > INTBLOB_LEN) { ret = SSH_ERR_INTERNAL_ERROR; goto out; } explicit_bzero(sigblob, SIGBLOB_LEN); BN_bn2bin(sig_r, sigblob + SIGBLOB_LEN - INTBLOB_LEN - rlen); BN_bn2bin(sig_s, sigblob + SIGBLOB_LEN - slen); if ((b = sshbuf_new()) == NULL) { ret = SSH_ERR_ALLOC_FAIL; goto out; } if ((ret = sshbuf_put_cstring(b, "ssh-dss")) != 0 || (ret = sshbuf_put_string(b, sigblob, SIGBLOB_LEN)) != 0) goto out; len = sshbuf_len(b); if (sigp != NULL) { if ((*sigp = malloc(len)) == NULL) { ret = SSH_ERR_ALLOC_FAIL; goto out; } memcpy(*sigp, sshbuf_ptr(b), len); } if (lenp != NULL) *lenp = len; ret = 0; out: explicit_bzero(digest, sizeof(digest)); DSA_SIG_free(sig); sshbuf_free(b); return ret; } static int ssh_dss_verify(const struct sshkey *key, const u_char *sig, size_t siglen, const u_char *data, size_t dlen, const char *alg, u_int compat, struct sshkey_sig_details **detailsp) { DSA_SIG *dsig = NULL; BIGNUM *sig_r = NULL, *sig_s = NULL; u_char digest[SSH_DIGEST_MAX_LENGTH], *sigblob = NULL; size_t len, hlen = ssh_digest_bytes(SSH_DIGEST_SHA1); int ret = SSH_ERR_INTERNAL_ERROR; struct sshbuf *b = NULL; char *ktype = NULL; if (key == NULL || key->dsa == NULL || sshkey_type_plain(key->type) != KEY_DSA || sig == NULL || siglen == 0) return SSH_ERR_INVALID_ARGUMENT; if (hlen == 0) return SSH_ERR_INTERNAL_ERROR; /* fetch signature */ if ((b = sshbuf_from(sig, siglen)) == NULL) return SSH_ERR_ALLOC_FAIL; if (sshbuf_get_cstring(b, &ktype, NULL) != 0 || sshbuf_get_string(b, &sigblob, &len) != 0) { ret = SSH_ERR_INVALID_FORMAT; goto out; } if (strcmp("ssh-dss", ktype) != 0) { ret = SSH_ERR_KEY_TYPE_MISMATCH; goto out; } if (sshbuf_len(b) != 0) { ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; goto out; } if (len != SIGBLOB_LEN) { ret = SSH_ERR_INVALID_FORMAT; goto out; } /* parse signature */ if ((dsig = DSA_SIG_new()) == NULL || (sig_r = BN_new()) == NULL || (sig_s = BN_new()) == NULL) { ret = SSH_ERR_ALLOC_FAIL; goto out; } if ((BN_bin2bn(sigblob, INTBLOB_LEN, sig_r) == NULL) || (BN_bin2bn(sigblob + INTBLOB_LEN, INTBLOB_LEN, sig_s) == NULL)) { ret = SSH_ERR_LIBCRYPTO_ERROR; goto out; } if (!DSA_SIG_set0(dsig, sig_r, sig_s)) { ret = SSH_ERR_LIBCRYPTO_ERROR; goto out; } sig_r = sig_s = NULL; /* transferred */ /* sha1 the data */ if ((ret = ssh_digest_memory(SSH_DIGEST_SHA1, data, dlen, digest, sizeof(digest))) != 0) goto out; switch (DSA_do_verify(digest, hlen, dsig, key->dsa)) { case 1: ret = 0; break; case 0: ret = SSH_ERR_SIGNATURE_INVALID; goto out; default: ret = SSH_ERR_LIBCRYPTO_ERROR; goto out; } out: explicit_bzero(digest, sizeof(digest)); DSA_SIG_free(dsig); BN_clear_free(sig_r); BN_clear_free(sig_s); sshbuf_free(b); free(ktype); if (sigblob != NULL) freezero(sigblob, len); return ret; } static const struct sshkey_impl_funcs sshkey_dss_funcs = { /* .size = */ ssh_dss_size, /* .alloc = */ ssh_dss_alloc, /* .cleanup = */ ssh_dss_cleanup, /* .equal = */ ssh_dss_equal, /* .ssh_serialize_public = */ ssh_dss_serialize_public, /* .ssh_deserialize_public = */ ssh_dss_deserialize_public, /* .ssh_serialize_private = */ ssh_dss_serialize_private, /* .ssh_deserialize_private = */ ssh_dss_deserialize_private, /* .generate = */ ssh_dss_generate, /* .copy_public = */ ssh_dss_copy_public, /* .sign = */ ssh_dss_sign, /* .verify = */ ssh_dss_verify, }; const struct sshkey_impl sshkey_dss_impl = { /* .name = */ "ssh-dss", /* .shortname = */ "DSA", /* .sigalg = */ NULL, /* .type = */ KEY_DSA, /* .nid = */ 0, /* .cert = */ 0, /* .sigonly = */ 0, /* .keybits = */ 0, /* .funcs = */ &sshkey_dss_funcs, }; const struct sshkey_impl sshkey_dsa_cert_impl = { /* .name = */ "ssh-dss-cert-v01@openssh.com", /* .shortname = */ "DSA-CERT", /* .sigalg = */ NULL, /* .type = */ KEY_DSA_CERT, /* .nid = */ 0, /* .cert = */ 1, /* .sigonly = */ 0, /* .keybits = */ 0, /* .funcs = */ &sshkey_dss_funcs, };