/* $OpenBSD: ssh-rsa.c,v 1.80 2024/08/15 00:51:51 djm Exp $ */ /* * Copyright (c) 2000, 2003 Markus Friedl * * Permission to use, copy, modify, and distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ #include #include #include #include #include "sshbuf.h" #include "ssherr.h" #define SSHKEY_INTERNAL #include "sshkey.h" #include "digest.h" #include "log.h" static u_int ssh_rsa_size(const struct sshkey *k) { if (k->pkey == NULL) return 0; return EVP_PKEY_bits(k->pkey); } static int ssh_rsa_alloc(struct sshkey *k) { if ((k->pkey = EVP_PKEY_new()) == NULL) return SSH_ERR_ALLOC_FAIL; return 0; } static void ssh_rsa_cleanup(struct sshkey *k) { EVP_PKEY_free(k->pkey); k->pkey = NULL; } static int ssh_rsa_equal(const struct sshkey *a, const struct sshkey *b) { if (a->pkey == NULL || b->pkey == NULL) return 0; return EVP_PKEY_cmp(a->pkey, b->pkey) == 1; } static int ssh_rsa_serialize_public(const struct sshkey *key, struct sshbuf *b, enum sshkey_serialize_rep opts) { int r; const BIGNUM *rsa_n, *rsa_e; const RSA *rsa; if (key->pkey == NULL) return SSH_ERR_INVALID_ARGUMENT; if ((rsa = EVP_PKEY_get0_RSA(key->pkey)) == NULL) return SSH_ERR_LIBCRYPTO_ERROR; RSA_get0_key(rsa, &rsa_n, &rsa_e, NULL); if ((r = sshbuf_put_bignum2(b, rsa_e)) != 0 || (r = sshbuf_put_bignum2(b, rsa_n)) != 0) return r; return 0; } static int ssh_rsa_serialize_private(const struct sshkey *key, struct sshbuf *b, enum sshkey_serialize_rep opts) { int r; const BIGNUM *rsa_n, *rsa_e, *rsa_d, *rsa_iqmp, *rsa_p, *rsa_q; const RSA *rsa; if ((rsa = EVP_PKEY_get0_RSA(key->pkey)) == NULL) return SSH_ERR_LIBCRYPTO_ERROR; RSA_get0_key(rsa, &rsa_n, &rsa_e, &rsa_d); RSA_get0_factors(rsa, &rsa_p, &rsa_q); RSA_get0_crt_params(rsa, NULL, NULL, &rsa_iqmp); if (!sshkey_is_cert(key)) { /* Note: can't reuse ssh_rsa_serialize_public: e, n vs. n, e */ if ((r = sshbuf_put_bignum2(b, rsa_n)) != 0 || (r = sshbuf_put_bignum2(b, rsa_e)) != 0) return r; } if ((r = sshbuf_put_bignum2(b, rsa_d)) != 0 || (r = sshbuf_put_bignum2(b, rsa_iqmp)) != 0 || (r = sshbuf_put_bignum2(b, rsa_p)) != 0 || (r = sshbuf_put_bignum2(b, rsa_q)) != 0) return r; return 0; } static int ssh_rsa_generate(struct sshkey *k, int bits) { EVP_PKEY_CTX *ctx = NULL; EVP_PKEY *res = NULL; int ret = SSH_ERR_INTERNAL_ERROR; if (bits < SSH_RSA_MINIMUM_MODULUS_SIZE || bits > SSHBUF_MAX_BIGNUM * 8) return SSH_ERR_KEY_LENGTH; if ((ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_RSA, NULL)) == NULL) { ret = SSH_ERR_ALLOC_FAIL; goto out; } if (EVP_PKEY_keygen_init(ctx) <= 0) { ret = SSH_ERR_LIBCRYPTO_ERROR; goto out; } if (EVP_PKEY_CTX_set_rsa_keygen_bits(ctx, bits) <= 0) { ret = SSH_ERR_KEY_LENGTH; goto out; } if (EVP_PKEY_keygen(ctx, &res) <= 0 || res == NULL) { ret = SSH_ERR_LIBCRYPTO_ERROR; goto out; } /* success */ k->pkey = res; ret = 0; out: EVP_PKEY_CTX_free(ctx); return ret; } static int ssh_rsa_copy_public(const struct sshkey *from, struct sshkey *to) { const BIGNUM *rsa_n, *rsa_e; BIGNUM *rsa_n_dup = NULL, *rsa_e_dup = NULL; int r = SSH_ERR_INTERNAL_ERROR; const RSA *rsa_from; RSA *rsa_to = NULL; if ((rsa_from = EVP_PKEY_get0_RSA(from->pkey)) == NULL || (rsa_to = RSA_new()) == NULL) return SSH_ERR_LIBCRYPTO_ERROR; RSA_get0_key(rsa_from, &rsa_n, &rsa_e, NULL); if ((rsa_n_dup = BN_dup(rsa_n)) == NULL || (rsa_e_dup = BN_dup(rsa_e)) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } if (!RSA_set0_key(rsa_to, rsa_n_dup, rsa_e_dup, NULL)) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } rsa_n_dup = rsa_e_dup = NULL; /* transferred */ if (EVP_PKEY_set1_RSA(to->pkey, rsa_to) != 1) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } /* success */ r = 0; out: RSA_free(rsa_to); BN_clear_free(rsa_n_dup); BN_clear_free(rsa_e_dup); return r; } static int ssh_rsa_deserialize_public(const char *ktype, struct sshbuf *b, struct sshkey *key) { int ret = SSH_ERR_INTERNAL_ERROR; BIGNUM *rsa_n = NULL, *rsa_e = NULL; RSA *rsa = NULL; if ((rsa = RSA_new()) == NULL) return SSH_ERR_LIBCRYPTO_ERROR; if (sshbuf_get_bignum2(b, &rsa_e) != 0 || sshbuf_get_bignum2(b, &rsa_n) != 0) { ret = SSH_ERR_INVALID_FORMAT; goto out; } if (!RSA_set0_key(rsa, rsa_n, rsa_e, NULL)) { ret = SSH_ERR_LIBCRYPTO_ERROR; goto out; } rsa_n = rsa_e = NULL; /* transferred */ if (EVP_PKEY_set1_RSA(key->pkey, rsa) != 1) { ret = SSH_ERR_LIBCRYPTO_ERROR; goto out; } if ((ret = sshkey_check_rsa_length(key, 0)) != 0) goto out; #ifdef DEBUG_PK RSA_print_fp(stderr, rsa, 8); #endif /* success */ ret = 0; out: RSA_free(rsa); BN_clear_free(rsa_n); BN_clear_free(rsa_e); return ret; } static int ssh_rsa_deserialize_private(const char *ktype, struct sshbuf *b, struct sshkey *key) { int r; BIGNUM *rsa_n = NULL, *rsa_e = NULL, *rsa_d = NULL; BIGNUM *rsa_iqmp = NULL, *rsa_p = NULL, *rsa_q = NULL; BIGNUM *rsa_dmp1 = NULL, *rsa_dmq1 = NULL; RSA *rsa = NULL; if (sshkey_is_cert(key)) { /* sshkey_private_deserialize already has pubkey from cert */ if ((rsa = EVP_PKEY_get1_RSA(key->pkey)) == NULL) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } } else { if ((rsa = RSA_new()) == NULL) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } /* Note: can't reuse ssh_rsa_deserialize_public: e,n vs. n,e */ if ((r = sshbuf_get_bignum2(b, &rsa_n)) != 0 || (r = sshbuf_get_bignum2(b, &rsa_e)) != 0) goto out; if (!RSA_set0_key(rsa, rsa_n, rsa_e, NULL)) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } rsa_n = rsa_e = NULL; /* transferred */ } if ((r = sshbuf_get_bignum2(b, &rsa_d)) != 0 || (r = sshbuf_get_bignum2(b, &rsa_iqmp)) != 0 || (r = sshbuf_get_bignum2(b, &rsa_p)) != 0 || (r = sshbuf_get_bignum2(b, &rsa_q)) != 0) goto out; if ((r = ssh_rsa_complete_crt_parameters(rsa_d, rsa_p, rsa_q, rsa_iqmp, &rsa_dmp1, &rsa_dmq1)) != 0) goto out; if (!RSA_set0_key(rsa, NULL, NULL, rsa_d)) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } rsa_d = NULL; /* transferred */ if (!RSA_set0_factors(rsa, rsa_p, rsa_q)) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } rsa_p = rsa_q = NULL; /* transferred */ if (!RSA_set0_crt_params(rsa, rsa_dmp1, rsa_dmq1, rsa_iqmp)) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } rsa_dmp1 = rsa_dmq1 = rsa_iqmp = NULL; if (RSA_blinding_on(rsa, NULL) != 1) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } if (EVP_PKEY_set1_RSA(key->pkey, rsa) != 1) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } if ((r = sshkey_check_rsa_length(key, 0)) != 0) goto out; /* success */ r = 0; out: RSA_free(rsa); BN_clear_free(rsa_n); BN_clear_free(rsa_e); BN_clear_free(rsa_d); BN_clear_free(rsa_p); BN_clear_free(rsa_q); BN_clear_free(rsa_iqmp); BN_clear_free(rsa_dmp1); BN_clear_free(rsa_dmq1); return r; } static const char * rsa_hash_alg_ident(int hash_alg) { switch (hash_alg) { case SSH_DIGEST_SHA1: return "ssh-rsa"; case SSH_DIGEST_SHA256: return "rsa-sha2-256"; case SSH_DIGEST_SHA512: return "rsa-sha2-512"; } return NULL; } /* * Returns the hash algorithm ID for a given algorithm identifier as used * inside the signature blob, */ static int rsa_hash_id_from_ident(const char *ident) { if (strcmp(ident, "ssh-rsa") == 0) return SSH_DIGEST_SHA1; if (strcmp(ident, "rsa-sha2-256") == 0) return SSH_DIGEST_SHA256; if (strcmp(ident, "rsa-sha2-512") == 0) return SSH_DIGEST_SHA512; return -1; } /* * Return the hash algorithm ID for the specified key name. This includes * all the cases of rsa_hash_id_from_ident() but also the certificate key * types. */ static int rsa_hash_id_from_keyname(const char *alg) { int r; if ((r = rsa_hash_id_from_ident(alg)) != -1) return r; if (strcmp(alg, "ssh-rsa-cert-v01@openssh.com") == 0) return SSH_DIGEST_SHA1; if (strcmp(alg, "rsa-sha2-256-cert-v01@openssh.com") == 0) return SSH_DIGEST_SHA256; if (strcmp(alg, "rsa-sha2-512-cert-v01@openssh.com") == 0) return SSH_DIGEST_SHA512; return -1; } int ssh_rsa_complete_crt_parameters(const BIGNUM *rsa_d, const BIGNUM *rsa_p, const BIGNUM *rsa_q, const BIGNUM *rsa_iqmp, BIGNUM **rsa_dmp1, BIGNUM **rsa_dmq1) { BIGNUM *aux = NULL, *d_consttime = NULL; BN_CTX *ctx = NULL; int r; *rsa_dmq1 = *rsa_dmp1 = NULL; if ((ctx = BN_CTX_new()) == NULL) return SSH_ERR_ALLOC_FAIL; if ((aux = BN_new()) == NULL || (*rsa_dmq1 = BN_new()) == NULL || (*rsa_dmp1 = BN_new()) == NULL) return SSH_ERR_ALLOC_FAIL; if ((d_consttime = BN_dup(rsa_d)) == NULL) { r = SSH_ERR_ALLOC_FAIL; goto out; } BN_set_flags(aux, BN_FLG_CONSTTIME); BN_set_flags(d_consttime, BN_FLG_CONSTTIME); if ((BN_sub(aux, rsa_q, BN_value_one()) == 0) || (BN_mod(*rsa_dmq1, d_consttime, aux, ctx) == 0) || (BN_sub(aux, rsa_p, BN_value_one()) == 0) || (BN_mod(*rsa_dmp1, d_consttime, aux, ctx) == 0)) { r = SSH_ERR_LIBCRYPTO_ERROR; goto out; } /* success */ r = 0; out: BN_clear_free(aux); BN_clear_free(d_consttime); BN_CTX_free(ctx); return r; } /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */ static int ssh_rsa_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) { u_char *sig = NULL; size_t diff, len = 0; int slen = 0; int hash_alg, ret = SSH_ERR_INTERNAL_ERROR; struct sshbuf *b = NULL; if (lenp != NULL) *lenp = 0; if (sigp != NULL) *sigp = NULL; if (alg == NULL || strlen(alg) == 0) hash_alg = SSH_DIGEST_SHA1; else hash_alg = rsa_hash_id_from_keyname(alg); if (key == NULL || key->pkey == NULL || hash_alg == -1 || sshkey_type_plain(key->type) != KEY_RSA) return SSH_ERR_INVALID_ARGUMENT; slen = EVP_PKEY_size(key->pkey); if (slen <= 0 || slen > SSHBUF_MAX_BIGNUM) return SSH_ERR_INVALID_ARGUMENT; if (EVP_PKEY_bits(key->pkey) < SSH_RSA_MINIMUM_MODULUS_SIZE) return SSH_ERR_KEY_LENGTH; if ((ret = sshkey_pkey_digest_sign(key->pkey, hash_alg, &sig, &len, data, datalen)) < 0) goto out; if (len < (size_t)slen) { diff = slen - len; memmove(sig + diff, sig, len); explicit_bzero(sig, diff); } else if (len > (size_t)slen) { ret = SSH_ERR_INTERNAL_ERROR; goto out; } /* encode signature */ if ((b = sshbuf_new()) == NULL) { ret = SSH_ERR_ALLOC_FAIL; goto out; } if ((ret = sshbuf_put_cstring(b, rsa_hash_alg_ident(hash_alg))) != 0 || (ret = sshbuf_put_string(b, sig, slen)) != 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: freezero(sig, slen); sshbuf_free(b); return ret; } static int ssh_rsa_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) { char *sigtype = NULL; int hash_alg, want_alg, ret = SSH_ERR_INTERNAL_ERROR; size_t len = 0, diff, modlen, rsasize; struct sshbuf *b = NULL; u_char digest[SSH_DIGEST_MAX_LENGTH], *osigblob, *sigblob = NULL; if (key == NULL || key->pkey == NULL || sshkey_type_plain(key->type) != KEY_RSA || sig == NULL || siglen == 0) return SSH_ERR_INVALID_ARGUMENT; if (EVP_PKEY_bits(key->pkey) < SSH_RSA_MINIMUM_MODULUS_SIZE) return SSH_ERR_KEY_LENGTH; if ((b = sshbuf_from(sig, siglen)) == NULL) return SSH_ERR_ALLOC_FAIL; if (sshbuf_get_cstring(b, &sigtype, NULL) != 0) { ret = SSH_ERR_INVALID_FORMAT; goto out; } if ((hash_alg = rsa_hash_id_from_ident(sigtype)) == -1) { ret = SSH_ERR_KEY_TYPE_MISMATCH; goto out; } /* * Allow ssh-rsa-cert-v01 certs to generate SHA2 signatures for * legacy reasons, but otherwise the signature type should match. */ if (alg != NULL && strcmp(alg, "ssh-rsa-cert-v01@openssh.com") != 0) { if ((want_alg = rsa_hash_id_from_keyname(alg)) == -1) { ret = SSH_ERR_INVALID_ARGUMENT; goto out; } if (hash_alg != want_alg) { ret = SSH_ERR_SIGNATURE_INVALID; goto out; } } if (sshbuf_get_string(b, &sigblob, &len) != 0) { ret = SSH_ERR_INVALID_FORMAT; goto out; } if (sshbuf_len(b) != 0) { ret = SSH_ERR_UNEXPECTED_TRAILING_DATA; goto out; } /* RSA_verify expects a signature of RSA_size */ modlen = EVP_PKEY_size(key->pkey); if (len > modlen) { ret = SSH_ERR_KEY_BITS_MISMATCH; goto out; } else if (len < modlen) { diff = modlen - len; osigblob = sigblob; if ((sigblob = realloc(sigblob, modlen)) == NULL) { sigblob = osigblob; /* put it back for clear/free */ ret = SSH_ERR_ALLOC_FAIL; goto out; } memmove(sigblob + diff, sigblob, len); explicit_bzero(sigblob, diff); len = modlen; } rsasize = EVP_PKEY_size(key->pkey); if (rsasize <= 0 || rsasize > SSHBUF_MAX_BIGNUM || len == 0 || len > rsasize) { ret = SSH_ERR_INVALID_ARGUMENT; goto out; } ret = sshkey_pkey_digest_verify(key->pkey, hash_alg, data, dlen, sigblob, len); out: freezero(sigblob, len); free(sigtype); sshbuf_free(b); explicit_bzero(digest, sizeof(digest)); return ret; } static const struct sshkey_impl_funcs sshkey_rsa_funcs = { /* .size = */ ssh_rsa_size, /* .alloc = */ ssh_rsa_alloc, /* .cleanup = */ ssh_rsa_cleanup, /* .equal = */ ssh_rsa_equal, /* .ssh_serialize_public = */ ssh_rsa_serialize_public, /* .ssh_deserialize_public = */ ssh_rsa_deserialize_public, /* .ssh_serialize_private = */ ssh_rsa_serialize_private, /* .ssh_deserialize_private = */ ssh_rsa_deserialize_private, /* .generate = */ ssh_rsa_generate, /* .copy_public = */ ssh_rsa_copy_public, /* .sign = */ ssh_rsa_sign, /* .verify = */ ssh_rsa_verify, }; const struct sshkey_impl sshkey_rsa_impl = { /* .name = */ "ssh-rsa", /* .shortname = */ "RSA", /* .sigalg = */ NULL, /* .type = */ KEY_RSA, /* .nid = */ 0, /* .cert = */ 0, /* .sigonly = */ 0, /* .keybits = */ 0, /* .funcs = */ &sshkey_rsa_funcs, }; const struct sshkey_impl sshkey_rsa_cert_impl = { /* .name = */ "ssh-rsa-cert-v01@openssh.com", /* .shortname = */ "RSA-CERT", /* .sigalg = */ NULL, /* .type = */ KEY_RSA_CERT, /* .nid = */ 0, /* .cert = */ 1, /* .sigonly = */ 0, /* .keybits = */ 0, /* .funcs = */ &sshkey_rsa_funcs, }; /* SHA2 signature algorithms */ const struct sshkey_impl sshkey_rsa_sha256_impl = { /* .name = */ "rsa-sha2-256", /* .shortname = */ "RSA", /* .sigalg = */ NULL, /* .type = */ KEY_RSA, /* .nid = */ 0, /* .cert = */ 0, /* .sigonly = */ 1, /* .keybits = */ 0, /* .funcs = */ &sshkey_rsa_funcs, }; const struct sshkey_impl sshkey_rsa_sha512_impl = { /* .name = */ "rsa-sha2-512", /* .shortname = */ "RSA", /* .sigalg = */ NULL, /* .type = */ KEY_RSA, /* .nid = */ 0, /* .cert = */ 0, /* .sigonly = */ 1, /* .keybits = */ 0, /* .funcs = */ &sshkey_rsa_funcs, }; const struct sshkey_impl sshkey_rsa_sha256_cert_impl = { /* .name = */ "rsa-sha2-256-cert-v01@openssh.com", /* .shortname = */ "RSA-CERT", /* .sigalg = */ "rsa-sha2-256", /* .type = */ KEY_RSA_CERT, /* .nid = */ 0, /* .cert = */ 1, /* .sigonly = */ 1, /* .keybits = */ 0, /* .funcs = */ &sshkey_rsa_funcs, }; const struct sshkey_impl sshkey_rsa_sha512_cert_impl = { /* .name = */ "rsa-sha2-512-cert-v01@openssh.com", /* .shortname = */ "RSA-CERT", /* .sigalg = */ "rsa-sha2-512", /* .type = */ KEY_RSA_CERT, /* .nid = */ 0, /* .cert = */ 1, /* .sigonly = */ 1, /* .keybits = */ 0, /* .funcs = */ &sshkey_rsa_funcs, };