| /* $OpenBSD: ssh-rsa.c,v 1.67 2018/07/03 11:39:54 djm Exp $ */ |
| /* |
| * Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org> |
| * |
| * 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 "includes.h" |
| |
| #ifdef WITH_OPENSSL |
| |
| #include <sys/types.h> |
| |
| #include <openssl/evp.h> |
| #include <openssl/err.h> |
| |
| #include <stdarg.h> |
| #include <string.h> |
| |
| #include "sshbuf.h" |
| #include "compat.h" |
| #include "ssherr.h" |
| #define SSHKEY_INTERNAL |
| #include "sshkey.h" |
| #include "digest.h" |
| #include "log.h" |
| |
| #include "openbsd-compat/openssl-compat.h" |
| |
| static int openssh_RSA_verify(int, u_char *, size_t, u_char *, size_t, RSA *); |
| |
| 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; |
| } |
| |
| static int |
| rsa_hash_alg_nid(int type) |
| { |
| switch (type) { |
| case SSH_DIGEST_SHA1: |
| return NID_sha1; |
| case SSH_DIGEST_SHA256: |
| return NID_sha256; |
| case SSH_DIGEST_SHA512: |
| return NID_sha512; |
| default: |
| return -1; |
| } |
| } |
| |
| int |
| ssh_rsa_complete_crt_parameters(struct sshkey *key, const BIGNUM *iqmp) |
| { |
| const BIGNUM *rsa_p, *rsa_q, *rsa_d; |
| BIGNUM *aux = NULL, *d_consttime = NULL; |
| BIGNUM *rsa_dmq1 = NULL, *rsa_dmp1 = NULL, *rsa_iqmp = NULL; |
| BN_CTX *ctx = NULL; |
| int r; |
| |
| if (key == NULL || key->rsa == NULL || |
| sshkey_type_plain(key->type) != KEY_RSA) |
| return SSH_ERR_INVALID_ARGUMENT; |
| |
| RSA_get0_key(key->rsa, NULL, NULL, &rsa_d); |
| RSA_get0_factors(key->rsa, &rsa_p, &rsa_q); |
| |
| 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 || |
| (rsa_iqmp = BN_dup(iqmp)) == 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; |
| } |
| if (!RSA_set0_crt_params(key->rsa, rsa_dmp1, rsa_dmq1, rsa_iqmp)) { |
| r = SSH_ERR_LIBCRYPTO_ERROR; |
| goto out; |
| } |
| rsa_dmp1 = rsa_dmq1 = rsa_iqmp = NULL; /* transferred */ |
| /* success */ |
| r = 0; |
| out: |
| BN_clear_free(aux); |
| BN_clear_free(d_consttime); |
| BN_clear_free(rsa_dmp1); |
| BN_clear_free(rsa_dmq1); |
| BN_clear_free(rsa_iqmp); |
| BN_CTX_free(ctx); |
| return r; |
| } |
| |
| /* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */ |
| int |
| ssh_rsa_sign(const struct sshkey *key, u_char **sigp, size_t *lenp, |
| const u_char *data, size_t datalen, const char *alg_ident) |
| { |
| const BIGNUM *rsa_n; |
| u_char digest[SSH_DIGEST_MAX_LENGTH], *sig = NULL; |
| size_t slen = 0; |
| u_int dlen, len; |
| int nid, hash_alg, ret = SSH_ERR_INTERNAL_ERROR; |
| struct sshbuf *b = NULL; |
| |
| if (lenp != NULL) |
| *lenp = 0; |
| if (sigp != NULL) |
| *sigp = NULL; |
| |
| if (alg_ident == NULL || strlen(alg_ident) == 0) |
| hash_alg = SSH_DIGEST_SHA1; |
| else |
| hash_alg = rsa_hash_id_from_keyname(alg_ident); |
| if (key == NULL || key->rsa == NULL || hash_alg == -1 || |
| sshkey_type_plain(key->type) != KEY_RSA) |
| return SSH_ERR_INVALID_ARGUMENT; |
| RSA_get0_key(key->rsa, &rsa_n, NULL, NULL); |
| if (BN_num_bits(rsa_n) < SSH_RSA_MINIMUM_MODULUS_SIZE) |
| return SSH_ERR_KEY_LENGTH; |
| slen = RSA_size(key->rsa); |
| if (slen <= 0 || slen > SSHBUF_MAX_BIGNUM) |
| return SSH_ERR_INVALID_ARGUMENT; |
| |
| /* hash the data */ |
| nid = rsa_hash_alg_nid(hash_alg); |
| if ((dlen = ssh_digest_bytes(hash_alg)) == 0) |
| return SSH_ERR_INTERNAL_ERROR; |
| if ((ret = ssh_digest_memory(hash_alg, data, datalen, |
| digest, sizeof(digest))) != 0) |
| goto out; |
| |
| if ((sig = malloc(slen)) == NULL) { |
| ret = SSH_ERR_ALLOC_FAIL; |
| goto out; |
| } |
| |
| if (RSA_sign(nid, digest, dlen, sig, &len, key->rsa) != 1) { |
| ret = SSH_ERR_LIBCRYPTO_ERROR; |
| goto out; |
| } |
| if (len < slen) { |
| size_t diff = slen - len; |
| memmove(sig + diff, sig, len); |
| explicit_bzero(sig, diff); |
| } else if (len > 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: |
| explicit_bzero(digest, sizeof(digest)); |
| freezero(sig, slen); |
| sshbuf_free(b); |
| return ret; |
| } |
| |
| int |
| ssh_rsa_verify(const struct sshkey *key, |
| const u_char *sig, size_t siglen, const u_char *data, size_t datalen, |
| const char *alg) |
| { |
| const BIGNUM *rsa_n; |
| char *sigtype = NULL; |
| int hash_alg, want_alg, ret = SSH_ERR_INTERNAL_ERROR; |
| size_t len = 0, diff, modlen, dlen; |
| struct sshbuf *b = NULL; |
| u_char digest[SSH_DIGEST_MAX_LENGTH], *osigblob, *sigblob = NULL; |
| |
| if (key == NULL || key->rsa == NULL || |
| sshkey_type_plain(key->type) != KEY_RSA || |
| sig == NULL || siglen == 0) |
| return SSH_ERR_INVALID_ARGUMENT; |
| RSA_get0_key(key->rsa, &rsa_n, NULL, NULL); |
| if (BN_num_bits(rsa_n) < 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 = RSA_size(key->rsa); |
| 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; |
| } |
| if ((dlen = ssh_digest_bytes(hash_alg)) == 0) { |
| ret = SSH_ERR_INTERNAL_ERROR; |
| goto out; |
| } |
| if ((ret = ssh_digest_memory(hash_alg, data, datalen, |
| digest, sizeof(digest))) != 0) |
| goto out; |
| |
| ret = openssh_RSA_verify(hash_alg, digest, dlen, sigblob, len, |
| key->rsa); |
| out: |
| freezero(sigblob, len); |
| free(sigtype); |
| sshbuf_free(b); |
| explicit_bzero(digest, sizeof(digest)); |
| return ret; |
| } |
| |
| /* |
| * See: |
| * http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/ |
| * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn |
| */ |
| |
| /* |
| * id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3) |
| * oiw(14) secsig(3) algorithms(2) 26 } |
| */ |
| static const u_char id_sha1[] = { |
| 0x30, 0x21, /* type Sequence, length 0x21 (33) */ |
| 0x30, 0x09, /* type Sequence, length 0x09 */ |
| 0x06, 0x05, /* type OID, length 0x05 */ |
| 0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */ |
| 0x05, 0x00, /* NULL */ |
| 0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */ |
| }; |
| |
| /* |
| * See http://csrc.nist.gov/groups/ST/crypto_apps_infra/csor/algorithms.html |
| * id-sha256 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) |
| * organization(1) gov(101) csor(3) nistAlgorithm(4) hashAlgs(2) |
| * id-sha256(1) } |
| */ |
| static const u_char id_sha256[] = { |
| 0x30, 0x31, /* type Sequence, length 0x31 (49) */ |
| 0x30, 0x0d, /* type Sequence, length 0x0d (13) */ |
| 0x06, 0x09, /* type OID, length 0x09 */ |
| 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, /* id-sha256 */ |
| 0x05, 0x00, /* NULL */ |
| 0x04, 0x20 /* Octet string, length 0x20 (32), followed by sha256 hash */ |
| }; |
| |
| /* |
| * See http://csrc.nist.gov/groups/ST/crypto_apps_infra/csor/algorithms.html |
| * id-sha512 OBJECT IDENTIFIER ::= { joint-iso-itu-t(2) country(16) us(840) |
| * organization(1) gov(101) csor(3) nistAlgorithm(4) hashAlgs(2) |
| * id-sha256(3) } |
| */ |
| static const u_char id_sha512[] = { |
| 0x30, 0x51, /* type Sequence, length 0x51 (81) */ |
| 0x30, 0x0d, /* type Sequence, length 0x0d (13) */ |
| 0x06, 0x09, /* type OID, length 0x09 */ |
| 0x60, 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x03, /* id-sha512 */ |
| 0x05, 0x00, /* NULL */ |
| 0x04, 0x40 /* Octet string, length 0x40 (64), followed by sha512 hash */ |
| }; |
| |
| static int |
| rsa_hash_alg_oid(int hash_alg, const u_char **oidp, size_t *oidlenp) |
| { |
| switch (hash_alg) { |
| case SSH_DIGEST_SHA1: |
| *oidp = id_sha1; |
| *oidlenp = sizeof(id_sha1); |
| break; |
| case SSH_DIGEST_SHA256: |
| *oidp = id_sha256; |
| *oidlenp = sizeof(id_sha256); |
| break; |
| case SSH_DIGEST_SHA512: |
| *oidp = id_sha512; |
| *oidlenp = sizeof(id_sha512); |
| break; |
| default: |
| return SSH_ERR_INVALID_ARGUMENT; |
| } |
| return 0; |
| } |
| |
| static int |
| openssh_RSA_verify(int hash_alg, u_char *hash, size_t hashlen, |
| u_char *sigbuf, size_t siglen, RSA *rsa) |
| { |
| size_t rsasize = 0, oidlen = 0, hlen = 0; |
| int ret, len, oidmatch, hashmatch; |
| const u_char *oid = NULL; |
| u_char *decrypted = NULL; |
| |
| if ((ret = rsa_hash_alg_oid(hash_alg, &oid, &oidlen)) != 0) |
| return ret; |
| ret = SSH_ERR_INTERNAL_ERROR; |
| hlen = ssh_digest_bytes(hash_alg); |
| if (hashlen != hlen) { |
| ret = SSH_ERR_INVALID_ARGUMENT; |
| goto done; |
| } |
| rsasize = RSA_size(rsa); |
| if (rsasize <= 0 || rsasize > SSHBUF_MAX_BIGNUM || |
| siglen == 0 || siglen > rsasize) { |
| ret = SSH_ERR_INVALID_ARGUMENT; |
| goto done; |
| } |
| if ((decrypted = malloc(rsasize)) == NULL) { |
| ret = SSH_ERR_ALLOC_FAIL; |
| goto done; |
| } |
| if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa, |
| RSA_PKCS1_PADDING)) < 0) { |
| ret = SSH_ERR_LIBCRYPTO_ERROR; |
| goto done; |
| } |
| if (len < 0 || (size_t)len != hlen + oidlen) { |
| ret = SSH_ERR_INVALID_FORMAT; |
| goto done; |
| } |
| oidmatch = timingsafe_bcmp(decrypted, oid, oidlen) == 0; |
| hashmatch = timingsafe_bcmp(decrypted + oidlen, hash, hlen) == 0; |
| if (!oidmatch || !hashmatch) { |
| ret = SSH_ERR_SIGNATURE_INVALID; |
| goto done; |
| } |
| ret = 0; |
| done: |
| freezero(decrypted, rsasize); |
| return ret; |
| } |
| #endif /* WITH_OPENSSL */ |