/* $OpenBSD: ssh-rsa.c,v 1.59 2016/04/21 06:08:02 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 <sys/types.h> #include <openssl/evp.h> #include <openssl/err.h> #include <string.h> #include "sshbuf.h" #include "compat.h" #include "ssherr.h" #define SSHKEY_INTERNAL #include "sshkey.h" #include "digest.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; } static int rsa_hash_alg_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; } 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; } } /* 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) { u_char digest[SSH_DIGEST_MAX_LENGTH], *sig = NULL; size_t slen; 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 || strncmp(alg_ident, "ssh-rsa-cert", strlen("ssh-rsa-cert")) == 0) hash_alg = SSH_DIGEST_SHA1; else hash_alg = rsa_hash_alg_from_ident(alg_ident); if (key == NULL || key->rsa == NULL || hash_alg == -1 || sshkey_type_plain(key->type) != KEY_RSA || BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) return SSH_ERR_INVALID_ARGUMENT; 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)); if (sig != NULL) { explicit_bzero(sig, slen); free(sig); } 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) { char *ktype = NULL; int hash_alg, ret = SSH_ERR_INTERNAL_ERROR; size_t len, 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 || BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE || sig == NULL || siglen == 0) return SSH_ERR_INVALID_ARGUMENT; if ((b = sshbuf_from(sig, siglen)) == NULL) return SSH_ERR_ALLOC_FAIL; if (sshbuf_get_cstring(b, &ktype, NULL) != 0) { ret = SSH_ERR_INVALID_FORMAT; goto out; } if ((hash_alg = rsa_hash_alg_from_ident(ktype)) == -1) { ret = SSH_ERR_KEY_TYPE_MISMATCH; 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: if (sigblob != NULL) { explicit_bzero(sigblob, len); free(sigblob); } free(ktype); 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: if (decrypted) { explicit_bzero(decrypted, rsasize); free(decrypted); } return ret; }