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-rw-r--r--ssh-rsa.c449
1 files changed, 449 insertions, 0 deletions
diff --git a/ssh-rsa.c b/ssh-rsa.c
new file mode 100644
index 0000000..9b14f9a
--- /dev/null
+++ b/ssh-rsa.c
@@ -0,0 +1,449 @@
+/* $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 */
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