259 lines
6.9 KiB
C
259 lines
6.9 KiB
C
/*
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* Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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#include "includes.h"
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RCSID("$OpenBSD: ssh-rsa.c,v 1.32 2005/06/17 02:44:33 djm Exp $");
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#include <openssl/evp.h>
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#include <openssl/err.h>
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#include "xmalloc.h"
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#include "log.h"
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#include "buffer.h"
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#include "bufaux.h"
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#include "key.h"
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#include "compat.h"
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#include "ssh.h"
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static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *);
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/* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
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int
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ssh_rsa_sign(const Key *key, u_char **sigp, u_int *lenp,
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const u_char *data, u_int datalen)
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{
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const EVP_MD *evp_md;
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EVP_MD_CTX md;
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u_char digest[EVP_MAX_MD_SIZE], *sig;
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u_int slen, dlen, len;
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int ok, nid;
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Buffer b;
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if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
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error("ssh_rsa_sign: no RSA key");
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return -1;
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}
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nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
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if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
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error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);
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return -1;
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}
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EVP_DigestInit(&md, evp_md);
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EVP_DigestUpdate(&md, data, datalen);
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EVP_DigestFinal(&md, digest, &dlen);
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slen = RSA_size(key->rsa);
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sig = xmalloc(slen);
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ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);
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memset(digest, 'd', sizeof(digest));
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if (ok != 1) {
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int ecode = ERR_get_error();
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error("ssh_rsa_sign: RSA_sign failed: %s",
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ERR_error_string(ecode, NULL));
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xfree(sig);
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return -1;
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}
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if (len < slen) {
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u_int diff = slen - len;
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debug("slen %u > len %u", slen, len);
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memmove(sig + diff, sig, len);
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memset(sig, 0, diff);
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} else if (len > slen) {
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error("ssh_rsa_sign: slen %u slen2 %u", slen, len);
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xfree(sig);
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return -1;
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}
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/* encode signature */
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buffer_init(&b);
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buffer_put_cstring(&b, "ssh-rsa");
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buffer_put_string(&b, sig, slen);
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len = buffer_len(&b);
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if (lenp != NULL)
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*lenp = len;
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if (sigp != NULL) {
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*sigp = xmalloc(len);
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memcpy(*sigp, buffer_ptr(&b), len);
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}
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buffer_free(&b);
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memset(sig, 's', slen);
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xfree(sig);
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return 0;
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}
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int
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ssh_rsa_verify(const Key *key, const u_char *signature, u_int signaturelen,
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const u_char *data, u_int datalen)
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{
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Buffer b;
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const EVP_MD *evp_md;
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EVP_MD_CTX md;
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char *ktype;
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u_char digest[EVP_MAX_MD_SIZE], *sigblob;
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u_int len, dlen, modlen;
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int rlen, ret, nid;
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if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
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error("ssh_rsa_verify: no RSA key");
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return -1;
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}
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if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
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error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",
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BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
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return -1;
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}
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buffer_init(&b);
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buffer_append(&b, signature, signaturelen);
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ktype = buffer_get_string(&b, NULL);
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if (strcmp("ssh-rsa", ktype) != 0) {
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error("ssh_rsa_verify: cannot handle type %s", ktype);
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buffer_free(&b);
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xfree(ktype);
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return -1;
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}
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xfree(ktype);
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sigblob = buffer_get_string(&b, &len);
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rlen = buffer_len(&b);
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buffer_free(&b);
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if (rlen != 0) {
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error("ssh_rsa_verify: remaining bytes in signature %d", rlen);
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xfree(sigblob);
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return -1;
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}
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/* RSA_verify expects a signature of RSA_size */
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modlen = RSA_size(key->rsa);
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if (len > modlen) {
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error("ssh_rsa_verify: len %u > modlen %u", len, modlen);
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xfree(sigblob);
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return -1;
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} else if (len < modlen) {
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u_int diff = modlen - len;
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debug("ssh_rsa_verify: add padding: modlen %u > len %u",
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modlen, len);
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sigblob = xrealloc(sigblob, modlen);
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memmove(sigblob + diff, sigblob, len);
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memset(sigblob, 0, diff);
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len = modlen;
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}
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nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;
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if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {
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error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);
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xfree(sigblob);
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return -1;
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}
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EVP_DigestInit(&md, evp_md);
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EVP_DigestUpdate(&md, data, datalen);
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EVP_DigestFinal(&md, digest, &dlen);
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ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
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memset(digest, 'd', sizeof(digest));
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memset(sigblob, 's', len);
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xfree(sigblob);
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debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
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return ret;
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}
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/*
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* See:
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* http://www.rsasecurity.com/rsalabs/pkcs/pkcs-1/
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* ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1.asn
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*/
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/*
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* id-sha1 OBJECT IDENTIFIER ::= { iso(1) identified-organization(3)
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* oiw(14) secsig(3) algorithms(2) 26 }
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*/
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static const u_char id_sha1[] = {
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0x30, 0x21, /* type Sequence, length 0x21 (33) */
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0x30, 0x09, /* type Sequence, length 0x09 */
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0x06, 0x05, /* type OID, length 0x05 */
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0x2b, 0x0e, 0x03, 0x02, 0x1a, /* id-sha1 OID */
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0x05, 0x00, /* NULL */
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0x04, 0x14 /* Octet string, length 0x14 (20), followed by sha1 hash */
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};
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/*
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* id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)
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* rsadsi(113549) digestAlgorithm(2) 5 }
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*/
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static const u_char id_md5[] = {
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0x30, 0x20, /* type Sequence, length 0x20 (32) */
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0x30, 0x0c, /* type Sequence, length 0x09 */
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0x06, 0x08, /* type OID, length 0x05 */
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0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */
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0x05, 0x00, /* NULL */
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0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */
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};
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static int
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openssh_RSA_verify(int type, u_char *hash, u_int hashlen,
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u_char *sigbuf, u_int siglen, RSA *rsa)
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{
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u_int ret, rsasize, oidlen = 0, hlen = 0;
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int len;
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const u_char *oid = NULL;
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u_char *decrypted = NULL;
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ret = 0;
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switch (type) {
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case NID_sha1:
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oid = id_sha1;
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oidlen = sizeof(id_sha1);
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hlen = 20;
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break;
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case NID_md5:
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oid = id_md5;
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oidlen = sizeof(id_md5);
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hlen = 16;
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break;
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default:
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goto done;
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break;
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}
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if (hashlen != hlen) {
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error("bad hashlen");
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goto done;
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}
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rsasize = RSA_size(rsa);
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if (siglen == 0 || siglen > rsasize) {
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error("bad siglen");
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goto done;
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}
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decrypted = xmalloc(rsasize);
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if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,
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RSA_PKCS1_PADDING)) < 0) {
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error("RSA_public_decrypt failed: %s",
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ERR_error_string(ERR_get_error(), NULL));
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goto done;
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}
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if (len < 0 || (u_int)len != hlen + oidlen) {
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error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
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goto done;
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}
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if (memcmp(decrypted, oid, oidlen) != 0) {
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error("oid mismatch");
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goto done;
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}
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if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
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error("hash mismatch");
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goto done;
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}
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ret = 1;
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done:
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if (decrypted)
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xfree(decrypted);
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return ret;
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}
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