/* $OpenBSD$ */

/*

* Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org>

* Copyright (c) 2011 Dr. Stephen Henson. All rights reserved.

* Copyright (c) 2011 Roumen Petrov. All rights reserved.

*

* 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"

#include <sys/types.h>

#include <openssl/evp.h>

#include <openssl/err.h>

#include <stdarg.h>

#include <string.h>

#include "xmalloc.h"

#include "log.h"

#include "buffer.h"

#include "key.h"

#include "compat.h"

#include "misc.h"

#include "ssh.h"

#include "evp-compat.h"

/*NOTE: Do not define USE_LEGACY_RSA_... if build

is with FIPS capable OpenSSL */

/* Define if you want yo use legacy sign code */

#undef USE_LEGACY_RSA_SIGN

/* Define if you want yo use legacy verify code */

#undef USE_LEGACY_RSA_VERIFY

#ifdef USE_LEGACY_RSA_VERIFY

static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int, RSA *);

#endif

/* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */

int

ssh_rsa_sign(const Key *key, u_char **sigp, u_int *lenp,

const u_char *data, u_int datalen)

{

const EVP_MD *evp_md;

EVP_MD_CTX md;

u_char *sig = NULL;

u_int slen = 0, len;

#ifdef USE_LEGACY_RSA_SIGN

u_char digest[EVP_MAX_MD_SIZE];

u_int dlen;

#endif

int ok, nid;

Buffer b;

if (key == NULL || key->rsa == NULL || (key->type != KEY_RSA &&

key->type != KEY_RSA_CERT && key->type != KEY_RSA_CERT_V00)) {

error("ssh_rsa_sign: no RSA key");

return -1;

}

nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;

if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {

error("ssh_rsa_sign: EVP_get_digestbynid %d failed", nid);

return -1;

}

#ifdef USE_LEGACY_RSA_SIGN

EVP_DigestInit(&md, evp_md);

EVP_DigestUpdate(&md, data, datalen);

EVP_DigestFinal(&md, digest, &dlen);

slen = RSA_size(key->rsa);

sig = xmalloc(slen);

ok = RSA_sign(nid, digest, dlen, sig, &len, key->rsa);

memset(digest, 'd', sizeof(digest));

#else /*ndef USE_LEGACY_RSA_SIGN*/

{

EVP_PKEY *pkey = NULL;

ok = -1;

pkey = EVP_PKEY_new();

if (pkey == NULL) {

error("%s: out of memory", __func__);

goto done;

}

EVP_PKEY_set1_RSA(pkey, key->rsa);

slen = EVP_PKEY_size(pkey);

sig = xmalloc(slen); /*fatal on error*/

ssh_EVP_MD_CTX_init(&md);

ok = ssh_EVP_SignInit_ex(&md, evp_md, NULL);

if (ok <= 0) {

char ebuf[256];

error("%s: EVP_SignInit_ex fail with errormsg='%.*s'"

, __func__

, (int)sizeof(ebuf), openssl_errormsg(ebuf, sizeof(ebuf)));

goto clean;

}

ok = ssh_EVP_SignUpdate(&md, data, datalen);

if (ok <= 0) {

char ebuf[256];

error("%s: EVP_SignUpdate fail with errormsg='%.*s'"

, __func__

, (int)sizeof(ebuf), openssl_errormsg(ebuf, sizeof(ebuf)));

goto clean;

}

ok = EVP_SignFinal(&md, sig, &len, pkey);

if (ok <= 0) {

char ebuf[256];

error("%s: SignFinal fail with errormsg='%.*s'"

, __func__

, (int)sizeof(ebuf), openssl_errormsg(ebuf, sizeof(ebuf)));

goto clean;

}

clean:

ssh_EVP_MD_CTX_cleanup(&md);

done:

if (pkey != NULL) EVP_PKEY_free(pkey);

}

#endif /*ndef USE_LEGACY_RSA_SIGN*/

if (ok <= 0) {

#ifdef USE_LEGACY_RSA_SIGN

int ecode = ERR_get_error();

error("ssh_rsa_sign: RSA_sign failed: %s",

ERR_error_string(ecode, NULL));

#endif /*def USE_LEGACY_RSA_SIGN*/

xfree(sig);

return -1;

}

if (len < slen) {

u_int diff = slen - len;

debug("slen %u > len %u", slen, len);

memmove(sig + diff, sig, len);

memset(sig, 0, diff);

} else if (len > slen) {

error("ssh_rsa_sign: slen %u slen2 %u", slen, len);

xfree(sig);

return -1;

}

/* encode signature */

buffer_init(&b);

buffer_put_cstring(&b, "ssh-rsa");

buffer_put_string(&b, sig, slen);

len = buffer_len(&b);

if (lenp != NULL)

*lenp = len;

if (sigp != NULL) {

*sigp = xmalloc(len);

memcpy(*sigp, buffer_ptr(&b), len);

}

buffer_free(&b);

memset(sig, 's', slen);

xfree(sig);

return 0;

}

int

ssh_rsa_verify(const Key *key, const u_char *signature, u_int signaturelen,

const u_char *data, u_int datalen)

{

Buffer b;

const EVP_MD *evp_md;

EVP_MD_CTX md;

char *ktype;

u_char *sigblob;

u_int len, modlen;

#ifdef USE_LEGACY_RSA_VERIFY

u_char digest[EVP_MAX_MD_SIZE];

u_int dlen;

#endif

int rlen, ret, nid;

if (key == NULL || key->rsa == NULL || (key->type != KEY_RSA &&

key->type != KEY_RSA_CERT && key->type != KEY_RSA_CERT_V00)) {

error("ssh_rsa_verify: no RSA key");

return -1;

}

if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {

error("ssh_rsa_verify: RSA modulus too small: %d < minimum %d bits",

BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);

return -1;

}

buffer_init(&b);

buffer_append(&b, signature, signaturelen);

ktype = buffer_get_cstring(&b, NULL);

if (strcmp("ssh-rsa", ktype) != 0) {

error("ssh_rsa_verify: cannot handle type %s", ktype);

buffer_free(&b);

xfree(ktype);

return -1;

}

xfree(ktype);

sigblob = buffer_get_string(&b, &len);

rlen = buffer_len(&b);

buffer_free(&b);

if (rlen != 0) {

error("ssh_rsa_verify: remaining bytes in signature %d", rlen);

xfree(sigblob);

return -1;

}

/* RSA_verify expects a signature of RSA_size */

modlen = RSA_size(key->rsa);

if (len > modlen) {

error("ssh_rsa_verify: len %u > modlen %u", len, modlen);

xfree(sigblob);

return -1;

} else if (len < modlen) {

u_int diff = modlen - len;

debug("ssh_rsa_verify: add padding: modlen %u > len %u",

modlen, len);

sigblob = xrealloc(sigblob, 1, modlen);

memmove(sigblob + diff, sigblob, len);

memset(sigblob, 0, diff);

len = modlen;

}

nid = (datafellows & SSH_BUG_RSASIGMD5) ? NID_md5 : NID_sha1;

if ((evp_md = EVP_get_digestbynid(nid)) == NULL) {

error("ssh_rsa_verify: EVP_get_digestbynid %d failed", nid);

xfree(sigblob);

return -1;

}

#ifdef USE_LEGACY_RSA_VERIFY

EVP_DigestInit(&md, evp_md);

EVP_DigestUpdate(&md, data, datalen);

EVP_DigestFinal(&md, digest, &dlen);

ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);

memset(digest, 'd', sizeof(digest));

#else /*ndef USE_LEGACY_RSA_VERIFY*/

{

EVP_PKEY *pkey;

ret = -1;

pkey = EVP_PKEY_new();

if (pkey == NULL) {

error("%s: out of memory", __func__);

goto done;

}

EVP_PKEY_set1_RSA(pkey, key->rsa);

ssh_EVP_MD_CTX_init(&md);

ret = ssh_EVP_VerifyInit(&md, evp_md);

if (ret <= 0) {

char ebuf[256];

error("%s: EVP_VerifyInit fail with errormsg='%.*s'"

, __func__

, (int)sizeof(ebuf), openssl_errormsg(ebuf, sizeof(ebuf)));

goto clean;

}

ret = ssh_EVP_VerifyUpdate(&md, data, datalen);

if (ret <= 0) {

char ebuf[256];

error("%s: EVP_VerifyUpdate fail with errormsg='%.*s'"

, __func__

, (int)sizeof(ebuf), openssl_errormsg(ebuf, sizeof(ebuf)));

goto clean;

}

ret = EVP_VerifyFinal(&md, sigblob, len, pkey);

if (ret <= 0) {

char ebuf[256];

error("%s: EVP_VerifyFinal fail with errormsg='%.*s'"

, __func__

, (int)sizeof(ebuf), openssl_errormsg(ebuf, sizeof(ebuf)));

goto clean;

}

clean:

ssh_EVP_MD_CTX_cleanup(&md);

done:

if (pkey != NULL) EVP_PKEY_free(pkey);

}

#endif /*ndef USE_LEGACY_RSA_VERIFY*/

memset(sigblob, 's', len);

xfree(sigblob);

debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");

return ret;

}

#ifdef USE_LEGACY_RSA_VERIFY

/*

* 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 */

};

/*

* id-md5 OBJECT IDENTIFIER ::= { iso(1) member-body(2) us(840)

* rsadsi(113549) digestAlgorithm(2) 5 }

*/

static const u_char id_md5[] = {

0x30, 0x20, /* type Sequence, length 0x20 (32) */

0x30, 0x0c, /* type Sequence, length 0x09 */

0x06, 0x08, /* type OID, length 0x05 */

0x2a, 0x86, 0x48, 0x86, 0xF7, 0x0D, 0x02, 0x05, /* id-md5 */

0x05, 0x00, /* NULL */

0x04, 0x10 /* Octet string, length 0x10 (16), followed by md5 hash */

};

static int

openssh_RSA_verify(int type, u_char *hash, u_int hashlen,

u_char *sigbuf, u_int siglen, RSA *rsa)

{

u_int ret, rsasize, oidlen = 0, hlen = 0;

int len, oidmatch, hashmatch;

const u_char *oid = NULL;

u_char *decrypted = NULL;

ret = 0;

switch (type) {

case NID_sha1:

oid = id_sha1;

oidlen = sizeof(id_sha1);

hlen = 20;

break;

case NID_md5:

oid = id_md5;

oidlen = sizeof(id_md5);

hlen = 16;

break;

default:

goto done;

}

if (hashlen != hlen) {

error("bad hashlen");

goto done;

}

rsasize = RSA_size(rsa);

if (siglen == 0 || siglen > rsasize) {

error("bad siglen");

goto done;

}

decrypted = xmalloc(rsasize);

if ((len = RSA_public_decrypt(siglen, sigbuf, decrypted, rsa,

RSA_PKCS1_PADDING)) < 0) {

error("RSA_public_decrypt failed: %s",

ERR_error_string(ERR_get_error(), NULL));

goto done;

}

if (len < 0 || (u_int)len != hlen + oidlen) {

error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);

goto done;

}

oidmatch = timingsafe_bcmp(decrypted, oid, oidlen) == 0;

hashmatch = timingsafe_bcmp(decrypted + oidlen, hash, hlen) == 0;

if (!oidmatch) {

error("oid mismatch");

goto done;

}

if (!hashmatch) {

error("hash mismatch");

goto done;

}

ret = 1;

done:

if (decrypted)

xfree(decrypted);

return ret;

}

#endif /*def USE_LEGACY_RSA_VERIFY*/