- markus@cvs.openbsd.org 2002/08/02 22:20:30
[ssh-rsa.c]
replace RSA_verify with our own version and avoid the OpenSSL ASN.1 parser
for authentication; ok deraadt/djm
diff --git a/ssh-rsa.c b/ssh-rsa.c
index 8271af4..44287fa 100644
--- a/ssh-rsa.c
+++ b/ssh-rsa.c
@@ -23,7 +23,7 @@
*/
#include "includes.h"
-RCSID("$OpenBSD: ssh-rsa.c,v 1.24 2002/08/02 21:23:41 markus Exp $");
+RCSID("$OpenBSD: ssh-rsa.c,v 1.25 2002/08/02 22:20:30 markus Exp $");
#include <openssl/evp.h>
#include <openssl/err.h>
@@ -37,6 +37,8 @@
#include "compat.h"
#include "ssh.h"
+static int openssh_RSA_verify(int, u_char *, u_int, u_char *, u_int , RSA *);
+
/* RSASSA-PKCS1-v1_5 (PKCS #1 v2.0 signature) with SHA1 */
int
ssh_rsa_sign(Key *key, u_char **sigp, u_int *lenp,
@@ -167,15 +169,99 @@
EVP_DigestUpdate(&md, data, datalen);
EVP_DigestFinal(&md, digest, &dlen);
- ret = RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
+ ret = openssh_RSA_verify(nid, digest, dlen, sigblob, len, key->rsa);
memset(digest, 'd', sizeof(digest));
memset(sigblob, 's', len);
xfree(sigblob);
- if (ret == 0) {
- int ecode = ERR_get_error();
- error("ssh_rsa_verify: RSA_verify failed: %s",
- ERR_error_string(ecode, NULL));
- }
debug("ssh_rsa_verify: signature %scorrect", (ret==0) ? "in" : "");
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 */
+};
+/*
+ * 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, len, oidlen = 0, hlen = 0;
+ 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;
+ break;
+ }
+ 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 != hlen + oidlen) {
+ error("bad decrypted len: %d != %d + %d", len, hlen, oidlen);
+ goto done;
+ }
+ if (memcmp(decrypted, oid, oidlen) != 0) {
+ error("oid mismatch");
+ goto done;
+ }
+ if (memcmp(decrypted + oidlen, hash, hlen) != 0) {
+ error("hash mismatch");
+ goto done;
+ }
+ ret = 1;
+done:
+ if (decrypted)
+ xfree(decrypted);
+ return ret;
+}