- markus@cvs.openbsd.org 2002/05/31 13:20:50

     [ssh-rsa.c]
     pad received signature with leading zeros, because RSA_verify expects
     a signature of RSA_size. the drafts says the signature is transmitted
     unpadded (e.g. putty does not pad), reported by anakin@pobox.com

1 files changed, 17 insertions, 2 deletions

diff --git a/ssh-rsa.c b/ssh-rsa.c
index fe4dc1f8d..458c9c840 100644
--- a/ssh-rsa.c
+++ b/ssh-rsa.c
@@ -23,7 +23,7 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: ssh-rsa.c,v 1.18 2002/04/02 20:11:38 markus Exp $");
+RCSID("$OpenBSD: ssh-rsa.c,v 1.19 2002/05/31 13:20:50 markus Exp $");
 
 #include <openssl/evp.h>
 #include <openssl/err.h>
@@ -115,7 +115,7 @@ ssh_rsa_verify(
         EVP_MD_CTX md;
         char *ktype;
         u_char digest[EVP_MAX_MD_SIZE], *sigblob;
-        u_int len, dlen;
+        u_int len, dlen, modlen;
         int rlen, ret, nid;
 
         if (key == NULL || key->type != KEY_RSA || key->rsa == NULL) {
@@ -145,6 +145,21 @@ ssh_rsa_verify(
                 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 %d > modlen %d", len, modlen);
+                xfree(sigblob);
+                return -1;
+        } else if (len < modlen) {
+                int diff = modlen - len;
+                debug("ssh_rsa_verify: add padding: modlen %d > len %d",
+                    modlen, len);
+                sigblob = xrealloc(sigblob, 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);