- 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

diff --git a/ChangeLog b/ChangeLog
index f1dd8a726be5a5b88774f818add2170c6fafc687..22a3a92d28107a7f018e49ccf69e57939f46059d 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -73,6 +73,11 @@
      add comment:
      key_verify returns 1 for a correct signature, 0 for an incorrect signature
      and -1 on error.
+   - 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
 
 20020604
  - (stevesk) [channels.c] bug #164 patch from YOSHIFUJI Hideaki (changed

diff --git a/ssh-rsa.c b/ssh-rsa.c
index fe4dc1f8dfffbd8da198e126ef63ab636bdec07c..458c9c840efab6d4375b655de7ce18d2a3090059 100644 (file)
--- 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);