[Bug 1611] New: ssh-keygen prints wrong randomart if bubblebabble is also printed

[bugzilla-daemon at bugzilla.mindrot.org]

https://bugzilla.mindrot.org/show_bug.cgi?id=1611

           Summary: ssh-keygen prints wrong randomart if bubblebabble is
                    also printed
           Product: Portable OpenSSH
           Version: 5.2p1
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: ssh-keygen
        AssignedTo: unassigned-bugs at mindrot.org
        ReportedBy: fwojcik+openssh at besh.com


Created an attachment (id=1651)
 --> (http://bugzilla.mindrot.org/attachment.cgi?id=1651)
Suggested fix to always print out randomart based on MD5

If ssh-keygen is used with both the -B option (to print the
bubblebabble digest of a key) and the -v option (which prints the
randomart), then the randomart will be different than if the -B option
was not used.

Steps to reproduce:
1) Generate a key:
<blockquote>
# ssh-keygen -v -t rsa -b 2048 -f /tmp/garbage
Generating public/private rsa key pair.
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /tmp/garbage.
Your public key has been saved in /tmp/garbage.pub.
The key fingerprint is:
eb:19:8d:76:9e:d8:ee:63:6a:3c:9f:19:d4:37:1c:cc user at hostname
The key's randomart image is:
+--[ RSA 2048]----+
|                 |
|             o   |
|              E  |
|           . . . |
|        S . . +  |
|         =   . . |
|       .= +      |
|       o+Bo=     |
|       .=BX.     |
+-----------------+
</blockquote>

2) Display the fingerprint with ssh-keygen:
<blockquote>
# ssh-keygen -v -l -f /tmp/garbage
2048 eb:19:8d:76:9e:d8:ee:63:6a:3c:9f:19:d4:37:1c:cc /tmp/garbage.pub
(RSA)
+--[ RSA 2048]----+
|                 |
|             o   |
|              E  |
|           . . . |
|        S . . +  |
|         =   . . |
|       .= +      |
|       o+Bo=     |
|       .=BX.     |
+-----------------+
</blockquote>

3) Display the fingerprint and bubblebabble with ssh-keygen:
<blockquote>
# ssh-keygen -B -v -l -f /tmp/garbage
2048 xecen-telud-badez-sozic-hopyd-cacov-tanig-dimov-monef-sytym-haxax
/tmp/garbage.pub (RSA)
+--[ RSA 2048]----+
|  .+.. ....+     |
|... = * =.=      |
|o  E * B *..     |
|. + = . =.o      |
| . .    S.       |
|                 |
|                 |
|                 |
|                 |
+-----------------+
</blockquote>

The problem is that bubblebabble uses the SHA1 digest to generate the
fingerprint, while randomart usually uses the MD5 digest. ssh-keygen.c
will generate randomart with the SHA1 digest if it is also producing
bubblebabble output.

This problem was found on openssh v5.2p1. It also appears to be in
OpenBSD's ssh-keygen.c v1.173.

Diff for fix attached.

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