Bug 428439

Description of problem:
Customer is always getting a segmentation fault whenever trying to authenticate
on  a sshd server with pam_krb5 configured to convert Krb5 credentials to Krb4.
This was a new feature added on request of this very customer with BZ#201265.

An uninitialized variable could be passed down the stack, after a quick chat
with the package maintainer (nalin) I have written the attached patch
"pam_krb5-2.1.17-1.navid_uninit_ctx.diff" which appears to solve the issue for
the customer.

Version-Release number of selected component (if applicable):
pam_krb5-2.1.17

How reproducible:
100%

Steps to Reproduce:
1. on the ssh server, edited /etc/krb5.conf and added:

[appdefaults]
pam = {
 krb4_convert = true
 external = sshd
}

2. on the ssh client, edited /etc/ssh/ssh_config and added:

GSSAPIDelegateCredentials=yes

3. Update pam system-auth to do the krb4 conversion
  
Actual results:
Connection is closed since sshd dies after successful authentication:
ssh(1562) debug1: Authentications that can continue:
publickey,gssapi-with-mic,password
ssh(1562) debug1: Next authentication method: gssapi-with-mic
ssh(1562) debug1: Delegating credentials
ssh(1562) debug1: Delegating credentials
ssh(1562) debug1: Authentication succeeded (gssapi-with-mic).
ssh(1562) debug1: channel 0: new [client-session]
ssh(1562) debug1: Entering interactive session.
ssh(1562) debug1: channel 0: free: client-session, nchannels 1
Connection to refrh4es-i386 closed by remote host.
Connection to refrh4es-i386 closed.
ssh(1562) debug1: Transferred: stdin 0, stdout 0, stderr 89 bytes in 0.2 seconds


Server-side:
debug3: mm_share_sync: Share sync
debug3: mm_share_sync: Share sync end
debug1: temporarily_use_uid: 0/0 (e=0/0)
debug1: restore_uid: 0/0
debug1: PAM: establishing credentials
debug3: PAM: opening session
Segmentation fault (core dumped)

Expected results:
sshd stays alive and authentication succeeds or sshd fails gracefully

Additional info: