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pam_krb5: Fix spoofing vulnerability

Description

pam_krb5: Fix spoofing vulnerability

An adversary on the network can log in via ssh as any user by spoofing
the KDC. When the machine has a keytab installed the keytab is used to
verify the service ticket. However, without a keytab there is no way
for pam_krb5 to verify the KDC's response and get a TGT with the
password.

If both the password _and_ the KDC are controlled by an adversary, the
adversary can provide a password that the adversary's spoofed KDC will
return a valid tgt for. Currently, without a keytab, pam_krb5 is
vulnerable to this attack.

Reported by: Taylor R Campbell <riastradh@netbsd.org> via emaste@
Reviewed by: so
Approved by: so
Security: FreeBSD-SA-23:04.pam_krb5
Security: CVE-2023-3326

(cherry picked from commit 813847e49e35439ba5d7bf16034b0691312068a4)

Details

Provenance
cyAuthored on May 31 2023, 7:20 PM
gordonCommitted on Jun 21 2023, 5:26 AM
Parents
rGf7d696685337: xdr(3): Fix a typo in a source code comment
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