[krbdev.mit.edu #9181] git commit

[Greg Hudson via RT]

<URL: https://krbdev.mit.edu/rt/Ticket/Display.html?id=9181 >


Fix krb5 GSS MIC verification

Commit 7ae0adcdf16687810f747e284c9fb571a561c5bd contains a pair of
bugs that, in combination, result in the acceptance of MIC tokens with
invalid checksums.

In kg_verify_checksum_v3(), properly set bytes 4..7 to 0xFF in the
composed token header for MIC tokens.  In verify_mic_v3(), properly
check the return value of kg_verify_checksum_v3().  In t_invalid.c,
test invalid MIC tokens by altering the bytes of a valid MIC.

Reported by Francis Dupont.

CVE-2025-57736:

MIT krb5 release 1.22 incorrectly accepts krb5 GSS-API MIC tokens with
invalid checksums.

https://github.com/krb5/krb5/commit/83cd76b11b069afbc6162edecb30096571e89dd5
Author: Greg Hudson <ghudson at mit.edu>
Commit: 83cd76b11b069afbc6162edecb30096571e89dd5
Branch: master
 src/lib/gssapi/krb5/util_crypt.c | 10 +++++++---
 src/lib/gssapi/krb5/verify_mic.c | 11 ++++-------
 src/tests/gssapi/t_invalid.c     | 29 +++++++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 10 deletions(-)