simon-git: putty (master): Simon Tatham

[Commits to Tartarus hosted VCS]

TL;DR:
  8957e613 Add missing sanity checks in ssh_dss_verify.

Repository:     https://git.tartarus.org/simon/putty.git
On the web:     https://git.tartarus.org/?p=simon/putty.git
Branch updated: master
Committer:      Simon Tatham <anakin at pobox.com>
Date:           2019-02-10 20:17:25

commit 8957e613bc1c2574a6ab1190244ae2b4868831ed
web diff https://git.tartarus.org/?p=simon/putty.git;a=commitdiff;h=8957e613bc1c2574a6ab1190244ae2b4868831ed;hp=22131a51fa9790fb57dc9d6cf783535e85e6edc8
Author: Simon Tatham <anakin at pobox.com>
Date:   Sun Feb 10 18:07:27 2019 +0000

    Add missing sanity checks in ssh_dss_verify.
    
    The standard says we should be checking that both r,s are in the range
    [1,q-1]. Previously we were effectively reducing s mod q in the course
    of inversion, and modinv() was guaranteeing never to return zero; the
    remaining missing checks were benign. But the change from Bignum to
    mp_int altered the error behaviour, and combined with the missing
    upper bound check on s, made it possible to continue verification with
    w == 0 mod q, which is a bad case.
    
    Added a small DSA test case, including a check that none of these
    types of signatures validates.

 sshdss.c           |  8 +++++++-
 test/cryptsuite.py | 22 ++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)