PR/58468 CVS commit: src/sys/external/isc/libsodium/include

["Taylor R Campbell" <riastradh%netbsd.org@localhost>]

The following reply was made to PR kern/58468; it has been noted by GNATS.

From: "Taylor R Campbell" <riastradh%netbsd.org@localhost>
To: gnats-bugs%gnats.NetBSD.org@localhost
Cc: 
Subject: PR/58468 CVS commit: src/sys/external/isc/libsodium/include
Date: Fri, 26 Jul 2024 18:27:48 +0000

 Module Name:	src
 Committed By:	riastradh
 Date:		Fri Jul 26 18:27:48 UTC 2024
 
 Modified Files:
 	src/sys/external/isc/libsodium/include: crypto_verify_16.h
 
 Log Message:
 sys/crypto/sodium: Fill out crypto_verify_16 stub.
 
 Without this change, libsodium silently accepts forgeries.
 
 This one's a doozy, and it's a sobering reminder that:
 
 (a) wg(4) is still experimental (only user of libsodium in kernel;
     both are available only through default-off optional modules).
 
 (b) Known-answer test vectors are critical, including negative tests
     (test that forgeries are rejected), and must be mandatory for all
     new crypto code -- and should be added to old crypto code too.
 
 (c) Crypto code must also have self-tests that run in the same
     environment, not just the same code in a different build or test
     environment -- the libsodium code itself is fine, but we built it
     differently and need to exercise it differently from upstream's
     automatic tests.
 
 It's my fault for not catching this earlier.  What happened is:
 
 1. ozaki-r@ adapted libsodium to build in the kernel with various
    glue to build code meant for standard userland C, like errno.h and
    string.h.
 
 2. Since libsodium's crypto_verify_16.c uses various SIMD intrinsics
    on various architectures, it couldn't be used directly in the
    kernel build, because -- at the time -- we hadn't wired up any
    header files for SIMD intrinsics or any runtime support for saving
    and restoring SIMD state appropriately in the kernel.
 
 3. ozaki-r@ put a similar glue header file crypto_verify_16.h to
    override libsodium's, with a stub to be implemented later, and
    presumably forgot to remind me about it.
 
 4. I missed the stub in crypto_verify_16.h when reviewing the
    libsodium import and wg(4) code because it was in the same
    directory as various other simple glue code that I deemed
    low-risk.
 
    (I did make one change to that glue code, to replace cprng_fast by
    cprng_strong, but I suspect I found that by searching for
    cprng_fast users rather than by reviewing this code.)
 
 5. I broke my own rule about always having known-answer test vectors
    for crypto code because I figured libsodium was well-enough
    exercised that we could skimp on it for now, and my focus was more
    on the state machine and synchronization logic than on the crypto.
 
 6. I had not yet written known-answer test vectors for the
    higher-level wg(4) protocol messages.
 
 Before we can remove the `experimental' tag from wg(4) we will need
 to (among other things):
 
   i. Write self-tests for the rest of (what we use from) libsodium.
  ii. Write extensive known-answer test vectors for all the wg(4)
      protocol messages (and ideally state machine transitions).
 iii. Write self-tests for a reasonable subset of the wg(4) KATs.
  iv. Review all of the libsodium glue code I neglected to review.
 
 PR kern/58468
 
 
 To generate a diff of this commit:
 cvs rdiff -u -r1.1 -r1.2 \
     src/sys/external/isc/libsodium/include/crypto_verify_16.h
 
 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.