[openssl/openssl] a24fbf: SLH-DSA: Fix Integer overflow in msg_encode leadin...

[Shane]

Branch: refs/heads/master
Home: https://github.com/openssl/openssl
Commit: a24fbf403a891ec026847f70bef1fd582b1e9601
https://github.com/openssl/openssl/commit/a24fbf403a891ec026847f70bef1fd582b1e9601
Author: slontis <shane....@oracle.com>
Date: 2026-03-22 (Sun, 22 Mar 2026)

Changed paths:
M crypto/slh_dsa/slh_dsa.c

Log Message:
-----------
SLH-DSA: Fix Integer overflow in msg_encode leading to buffer overflow

Reported by Zehua Qiao and m...@snkth.com

An encode message buffer M = 00 || CXT_LEN || CTX || MSG was being
allocated followed by memcpy's into the buffer for CTX and MSG.
If len(MSG) was close to size_t the allocated buffer would be
overwritten.

The fix uses WPACKET to perform the message encoding M = 00 || CXT_LEN || CTX || MSG

Although ML_DSA does a similiar operation, SLH-DSA has to buffer the
encoding because the encoded message is processed multiple times for
PRF_MSG and H_MSG. FOr ML_DSA the encoded message can just be hashed.

Fixes: 2f9e152d86a7 "Add SLH_DSA signature verification."

Reviewed-by: Tomas Mraz <to...@openssl.foundation>
Reviewed-by: Matt Caswell <ma...@openssl.foundation>
Reviewed-by: Eugene Syromiatnikov <es...@openssl.org>
MergeDate: Sun Mar 22 00:15:47 2026
(Merged from https://github.com/openssl/openssl/pull/30477)



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