[openssl/openssl] 0c0c96: EVP_CTRL_AEAD_SET_IV_FIXED: reject arg values belo...

  Branch: refs/heads/master
  Home:   https://github.com/openssl/openssl
  Commit: 0c0c96c2a37f57c92129a8aa7fc46b7a4703983a
      https://github.com/openssl/openssl/commit/0c0c96c2a37f57c92129a8aa7fc46b7a4703983a
  Author: Mohammad Hossein Abedini <[email protected]>
  Date:   2026-08-18 (Tue, 18 Aug 2026)

  Changed paths:
    M crypto/evp/evp_enc.c
    M providers/implementations/ciphers/ciphercommon_gcm.c

  Log Message:
  -----------
  EVP_CTRL_AEAD_SET_IV_FIXED: reject arg values below -1

EVP_CIPHER_CTX_ctrl() casts the signed int arg to size_t before
dispatching.  For EVP_CTRL_AEAD_SET_IV_FIXED the value -1 is an
intentional sentinel ("copy full IV"), so it must be preserved, but
any value below -1 wraps to a near-SIZE_MAX size_t.  The two guards
inside gcm_tls_iv_set_fixed() both fail to catch this:

  * the sentinel check tests for SIZE_MAX (i.e. (size_t)-1), not
    SIZE_MAX-1 or lower;
  * the bounds check back-casts len to int, undoing the wrap and
    making the comparison evaluate to false.

The result is memcpy(ctx->iv, iv, SIZE_MAX-1) — a heap overflow.

Fix the root cause in EVP_CIPHER_CTX_ctrl() by rejecting any arg
below -1 for EVP_CTRL_AEAD_SET_IV_FIXED, consistent with the guards
already present for EVP_CTRL_SET_KEY_LENGTH, EVP_CTRL_AEAD_SET_IVLEN,
EVP_CTRL_GCM_SET_IV_INV and others.

As a defense-in-depth measure, also replace the (int) back-cast in
gcm_tls_iv_set_fixed() with a safe size_t upper-bound check so that
the provider itself rejects any out-of-range length independently of
the caller.

Co-authored-by: Tomáš Mráz <[email protected]> (comment fix)
Reviewed-by: Jakub Zelenka <[email protected]>
Reviewed-by: Paul Dale <[email protected]>
Reviewed-by: Richard Levitte <[email protected]>
Merge-date: Tue Aug 18 07:41:57 2026
Merged-from: https://github.com/openssl/openssl/pull/31879



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