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Merge bitcoin-core/secp256k1#1783: Add VERIFY_CHECKs and documentation that flags must be 0 or 1

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ae00c552df Add VERIFY_CHECKs that flags are 0 or 1 (John Moffett)

Pull request description:

  Flags for constant-time masking rely on the values being exactly `0` or `1` rather than `0` or true (any nonzero). One function, `secp256k1_fe_cmov` [documents](e7f7083b53/src/field.h (L315)) and [`VERIFY_CHECK`s](e7f7083b53/src/field_impl.h (L365)) this, but most don't.

  This updates the documentation and adds `VERIFY_CHECK`s enforcing `flag == 0 || flag == 1` for:

  `secp256k1_fe_storage_cmov`
  `secp256k1_gej_cmov`
  `secp256k1_ge_storage_cmov`
  `secp256k1_scalar_cadd_bit`
  `secp256k1_scalar_cond_negate`
  `secp256k1_scalar_cmov`
  `secp256k1_int_cmov`

ACKs for top commit:
  furszy:
    ACK ae00c55
  hebasto:
    re-ACK ae00c552df.

Tree-SHA512: c9d358929d39d93b0aea602d318429f7e82af96bf601f048a1cdeb0621b8adc6d1204648d352aa2060cb0f63db6dcf0da863854375ed313cea44dfad61c19a18
This commit is contained in:
merge-script
2025-12-15 20:43:58 +01:00
parent aa2a39c1a7 ae00c552df
commit 8d445730ec
11 changed files with 30 additions and 8 deletions
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3
src/modules/musig/session_impl.h
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@@ -69,7 +69,8 @@ static int secp256k1_musig_secnonce_load(const secp256k1_context* ctx, secp256k1
return 1;
}
/* If flag is true, invalidate the secnonce; otherwise leave it. Constant-time. */
/* If flag is 1, invalidate the secnonce; if flag is 0, leave it.
* Constant-time. Flag must be 0 or 1. */
static void secp256k1_musig_secnonce_invalidate(const secp256k1_context* ctx, secp256k1_musig_secnonce *secnonce, int flag) {
secp256k1_memczero(secnonce->data, sizeof(secnonce->data), flag);
/* The flag argument is usually classified. So, the line above makes the