openssl_sign() cannot sign a precomputed digest

Description

Description

openssl_sign() currently always performs the digest operation internally before signing the data.

This causes a problem when the input is already a precomputed digest.

For example, when a SHA-256 digest is passed to openssl_sign() together with OPENSSL_ALGO_SHA256, the digest is hashed again:

signature = sign(SHA256(precomputed_sha256_digest))

instead of signing the existing digest directly:

signature = sign(precomputed_sha256_digest)

As a result, PHP currently has no straightforward way to sign an already computed digest using ext/openssl.

Expected behavior

It should be possible to pass a precomputed digest to the OpenSSL extension and sign it directly without applying another hashing operation.

The same should be possible for verification of a signature over a precomputed digest.

Actual behavior

openssl_sign() combines hashing and signing. Therefore, when the caller already has the digest, an additional hashing operation is performed.

Additional information

OpenSSL provides lower-level APIs such as EVP_PKEY_sign() and EVP_PKEY_verify() that can operate on already prepared input.

PHP's OpenSSL extension currently does not expose an equivalent way to perform this operation.

PHP Version

PHP 8.5

Operating System

all

PHP の ext/openssl にある openssl_sign() エントリポイントから開始し、現在のダイジェスト処理の動作を、言及されている EVP_PKEY_sign() および EVP_PKEY_verify() API と比較します。署名と検証の両方をカバーする、事前計算済み入力用のインターフェースを決定します。呼び出し側が既存のダイジェストを再度ハッシュせずに署名および検証できれば完了です。