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ext/hash: improve PBKDF2 performance #24188

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690e0ac
Improve PBKDF2 performance
Sjord Oct 8, 2026
5db5b7a
Fix const qualifier warning, don't put side-effect within assert
Sjord Oct 8, 2026
1ac5ffe
Fixup PBKDF2 performance fixes
Sjord Oct 17, 2026
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3 changes: 3 additions & 0 deletions NEWS
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,9 @@ PHP NEWS
. Fixed GHSA-62xp-839h-2637 (IPv6 ACL bypass in FastCGI listen.allowed_clients
due to partial address comparison). (CVE-2026-91768) (Alexandre Daubois)

- Hash:
. Improved performance of hash_pbkdf2. (Sjoerd Langkemper)

@LamentXU123 LamentXU123 Oct 8, 2026

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Feel free to add a UPGRADING entry.


- MySQLnd:
. Fixed GHSA-r6x9-5r99-36j7 (Various packet overreads in mysqlnd wire
protocol). (CVE-2025-1218) (Jakub Zelenka, Nora Dossche)
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4 changes: 4 additions & 0 deletions UPGRADING
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Expand Up @@ -592,3 +592,7 @@ PHP 8.2 UPGRADE NOTES
========================================
14. Performance Improvements
========================================

- Hash:
. hash_pbkdf2() is now faster. Applications using PBKDF2 may consider whether
their iteration count can be increased.
29 changes: 24 additions & 5 deletions ext/hash/hash.c
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Expand Up @@ -497,6 +497,12 @@ static inline void php_hash_hmac_round(unsigned char *final, const php_hash_ops
ops->hash_final(final, context);
}

static inline void php_hash_hmac_round_with_copy(unsigned char *final, const php_hash_ops *ops, void *base_context, void *context, const unsigned char *data, const zend_long data_size) {
ops->hash_copy(ops, base_context, context);
ops->hash_update(context, data, data_size);
ops->hash_final(final, context);
}

static void php_hash_do_hash_hmac(
zval *return_value, zend_string *algo, char *data, size_t data_len, char *key, size_t key_len, bool raw_output, bool isfilename
) /* {{{ */ {
Expand Down Expand Up @@ -996,7 +1002,7 @@ PHP_FUNCTION(hash_pbkdf2)
size_t pass_len, salt_len = 0;
bool raw_output = 0;
const php_hash_ops *ops;
void *context;
void *context, *inner_context, *outer_context;
HashTable *args = NULL;

if (zend_parse_parameters(ZEND_NUM_ARGS(), "Sssl|lbh", &algo, &pass, &pass_len, &salt, &salt_len, &iterations, &length, &raw_output, &args) == FAILURE) {
Expand Down Expand Up @@ -1027,6 +1033,9 @@ PHP_FUNCTION(hash_pbkdf2)
context = php_hash_alloc_context(ops);
ops->hash_init(context, args);

inner_context = php_hash_alloc_context(ops);
outer_context = php_hash_alloc_context(ops);

K1 = emalloc(ops->block_size);
K2 = emalloc(ops->block_size);
digest = emalloc(ops->digest_size);
Expand All @@ -1037,6 +1046,12 @@ PHP_FUNCTION(hash_pbkdf2)
/* Convert K1 to opad -- 0x6A = 0x36 ^ 0x5C */
php_hash_string_xor_char(K2, K1, 0x6A, ops->block_size);

/* Precompute the hash states after absorbing the ipad and opad blocks */
ops->hash_init(inner_context, NULL);
ops->hash_update(inner_context, K1, ops->block_size);
ops->hash_init(outer_context, NULL);
ops->hash_update(outer_context, K2, ops->block_size);

/* Setup Main Loop to build a long enough result */
if (length == 0) {
length = ops->digest_size;
Expand Down Expand Up @@ -1065,8 +1080,8 @@ PHP_FUNCTION(hash_pbkdf2)
computed_salt[salt_len + 2] = (unsigned char) ((i & 0xFF00) >> 8);
computed_salt[salt_len + 3] = (unsigned char) (i & 0xFF);

php_hash_hmac_round(digest, ops, context, K1, computed_salt, (zend_long) salt_len + 4);
php_hash_hmac_round(digest, ops, context, K2, digest, ops->digest_size);
php_hash_hmac_round_with_copy(digest, ops, inner_context, context, computed_salt, (zend_long) salt_len + 4);
php_hash_hmac_round_with_copy(digest, ops, outer_context, context, digest, ops->digest_size);
/* } */

/* temp = digest */
Expand All @@ -1078,8 +1093,8 @@ PHP_FUNCTION(hash_pbkdf2)
*/
for (j = 1; j < iterations; j++) {
/* digest = hash_hmac(digest, password) { */
php_hash_hmac_round(digest, ops, context, K1, digest, ops->digest_size);
php_hash_hmac_round(digest, ops, context, K2, digest, ops->digest_size);
php_hash_hmac_round_with_copy(digest, ops, inner_context, context, digest, ops->digest_size);
php_hash_hmac_round_with_copy(digest, ops, outer_context, context, digest, ops->digest_size);
/* } */
/* temp ^= digest */
php_hash_string_xor(temp, temp, digest, ops->digest_size);
Expand All @@ -1095,6 +1110,10 @@ PHP_FUNCTION(hash_pbkdf2)
efree(K2);
efree(computed_salt);
efree(context);
ZEND_SECURE_ZERO(inner_context, ops->context_size);
ZEND_SECURE_ZERO(outer_context, ops->context_size);
efree(inner_context);
efree(outer_context);
efree(digest);
efree(temp);

Expand Down
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