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Improve the performance of PBKDF2 #24178

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baefd51
Improve the performance of PBKDF2
Sjord Oct 7, 2026
ce7d853
Assert return value of hash_copy
Sjord Oct 7, 2026
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27 changes: 22 additions & 5 deletions ext/hash/hash.c
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Original file line number Diff line number Diff line change
Expand Up @@ -487,6 +487,12 @@ 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, const void *base_context, void *context, const unsigned char *data, const zend_long data_size) {
ZEND_ASSERT(SUCCESS == 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 @@ -982,7 +988,7 @@ PHP_FUNCTION(hash_pbkdf2)
size_t pass_len, salt_len = 0;
bool raw_output = false;
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 @@ -1013,6 +1019,9 @@ 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 @@ -1023,6 +1032,12 @@ 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 @@ -1051,8 +1066,8 @@ 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 @@ -1064,8 +1079,8 @@ 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 @@ -1081,6 +1096,8 @@ PHP_FUNCTION(hash_pbkdf2)
efree(K2);
efree(computed_salt);
php_hash_free_context(ops, context);
php_hash_free_context(ops, inner_context);
php_hash_free_context(ops, outer_context);
efree(digest);
efree(temp);

Expand Down
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