Description:
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in ./ext/hash/hash.c, line 559

The hash_copy() function does not copy the hash->key field. It only copies the pointer. Because of hash_final() clears the key, the result of hash_final of copied hashing resource gives wrong results. It causes random PHP crashes too, because the pointer to the HMAC key can be invalid (released within the other hashing context).

Test script:
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$h = hash_init('crc32b', HASH_HMAC, '123456' );
$h2 = hash_copy($h);
var_dump(hash_final($h));
var_dump(hash_final($h2));

echo '<-- These two results should be the same.';

Expected result:
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string(8) "278af264" string(8) "278af264" <-- These two results should be the same.

Actual result:
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string(8) "278af264" string(8) "07997b35" <-- These two results should be the same.