[PHP-INTERNALS] refcount problems created by openssl_public_encrypt(symbol table corruption and double free)

On 5/25/05, Kamesh Jayachandran wrote:
Hi Wez & Jani,
Following snippet causes double free of memory, corrupts the symbol
table.
<?php
$pk=false;//As openssl_get_publickey($nonsense) can give false
openssl_public_encrypt("Test",$encrypted,$pk);
$pk=false;
?>

The culprit is php_openssl_evp_from_zval which is called by
openssl_public_encrypt.
openssl_public_encrypt reduces the refcount of $pk from 2 to 1.
zend_ptr_stack_clear_multiple reduces it again to 0 as a normal cleanup
upon return from openssl_public_encrypt.
And hence zval associated with $pk is getting freed.
But symbol table still refers to freed pointer.

The patch for 5.0 Tree is available at,
http://puggy.symonds.net/~kameshj/openssl.c.patch.5.0

With regards
Kamesh Jayachandran

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The patch doesn't look quite right.

- convert_to_string_ex(val);
+ zval tmpz;
+ zval *tmpzp;
+ tmpz = *(*val);
+ zval_copy_ctor(&tmpz);
+ tmpz.refcount=1;
+ tmpzp = &tmpz;

I think that this is a place where convert_to_string(val) should be
used instead.

- in = BIO_new_mem_buf(Z_STRVAL_PP(val),
Z_STRLEN_PP(val));
+ in = BIO_new_mem_buf(Z_STRVAL_PP(&tmpzp),
Z_STRLEN_PP(&tmpzp));

If you still need to use zval* instead of zval**, you can use
Z_STRVAL_P(tmpzp) instead of taking the address and using
Z_STRVAL_PP().

Can you check your patch again using convert_to_string() instead?

--Wez.