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Fix bug #62397 - disable_functions does not work with eval. #4084

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Fix bug #62397 - disable_functions does not work with eval. #4084

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14 changes: 14 additions & 0 deletions Zend/tests/errmsg_046.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,14 @@
--TEST--
errmsg: disabled eval function
--INI--
disable_functions=eval
--FILE--
<?php

eval('echo "Eval";');

echo "Done\n";
?>
--EXPECTF--
Warning: eval() has been disabled for security reasons in %s on line %d
Done
12 changes: 12 additions & 0 deletions Zend/zend_API.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2751,6 +2751,12 @@ ZEND_API int zend_set_hash_symbol(zval *symbol, const char *name, int name_lengt

/* Disabled functions support */

zend_op_array *display_disabled_compile_string(zval *source_string, char *filename)
{
zend_error(E_WARNING, "eval() has been disabled for security reasons");
return NULL;
}

/* {{{ proto void display_disabled_function(void)
Dummy function which displays an error when a disabled function is called. */
ZEND_API ZEND_FUNCTION(display_disabled_function)
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@carusogabriel carusogabriel Apr 28, 2019 •
edited
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The added display_disabled_compile_string function is because we can't use this one?

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Yes, the signatures are different. display_disabled_function has the signature of an internal function and it can be replaced as function pointer in the function_table (see zend_disable_function just below this code in the same file).

The eval disable support makes use of the function pointer to zend_compile_string which can be replaced with different implementation using the same idea as the function table disable functionality.

Expand All @@ -2762,6 +2768,12 @@ ZEND_API ZEND_FUNCTION(display_disabled_function)
ZEND_API int zend_disable_function(char *function_name, size_t function_name_length) /* {{{ */
{
zend_internal_function *func;

if (strcmp(function_name, "eval") == 0) {
zend_compile_string = display_disabled_compile_string;
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This is a terrible idea. It makes Xdebug not being able to change variables, or allow for watches either, if eval is turned off this way. Xdebug uses zend_eval_string, which calls zend_compile_string that you now override with something broken. Not only that, as it is not easily chained, changing this back in an extension reliably is a pain. This should be reverted.

return SUCCESS;
}

if ((func = zend_hash_str_find_ptr(CG(function_table), function_name, function_name_length))) {
func->fn_flags &= ~(ZEND_ACC_VARIADIC | ZEND_ACC_HAS_TYPE_HINTS);
func->num_args = 0;
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