Fix OSS-Fuzz #428053935 (php#18969)

Registering the constant may happen under another name due to
lowercasing. This will cause the lookup to the constant to fail.
Instead of looking it up, just change the Zend API to return a pointer
instead.

Author: nielsdos

UPGRADING.INTERNALS

@@ -45,6 +45,8 @@ PHP 8.5 INTERNALS UPGRADE NOTES
     properties.
   . ZEND_IS_XDIGIT() macro was removed because it was unused and its name
     did not match its actual behavior.
+  . zend_register_constant() now returns a pointer to the added constant
+    on success and NULL on failure instead of SUCCESS/FAILURE.
 
 ========================
 2. Build system changes

Zend/tests/attributes/constants/oss_fuzz_428053935.phpt

@@ -0,0 +1,19 @@
+--TEST--
+OSS-Fuzz #428053935
+--FILE--
+<?php
+namespace Foo; // Capital letter is important for the ns lookup
+#[Attr]
+const MyConst = '';
+
+$rc = new \ReflectionConstant('Foo\\MyConst');
+var_dump($rc->getAttributes());
+?>
+--EXPECTF--
+array(1) {
+  [0]=>
+  object(ReflectionAttribute)#%d (1) {
+    ["name"]=>
+    string(8) "Foo\Attr"
+  }
+}

Zend/zend_builtin_functions.c

@@ -592,7 +592,7 @@ ZEND_FUNCTION(define)
 	/* non persistent */
 	ZEND_CONSTANT_SET_FLAGS(&c, 0, PHP_USER_CONSTANT);
 	c.name = zend_string_copy(name);
-	if (zend_register_constant(&c) == SUCCESS) {
+	if (zend_register_constant(&c) != NULL) {
 		RETURN_TRUE;
 	} else {
 		RETURN_FALSE;

Zend/zend_constants.c

@@ -505,11 +505,11 @@ static void* zend_hash_add_constant(HashTable *ht, zend_string *key, zend_consta
 	return ret;
 }
 
-ZEND_API zend_result zend_register_constant(zend_constant *c)
+ZEND_API zend_constant *zend_register_constant(zend_constant *c)
 {
 	zend_string *lowercase_name = NULL;
 	zend_string *name;
-	zend_result ret = SUCCESS;
+	zend_constant *ret = NULL;
 	bool persistent = (ZEND_CONSTANT_FLAGS(c) & CONST_PERSISTENT) != 0;
 
 #if 0
@@ -539,7 +539,7 @@ ZEND_API zend_result zend_register_constant(zend_constant *c)
 	/* Check if the user is trying to define any special constant */
 	if (zend_string_equals_literal(name, "__COMPILER_HALT_OFFSET__")
 		|| (!persistent && zend_get_special_const(ZSTR_VAL(name), ZSTR_LEN(name)))
-		|| zend_hash_add_constant(EG(zend_constants), name, c) == NULL
+		|| (ret = zend_hash_add_constant(EG(zend_constants), name, c)) == NULL
 	) {
 		zend_error(E_WARNING, "Constant %s already defined", ZSTR_VAL(name));
 		zend_string_release(c->name);
@@ -550,7 +550,6 @@ ZEND_API zend_result zend_register_constant(zend_constant *c)
 		if (!persistent) {
 			zval_ptr_dtor_nogc(&c->value);
 		}
-		ret = FAILURE;
 	}
 	if (lowercase_name) {
 		zend_string_release(lowercase_name);

Zend/zend_constants.h

@@ -97,7 +97,7 @@ ZEND_API void zend_register_long_constant(const char *name, size_t name_len, zen
 ZEND_API void zend_register_double_constant(const char *name, size_t name_len, double dval, int flags, int module_number);
 ZEND_API void zend_register_string_constant(const char *name, size_t name_len, const char *strval, int flags, int module_number);
 ZEND_API void zend_register_stringl_constant(const char *name, size_t name_len, const char *strval, size_t strlen, int flags, int module_number);
-ZEND_API zend_result zend_register_constant(zend_constant *c);
+ZEND_API zend_constant *zend_register_constant(zend_constant *c);
 void zend_constant_add_attributes(zend_constant *c, HashTable *attributes);
 #ifdef ZTS
 void zend_copy_constants(HashTable *target, HashTable *source);

Zend/zend_vm_def.h

@@ -8261,7 +8261,7 @@ ZEND_VM_HANDLER(143, ZEND_DECLARE_CONST, CONST, CONST)
 	ZEND_CONSTANT_SET_FLAGS(&c, 0, PHP_USER_CONSTANT);
 	c.name = zend_string_copy(Z_STR_P(name));
 
-	if (zend_register_constant(&c) == FAILURE) {
+	if (zend_register_constant(&c) == NULL) {
 	}
 
 	FREE_OP1();
@@ -8274,7 +8274,7 @@ ZEND_VM_HANDLER(210, ZEND_DECLARE_ATTRIBUTED_CONST, CONST, CONST)
 	USE_OPLINE
 	zval *name;
 	zval *val;
-	zend_constant c;
+	zend_constant c, *registered;
 
 	SAVE_OPLINE();
 	name  = GET_OP1_ZVAL_PTR(BP_VAR_R);
@@ -8293,17 +8293,16 @@ ZEND_VM_HANDLER(210, ZEND_DECLARE_ATTRIBUTED_CONST, CONST, CONST)
 	ZEND_CONSTANT_SET_FLAGS(&c, 0, PHP_USER_CONSTANT);
 	c.name = zend_string_copy(Z_STR_P(name));
 
-	if (zend_register_constant(&c) == FAILURE) {
+	registered = zend_register_constant(&c);
+	if (registered == NULL) {
 		FREE_OP1();
 		FREE_OP2();
 		/* two opcodes used, second one is the data with attributes */
 		ZEND_VM_NEXT_OPCODE_EX(1, 2);
 	}
 
 	HashTable *attributes = Z_PTR_P(GET_OP_DATA_ZVAL_PTR(BP_VAR_R));
-	zend_constant *registered = zend_get_constant_ptr(c.name);
 	ZEND_ASSERT(attributes != NULL);
-	ZEND_ASSERT(registered != NULL);
 	zend_constant_add_attributes(registered, attributes);
 
 	FREE_OP1();