Improve error reporting in random extension (php#9071)

* Use `php_random_bytes_throw()` in Secure engine's generate()

This exposes the underlying exception, improving debugging:

    Fatal error: Uncaught Exception: Cannot open source device in php-src/test.php:5
    Stack trace:
    #0 php-src/test.php(5): Random\Engine\Secure->generate()
    #1 {main}

    Next RuntimeException: Random number generation failed in php-src/test.php:5
    Stack trace:
    #0 php-src/test.php(5): Random\Engine\Secure->generate()
    #1 {main}
      thrown in php-src/test.php on line 5

* Use `php_random_int_throw()` in Secure engine's range()

This exposes the underlying exception, improving debugging:

    Exception: Cannot open source device in php-src/test.php:17
    Stack trace:
    #0 php-src/test.php(17): Random\Randomizer->getInt(1, 3)
    #1 {main}

    Next RuntimeException: Random number generation failed in php-src/test.php:17
    Stack trace:
    #0 php-src/test.php(17): Random\Randomizer->getInt(1, 3)
    #1 {main}

* Throw exception when a user engine returns an empty string

This improves debugging, because the actual reason for the failure is available
as a previous Exception:

    DomainException: The returned string must not be empty in php-src/test.php:17
    Stack trace:
    #0 php-src/test.php(17): Random\Randomizer->getBytes(123)
    #1 {main}

    Next RuntimeException: Random number generation failed in php-src/test.php:17
    Stack trace:
    #0 php-src/test.php(17): Random\Randomizer->getBytes(123)
    #1 {main}

* Throw exception when the range selector fails to get acceptable numbers in 50 attempts

This improves debugging, because the actual reason for the failure is available
as a previous Exception:

    RuntimeException: Failed to generate an acceptable random number in 50 attempts in php-src/test.php:17
    Stack trace:
    #0 php-src/test.php(17): Random\Randomizer->getInt(1, 3)
    #1 {main}

    Next RuntimeException: Random number generation failed in php-src/test.php:17
    Stack trace:
    #0 php-src/test.php(17): Random\Randomizer->getInt(1, 3)
    #1 {main}

* Improve user_unsafe test

Select parameters for ->getInt() that will actually lead to unsafe behavior.

* Fix user_unsafe test

If an engine fails once it will be permanently poisoned by setting
`->last_unsafe`. This is undesirable for the test, because it skews the
results.

Fix this by creating a fresh engine for each "assertion".

* Remove duplication in user_unsafe.phpt

* Catch `Throwable` in user_unsafe.phpt

As we print the full stringified exception we implicitly assert the type of the
exception. No need to be overly specific in the catch block.

* Throw an error if an engine returns an empty string

* Throw an Error if range fails to find an acceptable number in 50 attempts

Author: TimWolla

ext/random/engine_secure.c

@@ -29,7 +29,7 @@ static uint64_t generate(php_random_status *status)
 {
 	zend_ulong r = 0;
 
-	if (php_random_bytes_silent(&r, sizeof(zend_ulong)) == FAILURE) {
+	if (php_random_bytes_throw(&r, sizeof(zend_ulong)) == FAILURE) {
 		status->last_unsafe = true;
 	}
 
@@ -38,9 +38,9 @@ static uint64_t generate(php_random_status *status)
 
 static zend_long range(php_random_status *status, zend_long min, zend_long max)
 {
-	zend_long result;
+	zend_long result = 0;
 
-	if (php_random_int_silent(min, max, &result) == FAILURE) {
+	if (php_random_int_throw(min, max, &result) == FAILURE) {
 		status->last_unsafe = true;
 	}
 

ext/random/engine_user.c

@@ -50,6 +50,7 @@ static uint64_t generate(php_random_status *status)
 			result += ((uint64_t) (unsigned char) Z_STRVAL(retval)[i]) << (8 * i);
 		}
 	} else {
+		zend_throw_error(NULL, "A random engine must return a non-empty string");
 		status->last_unsafe = true;
 		return 0;
 	}

ext/random/random.c

@@ -82,6 +82,8 @@ static zend_object_handlers random_engine_xoshiro256starstar_object_handlers;
 static zend_object_handlers random_engine_secure_object_handlers;
 static zend_object_handlers random_randomizer_object_handlers;
 
+#define RANDOM_RANGE_ATTEMPTS (50)
+
 static inline uint32_t rand_range32(const php_random_algo *algo, php_random_status *status, uint32_t umax)
 {
 	uint32_t result, limit, r;
@@ -118,7 +120,8 @@ static inline uint32_t rand_range32(const php_random_algo *algo, php_random_stat
 	/* Discard numbers over the limit to avoid modulo bias */
 	while (UNEXPECTED(result > limit)) {
 		/* If the requirements cannot be met in a cycles, return fail */
-		if (++count > 50) {
+		if (++count > RANDOM_RANGE_ATTEMPTS) {
+			zend_throw_error(NULL, "Failed to generate an acceptable random number in %d attempts", RANDOM_RANGE_ATTEMPTS);
 			status->last_unsafe = true;
 			return 0;
 		}
@@ -174,7 +177,8 @@ static inline uint64_t rand_range64(const php_random_algo *algo, php_random_stat
 	/* Discard numbers over the limit to avoid modulo bias */
 	while (UNEXPECTED(result > limit)) {
 		/* If the requirements cannot be met in a cycles, return fail */
-		if (++count > 50) {
+		if (++count > RANDOM_RANGE_ATTEMPTS) {
+			zend_throw_error(NULL, "Failed to generate an acceptable random number in %d attempts", RANDOM_RANGE_ATTEMPTS);
 			status->last_unsafe = true;
 			return 0;
 		}

ext/random/tests/03_randomizer/user_unsafe.phpt

@@ -3,81 +3,155 @@ Random: Randomizer: User: Engine unsafe
 --FILE--
 <?php
 
-// Empty generator
-$randomizer = (new \Random\Randomizer(
-    new class () implements \Random\Engine {
-        public function generate(): string
-        {
-            return '';
-        }
-    }
-));
+use Random\Randomizer;
 
-try {
-    var_dump($randomizer->getInt(\PHP_INT_MIN, \PHP_INT_MAX));
-} catch (\RuntimeException $e) {
-    echo $e->getMessage() . PHP_EOL;
+final class EmptyStringEngine implements \Random\Engine {
+    public function generate(): string
+    {
+        return '';
+    }
 }
 
-try {
-    var_dump(bin2hex($randomizer->getBytes(1)));
-} catch (\RuntimeException $e) {
-    echo $e->getMessage() . PHP_EOL;
+final class HeavilyBiasedEngine implements \Random\Engine {
+    public function generate(): string
+    {
+        return "\xff\xff\xff\xff\xff\xff\xff\xff";
+    }
 }
 
-try {
-    var_dump($randomizer->shuffleArray(\range(1, 10)));
-} catch (\RuntimeException $e) {
-    echo $e->getMessage() . PHP_EOL;
-}
+echo "=====================", PHP_EOL;
 
-try {
-    var_dump($randomizer->shuffleBytes('foobar'));
-} catch (\RuntimeException $e) {
-    echo $e->getMessage() . PHP_EOL;
-}
+foreach ([
+    EmptyStringEngine::class,
+    HeavilyBiasedEngine::class,
+] as $engine) {
+    echo $engine, PHP_EOL, "=====================", PHP_EOL, PHP_EOL;
 
-// Infinite loop
-$randomizer = (new \Random\Randomizer(
-    new class () implements \Random\Engine {
-        public function generate(): string
-        {
-            return "\xff\xff\xff\xff\xff\xff\xff\xff";
-        }
+    try {
+        var_dump((new Randomizer(new $engine()))->getInt(0, 123));
+    } catch (Throwable $e) {
+        echo $e, PHP_EOL;
+    }
+    
+    echo PHP_EOL, "-------", PHP_EOL, PHP_EOL;
+    
+    try {
+        var_dump(bin2hex((new Randomizer(new $engine()))->getBytes(1)));
+    } catch (Throwable $e) {
+        echo $e, PHP_EOL;
+    }
+    
+    echo PHP_EOL, "-------", PHP_EOL, PHP_EOL;
+    
+    try {
+        var_dump((new Randomizer(new $engine()))->shuffleArray(\range(1, 10)));
+    } catch (Throwable $e) {
+        echo $e, PHP_EOL;
+    }
+    
+    echo PHP_EOL, "-------", PHP_EOL, PHP_EOL;
+    
+    try {
+        var_dump((new Randomizer(new $engine()))->shuffleBytes('foobar'));
+    } catch (Throwable $e) {
+        echo $e, PHP_EOL;
     }
-));
 
-try {
-    var_dump($randomizer->getInt(\PHP_INT_MIN, \PHP_INT_MAX));
-} catch (\RuntimeException $e) {
-    echo $e->getMessage() . PHP_EOL;
+    echo PHP_EOL, "=====================", PHP_EOL;
 }
 
-try {
-    var_dump(bin2hex($randomizer->getBytes(1)));
-} catch (\RuntimeException $e) {
-    echo $e->getMessage() . PHP_EOL;
-}
+?>
+--EXPECTF--
+=====================
+EmptyStringEngine
+=====================
 
-try {
-    var_dump($randomizer->shuffleArray(\range(1, 10)));
-} catch (\RuntimeException $e) {
-    echo $e->getMessage() . PHP_EOL;
-}
+Error: A random engine must return a non-empty string in %s:%d
+Stack trace:
+#0 %s(%d): Random\Randomizer->getInt(0, 123)
+#1 {main}
 
-try {
-    var_dump($randomizer->shuffleBytes('foobar'));
-} catch (\RuntimeException $e) {
-    echo $e->getMessage() . PHP_EOL;
-}
+Next RuntimeException: Random number generation failed in %s:%d
+Stack trace:
+#0 %s(%d): Random\Randomizer->getInt(0, 123)
+#1 {main}
+
+-------
+
+Error: A random engine must return a non-empty string in %s:%d
+Stack trace:
+#0 %s(%d): Random\Randomizer->getBytes(1)
+#1 {main}
+
+Next RuntimeException: Random number generation failed in %s:%d
+Stack trace:
+#0 %s(%d): Random\Randomizer->getBytes(1)
+#1 {main}
+
+-------
+
+Error: A random engine must return a non-empty string in %s:%d
+Stack trace:
+#0 %s(%d): Random\Randomizer->shuffleArray(Array)
+#1 {main}
+
+Next RuntimeException: Random number generation failed in %s:%d
+Stack trace:
+#0 %s(%d): Random\Randomizer->shuffleArray(Array)
+#1 {main}
+
+-------
+
+Error: A random engine must return a non-empty string in %s:%d
+Stack trace:
+#0 %s(%d): Random\Randomizer->shuffleBytes('foobar')
+#1 {main}
+
+Next RuntimeException: Random number generation failed in %s:%d
+Stack trace:
+#0 %s(%d): Random\Randomizer->shuffleBytes('foobar')
+#1 {main}
+
+=====================
+HeavilyBiasedEngine
+=====================
+
+Error: Failed to generate an acceptable random number in 50 attempts in %s:%d
+Stack trace:
+#0 %s(%d): Random\Randomizer->getInt(0, 123)
+#1 {main}
+
+Next RuntimeException: Random number generation failed in %s:%d
+Stack trace:
+#0 %s(%d): Random\Randomizer->getInt(0, 123)
+#1 {main}
+
+-------
 
-?>
---EXPECTF--
-Random number generation failed
-Random number generation failed
-Random number generation failed
-Random number generation failed
-int(%d)
 string(2) "ff"
-Random number generation failed
-Random number generation failed
+
+-------
+
+Error: Failed to generate an acceptable random number in 50 attempts in %s:%d
+Stack trace:
+#0 %s(%d): Random\Randomizer->shuffleArray(Array)
+#1 {main}
+
+Next RuntimeException: Random number generation failed in %s:%d
+Stack trace:
+#0 %s(%d): Random\Randomizer->shuffleArray(Array)
+#1 {main}
+
+-------
+
+Error: Failed to generate an acceptable random number in 50 attempts in %s:%d
+Stack trace:
+#0 %s(%d): Random\Randomizer->shuffleBytes('foobar')
+#1 {main}
+
+Next RuntimeException: Random number generation failed in %s:%d
+Stack trace:
+#0 %s(%d): Random\Randomizer->shuffleBytes('foobar')
+#1 {main}
+
+=====================