Implement getentropy via __wasi_random_get

This allows it to work in standalone mode.

Fixes: emscripten-core#22782

src/library.js

@@ -1292,65 +1292,6 @@ addToLibrary({
 
 #endif // PROXY_POSIX_SOCKETS == 0
 
-  // random.h
-
-  $initRandomFill: () => {
-    if (typeof crypto == 'object' && typeof crypto['getRandomValues'] == 'function') {
-      // for modern web browsers
-#if SHARED_MEMORY
-      // like with most Web APIs, we can't use Web Crypto API directly on shared memory,
-      // so we need to create an intermediate buffer and copy it to the destination
-      return (view) => (
-        view.set(crypto.getRandomValues(new Uint8Array(view.byteLength))),
-        // Return the original view to match modern native implementations.
-        view
-      );
-#else
-      return (view) => crypto.getRandomValues(view);
-#endif
-    } else
-#if ENVIRONMENT_MAY_BE_NODE
-    if (ENVIRONMENT_IS_NODE) {
-      // for nodejs with or without crypto support included
-      try {
-        var crypto_module = require('crypto');
-        var randomFillSync = crypto_module['randomFillSync'];
-        if (randomFillSync) {
-          // nodejs with LTS crypto support
-          return (view) => crypto_module['randomFillSync'](view);
-        }
-        // very old nodejs with the original crypto API
-        var randomBytes = crypto_module['randomBytes'];
-        return (view) => (
-          view.set(randomBytes(view.byteLength)),
-          // Return the original view to match modern native implementations.
-          view
-        );
-      } catch (e) {
-        // nodejs doesn't have crypto support
-      }
-    }
-#endif // ENVIRONMENT_MAY_BE_NODE
-    // we couldn't find a proper implementation, as Math.random() is not suitable for /dev/random, see emscripten-core/emscripten/pull/7096
-#if ASSERTIONS
-    abort('no cryptographic support found for randomDevice. consider polyfilling it if you want to use something insecure like Math.random(), e.g. put this in a --pre-js: var crypto = { getRandomValues: (array) => { for (var i = 0; i < array.length; i++) array[i] = (Math.random()*256)|0 } };');
-#else
-    abort('initRandomDevice');
-#endif
-  },
-
-  $randomFill__deps: ['$initRandomFill'],
-  $randomFill: (view) => {
-    // Lazily init on the first invocation.
-    return (randomFill = initRandomFill())(view);
-  },
-
-  getentropy__deps: ['$randomFill'],
-  getentropy: (buffer, size) => {
-    randomFill(HEAPU8.subarray(buffer, buffer + size));
-    return 0;
-  },
-
   $timers: {},
 
   // Helper function for setitimer that registers timers with the eventloop.

src/library_wasi.js

@@ -568,6 +568,65 @@ var WasiLibrary = {
 #endif // SYSCALLS_REQUIRE_FILESYSTEM
   },
   fd_sync__async: true,
+
+  // random.h
+
+  $initRandomFill: () => {
+    if (typeof crypto == 'object' && typeof crypto['getRandomValues'] == 'function') {
+      // for modern web browsers
+#if SHARED_MEMORY
+      // like with most Web APIs, we can't use Web Crypto API directly on shared memory,
+      // so we need to create an intermediate buffer and copy it to the destination
+      return (view) => (
+        view.set(crypto.getRandomValues(new Uint8Array(view.byteLength))),
+        // Return the original view to match modern native implementations.
+        view
+      );
+#else
+      return (view) => crypto.getRandomValues(view);
+#endif
+    } else
+#if ENVIRONMENT_MAY_BE_NODE
+    if (ENVIRONMENT_IS_NODE) {
+      // for nodejs with or without crypto support included
+      try {
+        var crypto_module = require('crypto');
+        var randomFillSync = crypto_module['randomFillSync'];
+        if (randomFillSync) {
+          // nodejs with LTS crypto support
+          return (view) => crypto_module['randomFillSync'](view);
+        }
+        // very old nodejs with the original crypto API
+        var randomBytes = crypto_module['randomBytes'];
+        return (view) => (
+          view.set(randomBytes(view.byteLength)),
+          // Return the original view to match modern native implementations.
+          view
+        );
+      } catch (e) {
+        // nodejs doesn't have crypto support
+      }
+    }
+#endif // ENVIRONMENT_MAY_BE_NODE
+    // we couldn't find a proper implementation, as Math.random() is not suitable for /dev/random, see emscripten-core/emscripten/pull/7096
+#if ASSERTIONS
+    abort('no cryptographic support found for randomDevice. consider polyfilling it if you want to use something insecure like Math.random(), e.g. put this in a --pre-js: var crypto = { getRandomValues: (array) => { for (var i = 0; i < array.length; i++) array[i] = (Math.random()*256)|0 } };');
+#else
+    abort('initRandomDevice');
+#endif
+  },
+
+  $randomFill__deps: ['$initRandomFill'],
+  $randomFill: (view) => {
+    // Lazily init on the first invocation.
+    return (randomFill = initRandomFill())(view);
+  },
+
+  random_get__deps: ['$randomFill'],
+  random_get: (buffer, size) => {
+    randomFill(HEAPU8.subarray(buffer, buffer + size));
+    return 0;
+  },
 };
 
 for (var x in WasiLibrary) {

system/lib/libc/musl/src/linux/getrandom.c

@@ -3,5 +3,9 @@
 
 ssize_t getrandom(void *buf, size_t buflen, unsigned flags)
 {
+#if __EMSCRIPTEN__
+	return __wasi_syscall_ret(__wasi_random_get(buffer, length));
+#else
 	return syscall_cp(SYS_getrandom, buf, buflen, flags);
+#endif
 }

system/lib/libc/musl/src/misc/getentropy.c

@@ -4,6 +4,10 @@
 #include <pthread.h>
 #include <errno.h>
 
+#ifdef __EMSCRIPTEN__
+#include <wasi/wasi-helpers.h>
+#endif
+
 int getentropy(void *buffer, size_t len)
 {
 	int cs, ret = 0;
@@ -16,6 +20,9 @@ int getentropy(void *buffer, size_t len)
 
 	pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
 
+#ifdef __EMSCRIPTEN__
+	ret = __wasi_syscall_ret(__wasi_random_get(buffer, len));
+#else
 	while (len) {
 		ret = getrandom(pos, len, 0);
 		if (ret < 0) {
@@ -26,6 +33,7 @@ int getentropy(void *buffer, size_t len)
 		len -= ret;
 		ret = 0;
 	}
+#endif
 
 	pthread_setcancelstate(cs, 0);
 

system/lib/standalone/standalone.c

@@ -136,12 +136,6 @@ weak int __syscall_lstat64(intptr_t path, intptr_t buf) {
   return -ENOSYS;
 }
 
-// There is no good source of entropy without an import. Make this weak so that
-// it can be replaced with a pRNG or a proper import.
-weak int getentropy(void* buffer, size_t length) {
-  abort();
-}
-
 // Emscripten additions
 
 size_t emscripten_get_heap_max() {

tools/system_libs.py

@@ -1098,7 +1098,6 @@ def get_files(self):
         'ppoll.c',
         'syscall.c', 'popen.c', 'pclose.c',
         'getgrouplist.c', 'initgroups.c', 'wordexp.c', 'timer_create.c',
-        'getentropy.c',
         'getauxval.c',
         'lookup_name.c',
         # 'process' exclusion