Port random numbers to use wasip2 methods

Author: catamorphism

libc-bottom-half/sources/getentropy.c

@@ -1,19 +1,43 @@
 #include <errno.h>
 #include <unistd.h>
+#ifdef __wasilibc_use_wasip2
+#include <wasi/wasip2.h>
+#else
 #include <wasi/api.h>
+#endif
 
 int __getentropy(void *buffer, size_t len) {
     if (len > 256) {
         errno = EIO;
         return -1;
     }
 
-    int r = __wasi_random_get(buffer, len);
+#ifdef __wasilibc_use_wasip2
+    // Set up a WASI byte list to receive the results
+    wasip2_list_u8_t wasi_list;
+
+    // Get random bytes
+    random_get_random_bytes(len, &wasi_list);
+
+    // Copy the result into the provided buffer
+    memcpy(buffer, wasi_list.ptr, wasi_list.len);
+
+    // Free the WASI byte list
+    wasip2_list_u8_free(&wasi_list);
 
+    // It's an error if random_get_random_bytes returned
+    // fewer (or more) bytes than requested
+    if (wasi_list.len != len) {
+        errno = EINVAL;
+        return -1;
+    }
+#else
+    int r = __wasi_random_get(buffer, len);
     if (r != 0) {
         errno = r;
         return -1;
     }
+#endif
 
     return 0;
 }

libc-top-half/musl/src/env/__stack_chk_fail.c

@@ -38,12 +38,36 @@ hidden void __stack_chk_fail_local(void);
 weak_alias(__stack_chk_fail, __stack_chk_fail_local);
 
 #ifndef __wasilibc_unmodified_upstream
+#ifdef __wasilibc_use_wasip2
+# include <wasi/wasip2.h>
+#else
 # include <wasi/api.h>
+#endif
 
 __attribute__((constructor(60)))
 static void __wasilibc_init_ssp(void) {
 	uintptr_t entropy;
+#ifdef __wasilibc_use_wasip2
+        int r = 0;
+        int len = sizeof(uintptr_t);
+
+        // Set up a WASI byte list to receive the results
+        wasip2_list_u8_t wasi_list;
+
+        // Get random bytes
+        random_get_random_bytes(len, &wasi_list);
+        if (wasi_list.len != len)
+            r = -1;
+        else {
+            // Copy the result
+            memcpy(&entropy, wasi_list.ptr, len);
+        }
+
+        // Free the WASI byte list
+        wasip2_list_u8_free(&wasi_list);
+#else
 	int r = __wasi_random_get((uint8_t *)&entropy, sizeof(uintptr_t));
+#endif
 	__init_ssp(r ? NULL : &entropy);
 }
 #endif

test/src/misc/getentropy.c

@@ -0,0 +1,31 @@
+//! add-flags.py(CFLAGS): -I.
+//! add-flags.py(ARGS): foo bar
+#include <limits.h>
+#include <stdio.h>
+#include "test.h"
+
+#define TEST(c, ...) \
+	( (c) || (t_error(#c " failed: " __VA_ARGS__),0) )
+
+int main()
+{
+        size_t len = 256;
+        uint8_t buffer[len];
+
+        TEST(getentropy(&buffer, len) == 0, "getentropy() should return 0");
+        int all_zeroes = 1;
+
+        for (size_t i = 0; i < len; i++) {
+            if (buffer[i] != 0) {
+                all_zeroes = 0;
+                break;
+            }
+        }
+
+        TEST(all_zeroes == 0, "getentropy() returned 256 zeroes");
+
+        // More than 256 bytes is an error
+        TEST(getentropy(&buffer, 257)==-1);
+
+        return t_status;
+}