Port random numbers to use wasip2 methods (#612)

Author: catamorphism

expected/wasm32-wasip2/defined-symbols.txt

@@ -381,6 +381,7 @@ __wasilibc_nocwd_utimensat
 __wasilibc_open_nomode
 __wasilibc_populate_preopens
 __wasilibc_pthread_self
+__wasilibc_random
 __wasilibc_register_preopened_fd
 __wasilibc_rename_newat
 __wasilibc_rename_oldat

libc-bottom-half/headers/public/wasi/libc.h

@@ -3,6 +3,7 @@
 
 #include <__typedef_off_t.h>
 #include <__struct_timespec.h>
+#include <unistd.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -67,6 +68,10 @@ int __wasilibc_rename_newat(const char *oldpath, int newdirfd, const char *newpa
 /// Enable busywait in futex on current thread.
 void __wasilibc_enable_futex_busywait_on_current_thread(void);
 
+/// Fill a buffer with random bytes
+int __wasilibc_random(void* buffer, size_t len)
+   __attribute__((__warn_unused_result__));
+
 #ifdef __cplusplus
 }
 #endif

libc-bottom-half/sources/__wasilibc_random.c

@@ -0,0 +1,29 @@
+#include <errno.h>
+#include <unistd.h>
+#ifdef __wasilibc_use_wasip2
+#include <wasi/wasip2.h>
+#include <sysexits.h>
+
+int __wasilibc_random(void *buffer, size_t len) {
+
+        // 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);
+
+        // The spec for get-random-bytes specifies that wasi_list.len
+        // will be equal to len.
+        if (wasi_list.len != len)
+            _Exit(EX_OSERR);
+        else {
+            // Copy the result
+            memcpy(buffer, wasi_list.ptr, len);
+        }
+
+        // Free the WASI byte list
+        wasip2_list_u8_free(&wasi_list);
+
+        return 0;
+}
+#endif

libc-bottom-half/sources/getentropy.c

@@ -1,20 +1,26 @@
 #include <errno.h>
 #include <unistd.h>
+#ifdef __wasilibc_use_wasip2
+#include <wasi/libc.h>
+#else
 #include <wasi/api.h>
+#endif
 
 int __getentropy(void *buffer, size_t len) {
     if (len > 256) {
         errno = EIO;
         return -1;
     }
 
+#ifdef __wasilibc_use_wasip2
+    int r = __wasilibc_random(buffer, len);
+#else
     int r = __wasi_random_get(buffer, len);
-
+#endif
     if (r != 0) {
         errno = r;
         return -1;
     }
-
     return 0;
 }
 weak_alias(__getentropy, getentropy);

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

@@ -38,12 +38,22 @@ 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/libc.h>
+#else
 # include <wasi/api.h>
+#endif
 
 __attribute__((constructor(60)))
 static void __wasilibc_init_ssp(void) {
 	uintptr_t entropy;
+#ifdef __wasilibc_use_wasip2
+        int len = sizeof(uintptr_t);
+
+        int r = __wasilibc_random(&entropy, len);
+#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\n");
+        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\n");
+
+        // More than 256 bytes is an error
+        TEST(getentropy(&buffer, 257)==-1, "requesting > 256 bytes should be an error\n");
+
+        return t_status;
+}