Export wasi_random_get(). (#68)

Signed-off-by: Piotr Sikora <piotrsikora@google.com>

BUILD

@@ -33,6 +33,7 @@ cc_library(
     copts = COPTS,
     deps = [
         ":include",
+        "@boringssl//:crypto",
         "@com_google_protobuf//:protobuf_lite",
         "@proxy_wasm_cpp_sdk//:api_lib",
     ],

WORKSPACE

@@ -38,6 +38,13 @@ git_repository(
     shallow_since = "1565024848 -0700",
 )
 
+http_archive(
+    name = "boringssl",
+    sha256 = "bb55b0ed2f0cb548b5dce6a6b8307ce37f7f748eb9f1be6bfe2d266ff2b4d52b",
+    strip_prefix = "boringssl-2192bbc878822cf6ab5977d4257a1339453d9d39",
+    urls = ["https://github.com/google/boringssl/archive/2192bbc878822cf6ab5977d4257a1339453d9d39.tar.gz"],
+)
+
 http_archive(
     name = "com_google_googletest",
     sha256 = "9dc9157a9a1551ec7a7e43daea9a694a0bb5fb8bec81235d8a1e6ef64c716dcb",

include/proxy-wasm/exports.h

@@ -145,6 +145,7 @@ Word wasi_unstable_args_get(void *raw_context, Word argc_ptr, Word argv_buf_size
 Word wasi_unstable_args_sizes_get(void *raw_context, Word argc_ptr, Word argv_buf_size_ptr);
 void wasi_unstable_proc_exit(void *, Word);
 Word wasi_unstable_clock_time_get(void *, Word, uint64_t, Word);
+Word wasi_unstable_random_get(void *, Word, Word);
 Word pthread_equal(void *, Word left, Word right);
 
 // Support for embedders, not exported to Wasm.

src/exports.cc

@@ -15,6 +15,8 @@
 //
 #include "include/proxy-wasm/wasm.h"
 
+#include <openssl/rand.h>
+
 #define WASM_CONTEXT(_c)                                                                           \
   (ContextOrEffectiveContext(static_cast<ContextBase *>((void)_c, current_context_)))
 
@@ -814,6 +816,17 @@ Word wasi_unstable_clock_time_get(void *raw_context, Word clock_id, uint64_t pre
   return 0; // __WASI_ESUCCESS
 }
 
+// __wasi_errno_t __wasi_random_get(uint8_t *buf, size_t buf_len);
+Word wasi_unstable_random_get(void *raw_context, Word result_buf_ptr, Word buf_len) {
+  auto context = WASM_CONTEXT(raw_context);
+  std::vector<uint8_t> random(buf_len);
+  RAND_bytes(random.data(), random.size());
+  if (!context->wasmVm()->setMemory(result_buf_ptr, random.size(), random.data())) {
+    return 21; // __WASI_EFAULT
+  }
+  return 0; // __WASI_ESUCCESS
+}
+
 // void __wasi_proc_exit(__wasi_exitcode_t rval);
 void wasi_unstable_proc_exit(void *raw_context, Word) {
   auto context = WASM_CONTEXT(raw_context);

src/wasm.cc

@@ -132,6 +132,7 @@ void WasmBase::registerCallbacks() {
   _REGISTER_WASI(args_get);
   _REGISTER_WASI(args_sizes_get);
   _REGISTER_WASI(clock_time_get);
+  _REGISTER_WASI(random_get);
   _REGISTER_WASI(proc_exit);
 #undef _REGISTER_WASI