From c960b3b0c6e430ff2dfdb776bf1c990e62f3f18b Mon Sep 17 00:00:00 2001
From: Frank Denis <github@pureftpd.org>
Date: Tue, 22 Sep 2026 10:36:31 +0200
Subject: [PATCH] Emscripten: simplify randomness extraction

Use getentropy() for small buffers and WASI random_get for
larger buffers.
---
 dist-build/emscripten.sh                | 48 +------------
 src/libsodium/randombytes/randombytes.c | 91 ++++++-------------------
 2 files changed, 21 insertions(+), 118 deletions(-)

diff --git a/dist-build/emscripten.sh b/dist-build/emscripten.sh
index a8ff7893..2d548719 100755
--- a/dist-build/emscripten.sh
+++ b/dist-build/emscripten.sh
@@ -156,49 +156,6 @@ if [ "$DIST" = yes ]; then
         root = window;
       }
     }
-    if (typeof Module.getRandomValue === 'undefined') {
-      try {
-        var window_ = 'object' === typeof window ? window : self;
-        var crypto_ = typeof window_.crypto !== 'undefined' ? window_.crypto : window_.msCrypto;
-        var randomValuesStandard = function() {
-          var buf = new Uint32Array(1);
-          crypto_.getRandomValues(buf);
-          return buf[0] >>> 0;
-        };
-        randomValuesStandard();
-        Module.getRandomValue = randomValuesStandard;
-        Module.getRandomBytes = function(ptr, size) {
-          var heapu8 = Module.HEAPU8;
-          var chunk = 65536;
-          while (size > chunk) {
-            var buf = new Uint8Array(chunk);
-            crypto_.getRandomValues(buf);
-            heapu8.set(buf, ptr);
-            ptr += chunk;
-            size -= chunk;
-          }
-          var buf = new Uint8Array(size);
-          crypto_.getRandomValues(buf);
-          heapu8.set(buf, ptr);
-        };
-      } catch (e) {
-        try {
-          var crypto = require('crypto');
-          var randomValueNodeJS = function() {
-            var buf = crypto['randomBytes'](4);
-            return (buf[0] << 24 | buf[1] << 16 | buf[2] << 8 | buf[3]) >>> 0;
-          };
-          randomValueNodeJS();
-          Module.getRandomValue = randomValueNodeJS;
-          Module.getRandomBytes = function(ptr, size) {
-            var buf = crypto['randomBytes'](size);
-            Module.HEAPU8.set(buf, ptr);
-          };
-        } catch (e) {
-          throw 'No secure random number generator found';
-        }
-      }
-    }
     var _Module = Module;
     Module.ready = new Promise(function(resolve, reject) {
       var Module = _Module;
@@ -222,13 +179,10 @@ if [ "$DIST" = yes ]; then
         return new Promise(function(resolve, reject) {
           var Module = {};
           Module.onAbort = reject;
-          Module.getRandomValue = _Module.getRandomValue;
 
           Module.onRuntimeInitialized = function() {
             Object.keys(_Module).forEach(function(k) {
-              if (k !== 'getRandomValue') {
-                delete _Module[k];
-              }
+              delete _Module[k];
             });
             Object.keys(Module).forEach(function(k) {
               _Module[k] = Module[k];
diff --git a/src/libsodium/randombytes/randombytes.c b/src/libsodium/randombytes/randombytes.c
index 3ef16fb4..68583c65 100644
--- a/src/libsodium/randombytes/randombytes.c
+++ b/src/libsodium/randombytes/randombytes.c
@@ -7,7 +7,8 @@
 #include <sys/types.h>
 
 #ifdef __EMSCRIPTEN__
-# include <emscripten.h>
+# include <unistd.h>
+# include <wasi/api.h>
 #endif
 
 #include "core.h"
@@ -44,85 +45,33 @@ javascript_implementation_name(void)
 static uint32_t
 javascript_random(void)
 {
-    return EM_ASM_INT_V({
-        return Module.getRandomValue();
-    });
+    uint32_t r;
+
+    if (getentropy(&r, sizeof r) != 0) {
+        sodium_misuse();
+    }
+    return r;
 }
 
 static void
 javascript_stir(void)
 {
-    EM_ASM({
-        if (Module.getRandomValue === undefined) {
-            try {
-                var window_ = 'object' === typeof window ? window : self;
-                var crypto_ = typeof window_.crypto !== 'undefined' ? window_.crypto : window_.msCrypto;
-                crypto_ = (crypto_ === undefined) ? crypto : crypto_;
-                var randomValuesStandard = function() {
-                    var buf = new Uint32Array(1);
-                    crypto_.getRandomValues(buf);
-                    return buf[0] >>> 0;
-                };
-                randomValuesStandard();
-                Module.getRandomValue = randomValuesStandard;
-                Module.getRandomBytes = function(ptr, size) {
-                    var heapu8 = HEAPU8;
-                    var chunk = 65536;
-                    while (size > chunk) {
-                        var buf = new Uint8Array(chunk);
-                        crypto_.getRandomValues(buf);
-                        heapu8.set(buf, ptr);
-                        ptr += chunk;
-                        size -= chunk;
-                    }
-                    var buf = new Uint8Array(size);
-                    crypto_.getRandomValues(buf);
-                    heapu8.set(buf, ptr);
-                };
-            } catch (e) {
-                try {
-                    var crypto = require('crypto');
-                    var randomValueNodeJS = function() {
-                        var buf = crypto['randomBytes'](4);
-                        return (buf[0] << 24 | buf[1] << 16 | buf[2] << 8 | buf[3]) >>> 0;
-                    };
-                    randomValueNodeJS();
-                    Module.getRandomValue = randomValueNodeJS;
-                    Module.getRandomBytes = function(ptr, size) {
-                        var buf = crypto['randomBytes'](size);
-                        HEAPU8.set(buf, ptr);
-                    };
-                } catch (e) {
-                    throw 'No secure random number generator found';
-                }
-            }
-        }
-        if (Module.getRandomBytes === undefined) {
-            Module.getRandomBytes = function(ptr, size) {
-                var heapu8 = HEAPU8;
-                for (var i = 0; i < size; i++) {
-                    heapu8[ptr + i] = Module.getRandomValue() & 0xff;
-                }
-            };
-        }
-    });
+    (void) javascript_random();
 }
 
 static void
-javascript_buf(void * const buf, const size_t size)
+javascript_buf(void * const buf, size_t size)
 {
-    if (size > (size_t) 0U) {
-        EM_ASM({
-            if (Module.getRandomBytes === undefined) {
-                Module.getRandomBytes = function(ptr, size) {
-                    var heapu8 = HEAPU8;
-                    for (var i = 0; i < size; i++) {
-                        heapu8[ptr + i] = Module.getRandomValue() & 0xff;
-                    }
-                };
-            }
-            Module.getRandomBytes($0, $1);
-        }, buf, size);
+    unsigned char *p = (unsigned char *) buf;
+    size_t         chunk_size;
+
+    while (size > (size_t) 0U) {
+        chunk_size = size > 65536U ? 65536U : size;
+        if (__wasi_random_get(p, chunk_size) != 0) {
+            sodium_misuse();
+        }
+        p += chunk_size;
+        size -= chunk_size;
     }
 }
 #endif