fix: Fix OOB on String.UTF8.encode when nullTerminated (#2173)

Author: romdotdog

std/assembly/string.ts

@@ -709,6 +709,8 @@ export namespace String {
         if (c1 < 128) {
           store<u8>(bufOff, c1);
           bufOff++;
+          // @ts-ignore: cast
+          if (nullTerminated & !c1) return bufOff - buf;
         } else if (c1 < 2048) {
           let b0 = c1 >> 6 | 192;
           let b1 = c1 & 63 | 128;

tests/compiler/std-wasi/crypto.untouched.wat

@@ -208,6 +208,16 @@
      i32.const 1
      i32.add
      local.set $6
+     local.get $3
+     local.get $8
+     i32.eqz
+     i32.and
+     if
+      local.get $6
+      local.get $2
+      i32.sub
+      return
+     end
     else
      local.get $8
      i32.const 2048
@@ -341,7 +351,7 @@
         if
          i32.const 32
          i32.const 96
-         i32.const 739
+         i32.const 741
          i32.const 49
          call $~lib/wasi/index/abort
          unreachable

tests/compiler/std-wasi/process.untouched.wat

@@ -232,6 +232,16 @@
      i32.const 1
      i32.add
      local.set $6
+     local.get $3
+     local.get $8
+     i32.eqz
+     i32.and
+     if
+      local.get $6
+      local.get $2
+      i32.sub
+      return
+     end
     else
      local.get $8
      i32.const 2048
@@ -365,7 +375,7 @@
         if
          i32.const 112
          i32.const 176
-         i32.const 739
+         i32.const 741
          i32.const 49
          call $~lib/wasi/index/abort
          unreachable
@@ -7825,7 +7835,7 @@
   if
    i32.const 0
    i32.const 176
-   i32.const 767
+   i32.const 769
    i32.const 7
    call $~lib/wasi/index/abort
    unreachable

tests/compiler/std/string-encoding.optimized.wat

@@ -89,6 +89,9 @@ function testUTF8EncodeNullTerminated(): void {
   assert(load<u8>(ptr, 8) == 0xAD);
   assert(load<u8>(ptr, 9) == 0xA2);
   assert(load<u8>(ptr, 10) == 0x00);
+  var str2 ="aaaaaaaaaaaaaaaaaaaaaaaaaaa\0";
+  var buf2 = String.UTF8.encode(str2, true);
+  assert(buf2.byteLength == String.UTF8.byteLength(str2, true));
 }
 testUTF8EncodeNullTerminated();
 

tests/compiler/std/string-encoding.ts

@@ -77,6 +77,16 @@
      i32.const 1
      i32.add
      local.set $6
+     local.get $3
+     local.get $8
+     i32.eqz
+     i32.and
+     if
+      local.get $6
+      local.get $2
+      i32.sub
+      return
+     end
     else
      local.get $8
      i32.const 2048
@@ -210,7 +220,7 @@
         if
          i32.const 32
          i32.const 96
-         i32.const 739
+         i32.const 741
          i32.const 49
          call $~lib/wasi/index/abort
          unreachable

tests/compiler/std/string-encoding.untouched.wat

@@ -206,6 +206,16 @@
      i32.const 1
      i32.add
      local.set $6
+     local.get $3
+     local.get $8
+     i32.eqz
+     i32.and
+     if
+      local.get $6
+      local.get $2
+      i32.sub
+      return
+     end
     else
      local.get $8
      i32.const 2048
@@ -339,7 +349,7 @@
         if
          i32.const 80
          i32.const 144
-         i32.const 739
+         i32.const 741
          i32.const 49
          call $~lib/wasi/index/abort
          unreachable