Add cflite and document normalize path (#280)

* make it clear resolve_path expects null-terminated string

Signed-off-by: David Korczynski <david@adalogics.com>

Author: DavidKorczynski

.clusterfuzzlite/Dockerfile

@@ -0,0 +1,6 @@
+FROM gcr.io/oss-fuzz-base/base-builder
+RUN apt-get update && apt-get install -y make autoconf automake libtool
+COPY . $SRC/uvwasi
+COPY .clusterfuzzlite/build.sh $SRC/build.sh
+COPY .clusterfuzzlite/*.c $SRC/
+WORKDIR uvwasi

.clusterfuzzlite/build.sh

@@ -0,0 +1,11 @@
+# Disable building of shared library
+#sed -i 's/add\_library(uvwasi SHARED/# /g' CMakeLists.txt
+mkdir build
+cd build
+cmake ../
+make uvwasi_a
+
+$CC $CFLAGS $LIB_FUZZING_ENGINE ../.clusterfuzzlite/fuzz_normalize_path.c \
+  -o $OUT/fuzz_normalize_path \
+  ./libuvwasi_a.a _deps/libuv-build/libuv_a.a \
+  -I$SRC/uvwasi/include -I$PWD/_deps/libuv-src/include/

.clusterfuzzlite/fuzz_normalize_path.c

@@ -0,0 +1,25 @@
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "../src/path_resolver.h"
+
+#define BUFFER_SIZE 128
+
+char normalized_buffer[BUFFER_SIZE+1];
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+  char *new_str = (char *)malloc(size + 1);
+  if (new_str == NULL) {
+    return 0;
+  }
+  memcpy(new_str, data, size);
+  new_str[size] = '\0';
+
+  memset(normalized_buffer, 0, BUFFER_SIZE);
+
+  uvwasi__normalize_path(new_str, size, normalized_buffer, BUFFER_SIZE);
+
+  free(new_str);
+  return 0;
+}

.clusterfuzzlite/project.yaml

@@ -0,0 +1 @@
+language: c

.github/workflows/cflite.yml

@@ -0,0 +1,29 @@
+name: ClusterFuzzLite PR fuzzing
+on:
+  workflow_dispatch:
+  pull_request:
+    branches: [ main ]
+permissions: read-all
+jobs:
+  PR:
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        sanitizer: [address]
+    steps:
+    - name: Build Fuzzers (${{ matrix.sanitizer }})
+      id: build
+      uses: google/clusterfuzzlite/actions/build_fuzzers@v1
+      with:
+        sanitizer: ${{ matrix.sanitizer }}
+        language: c
+        bad-build-check: false
+    - name: Run Fuzzers (${{ matrix.sanitizer }})
+      id: run
+      uses: google/clusterfuzzlite/actions/run_fuzzers@v1
+      with:
+        fuzz-seconds: 100
+        mode: 'code-change'
+        report-unreproducible-crashes: false
+        sanitizer: ${{ matrix.sanitizer }}

README.md

@@ -2500,6 +2500,26 @@ To do a release complete the following steps:
 * Update uvwasi in Node.js or any projects you want to update - there are several
   other projects that use uvwasi.
 
+## Running fuzzers locally
+
+We support fuzzing by way of [ClusterFuzzLite](https://google.github.io/clusterfuzzlite/),
+which is run automatically against pull requests. You can run these fuzzers
+locally with the [OSS-Fuzz](https://github.com/google/oss-fuzz)  fuzzing
+infrastructure, using the following steps:
+
+```sh
+git clone https://github.com/google/oss-fuzz
+git clone https://github.com/nodejs/uvwasi
+cd uvwasi
+
+# Build the fuzzers in .clusterfuzzlite
+python3 ../oss-fuzz/infra/helper.py build_fuzzers --external $PWD
+
+# Run the fuzzer for 10 seconds
+python3 ../oss-fuzz/infra/helper.py run_fuzzer --external $PWD fuzz_normalize_path -- -max_total_time=10
+```
+
+
 [WASI]: https://github.com/WebAssembly/WASI
 [libuv]: https://github.com/libuv/libuv
 [preview 1]: https://github.com/WebAssembly/WASI/blob/main/legacy/preview1/docs.md

src/path_resolver.c

@@ -72,6 +72,10 @@ uvwasi_errno_t uvwasi__normalize_path(const char* path,
                                       uvwasi_size_t path_len,
                                       char* normalized_path,
                                       uvwasi_size_t normalized_len) {
+  /* Normalizes path and stores the resulting buffer in normalized_path.
+     the sizes of the buffers must correspond to strlen() of the relevant
+     buffers, i.e. there must be room in the relevant buffers for a
+     NULL-byte. */
   const char* cur;
   char* ptr;
   char* next;
@@ -345,7 +349,8 @@ static uvwasi_errno_t uvwasi__resolve_path_to_host(
                                               char** resolved_path,
                                               uvwasi_size_t* resolved_len
                                             ) {
-  /* Return the normalized path, but resolved to the host's real path. */
+  /* Return the normalized path, but resolved to the host's real path.
+     `path` must be a NULL-terminated string. */
   char* res_path;
   char* stripped_path;
   int real_path_len;