Add fuzz target

.github/workflows/on_PR_linux_fuzz.yml

@@ -0,0 +1,30 @@
+# Builds and runs the fuzz target for a short amount of time.  This is
+# mainly to protect the fuzz target from bitrot, but hopefully will
+# also help to quickly catch some bugs before the PR is merged.
+
+name: Linux-Ubuntu Quick Fuzz on PRs
+
+on:
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  Linux:
+    name: 'Ubuntu 20.04 - clang/libFuzzer'
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: install dependencies
+      run: sudo ./ci/install_dependencies.sh
+    - name: build and compile
+      run: |
+        mkdir build && cd build
+        cmake -DEXIV2_ENABLE_PNG=ON -DEXIV2_ENABLE_WEBREADY=ON -DEXIV2_ENABLE_CURL=ON -DEXIV2_ENABLE_BMFF=ON -DEXIV2_TEAM_WARNINGS_AS_ERRORS=ON -DCMAKE_CXX_COMPILER=$(which clang++) -DEXIV2_BUILD_FUZZ_TESTS=ON -DEXIV2_TEAM_USE_SANITIZERS=ON ..
+        make -j $(nproc)
+
+    - name: Fuzz
+      run: |
+        cd build
+        mkdir corpus
+        ./bin/fuzz-read-print-write corpus ../test/data/ -jobs=$(nproc) -workers=$(nproc) -max_total_time=120 -max_len=4096

CMakeLists.txt

@@ -35,6 +35,7 @@ option( EXIV2_ENABLE_BMFF             "Build with BMFF support"
 option( EXIV2_BUILD_SAMPLES           "Build sample applications"                             ON  )
 option( EXIV2_BUILD_EXIV2_COMMAND     "Build exiv2 command-line executable"                   ON  )
 option( EXIV2_BUILD_UNIT_TESTS        "Build unit tests"                                      OFF )
+option( EXIV2_BUILD_FUZZ_TESTS        "Build fuzz tests (libFuzzer)"                          OFF )
 option( EXIV2_BUILD_DOC               "Add 'doc' target to generate documentation"            OFF )
 
 # Only intended to be used by Exiv2 developers/contributors
@@ -91,6 +92,14 @@ if( EXIV2_BUILD_UNIT_TESTS )
     add_subdirectory ( unitTests )
 endif()
 
+if( EXIV2_BUILD_FUZZ_TESTS )
+    if ((NOT COMPILER_IS_CLANG) OR (NOT EXIV2_TEAM_USE_SANITIZERS))
+        message(FATAL_ERROR "You need to build with Clang and sanitizers for the fuzzers to work. "
+                "Use Clang and -DEXIV2_TEAM_USE_SANITIZERS=ON")
+    endif()
+    add_subdirectory ( fuzz )
+endif()
+
 if( EXIV2_BUILD_SAMPLES )
     add_subdirectory( samples )
     get_directory_property(SAMPLES DIRECTORY samples DEFINITION APPLICATIONS)

README.md

@@ -64,6 +64,7 @@ The file ReadMe.txt in a build bundle describes how to install the library on th
     3. [Unit tests](#4-3)
     4. [Python tests](#4-4)
     5. [Test Summary](#4-5)
+    6. [Fuzzing](#4-6)
 5. [Platform Notes](#5)
     1. [Linux](#5-1)
     2. [macOS](#5-2)
@@ -1039,6 +1040,30 @@ $ cd <exiv2dir>/build
 $ make python_tests 2>&1 | grep FAIL
 ```
 
+### 4.6 Fuzzing
+
+The code for the fuzzers is in `exiv2dir/fuzz`
+
+To build the fuzzers, use the *cmake* option `-DEXIV2_BUILD_FUZZ_TESTS=ON` and `-DEXIV2_TEAM_USE_SANITIZERS=ON`.
+Note that it only works with clang compiler as libFuzzer is integrate with clang > 6.0
+
+To build the fuzzers:
+
+```bash
+$ cd <exiv2dir>
+$ rm -rf build-fuzz ; mkdir build-fuzz ; cd build-fuzz
+$ cmake .. -DCMAKE_CXX_COMPILER=$(which clang++) -DEXIV2_BUILD_FUZZ_TESTS=ON -DEXIV2_TEAM_USE_SANITIZERS=ON
+$ cmake --build .
+```
+
+To execute a fuzzer:
+
+```bash
+cd <exiv2dir>/build-fuzz
+mkdir corpus
+./bin/fuzz-read-print-write corpus ../test/data/ -jobs=$(nproc) -workers=$(nproc) -max_len=4096
+```
+
 [TOC](#TOC)
 <div id="4-5">
 

cmake/compilerFlags.cmake

@@ -82,7 +82,9 @@ if ( MINGW OR UNIX OR MSYS ) # MINGW, Linux, APPLE, CYGWIN
                     set(SANITIZER_FLAGS "-fno-omit-frame-pointer -fsanitize=address")
                 endif()
             elseif( COMPILER_IS_CLANG )
-                if ( CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 4.9 )
+                if ( EXIV2_BUILD_FUZZ_TESTS )
+                    set(SANITIZER_FLAGS "-fsanitize=fuzzer-no-link")
+                elseif ( CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 4.9 )
                     set(SANITIZER_FLAGS "-fno-omit-frame-pointer -fsanitize=address,undefined -fno-sanitize-recover=all")
                 elseif ( CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 3.4 )
                     set(SANITIZER_FLAGS "-fno-omit-frame-pointer -fsanitize=address,undefined")

cmake/printSummary.cmake

@@ -66,6 +66,7 @@ endif()
 OptionOutput( "Building exiv2 command:             " EXIV2_BUILD_EXIV2_COMMAND       )
 OptionOutput( "Building samples:                   " EXIV2_BUILD_SAMPLES             )
 OptionOutput( "Building unit tests:                " EXIV2_BUILD_UNIT_TESTS          )
+OptionOutput( "Building fuzz tests:                " EXIV2_BUILD_FUZZ_TESTS          )
 OptionOutput( "Building doc:                       " EXIV2_BUILD_DOC                 )
 OptionOutput( "Building with coverage flags:       " BUILD_WITH_COVERAGE             )
 OptionOutput( "Using ccache:                       " BUILD_WITH_CCACHE               )

fuzz/CMakeLists.txt

@@ -0,0 +1,14 @@
+
+macro(fuzzer name)
+    add_executable(${name} ${name}.cpp)
+    set_target_properties(${name}
+            PROPERTIES
+                COMPILE_FLAGS "-fsanitize=fuzzer"
+                LINK_FLAGS "-fsanitize=fuzzer")
+    target_link_libraries(${name}
+            PRIVATE
+            exiv2lib
+            )
+endmacro()
+
+fuzzer(fuzz-read-print-write)

fuzz/fuzz-read-print-write.cpp

@@ -0,0 +1,35 @@
+#include <exiv2/exiv2.hpp>
+
+#include <iostream>
+#include <iomanip>
+#include <cassert>
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t * data, size_t size) {
+  // Invalid files generate a lot of warnings, so switch off logging.
+  Exiv2::LogMsg::setLevel(Exiv2::LogMsg::mute);
+
+  Exiv2::XmpParser::initialize();
+  ::atexit(Exiv2::XmpParser::terminate);
+
+  try {
+    Exiv2::DataBuf data_copy(data, size);
+    Exiv2::Image::UniquePtr image =
+      Exiv2::ImageFactory::open(data_copy.pData_, size);
+    assert(image.get() != 0);
+
+    image->readMetadata();
+    image->exifData();
+
+    // Print to a std::ostringstream so that the fuzzer doesn't
+    // produce lots of garbage on stdout.
+    std::ostringstream buffer;
+    image->printStructure(buffer, Exiv2::kpsNone);
+
+    image->writeMetadata();
+
+  } catch(...) {
+    // Exiv2 throws an exception if the metadata is invalid.
+  }
+
+  return 0;
+}

src/iptc.cpp

@@ -474,13 +474,13 @@ namespace Exiv2 {
 #endif
                 }
             }
-#ifndef SUPPRESS_WARNINGS
             else {
+#ifndef SUPPRESS_WARNINGS
                 EXV_WARNING << "IPTC dataset " << IptcKey(dataSet, record)
                             << " has invalid size " << sizeData << "; skipped.\n";
+#endif
                 return 7;
             }
-#endif
             pRead += sizeData;
         }
 

src/jpgimage.cpp

@@ -181,7 +181,7 @@ namespace Exiv2 {
 #endif
                 return -2;
             }
-#ifndef EXIV2_DEBUG_MESSAGES
+#ifdef EXIV2_DEBUG_MESSAGES
             if (   (dataSize & 1)
                 && position + dataSize == static_cast<uint32_t>(sizePsData)) {
                 std::cerr << "Warning: "

src/tiffvisitor_int.cpp

@@ -1335,7 +1335,9 @@ namespace Exiv2 {
                 tc->setStart(p);
                 object->addChild(std::move(tc));
             } else {
+#ifndef SUPPRESS_WARNINGS
                EXV_WARNING << "Unable to handle tag " << tag << ".\n";
+#endif
             }
             p += 12;
         }