Merge pull request #1035 from adrianherrera/optimin-util

add optimin corpus minimizer

10 files changed, 765 insertions, 0 deletions

diff --git a/utils/README.md b/utils/README.md
index b157424f..92619fd0 100644
--- a/utils/README.md
+++ b/utils/README.md
@@ -40,6 +40,8 @@ Here's a quick overview of the stuff you can find in this directory:
 
   - libpng_no_checksum   - a sample patch for removing CRC checks in libpng.
 
+  - optimin              - An optimal corpus minimizer.
+
   - persistent_mode      - an example of how to use the LLVM persistent process
                            mode to speed up certain fuzzing jobs.
 
diff --git a/utils/optimin/.gitignore b/utils/optimin/.gitignore
new file mode 100644
index 00000000..46f42f8f
--- /dev/null
+++ b/utils/optimin/.gitignore
@@ -0,0 +1,11 @@
+CMakeLists.txt.user
+CMakeCache.txt
+CMakeFiles
+CMakeScripts
+Testing
+Makefile
+cmake_install.cmake
+install_manifest.txt
+compile_commands.json
+CTestTestfile.cmake
+_deps
diff --git a/utils/optimin/CMakeLists.txt b/utils/optimin/CMakeLists.txt
new file mode 100644
index 00000000..b45dd004
--- /dev/null
+++ b/utils/optimin/CMakeLists.txt
@@ -0,0 +1,22 @@
+cmake_minimum_required(VERSION 3.10)
+
+project(optimin
+    LANGUAGES CXX
+    DESCRIPTION "MaxSAT-based fuzzing corpus minimizer"
+)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_EXTENSIONS OFF)
+
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra")
+
+# Add LLVM
+find_package(LLVM REQUIRED CONFIG)
+message(STATUS "Found LLVM ${LLVM_PACKAGE_VERSION}")
+
+include_directories(${LLVM_INCLUDE_DIRS})
+add_definitions(${LLVM_DEFINITIONS} -DNDEBUG)
+
+add_subdirectory(EvalMaxSAT)
+add_subdirectory(src)
diff --git a/utils/optimin/EVALMAXSAT_VERSION b/utils/optimin/EVALMAXSAT_VERSION
new file mode 100644
index 00000000..d836ff1c
--- /dev/null
+++ b/utils/optimin/EVALMAXSAT_VERSION
@@ -0,0 +1 @@
+440bf90edf88f6ab940934129e3c5b3b93764295
diff --git a/utils/optimin/EvalMaxSAT b/utils/optimin/EvalMaxSAT
new file mode 160000
+Subproject 440bf90edf88f6ab940934129e3c5b3b9376429
diff --git a/utils/optimin/README.md b/utils/optimin/README.md
new file mode 100644
index 00000000..5001b59d
--- /dev/null
+++ b/utils/optimin/README.md
@@ -0,0 +1,74 @@
+# OptiMin
+
+OptiMin is a corpus minimizer that uses a
+[MaxSAT](https://en.wikipedia.org/wiki/Maximum_satisfiability_problem) solver
+to identify a subset of functionally distinct files that exercise different code
+paths in a target program.
+
+Unlike most corpus minimizers, such as `afl-cmin`, OptiMin does not rely on
+heuristic and/or greedy algorithms to identify these functionally distinct
+files. This means that minimized corpora are generally much smaller than those
+produced by other tools.
+
+## Usage
+
+To build the `optimin` executable (when cloned from github):
+
+```bash
+# Ensure EvalMaxSAT is available
+git submodule init
+git submodule update
+
+mkdir build
+cd build
+
+# You may have to specify -DLLVM_DIR=`llvm-config --cmakedir` if you have a
+# non-standard LLVM install (e.g., install via apt)
+cmake ..
+make -j
+make install
+```
+
+Otherwise, run the `build_optimin.sh` script. Running `optimin` is the same as
+running `afl-cmin`.
+
+### Weighted Minimizations
+
+OptiMin allows for weighted minimizations. For examples, seeds can be weighted
+by file size (or execution time), thus preferencing the selection of smaller (or
+faster) seeds.
+
+To perform a weighted minimization, supply a CSV file with the `-w` option. This
+CSV file is formatted as follows:
+
+```
+SEED_1,WEIGHT_1
+SEED_2,WEIGHT_2
+...
+SEED_N,WEIGHT_N
+```
+
+Where `SEED_N` is the file name (**not** path) of a seed in the input directory,
+and `WEIGHT_N` is an integer weight.
+
+## Further Details and Citation
+
+For more details, please see the paper [Seed Selection for Successful
+Fuzzing](https://dl.acm.org/doi/10.1145/3460319.3464795). If you use OptiMin in
+your research, please cite this paper.
+
+Bibtex:
+
+```bibtex
+@inproceedings{Herrera:2021:FuzzSeedSelection,
+  author = {Adrian Herrera and Hendra Gunadi and Shane Magrath and Michael Norrish and Mathias Payer and Antony L. Hosking},
+  title = {Seed Selection for Successful Fuzzing},
+  booktitle = {30th ACM SIGSOFT International Symposium on Software Testing and Analysis},
+  series = {ISSTA},
+  year = {2021},
+  pages = {230--243},
+  numpages = {14},
+  location = {Virtual, Denmark},
+  publisher = {Association for Computing Machinery},
+}
+```
diff --git a/utils/optimin/build_optimin.sh b/utils/optimin/build_optimin.sh
new file mode 100755
index 00000000..7397aa45
--- /dev/null
+++ b/utils/optimin/build_optimin.sh
@@ -0,0 +1,130 @@
+#!/bin/sh
+#
+# american fuzzy lop++ - optimin build script
+# ------------------------------------------------
+#
+# Originally written by Nathan Voss <njvoss99@gmail.com>
+#
+# Adapted from code by Andrew Griffiths <agriffiths@google.com> and
+#                      Michal Zalewski
+#
+# Adapted for AFLplusplus by Dominik Maier <mail@dmnk.co>
+#
+# Copyright 2017 Battelle Memorial Institute. All rights reserved.
+# Copyright 2019-2020 AFLplusplus Project. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at:
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# This script builds the OptiMin corpus minimizer.
+
+EVALMAXSAT_VERSION="$(cat ./EVALMAXSAT_VERSION)"
+EVALMAXSAT_REPO="https://github.com/FlorentAvellaneda/EvalMaxSAT"
+
+echo "================================================="
+echo "OptiMin build script"
+echo "================================================="
+echo
+
+echo "[*] Performing basic sanity checks..."
+
+PLT=`uname -s`
+
+if [ ! -f "../../config.h" ]; then
+
+  echo "[-] Error: key files not found - wrong working directory?"
+  exit 1
+
+fi
+
+LLVM_CONFIG="${LLVM_CONFIG:-llvm-config}"
+CMAKECMD=cmake
+MAKECMD=make
+TARCMD=tar
+
+if [ "$PLT" = "Darwin" ]; then
+  CORES=`sysctl -n hw.ncpu`
+  TARCMD=tar
+fi
+
+if [ "$PLT" = "FreeBSD" ]; then
+  MAKECMD=gmake
+  CORES=`sysctl -n hw.ncpu`
+  TARCMD=gtar
+fi
+
+if [ "$PLT" = "NetBSD" ] || [ "$PLT" = "OpenBSD" ]; then
+  MAKECMD=gmake
+  CORES=`sysctl -n hw.ncpu`
+  TARCMD=gtar
+fi
+
+PREREQ_NOTFOUND=
+for i in git $CMAKECMD $MAKECMD $TARCMD; do
+
+  T=`command -v "$i" 2>/dev/null`
+
+  if [ "$T" = "" ]; then
+
+    echo "[-] Error: '$i' not found. Run 'sudo apt-get install $i' or similar."
+    PREREQ_NOTFOUND=1
+
+  fi
+
+done
+
+if echo "$CC" | grep -qF /afl-; then
+
+  echo "[-] Error: do not use afl-gcc or afl-clang to compile this tool."
+  PREREQ_NOTFOUND=1
+
+fi
+
+if [ "$PREREQ_NOTFOUND" = "1" ]; then
+  exit 1
+fi
+
+echo "[+] All checks passed!"
+
+echo "[*] Making sure EvalMaxSAT is checked out"
+
+git status 1>/dev/null 2>/dev/null
+if [ $? -eq 0 ]; then
+  echo "[*] initializing EvalMaxSAT submodule"
+  git submodule init || exit 1
+  git submodule update ./EvalMaxSAT 2>/dev/null # ignore errors
+else
+  echo "[*] cloning EvalMaxSAT"
+  test -d EvalMaxSAT || {
+    CNT=1
+    while [ '!' -d EvalMaxSAT -a "$CNT" -lt 4 ]; do
+      echo "Trying to clone EvalMaxSAT (attempt $CNT/3)"
+      git clone "$GRAMMAR_REPO"
+      CNT=`expr "$CNT" + 1`
+    done
+  }
+fi
+
+test -d EvalMaxSAT || { echo "[-] not checked out, please install git or check your internet connection." ; exit 1 ; }
+echo "[+] Got EvalMaxSAT."
+
+cd "EvalMaxSAT" || exit 1
+echo "[*] Checking out $EVALMAXSAT_VERSION"
+sh -c 'git stash && git stash drop' 1>/dev/null 2>/dev/null
+git checkout "$EVALMAXSAT_VERSION" || exit 1
+cd ..
+
+echo
+echo
+echo "[+] EvalMaxSAT successfully prepared!"
+echo "[+] Building OptiMin now."
+mkdir -p build
+cd build
+cmake .. -DLLVM_DIR=`$LLVM_CONFIG --cmakedir`
+make -j$CORES
+cd ..
+echo
+echo "[+] OptiMin successfully built!"
diff --git a/utils/optimin/src/CMakeLists.txt b/utils/optimin/src/CMakeLists.txt
new file mode 100644
index 00000000..f31ceeaf
--- /dev/null
+++ b/utils/optimin/src/CMakeLists.txt
@@ -0,0 +1,12 @@
+add_executable(optimin OptiMin.cpp)
+
+foreach(LIB MaLib EvalMaxSAT glucose)
+    target_include_directories(optimin PRIVATE
+        "${CMAKE_SOURCE_DIR}/EvalMaxSAT/lib/${LIB}/src")
+    target_link_libraries(optimin ${LIB})
+endforeach(LIB)
+
+llvm_map_components_to_libnames(LLVM_LIBS support)
+target_link_libraries(optimin ${LLVM_LIBS})
+
+install(TARGETS optimin RUNTIME DESTINATION bin)
diff --git a/utils/optimin/src/OptiMin.cpp b/utils/optimin/src/OptiMin.cpp
new file mode 100644
index 00000000..e02fcbe5
--- /dev/null
+++ b/utils/optimin/src/OptiMin.cpp
@@ -0,0 +1,455 @@
+/*
+ * OptiMin, an optimal fuzzing corpus minimizer.
+ *
+ * Author: Adrian Herrera
+ */
+
+#include <cstdint>
+#include <vector>
+
+#include <llvm/ADT/DenseSet.h>
+#include <llvm/ADT/DenseMap.h>
+#include <llvm/ADT/SmallVector.h>
+#include <llvm/ADT/StringExtras.h>
+#include <llvm/ADT/StringMap.h>
+#include <llvm/Support/Chrono.h>
+#include <llvm/Support/CommandLine.h>
+#include <llvm/Support/FileSystem.h>
+#include <llvm/Support/MemoryBuffer.h>
+#include <llvm/Support/Path.h>
+#include <llvm/Support/Program.h>
+#include <llvm/Support/WithColor.h>
+
+#include "EvalMaxSAT.h"
+#include "ProgressBar.h"
+
+using namespace llvm;
+
+namespace {
+
+// -------------------------------------------------------------------------- //
+// Classes
+// -------------------------------------------------------------------------- //
+
+/// Ensure seed weights default to 1
+class Weight {
+ public:
+  Weight() : Weight(1){};
+  Weight(uint32_t V) : Value(V){};
+
+  operator unsigned() const {
+    return Value;
+  }
+
+ private:
+  const unsigned Value;
+};
+
+// -------------------------------------------------------------------------- //
+// Typedefs
+// -------------------------------------------------------------------------- //
+
+/// AFL tuple (edge) ID
+using AFLTupleID = uint32_t;
+
+/// Pair of tuple ID and hit count
+using AFLTuple = std::pair<AFLTupleID, /* Frequency */ unsigned>;
+
+/// Coverage for a given seed file
+using AFLCoverageVector = std::vector<AFLTuple>;
+
+/// Maps seed file paths to a weight
+using WeightsMap = StringMap<Weight>;
+
+/// A seed identifier in the MaxSAT solver
+using SeedID = int;
+
+/// Associates seed identifiers to seed files
+using MaxSATSeeds =
+    SmallVector<std::pair<SeedID, /* Seed file */ std::string>, 0>;
+
+/// Set of literal identifiers
+using MaxSATSeedSet = DenseSet<SeedID>;
+
+/// Maps tuple IDs to the literal identifiers that "cover" that tuple
+using MaxSATCoverageMap = DenseMap<AFLTupleID, MaxSATSeedSet>;
+
+// -------------------------------------------------------------------------- //
+// Global variables
+// -------------------------------------------------------------------------- //
+
+// This is based on the human class count in `count_class_human[256]` in
+// `afl-showmap.c`
+static constexpr uint32_t MAX_EDGE_FREQ = 8;
+
+static sys::TimePoint<>     StartTime, EndTime;
+static std::chrono::seconds Duration;
+
+static std::string AFLShowmapPath;
+static bool        TargetArgsHasAtAt = false;
+
+static const auto ErrMsg = [] {
+  return WithColor(errs(), HighlightColor::Error) << "[-] ";
+};
+static const auto WarnMsg = [] {
+  return WithColor(errs(), HighlightColor::Warning) << "[-] ";
+};
+static const auto SuccMsg = [] {
+  return WithColor(outs(), HighlightColor::String) << "[+] ";
+};
+static const auto StatMsg = [] {
+  return WithColor(outs(), HighlightColor::Remark) << "[*] ";
+};
+
+static cl::opt<std::string>  CorpusDir("i", cl::desc("Input directory"),
+                                      cl::value_desc("dir"), cl::Required);
+static cl::opt<std::string>  OutputDir("o", cl::desc("Output directory"),
+                                      cl::value_desc("dir"), cl::Required);
+static cl::opt<bool>         EdgesOnly("f", cl::desc("Include edge hit counts"),
+                               cl::init(true));
+static cl::opt<bool>         ShowProgBar("p", cl::desc("Display progress bar"));
+static cl::opt<std::string>  WeightsFile("w", cl::desc("Weights file"),
+                                        cl::value_desc("csv"));
+static cl::opt<std::string>  TargetProg(cl::Positional,
+                                       cl::desc("<target program>"),
+                                       cl::Required);
+static cl::list<std::string> TargetArgs(cl::ConsumeAfter,
+                                        cl::desc("[target args...]"));
+static cl::opt<std::string>  MemLimit(
+    "m", cl::desc("Memory limit for child process (default=none)"),
+    cl::value_desc("megs"), cl::init("none"));
+static cl::opt<std::string> Timeout(
+    "t", cl::desc("Run time limit for child process (default=none)"),
+    cl::value_desc("msec"), cl::init("none"));
+static cl::opt<bool> CrashMode(
+    "C", cl::desc("Keep crashing inputs, reject everything else"));
+static cl::opt<bool> QemuMode("Q", cl::desc("Use binary-only instrumentation"));
+}  // anonymous namespace
+
+// -------------------------------------------------------------------------- //
+// Helper functions
+// -------------------------------------------------------------------------- //
+
+static void GetWeights(const MemoryBuffer &MB, WeightsMap &Weights) {
+  SmallVector<StringRef, 0> Lines;
+  MB.getBuffer().trim().split(Lines, '\n');
+
+  unsigned Weight = 0;
+
+  for (const auto &Line : Lines) {
+    const auto &[Seed, WeightStr] = Line.split(',');
+
+    if (to_integer(WeightStr, Weight, 10)) {
+      Weights.try_emplace(Seed, Weight);
+    } else {
+      WarnMsg() << "Failed to read weight for `" << Seed << "`. Skipping...\n";
+    }
+  }
+}
+
+[[nodiscard]] static std::error_code getAFLCoverage(const StringRef    Seed,
+                                                    AFLCoverageVector &Cov) {
+  Optional<StringRef> Redirects[] = {None, None, None};
+  std::error_code     EC;
+
+  // Create temporary output file
+  SmallString<64> OutputPath;
+  if (EC = sys::fs::createTemporaryFile("showmap", "txt", OutputPath))
+    return EC;
+
+  // Prepare afl-showmap arguments
+  SmallVector<StringRef, 12> AFLShowmapArgs{
+      AFLShowmapPath, "-m", MemLimit, "-t", Timeout, "-q", "-o", OutputPath};
+
+  if (TargetArgsHasAtAt)
+    AFLShowmapArgs.append({"-A", Seed});
+  else
+    Redirects[/* stdin */ 0] = Seed;
+
+  if (QemuMode) AFLShowmapArgs.push_back("-Q");
+  if (CrashMode) AFLShowmapArgs.push_back("-C");
+
+  AFLShowmapArgs.append({"--", TargetProg});
+  AFLShowmapArgs.append(TargetArgs.begin(), TargetArgs.end());
+
+  // Run afl-showmap
+  const int RC = sys::ExecuteAndWait(AFLShowmapPath, AFLShowmapArgs,
+                                     /*env=*/None, Redirects);
+  if (RC) return std::make_error_code(std::errc::executable_format_error);
+
+  // Parse afl-showmap output
+  const auto CovOrErr = MemoryBuffer::getFile(OutputPath);
+  if (EC = CovOrErr.getError()) {
+    sys::fs::remove(OutputPath);
+    return EC;
+  }
+
+  SmallVector<StringRef, 0> Lines;
+  CovOrErr.get()->getBuffer().trim().split(Lines, '\n');
+
+  AFLTupleID Edge = 0;
+  unsigned   Freq = 0;
+
+  for (const auto &Line : Lines) {
+    const auto &[EdgeStr, FreqStr] = Line.split(':');
+
+    to_integer(EdgeStr, Edge, 10);
+    to_integer(FreqStr, Freq, 10);
+    Cov.push_back({Edge, Freq});
+  }
+
+  return sys::fs::remove(OutputPath);
+}
+
+static inline void StartTimer(bool ShowProgBar) {
+  StartTime = std::chrono::system_clock::now();
+}
+
+static inline void EndTimer(bool ShowProgBar) {
+  EndTime = std::chrono::system_clock::now();
+  Duration =
+      std::chrono::duration_cast<std::chrono::seconds>(EndTime - StartTime);
+
+  if (ShowProgBar)
+    outs() << '\n';
+  else
+    outs() << Duration.count() << "s\n";
+}
+
+// -------------------------------------------------------------------------- //
+// Main function
+// -------------------------------------------------------------------------- //
+
+int main(int argc, char *argv[]) {
+  WeightsMap      Weights;
+  ProgressBar     ProgBar;
+  std::error_code EC;
+
+  // ------------------------------------------------------------------------ //
+  // Parse command-line options
+  //
+  // Also check the target arguments, as this determines how we run afl-showmap.
+  // ------------------------------------------------------------------------ //
+
+  cl::ParseCommandLineOptions(argc, argv, "Optimal corpus minimizer");
+
+  if (!sys::fs::is_directory(OutputDir)) {
+    ErrMsg() << "Invalid output directory `" << OutputDir << "`\n";
+    return 1;
+  }
+
+  for (const auto &Arg : TargetArgs)
+    if (Arg == "@@") TargetArgsHasAtAt = true;
+
+  // ------------------------------------------------------------------------ //
+  // Find afl-showmap
+  // ------------------------------------------------------------------------ //
+
+  const auto AFLShowmapOrErr = sys::findProgramByName("afl-showmap");
+  if (AFLShowmapOrErr.getError()) {
+    ErrMsg() << "Failed to find afl-showmap. Check your PATH\n";
+    return 1;
+  }
+  AFLShowmapPath = *AFLShowmapOrErr;
+
+  // ------------------------------------------------------------------------ //
+  // Parse weights
+  //
+  // Weights are stored in CSV file mapping a seed file name to an integer
+  // greater than zero.
+  // ------------------------------------------------------------------------ //
+
+  if (WeightsFile != "") {
+    StatMsg() << "Reading weights from `" << WeightsFile << "`... ";
+    StartTimer(/*ShowProgBar=*/false);
+
+    const auto WeightsOrErr = MemoryBuffer::getFile(WeightsFile);
+    if (EC = WeightsOrErr.getError()) {
+      ErrMsg() << "Failed to read weights from `" << WeightsFile
+               << "`: " << EC.message() << '\n';
+      return 1;
+    }
+
+    GetWeights(*WeightsOrErr.get(), Weights);
+
+    EndTimer(/*ShowProgBar=*/false);
+  }
+
+  // ------------------------------------------------------------------------ //
+  // Traverse corpus directory
+  //
+  // Find the seed files inside this directory.
+  // ------------------------------------------------------------------------ //
+
+  StatMsg() << "Locating seeds in `" << CorpusDir << "`... ";
+  StartTimer(/*ShowProgBar=*/false);
+
+  std::vector<std::string> SeedFiles;
+  sys::fs::file_status     Status;
+
+  for (sys::fs::directory_iterator Dir(CorpusDir, EC), DirEnd;
+       Dir != DirEnd && !EC; Dir.increment(EC)) {
+    if (EC) {
+      ErrMsg() << "Failed to traverse corpus directory `" << CorpusDir
+               << "`: " << EC.message() << '\n';
+      return 1;
+    }
+
+    const auto &Path = Dir->path();
+    if (EC = sys::fs::status(Path, Status)) {
+      WarnMsg() << "Failed to access seed file `" << Path
+                << "`: " << EC.message() << ". Skipping...\n";
+      continue;
+    }
+
+    switch (Status.type()) {
+      case sys::fs::file_type::regular_file:
+      case sys::fs::file_type::symlink_file:
+      case sys::fs::file_type::type_unknown:
+        SeedFiles.push_back(Path);
+      default:
+        /* Ignore */
+        break;
+    }
+  }
+
+  EndTimer(/*ShowProgBar=*/false);
+
+  // ------------------------------------------------------------------------ //
+  // Generate seed coverage
+  //
+  // Iterate over the corpus directory, which should contain seed files. Execute
+  // these seeds in the target program to generate coverage information, and
+  // then store this coverage information in the appropriate data structures.
+  // ------------------------------------------------------------------------ //
+
+  size_t       SeedCount = 0;
+  const size_t NumSeeds = SeedFiles.size();
+
+  if (!ShowProgBar)
+    StatMsg() << "Generating coverage for " << NumSeeds << " seeds... ";
+  StartTimer(ShowProgBar);
+
+  EvalMaxSAT        Solver(/*nbMinimizeThread=*/0);
+  MaxSATSeeds       SeedVars;
+  MaxSATCoverageMap SeedCoverage;
+  AFLCoverageVector Cov;
+
+  for (const auto &SeedFile : SeedFiles) {
+    // Execute seed
+    Cov.clear();
+    if (EC = getAFLCoverage(SeedFile, Cov)) {
+      ErrMsg() << "Failed to get coverage for seed " << SeedFile << ": "
+               << EC.message() << '\n';
+      return 1;
+    }
+
+    // Create a variable to represent the seed
+    const SeedID Var = Solver.newVar();
+    SeedVars.push_back({Var, SeedFile});
+
+    // Record the set of seeds that cover a particular edge
+    for (const auto &[Edge, Freq] : Cov) {
+      if (EdgesOnly) {
+        // Ignore edge frequency
+        SeedCoverage[Edge].insert(Var);
+      } else {
+        // Executing edge `E` `N` times means that it was executed `N - 1` times
+        for (unsigned I = 0; I < Freq; ++I)
+          SeedCoverage[MAX_EDGE_FREQ * Edge + I].insert(Var);
+      }
+    }
+
+    if ((++SeedCount % 10 == 0) && ShowProgBar)
+      ProgBar.update(SeedCount * 100 / NumSeeds, "Generating seed coverage");
+  }
+
+  EndTimer(ShowProgBar);
+
+  // ------------------------------------------------------------------------ //
+  // Set the hard and soft constraints in the solver
+  // ------------------------------------------------------------------------ //
+
+  if (!ShowProgBar) StatMsg() << "Generating constraints... ";
+  StartTimer(ShowProgBar);
+
+  SeedCount = 0;
+
+  // Ensure that at least one seed is selected that covers a particular edge
+  // (hard constraint)
+  std::vector<SeedID> Clauses;
+  for (const auto &[_, Seeds] : SeedCoverage) {
+    if (Seeds.empty()) continue;
+
+    Clauses.clear();
+    for (const auto &Seed : Seeds)
+      Clauses.push_back(Seed);
+
+    Solver.addClause(Clauses);
+
+    if ((++SeedCount % 10 == 0) && ShowProgBar)
+      ProgBar.update(SeedCount * 100 / SeedCoverage.size(),
+                     "Generating clauses");
+  }
+
+  // Select the minimum number of seeds that cover a particular set of edges
+  // (soft constraint)
+  for (const auto &[Var, Seed] : SeedVars)
+    Solver.addWeightedClause({-Var}, Weights[sys::path::filename(Seed)]);
+
+  EndTimer(ShowProgBar);
+
+  // ------------------------------------------------------------------------ //
+  // Generate a solution
+  // ------------------------------------------------------------------------ //
+
+  StatMsg() << "Solving... ";
+  StartTimer(/*ShowProgBar=*/false);
+
+  const bool Solved = Solver.solve();
+
+  EndTimer(/*ShowProgBar=*/false);
+
+  // ------------------------------------------------------------------------ //
+  // Save the solution
+  //
+  // This will copy the selected seeds to the given output directory.
+  // ------------------------------------------------------------------------ //
+
+  SmallVector<StringRef, 64> Solution;
+  SmallString<32>            OutputSeed;
+
+  if (Solved) {
+    for (const auto &[Var, Seed] : SeedVars)
+      if (Solver.getValue(Var) > 0) Solution.push_back(Seed);
+  } else {
+    ErrMsg() << "Failed to find an optimal solution for `" << CorpusDir
+             << "`\n";
+    return 1;
+  }
+
+  SuccMsg() << "Minimized corpus size: " << Solution.size() << " seeds\n";
+
+  if (!ShowProgBar) StatMsg() << "Copying to `" << OutputDir << "`... ";
+  StartTimer(ShowProgBar);
+
+  SeedCount = 0;
+
+  for (const auto &Seed : Solution) {
+    OutputSeed = OutputDir;
+    sys::path::append(OutputSeed, sys::path::filename(Seed));
+
+    if (EC = sys::fs::copy_file(Seed, OutputSeed)) {
+      WarnMsg() << "Failed to copy `" << Seed << "` to `" << OutputDir
+                << "`: " << EC.message() << '\n';
+    }
+
+    if ((++SeedCount % 10 == 0) && ShowProgBar)
+      ProgBar.update(SeedCount * 100 / Solution.size(), "Copying seeds");
+  }
+
+  EndTimer(ShowProgBar);
+  SuccMsg() << "Done!\n";
+
+  return 0;
+}
diff --git a/utils/optimin/src/ProgressBar.h b/utils/optimin/src/ProgressBar.h
new file mode 100644
index 00000000..2f8d7403
--- /dev/null
+++ b/utils/optimin/src/ProgressBar.h
@@ -0,0 +1,58 @@
+/**
+ *  Progress bar.
+ *
+ *  Adapted from https://www.bfilipek.com/2020/02/inidicators.html
+ */
+
+#pragma once
+
+#include <llvm/ADT/StringRef.h>
+#include <llvm/Support/raw_ostream.h>
+
+/// Display a progress bar in the terminal
+class ProgressBar {
+ private:
+  const size_t      BarWidth;
+  const std::string Fill;
+  const std::string Remainder;
+
+ public:
+  ProgressBar() : ProgressBar(60, "#", " ") {
+  }
+
+  ProgressBar(size_t Width, const llvm::StringRef F, const llvm::StringRef R)
+      : BarWidth(Width), Fill(F), Remainder(R) {
+  }
+
+  void update(float Progress, const llvm::StringRef Status = "",
+              llvm::raw_ostream &OS = llvm::outs()) {
+    // No need to write once progress is 100%
+    if (Progress > 100.0f) return;
+
+    // Move cursor to the first position on the same line and flush
+    OS << '\r';
+    OS.flush();
+
+    // Start bar
+    OS << '[';
+
+    const auto Completed =
+        static_cast<size_t>(Progress * static_cast<float>(BarWidth) / 100.0);
+    for (size_t I = 0; I < BarWidth; ++I) {
+      if (I <= Completed) {
+        OS << Fill;
+      } else {
+        OS << Remainder;
+      }
+    }
+
+    // End bar
+    OS << ']';
+
+    // Write progress percentage
+    OS << ' ' << std::min(static_cast<size_t>(Progress), size_t(100)) << '%';
+
+    // Write status text
+    OS << "  " << Status;
+  }
+};