path: root/third_party/nix/src/libutil/archive.cc

#include "libutil/archive.hh"

#include <algorithm>
#include <cerrno>
#include <map>
#include <vector>

#include <dirent.h>
#include <fcntl.h>
#include <glog/logging.h>
#include <strings.h>  // for strcasecmp
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include "libutil/config.hh"
#include "libutil/util.hh"

namespace nix {

struct ArchiveSettings : Config {
  Setting<bool> useCaseHack {
    this,
#if __APPLE__
        true,
#else
        false,
#endif
        "use-case-hack",
        "Whether to enable a Darwin-specific hack for dealing with file name "
        "collisions."
  };
};

static ArchiveSettings archiveSettings;

static GlobalConfig::Register r1(&archiveSettings);

constexpr std::string_view kCaseHackSuffix = "~nix~case~hack~";

PathFilter defaultPathFilter = [](const Path& /*unused*/) { return true; };

static void dumpContents(const Path& path, size_t size, Sink& sink) {
  sink << "contents" << size;

  AutoCloseFD fd(open(path.c_str(), O_RDONLY | O_CLOEXEC));
  if (!fd) {
    throw SysError(format("opening file '%1%'") % path);
  }

  std::vector<unsigned char> buf(65536);
  size_t left = size;

  while (left > 0) {
    auto n = std::min(left, buf.size());
    readFull(fd.get(), buf.data(), n);
    left -= n;
    sink(buf.data(), n);
  }

  writePadding(size, sink);
}

static void dump(const Path& path, Sink& sink, PathFilter& filter) {
  checkInterrupt();

  struct stat st;
  if (lstat(path.c_str(), &st) != 0) {
    throw SysError(format("getting attributes of path '%1%'") % path);
  }

  sink << "(";

  if (S_ISREG(st.st_mode)) {
    sink << "type"
         << "regular";
    if ((st.st_mode & S_IXUSR) != 0u) {
      sink << "executable"
           << "";
    }
    dumpContents(path, static_cast<size_t>(st.st_size), sink);
  }

  else if (S_ISDIR(st.st_mode)) {
    sink << "type"
         << "directory";

    /* If we're on a case-insensitive system like macOS, undo
       the case hack applied by restorePath(). */
    std::map<std::string, std::string> unhacked;
    for (auto& i : readDirectory(path)) {
      if (archiveSettings.useCaseHack) {
        std::string name(i.name);
        size_t pos = i.name.find(kCaseHackSuffix);
        if (pos != std::string::npos) {
          DLOG(INFO) << "removing case hack suffix from " << path << "/"
                     << i.name;

          name.erase(pos);
        }
        if (unhacked.find(name) != unhacked.end()) {
          throw Error(format("file name collision in between '%1%' and '%2%'") %
                      (path + "/" + unhacked[name]) % (path + "/" + i.name));
        }
        unhacked[name] = i.name;
      } else {
        unhacked[i.name] = i.name;
      }
    }

    for (auto& i : unhacked) {
      if (filter(path + "/" + i.first)) {
        sink << "entry"
             << "("
             << "name" << i.first << "node";
        dump(path + "/" + i.second, sink, filter);
        sink << ")";
      }
    }
  }

  else if (S_ISLNK(st.st_mode)) {
    sink << "type"
         << "symlink"
         << "target" << readLink(path);

  } else {
    throw Error(format("file '%1%' has an unsupported type") % path);
  }

  sink << ")";
}

void dumpPath(const Path& path, Sink& sink, PathFilter& filter) {
  sink << std::string(kNarVersionMagic1);
  dump(path, sink, filter);
}

void dumpString(const std::string& s, Sink& sink) {
  sink << std::string(kNarVersionMagic1) << "("
       << "type"
       << "regular"
       << "contents" << s << ")";
}

static SerialisationError badArchive(const std::string& s) {
  return SerialisationError("bad archive: " + s);
}

#if 0
static void skipGeneric(Source & source)
{
    if (readString(source) == "(") {
        while (readString(source) != ")")
            skipGeneric(source);
    }
}
#endif

static void parseContents(ParseSink& sink, Source& source, const Path& path) {
  unsigned long long size = readLongLong(source);

  sink.preallocateContents(size);

  unsigned long long left = size;
  std::vector<unsigned char> buf(65536);

  while (left != 0u) {
    checkInterrupt();
    auto n = buf.size();
    if (static_cast<unsigned long long>(n) > left) {
      n = left;
    }
    source(buf.data(), n);
    sink.receiveContents(buf.data(), n);
    left -= n;
  }

  readPadding(size, source);
}

struct CaseInsensitiveCompare {
  bool operator()(const std::string& a, const std::string& b) const {
    return strcasecmp(a.c_str(), b.c_str()) < 0;
  }
};

static void parse(ParseSink& sink, Source& source, const Path& path) {
  std::string s;

  s = readString(source);
  if (s != "(") {
    throw badArchive("expected open tag");
  }

  enum { tpUnknown, tpRegular, tpDirectory, tpSymlink } type = tpUnknown;

  std::map<Path, int, CaseInsensitiveCompare> names;

  while (true) {
    checkInterrupt();

    s = readString(source);

    if (s == ")") {
      break;
    }

    if (s == "type") {
      if (type != tpUnknown) {
        throw badArchive("multiple type fields");
      }
      std::string t = readString(source);

      if (t == "regular") {
        type = tpRegular;
        sink.createRegularFile(path);
      }

      else if (t == "directory") {
        sink.createDirectory(path);
        type = tpDirectory;
      }

      else if (t == "symlink") {
        type = tpSymlink;
      }

      else {
        throw badArchive("unknown file type " + t);
      }

    }

    else if (s == "contents" && type == tpRegular) {
      parseContents(sink, source, path);
    }

    else if (s == "executable" && type == tpRegular) {
      auto s = readString(source);
      if (!s.empty()) {
        throw badArchive("executable marker has non-empty value");
      }
      sink.isExecutable();
    }

    else if (s == "entry" && type == tpDirectory) {
      std::string name;
      std::string prevName;

      s = readString(source);
      if (s != "(") {
        throw badArchive("expected open tag");
      }

      while (true) {
        checkInterrupt();

        s = readString(source);

        if (s == ")") {
          break;
        }
        if (s == "name") {
          name = readString(source);
          if (name.empty() || name == "." || name == ".." ||
              name.find('/') != std::string::npos ||
              name.find(static_cast<char>(0)) != std::string::npos) {
            throw Error(format("NAR contains invalid file name '%1%'") % name);
          }
          if (name <= prevName) {
            throw Error("NAR directory is not sorted");
          }
          prevName = name;
          if (archiveSettings.useCaseHack) {
            auto i = names.find(name);
            if (i != names.end()) {
              DLOG(INFO) << "case collision between '" << i->first << "' and '"
                         << name << "'";
              name += kCaseHackSuffix;
              name += std::to_string(++i->second);
            } else {
              names[name] = 0;
            }
          }
        } else if (s == "node") {
          if (s.empty()) {
            throw badArchive("entry name missing");
          }
          parse(sink, source, path + "/" + name);
        } else {
          throw badArchive("unknown field " + s);
        }
      }
    }

    else if (s == "target" && type == tpSymlink) {
      std::string target = readString(source);
      sink.createSymlink(path, target);
    }

    else {
      throw badArchive("unknown field " + s);
    }
  }
}

void parseDump(ParseSink& sink, Source& source) {
  std::string version;
  try {
    version = readString(source, kNarVersionMagic1.size());
  } catch (SerialisationError& e) {
    /* This generally means the integer at the start couldn't be
       decoded.  Ignore and throw the exception below. */
  }
  if (version != kNarVersionMagic1) {
    throw badArchive("input doesn't look like a Nix archive");
  }
  parse(sink, source, "");
}

struct RestoreSink : ParseSink {
  Path dstPath;
  AutoCloseFD fd;

  void createDirectory(const Path& path) override {
    Path p = dstPath + path;
    if (mkdir(p.c_str(), 0777) == -1) {
      throw SysError(format("creating directory '%1%'") % p);
    }
  };

  void createRegularFile(const Path& path) override {
    Path p = dstPath + path;
    fd = AutoCloseFD(
        open(p.c_str(), O_CREAT | O_EXCL | O_WRONLY | O_CLOEXEC, 0666));
    if (!fd) {
      throw SysError(format("creating file '%1%'") % p);
    }
  }

  void isExecutable() override {
    struct stat st;
    if (fstat(fd.get(), &st) == -1) {
      throw SysError("fstat");
    }
    if (fchmod(fd.get(), st.st_mode | (S_IXUSR | S_IXGRP | S_IXOTH)) == -1) {
      throw SysError("fchmod");
    }
  }

  void preallocateContents(unsigned long long len) override {
#if HAVE_POSIX_FALLOCATE
    if (len != 0u) {
      errno = posix_fallocate(fd.get(), 0, len);
      /* Note that EINVAL may indicate that the underlying
         filesystem doesn't support preallocation (e.g. on
         OpenSolaris).  Since preallocation is just an
         optimisation, ignore it. */
      if (errno && errno != EINVAL && errno != EOPNOTSUPP && errno != ENOSYS) {
        throw SysError(format("preallocating file of %1% bytes") % len);
      }
    }
#endif
  }

  void receiveContents(unsigned char* data, unsigned int len) override {
    writeFull(fd.get(), data, len);
  }

  void createSymlink(const Path& path, const std::string& target) override {
    Path p = dstPath + path;
    nix::createSymlink(target, p);
  }
};

void restorePath(const Path& path, Source& source) {
  RestoreSink sink;
  sink.dstPath = path;
  parseDump(sink, source);
}

void copyNAR(Source& source, Sink& sink) {
  // FIXME: if 'source' is the output of dumpPath() followed by EOF,
  // we should just forward all data directly without parsing.

  ParseSink parseSink; /* null sink; just parse the NAR */

  LambdaSource wrapper([&](unsigned char* data, size_t len) {
    auto n = source.read(data, len);
    sink(data, n);
    return n;
  });

  parseDump(parseSink, wrapper);
}

}  // namespace nix