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

#include "archive.hh"
#include <dirent.h>
#include <fcntl.h>
#include <strings.h>  // for strcasecmp
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#include <algorithm>
#include <cerrno>
#include <map>
#include <vector>
#include "config.hh"
#include "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);

const std::string narVersionMagic1 = "nix-archive-1";

static string caseHackSuffix = "~nix~case~hack~";

PathFilter defaultPathFilter = [](const Path&) { 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))
    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)
      sink << "executable"
           << "";
    dumpContents(path, (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<string, string> unhacked;
    for (auto& i : readDirectory(path))
      if (archiveSettings.useCaseHack) {
        string name(i.name);
        size_t pos = i.name.find(caseHackSuffix);
        if (pos != string::npos) {
          debug(format("removing case hack suffix from '%1%'") %
                (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 << narVersionMagic1;
  dump(path, sink, filter);
}

void dumpString(const std::string& s, Sink& sink) {
  sink << narVersionMagic1 << "("
       << "type"
       << "regular"
       << "contents" << s << ")";
}

static SerialisationError badArchive(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) {
    checkInterrupt();
    auto n = buf.size();
    if ((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 string& a, const string& b) const {
    return strcasecmp(a.c_str(), b.c_str()) < 0;
  }
};

static void parse(ParseSink& sink, Source& source, const Path& path) {
  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 (1) {
    checkInterrupt();

    s = readString(source);

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

    else if (s == "type") {
      if (type != tpUnknown) throw badArchive("multiple type fields");
      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 != "") throw badArchive("executable marker has non-empty value");
      sink.isExecutable();
    }

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

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

      while (1) {
        checkInterrupt();

        s = readString(source);

        if (s == ")") {
          break;
        } else if (s == "name") {
          name = readString(source);
          if (name.empty() || name == "." || name == ".." ||
              name.find('/') != string::npos ||
              name.find((char)0) != 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()) {
              debug(format("case collision between '%1%' and '%2%'") %
                    i->first % name);
              name += caseHackSuffix;
              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) {
      string target = readString(source);
      sink.createSymlink(path, target);
    }

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

void parseDump(ParseSink& sink, Source& source) {
  string version;
  try {
    version = readString(source, narVersionMagic1.size());
  } catch (SerialisationError& e) {
    /* This generally means the integer at the start couldn't be
       decoded.  Ignore and throw the exception below. */
  }
  if (version != narVersionMagic1)
    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) {
    Path p = dstPath + path;
    if (mkdir(p.c_str(), 0777) == -1)
      throw SysError(format("creating directory '%1%'") % p);
  };

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

  void isExecutable() {
    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) {
#if HAVE_POSIX_FALLOCATE
    if (len) {
      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) {
    writeFull(fd.get(), data, len);
  }

  void createSymlink(const Path& path, const string& target) {
    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