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* Don't use FIFOs to make Nix create the output path on behalf of the 

builder.  Instead, require that the Nix store has sticky permission
  (S_ISVTX); everyone can created files in the Nix store, but they
  cannot delete, rename or modify files created by others.
This commit is contained in:
Eelco Dolstra 2005-10-17 16:52:29 +00:00
parent 32282abcea
commit 7ef574e5d0
1 changed files with 17 additions and 68 deletions
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85
src/libstore/build.cc
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@ -348,13 +348,6 @@ private:
/* File descriptor for the log file. */
AutoCloseFD fdLogFile;
/* File descriptor for the output creation fifo. */
AutoCloseFD fdCreateOutput;
AutoCloseFD fdOutputCreated;
Path pathCreateOutput;
Path pathOutputCreated;
/* Pipe for the builder's standard output/error. */
Pipe logPipe;
@ -1075,24 +1068,6 @@ void DerivationGoal::startBuilder()
env["NIX_OUTPUT_CHECKED"] = "1";
/* Create the FIFOs through which the child can tell this process
to create the output path. */
pathCreateOutput = tmpDir + "/.create-output.fifo";
pathOutputCreated = tmpDir + "/.output-created.fifo";
if (mkfifo(pathCreateOutput.c_str(), 0622) == -1 ||
chmod(pathCreateOutput.c_str(), 0622) == -1)
throw SysError(format("cannot create FIFO `%1%'") % pathCreateOutput);
if (mkfifo(pathOutputCreated.c_str(), 0700) == -1 ||
chmod(pathOutputCreated.c_str(), 0622) == -1)
throw SysError(format("cannot create FIFO `%1%'") % pathOutputCreated);
fdCreateOutput = open(pathCreateOutput.c_str(), O_RDONLY | O_NONBLOCK);
if (fdCreateOutput == -1)
throw SysError(format("cannot open FIFO `%1%'") % pathCreateOutput);
/* If we are running as root, and the `build-allow-root' setting
is `false', then we have to build as one of the users listed in
`build-users'. */
@ -1104,6 +1079,21 @@ void DerivationGoal::startBuilder()
/* Change ownership of the temporary build directory. !!! gid */
if (chown(tmpDir.c_str(), buildUser, (gid_t) -1) == -1)
throw SysError(format("cannot change ownership of `%1%'") % tmpDir);
/* Check that the Nix store has the appropriate permissions,
i.e., owned by root and mode 1777 (sticky bit on so that
the builder can create its output but not mess with the
outputs of other processes). */
struct stat st;
if (stat(nixStore.c_str(), &st) == -1)
throw SysError(format("cannot stat `%1%'") % nixStore);
if (st.st_uid != rootUserId)
throw Error(format("`%1%' is not owned by root") % nixStore);
if (!(st.st_mode & S_ISVTX) ||
((st.st_mode & S_IRWXO) != S_IRWXO))
throw Error(format(
"builder does not have write permission to `%1%'; "
"try `chmod 1777 %1%'") % nixStore);
}
@ -1181,10 +1171,8 @@ void DerivationGoal::startBuilder()
/* parent */
pid.setSeparatePG(true);
logPipe.writeSide.close();
set<int> fds;
fds.insert(logPipe.readSide);
fds.insert(fdCreateOutput);
worker.childStarted(shared_from_this(), pid, fds, true);
worker.childStarted(shared_from_this(), pid,
singleton<set<int> >(logPipe.readSide), true);
}
@ -1381,45 +1369,6 @@ void DerivationGoal::handleChildOutput(int fd, const string & data)
writeFull(fdLogFile, (unsigned char *) data.c_str(), data.size());
}
else if (fd == fdCreateOutput) {
/* The child sent us a command to create the output path. */
debug(format("got output creation command `%1%'") % data);
istringstream str(data);
string id, type;
str >> id >> type;
if (id != "out") throw Error("not supported!"); /* !!! */
Path path;
for (DerivationOutputs::const_iterator i = drv.outputs.begin();
i != drv.outputs.end(); ++i)
if (i->first == "out") path = i->second.path.c_str();
if (path.empty()) throw Error(format("unknown output ID `%1%'") % id);
if (type == "d") {
if (mkdir(path.c_str(), 0700) == -1)
throw SysError(format("creating directory `%1%'") % path);
} else if (type == "f") {
AutoCloseFD fd = open(path.c_str(), O_CREAT | O_EXCL | O_RDONLY, 0600);
if (fd == -1)
throw SysError(format("creating file `%1%'") % path);
} else
throw Error(format("bad output creation command `%1%'") % type);
if (chown(path.c_str(), buildUser, (gid_t) -1) == -1) /* !!! */
throw SysError(format("cannot change ownership of `%1%'") % path);
/* The builder must open this FIFO for writing. This will
block until we have opened it for reading. Here we do
so, causing the builder to unblock and proceed. */
fdOutputCreated = open(pathOutputCreated.c_str(), O_RDONLY | O_NONBLOCK);
if (fdOutputCreated == -1)
throw SysError(format("cannot open FIFO `%1%'") % pathOutputCreated);
}
else abort();
}