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* If Nix is not running as root, call the setuid helper to start the

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builder under the desired build user.
This commit is contained in:
Eelco Dolstra 2006-12-07 00:42:30 +00:00
parent 813a7c65c9
commit a45c498e4e
2 changed files with 41 additions and 26 deletions
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58
src/libstore/build.cc
View file

@ -1342,11 +1342,6 @@ void DerivationGoal::startBuilder()
initChild();
/* Fill in the arguments. */
Strings args(drv.args);
args.push_front(baseNameOf(drv.builder));
const char * * argArr = strings2CharPtrs(args);
/* Fill in the environment. */
Strings envStrs;
for (Environment::const_iterator i = env.begin();
@ -1354,32 +1349,53 @@ void DerivationGoal::startBuilder()
envStrs.push_back(i->first + "=" + i->second);
const char * * envArr = strings2CharPtrs(envStrs);
Path program = drv.builder.c_str();
std::vector<const char *> args; /* careful with c_str()! */
/* If we are running in `build-users' mode, then switch to
the user we allocated above. Make sure that we drop
all root privileges. Note that initChild() above has
closed all file descriptors except std*, so that's
safe. Also note that setuid() when run as root sets
the real, effective and saved UIDs. */
if (buildUser.getUID() != 0) {
if (buildUser.enabled()) {
printMsg(lvlInfo, format("switching to uid `%1%'") % buildUser.getUID());
if (setgroups(0, 0) == -1)
throw SysError("cannot clear the set of supplementary groups");
if (setgid(buildUser.getGID()) == -1 ||
getgid() != buildUser.getGID() ||
getegid() != buildUser.getGID())
throw SysError("setgid failed");
if (setuid(buildUser.getUID()) == -1 ||
getuid() != buildUser.getUID() ||
geteuid() != buildUser.getUID())
throw SysError("setuid failed");
if (amPrivileged()) {
if (setgroups(0, 0) == -1)
throw SysError("cannot clear the set of supplementary groups");
if (setgid(buildUser.getGID()) == -1 ||
getgid() != buildUser.getGID() ||
getegid() != buildUser.getGID())
throw SysError("setgid failed");
if (setuid(buildUser.getUID()) == -1 ||
getuid() != buildUser.getUID() ||
geteuid() != buildUser.getUID())
throw SysError("setuid failed");
} else {
/* Let the setuid helper take care of it. */
program = nixLibexecDir + "/nix-setuid-helper";
args.push_back(program.c_str());
args.push_back("run-builder");
args.push_back("nix-builder-1"); /* !!! TODO */
args.push_back(drv.builder.c_str());
}
}
/* Fill in the arguments. */
string builderBasename = baseNameOf(drv.builder);
args.push_back(builderBasename.c_str());
for (Strings::iterator i = drv.args.begin();
i != drv.args.end(); ++i)
args.push_back(i->c_str());
args.push_back(0);
/* Execute the program. This should not return. */
execve(drv.builder.c_str(),
(char * *) argArr, (char * *) envArr);
execve(program.c_str(), (char * *) &args[0], (char * *) envArr);
throw SysError(format("executing `%1%'")
% drv.builder);
@ -1484,7 +1500,7 @@ void DerivationGoal::computeClosure()
build. Also, the output should be owned by the build
user. */
if ((st.st_mode & (S_IWGRP | S_IWOTH)) ||
(buildUser.getUID() != 0 && st.st_uid != buildUser.getUID()))
(buildUser.enabled() && st.st_uid != buildUser.getUID()))
throw Error(format("suspicious ownership or permission on `%1%'; rejecting this build output") % path);
#endif

9
src/nix-setuid-helper/main.cc
View file

@ -57,7 +57,7 @@ static uid_t nameToUid(const string & userName)
user. */
static void runBuilder(uid_t uidNix,
const string & buildUsersGroup, const string & targetUser,
string program, int argc, char * * argv)
string program, int argc, char * * argv, char * * env)
{
uid_t uidTargetUser = nameToUid(targetUser);
@ -107,12 +107,11 @@ static void runBuilder(uid_t uidNix,
/* Execute the program. */
std::vector<const char *> args;
args.push_back(program.c_str());
for (int i = 0; i < argc; ++i)
args.push_back(argv[i]);
args.push_back(0);
if (execve(program.c_str(), (char * *) &args[0], 0) == -1)
if (execve(program.c_str(), (char * *) &args[0], env) == -1)
throw SysError(format("cannot execute `%1%'") % program);
}
@ -180,10 +179,10 @@ static void run(int argc, char * * argv)
if (command == "run-builder") {
/* Syntax: nix-setuid-helper run-builder <username> <program>
<args...> */
<arg0 arg1...> */
if (argc < 4) throw Error("missing user name / program name");
runBuilder(uidNix, buildUsersGroup,
argv[2], argv[3], argc - 4, argv + 4);
argv[2], argv[3], argc - 4, argv + 4, oldEnviron);
}
else if (command == "fix-ownership") {