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Don't allow writing to /etc

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Yorick 2023-02-14 12:03:34 +01:00
parent df9a71f6ea
commit db41f74af3
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2 changed files with 6 additions and 1 deletions
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4
src/libstore/build/local-derivation-goal.cc
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@ -670,7 +670,6 @@ void LocalDerivationGoal::startBuilder()
nobody account. The latter is kind of a hack to support nobody account. The latter is kind of a hack to support
Samba-in-QEMU. */ Samba-in-QEMU. */
createDirs(chrootRootDir + "/etc"); createDirs(chrootRootDir + "/etc");
chownToBuilder(chrootRootDir + "/etc");
if (parsedDrv->useUidRange() && (!buildUser || buildUser->getUIDCount() < 65536)) if (parsedDrv->useUidRange() && (!buildUser || buildUser->getUIDCount() < 65536))
throw Error("feature 'uid-range' requires the setting '%s' to be enabled", settings.autoAllocateUids.name); throw Error("feature 'uid-range' requires the setting '%s' to be enabled", settings.autoAllocateUids.name);
@ -970,6 +969,9 @@ void LocalDerivationGoal::startBuilder()
"nobody:x:65534:65534:Nobody:/:/noshell\n", "nobody:x:65534:65534:Nobody:/:/noshell\n",
sandboxUid(), sandboxGid(), settings.sandboxBuildDir)); sandboxUid(), sandboxGid(), settings.sandboxBuildDir));
/* Make /etc unwritable */
chmod_(chrootRootDir + "/etc", 0555);
/* Save the mount- and user namespace of the child. We have to do this /* Save the mount- and user namespace of the child. We have to do this
*before* the child does a chroot. */ *before* the child does a chroot. */
sandboxMountNamespace = open(fmt("/proc/%d/ns/mnt", (pid_t) pid).c_str(), O_RDONLY); sandboxMountNamespace = open(fmt("/proc/%d/ns/mnt", (pid_t) pid).c_str(), O_RDONLY);

3
tests/linux-sandbox.sh
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@ -37,3 +37,6 @@ nix-build check.nix -A nondeterministic --sandbox-paths /nix/store --no-out-link
(! nix-build check.nix -A nondeterministic --sandbox-paths /nix/store --no-out-link --check -K 2> $TEST_ROOT/log) (! nix-build check.nix -A nondeterministic --sandbox-paths /nix/store --no-out-link --check -K 2> $TEST_ROOT/log)
if grep -q 'error: renaming' $TEST_ROOT/log; then false; fi if grep -q 'error: renaming' $TEST_ROOT/log; then false; fi
grep -q 'may not be deterministic' $TEST_ROOT/log grep -q 'may not be deterministic' $TEST_ROOT/log
# Test that sandboxed builds cannot write to /etc easily
(! nix-build -E 'with import ./config.nix; mkDerivation { name = "etc-write"; buildCommand = "echo > /etc/test"; }' --no-out-link --sandbox-paths /nix/store)