From d3ed9baac0dc967eaf6d3e3f986cafe60604121a Mon Sep 17 00:00:00 2001 From: Michael Pratt Date: Wed, 5 Jun 2019 13:59:01 -0700 Subject: Implement dumpability tracking and checks We don't actually support core dumps, but some applications want to get/set dumpability, which still has an effect in procfs. Lack of support for set-uid binaries or fs creds simplifies things a bit. As-is, processes started via CreateProcess (i.e., init and sentryctl exec) have normal dumpability. I'm a bit torn on whether sentryctl exec tasks should be dumpable, but at least since they have no parent normal UID/GID checks should protect them. PiperOrigin-RevId: 251712714 --- pkg/sentry/kernel/task_identity.go | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-) (limited to 'pkg/sentry/kernel/task_identity.go') diff --git a/pkg/sentry/kernel/task_identity.go b/pkg/sentry/kernel/task_identity.go index 17f08729a..ec95f78d0 100644 --- a/pkg/sentry/kernel/task_identity.go +++ b/pkg/sentry/kernel/task_identity.go @@ -17,6 +17,7 @@ package kernel import ( "gvisor.googlesource.com/gvisor/pkg/abi/linux" "gvisor.googlesource.com/gvisor/pkg/sentry/kernel/auth" + "gvisor.googlesource.com/gvisor/pkg/sentry/mm" "gvisor.googlesource.com/gvisor/pkg/syserror" ) @@ -206,8 +207,17 @@ func (t *Task) setKUIDsUncheckedLocked(newR, newE, newS auth.KUID) { // (filesystem UIDs aren't implemented, nor are any of the capabilities in // question) - // Not documented, but compare Linux's kernel/cred.c:commit_creds(). if oldE != newE { + // "[dumpability] is reset to the current value contained in + // the file /proc/sys/fs/suid_dumpable (which by default has + // the value 0), in the following circumstances: The process's + // effective user or group ID is changed." - prctl(2) + // + // (suid_dumpable isn't implemented, so we just use the + // default. + t.MemoryManager().SetDumpability(mm.NotDumpable) + + // Not documented, but compare Linux's kernel/cred.c:commit_creds(). t.parentDeathSignal = 0 } } @@ -303,8 +313,18 @@ func (t *Task) setKGIDsUncheckedLocked(newR, newE, newS auth.KGID) { t.creds = t.creds.Fork() // See doc for creds. t.creds.RealKGID, t.creds.EffectiveKGID, t.creds.SavedKGID = newR, newE, newS - // Not documented, but compare Linux's kernel/cred.c:commit_creds(). if oldE != newE { + // "[dumpability] is reset to the current value contained in + // the file /proc/sys/fs/suid_dumpable (which by default has + // the value 0), in the following circumstances: The process's + // effective user or group ID is changed." - prctl(2) + // + // (suid_dumpable isn't implemented, so we just use the + // default. + t.MemoryManager().SetDumpability(mm.NotDumpable) + + // Not documented, but compare Linux's + // kernel/cred.c:commit_creds(). t.parentDeathSignal = 0 } } -- cgit v1.2.3