Allow restricted clock_nanosleep in Linux sandbox

To support glibc 2.30, allow clock_nanosleep in the baseline BPF policy, with the same clock_id restrictions as clock_gettime and other clock_* syscalls. Bug: 1025739 Change-Id: Ic53a782fef01049bc61c535b50735a4a7d4c23c0 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1935715 Commit-Queue: Matthew Denton <mpdenton@chromium.org> Reviewed-by: Robert Sesek <rsesek@chromium.org> Cr-Commit-Position: refs/heads/master@{#719421}
chromium · Nov 26, 2019 · 54407b4 · 54407b4
1 parent d1bda4d
commit 54407b4
Show file tree

Hide file tree

Showing 5 changed files with 54 additions and 11 deletions.
diff --git a/sandbox/linux/seccomp-bpf-helpers/baseline_policy.cc b/sandbox/linux/seccomp-bpf-helpers/baseline_policy.cc
@@ -148,7 +148,7 @@ ResultExpr EvaluateSyscallImpl(int fs_denied_errno,
     return Allow();
 #endif
 
-  if (sysno == __NR_clock_gettime) {
+  if (sysno == __NR_clock_gettime || sysno == __NR_clock_nanosleep) {
     return RestrictClockID();
   }
 

diff --git a/sandbox/linux/seccomp-bpf-helpers/baseline_policy_unittest.cc b/sandbox/linux/seccomp-bpf-helpers/baseline_policy_unittest.cc
@@ -398,6 +398,17 @@ BPF_DEATH_TEST_C(BaselinePolicy,
   syscall(SYS_clock_gettime, (~0) | CLOCKFD, &ts);
 }
 
+BPF_DEATH_TEST_C(BaselinePolicy,
+                 ClockNanosleepWithDisallowedClockCrashes,
+                 DEATH_SEGV_MESSAGE(GetErrorMessageContentForTests()),
+                 BaselinePolicy) {
+  struct timespec ts;
+  struct timespec out_ts;
+  ts.tv_sec = 0;
+  ts.tv_nsec = 0;
+  syscall(SYS_clock_nanosleep, (~0) | CLOCKFD, 0, &ts, &out_ts);
+}
+
 #if !defined(GRND_RANDOM)
 #define GRND_RANDOM 2
 #endif

diff --git a/sandbox/linux/seccomp-bpf-helpers/syscall_parameters_restrictions.h b/sandbox/linux/seccomp-bpf-helpers/syscall_parameters_restrictions.h
@@ -86,13 +86,13 @@ SANDBOX_EXPORT bpf_dsl::ResultExpr RestrictPrlimit64(pid_t target_pid);
 // process).
 SANDBOX_EXPORT bpf_dsl::ResultExpr RestrictGetrusage();
 
-// Restrict |clk_id| for clock_getres(), clock_gettime() and clock_settime(). We
-// allow accessing only CLOCK_BOOTTIME, CLOCK_MONOTONIC{,_RAW,_COARSE},
-// CLOCK_PROCESS_CPUTIME_ID, CLOCK_REALTIME{,_COARSE}, and
-// CLOCK_THREAD_CPUTIME_ID.  In particular, this disallows access to arbitrary
-// per-{process,thread} CPU-time clock IDs (such as those returned by
-// {clock,pthread}_getcpuclockid), which can leak information about the state of
-// the host OS.
+// Restrict |clk_id| for clock_getres(), clock_gettime(), clock_settime(), and
+// clock_nanosleep(). We allow accessing only CLOCK_BOOTTIME,
+// CLOCK_MONOTONIC{,_RAW,_COARSE}, CLOCK_PROCESS_CPUTIME_ID,
+// CLOCK_REALTIME{,_COARSE}, and CLOCK_THREAD_CPUTIME_ID.  In particular, on
+// non-Android platforms this disallows access to arbitrary per-{process,thread}
+// CPU-time clock IDs (such as those returned by {clock,pthread}_getcpuclockid),
+// which can leak information about the state of the host OS.
 SANDBOX_EXPORT bpf_dsl::ResultExpr RestrictClockID();
 
 // Restrict the flags argument to getrandom() to allow only no flags, or

diff --git a/sandbox/linux/seccomp-bpf-helpers/syscall_parameters_restrictions_unittests.cc b/sandbox/linux/seccomp-bpf-helpers/syscall_parameters_restrictions_unittests.cc
@@ -59,6 +59,7 @@ class RestrictClockIdPolicy : public bpf_dsl::Policy {
     switch (sysno) {
       case __NR_clock_gettime:
       case __NR_clock_getres:
+      case __NR_clock_nanosleep:
         return RestrictClockID();
       default:
         return Allow();
@@ -98,6 +99,25 @@ BPF_TEST_C(ParameterRestrictions,
 #endif
 }
 
+void CheckClockNanosleep(clockid_t clockid) {
+  struct timespec ts;
+  struct timespec out_ts;
+  ts.tv_sec = 0;
+  ts.tv_nsec = 0;
+  clock_nanosleep(clockid, 0, &ts, &out_ts);
+}
+
+BPF_TEST_C(ParameterRestrictions,
+           clock_nanosleep_allowed,
+           RestrictClockIdPolicy) {
+  CheckClockNanosleep(CLOCK_MONOTONIC);
+  CheckClockNanosleep(CLOCK_MONOTONIC_COARSE);
+  CheckClockNanosleep(CLOCK_MONOTONIC_RAW);
+  CheckClockNanosleep(CLOCK_BOOTTIME);
+  CheckClockNanosleep(CLOCK_REALTIME);
+  CheckClockNanosleep(CLOCK_REALTIME_COARSE);
+}
+
 BPF_DEATH_TEST_C(ParameterRestrictions,
                  clock_gettime_crash_clock_fd,
                  DEATH_SEGV_MESSAGE(sandbox::GetErrorMessageContentForTests()),
@@ -106,6 +126,17 @@ BPF_DEATH_TEST_C(ParameterRestrictions,
   syscall(SYS_clock_gettime, (~0) | CLOCKFD, &ts);
 }
 
+BPF_DEATH_TEST_C(ParameterRestrictions,
+                 clock_nanosleep_crash_clock_fd,
+                 DEATH_SEGV_MESSAGE(sandbox::GetErrorMessageContentForTests()),
+                 RestrictClockIdPolicy) {
+  struct timespec ts;
+  struct timespec out_ts;
+  ts.tv_sec = 0;
+  ts.tv_nsec = 0;
+  syscall(SYS_clock_nanosleep, (~0) | CLOCKFD, 0, &ts, &out_ts);
+}
+
 #if !defined(OS_ANDROID)
 BPF_DEATH_TEST_C(ParameterRestrictions,
                  clock_gettime_crash_cpu_clock,

diff --git a/sandbox/linux/seccomp-bpf-helpers/syscall_sets.cc b/sandbox/linux/seccomp-bpf-helpers/syscall_sets.cc
@@ -35,9 +35,10 @@ bool SyscallSets::IsAllowedGettime(int sysno) {
       return true;
     case __NR_adjtimex:         // Privileged.
     case __NR_clock_adjtime:    // Privileged.
-    case __NR_clock_getres:     // Could be allowed.
-    case __NR_clock_gettime:
-    case __NR_clock_nanosleep:  // Could be allowed.
+    case __NR_clock_getres:     // Allowed only on Android with parameters
+                                // filtered by RestrictClokID().
+    case __NR_clock_gettime:    // Parameters filtered by RestrictClockID().
+    case __NR_clock_nanosleep:  // Parameters filtered by RestrictClockID().
     case __NR_clock_settime:    // Privileged.
 #if defined(__i386__) || \
     (defined(ARCH_CPU_MIPS_FAMILY) && defined(ARCH_CPU_32_BITS))