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Fix bypass for enabling ptrace/bpf

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PiperOrigin-RevId: 555847265
Change-Id: I671c0650caeefaac590d3d0030ff90e18fda6bbd
This commit is contained in:
Wiktor Garbacz 2023-08-11 01:33:46 -07:00 committed by Copybara-Service
parent 3079d2b4e0
commit 01e14e0bb7
2 changed files with 19 additions and 4 deletions
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11
sandboxed_api/sandbox2/policybuilder.cc
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@ -1106,6 +1106,11 @@ PolicyBuilder& PolicyBuilder::AddPolicyOnSyscalls(
constexpr size_t kMaxShortJump = 255; constexpr size_t kMaxShortJump = 255;
bool last = true; bool last = true;
for (auto it = std::rbegin(nums); it != std::rend(nums); ++it) { for (auto it = std::rbegin(nums); it != std::rend(nums); ++it) {
if (*it == __NR_bpf || *it == __NR_ptrace) {
SetError(absl::InvalidArgumentError(
"cannot add policy for bpf/ptrace syscall"));
return *this;
}
// If syscall is not matched try with the next one. // If syscall is not matched try with the next one.
uint8_t jf = 0; uint8_t jf = 0;
// If last syscall on the list does not match skip the policy by jumping // If last syscall on the list does not match skip the policy by jumping
@ -1479,8 +1484,10 @@ PolicyBuilder& PolicyBuilder::AddNetworkProxyHandlerPolicy() {
} }
PolicyBuilder& PolicyBuilder::TrapPtrace() { PolicyBuilder& PolicyBuilder::TrapPtrace() {
AddPolicyOnSyscall(__NR_ptrace, {TRAP(0)}); if (handled_syscalls_.insert(__NR_ptrace).second) {
user_policy_handles_ptrace_ = true; user_policy_.insert(user_policy_.end(), {SYSCALL(__NR_ptrace, TRAP(0))});
user_policy_handles_ptrace_ = true;
}
return *this; return *this;
} }

12
sandboxed_api/sandbox2/policybuilder_test.cc
View File

@ -17,6 +17,7 @@
#include <syscall.h> #include <syscall.h>
#include <unistd.h> #include <unistd.h>
#include <cerrno>
#include <memory> #include <memory>
#include <string> #include <string>
#include <utility> #include <utility>
@ -48,12 +49,12 @@ class PolicyBuilderPeer {
namespace { namespace {
using ::sapi::IsOk;
using ::sapi::StatusIs;
using ::testing::Eq; using ::testing::Eq;
using ::testing::Lt; using ::testing::Lt;
using ::testing::StartsWith; using ::testing::StartsWith;
using ::testing::StrEq; using ::testing::StrEq;
using ::sapi::IsOk;
using ::sapi::StatusIs;
TEST(PolicyBuilderTest, Testpolicy_size) { TEST(PolicyBuilderTest, Testpolicy_size) {
ssize_t last_size = 0; ssize_t last_size = 0;
@ -152,5 +153,12 @@ TEST(PolicyBuilderTest, TestIsCopyable) {
EXPECT_THAT(builder.TryBuild(), IsOk()); EXPECT_THAT(builder.TryBuild(), IsOk());
EXPECT_THAT(copy.TryBuild(), IsOk()); EXPECT_THAT(copy.TryBuild(), IsOk());
} }
TEST(PolicyBuilderTest, CanBypassPtrace) {
PolicyBuilder builder;
builder.AddPolicyOnSyscall(__NR_ptrace, {ALLOW})
.BlockSyscallWithErrno(__NR_ptrace, ENOENT);
EXPECT_THAT(builder.TryBuild(), Not(IsOk()));
}
} // namespace } // namespace
} // namespace sandbox2 } // namespace sandbox2