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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "sandbox/linux/seccomp-bpf/syscall.h"
#include <asm/unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <stddef.h>
#include <stdint.h>
#include <sys/mman.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>
#include <vector>
#include "base/posix/eintr_wrapper.h"
#include "base/process/process_metrics.h"
#include "base/stl_util.h"
#include "build/build_config.h"
#include "sandbox/linux/bpf_dsl/bpf_dsl.h"
#include "sandbox/linux/bpf_dsl/policy.h"
#include "sandbox/linux/seccomp-bpf/bpf_tests.h"
#include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
#include "sandbox/linux/tests/unit_tests.h"
#include "testing/gtest/include/gtest/gtest.h"
using sandbox::bpf_dsl::Allow;
using sandbox::bpf_dsl::ResultExpr;
using sandbox::bpf_dsl::Trap;
namespace sandbox {
namespace {
TEST(Syscall, InvalidCallReturnsENOSYS) {
EXPECT_EQ(-ENOSYS, Syscall::InvalidCall());
}
TEST(Syscall, WellKnownEntryPoint) {
// Test that Syscall::Call(-1) is handled specially. Don't do this on ARM,
// where syscall(-1) crashes with SIGILL. Not running the test is fine, as we
// are still testing ARM code in the next set of tests.
#if !defined(__arm__) && !defined(__aarch64__)
EXPECT_NE(Syscall::Call(-1), syscall(-1));
#endif
// If possible, test that Syscall::Call(-1) returns the address right
// after
// a kernel entry point.
#if defined(__i386__)
EXPECT_EQ(0x80CDu, ((uint16_t*)Syscall::Call(-1))[-1]); // INT 0x80
#elif defined(__x86_64__)
EXPECT_EQ(0x050Fu, ((uint16_t*)Syscall::Call(-1))[-1]); // SYSCALL
#elif defined(__arm__)
#if defined(__thumb__)
EXPECT_EQ(0xDF00u, ((uint16_t*)Syscall::Call(-1))[-1]); // SWI 0
#else
EXPECT_EQ(0xEF000000u, ((uint32_t*)Syscall::Call(-1))[-1]); // SVC 0
#endif
#elif defined(__mips__)
// Opcode for MIPS sycall is in the lower 16-bits
EXPECT_EQ(0x0cu, (((uint32_t*)Syscall::Call(-1))[-1]) & 0x0000FFFF);
#elif defined(__aarch64__)
EXPECT_EQ(0xD4000001u, ((uint32_t*)Syscall::Call(-1))[-1]); // SVC 0
#else
#warning Incomplete test case; need port for target platform
#endif
}
TEST(Syscall, TrivialSyscallNoArgs) {
// Test that we can do basic system calls
EXPECT_EQ(Syscall::Call(__NR_getpid), syscall(__NR_getpid));
}
TEST(Syscall, TrivialSyscallOneArg) {
int new_fd;
// Duplicate standard error and close it.
ASSERT_GE(new_fd = Syscall::Call(__NR_dup, 2), 0);
int close_return_value = IGNORE_EINTR(Syscall::Call(__NR_close, new_fd));
ASSERT_EQ(close_return_value, 0);
}
TEST(Syscall, TrivialFailingSyscall) {
errno = -42;
int ret = Syscall::Call(__NR_dup, -1);
ASSERT_EQ(-EBADF, ret);
// Verify that Syscall::Call does not touch errno.
ASSERT_EQ(-42, errno);
}
// SIGSYS trap handler that will be called on __NR_uname.
intptr_t CopySyscallArgsToAux(const struct arch_seccomp_data& args, void* aux) {
// |aux| is our BPF_AUX pointer.
std::vector<uint64_t>* const seen_syscall_args =
static_cast<std::vector<uint64_t>*>(aux);
BPF_ASSERT(base::size(args.args) == 6);
seen_syscall_args->assign(args.args, args.args + base::size(args.args));
return -ENOMEM;
}
class CopyAllArgsOnUnamePolicy : public bpf_dsl::Policy {
public:
explicit CopyAllArgsOnUnamePolicy(std::vector<uint64_t>* aux) : aux_(aux) {}
~CopyAllArgsOnUnamePolicy() override {}
ResultExpr EvaluateSyscall(int sysno) const override {
DCHECK(SandboxBPF::IsValidSyscallNumber(sysno));
if (sysno == __NR_uname) {
return Trap(CopySyscallArgsToAux, aux_);
} else {
return Allow();
}
}
private:
std::vector<uint64_t>* aux_;
DISALLOW_COPY_AND_ASSIGN(CopyAllArgsOnUnamePolicy);
};
// We are testing Syscall::Call() by making use of a BPF filter that
// allows us
// to inspect the system call arguments that the kernel saw.
BPF_TEST(Syscall,
SyntheticSixArgs,
CopyAllArgsOnUnamePolicy,
std::vector<uint64_t> /* (*BPF_AUX) */) {
const int kExpectedValue = 42;
// In this test we only pass integers to the kernel. We might want to make
// additional tests to try other types. What we will see depends on
// implementation details of kernel BPF filters and we will need to document
// the expected behavior very clearly.
int syscall_args[6];
for (size_t i = 0; i < base::size(syscall_args); ++i) {
syscall_args[i] = kExpectedValue + i;
}
// We could use pretty much any system call we don't need here. uname() is
// nice because it doesn't have any dangerous side effects.
BPF_ASSERT(Syscall::Call(__NR_uname,
syscall_args[0],
syscall_args[1],
syscall_args[2],
syscall_args[3],
syscall_args[4],
syscall_args[5]) == -ENOMEM);
// We expect the trap handler to have copied the 6 arguments.
BPF_ASSERT(BPF_AUX->size() == 6);
// Don't loop here so that we can see which argument does cause the failure
// easily from the failing line.
// uint64_t is the type passed to our SIGSYS handler.
BPF_ASSERT((*BPF_AUX)[0] == static_cast<uint64_t>(syscall_args[0]));
BPF_ASSERT((*BPF_AUX)[1] == static_cast<uint64_t>(syscall_args[1]));
BPF_ASSERT((*BPF_AUX)[2] == static_cast<uint64_t>(syscall_args[2]));
BPF_ASSERT((*BPF_AUX)[3] == static_cast<uint64_t>(syscall_args[3]));
BPF_ASSERT((*BPF_AUX)[4] == static_cast<uint64_t>(syscall_args[4]));
BPF_ASSERT((*BPF_AUX)[5] == static_cast<uint64_t>(syscall_args[5]));
}
TEST(Syscall, ComplexSyscallSixArgs) {
int fd;
const size_t kPageSize = base::GetPageSize();
ASSERT_LE(0,
fd = Syscall::Call(__NR_openat, AT_FDCWD, "/dev/null", O_RDWR, 0L));
// Use mmap() to allocate some read-only memory
char* addr0;
ASSERT_NE(
(char*)NULL,
addr0 = reinterpret_cast<char*>(Syscall::Call(kMMapNr,
(void*)NULL,
kPageSize,
PROT_READ,
MAP_PRIVATE | MAP_ANONYMOUS,
fd,
0L)));
// Try to replace the existing mapping with a read-write mapping
char* addr1;
ASSERT_EQ(addr0,
addr1 = reinterpret_cast<char*>(
Syscall::Call(kMMapNr,
addr0,
kPageSize,
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
fd,
0L)));
++*addr1; // This should not seg fault
// Clean up
EXPECT_EQ(0, Syscall::Call(__NR_munmap, addr1, kPageSize));
EXPECT_EQ(0, IGNORE_EINTR(Syscall::Call(__NR_close, fd)));
// Check that the offset argument (i.e. the sixth argument) is processed
// correctly.
ASSERT_GE(
fd = Syscall::Call(__NR_openat, AT_FDCWD, "/proc/self/exe", O_RDONLY, 0L),
0);
char* addr2, *addr3;
ASSERT_NE((char*)NULL,
addr2 = reinterpret_cast<char*>(Syscall::Call(kMMapNr,
(void*)NULL,
2 * kPageSize,
PROT_READ,
MAP_PRIVATE,
fd,
0L
)));
ASSERT_NE((char*)NULL,
addr3 = reinterpret_cast<char*>(Syscall::Call(kMMapNr,
(void*)NULL,
kPageSize,
PROT_READ,
MAP_PRIVATE,
fd,
#if defined(__NR_mmap2)
1L
#else
kPageSize
#endif
)));
EXPECT_EQ(0, memcmp(addr2 + kPageSize, addr3, kPageSize));
// Just to be absolutely on the safe side, also verify that the file
// contents matches what we are getting from a read() operation.
char buf[2 * kPageSize];
EXPECT_EQ(2 * kPageSize, static_cast<size_t>(Syscall::Call(__NR_read,
fd,
buf,
2 * kPageSize
)));
EXPECT_EQ(0, memcmp(addr2, buf, 2 * kPageSize));
// Clean up
EXPECT_EQ(0, Syscall::Call(__NR_munmap, addr2, 2 * kPageSize));
EXPECT_EQ(0, Syscall::Call(__NR_munmap, addr3, kPageSize));
EXPECT_EQ(0, IGNORE_EINTR(Syscall::Call(__NR_close, fd)));
}
} // namespace
} // namespace sandbox
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