1 files changed, 297 insertions, 0 deletions
diff --git a/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc b/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc
new file mode 100644
index 0000000000..05250d147f
--- /dev/null
+++ b/sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.cc
@@ -0,0 +1,297 @@
+// Copyright (c) 2013 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.
+
+// Note: any code in this file MUST be async-signal safe.
+
+#include "sandbox/linux/seccomp-bpf-helpers/sigsys_handlers.h"
+
+#include <sys/syscall.h>
+#include <unistd.h>
+
+#include "base/logging.h"
+#include "base/posix/eintr_wrapper.h"
+#include "build/build_config.h"
+#include "sandbox/linux/bpf_dsl/bpf_dsl.h"
+#include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
+#include "sandbox/linux/seccomp-bpf/syscall.h"
+#include "sandbox/linux/services/syscall_wrappers.h"
+#include "sandbox/linux/system_headers/linux_syscalls.h"
+
+#if defined(__mips__)
+// __NR_Linux, is defined in <asm/unistd.h>.
+#include <asm/unistd.h>
+#endif
+
+#define SECCOMP_MESSAGE_COMMON_CONTENT "seccomp-bpf failure"
+#define SECCOMP_MESSAGE_CLONE_CONTENT "clone() failure"
+#define SECCOMP_MESSAGE_PRCTL_CONTENT "prctl() failure"
+#define SECCOMP_MESSAGE_IOCTL_CONTENT "ioctl() failure"
+#define SECCOMP_MESSAGE_KILL_CONTENT "(tg)kill() failure"
+#define SECCOMP_MESSAGE_FUTEX_CONTENT "futex() failure"
+
+namespace {
+
+inline bool IsArchitectureX86_64() {
+#if defined(__x86_64__)
+  return true;
+#else
+  return false;
+#endif
+}
+
+// Write |error_message| to stderr. Similar to RawLog(), but a bit more careful
+// about async-signal safety. |size| is the size to write and should typically
+// not include a terminating \0.
+void WriteToStdErr(const char* error_message, size_t size) {
+  while (size > 0) {
+    // TODO(jln): query the current policy to check if send() is available and
+    // use it to perform a non-blocking write.
+    const int ret = HANDLE_EINTR(write(STDERR_FILENO, error_message, size));
+    // We can't handle any type of error here.
+    if (ret <= 0 || static_cast<size_t>(ret) > size) break;
+    size -= ret;
+    error_message += ret;
+  }
+}
+
+// Invalid syscall values are truncated to zero.
+// On architectures where base value is zero (Intel and Arm),
+// syscall number is the same as offset from base.
+// This function returns values between 0 and 1023 on all architectures.
+// On architectures where base value is different than zero (currently only
+// Mips), we are truncating valid syscall values to offset from base.
+uint32_t SyscallNumberToOffsetFromBase(uint32_t sysno) {
+#if defined(__mips__)
+  // On MIPS syscall numbers are in different range than on x86 and ARM.
+  // Valid MIPS O32 ABI syscall __NR_syscall will be truncated to zero for
+  // simplicity.
+  sysno = sysno - __NR_Linux;
+#endif
+
+  if (sysno >= 1024)
+    sysno = 0;
+
+  return sysno;
+}
+
+// Print a seccomp-bpf failure to handle |sysno| to stderr in an
+// async-signal safe way.
+void PrintSyscallError(uint32_t sysno) {
+  if (sysno >= 1024)
+    sysno = 0;
+  // TODO(markus): replace with async-signal safe snprintf when available.
+  const size_t kNumDigits = 4;
+  char sysno_base10[kNumDigits];
+  uint32_t rem = sysno;
+  uint32_t mod = 0;
+  for (int i = kNumDigits - 1; i >= 0; i--) {
+    mod = rem % 10;
+    rem /= 10;
+    sysno_base10[i] = '0' + mod;
+  }
+#if defined(__mips__) && (_MIPS_SIM == _MIPS_SIM_ABI32)
+  static const char kSeccompErrorPrefix[] = __FILE__
+      ":**CRASHING**:" SECCOMP_MESSAGE_COMMON_CONTENT " in syscall 4000 + ";
+#else
+  static const char kSeccompErrorPrefix[] =
+      __FILE__":**CRASHING**:" SECCOMP_MESSAGE_COMMON_CONTENT " in syscall ";
+#endif
+  static const char kSeccompErrorPostfix[] = "\n";
+  WriteToStdErr(kSeccompErrorPrefix, sizeof(kSeccompErrorPrefix) - 1);
+  WriteToStdErr(sysno_base10, sizeof(sysno_base10));
+  WriteToStdErr(kSeccompErrorPostfix, sizeof(kSeccompErrorPostfix) - 1);
+}
+
+}  // namespace.
+
+namespace sandbox {
+
+intptr_t CrashSIGSYS_Handler(const struct arch_seccomp_data& args, void* aux) {
+  uint32_t syscall = SyscallNumberToOffsetFromBase(args.nr);
+
+  PrintSyscallError(syscall);
+
+  // Encode 8-bits of the 1st two arguments too, so we can discern which socket
+  // type, which fcntl, ... etc., without being likely to hit a mapped
+  // address.
+  // Do not encode more bits here without thinking about increasing the
+  // likelihood of collision with mapped pages.
+  syscall |= ((args.args[0] & 0xffUL) << 12);
+  syscall |= ((args.args[1] & 0xffUL) << 20);
+  // Purposefully dereference the syscall as an address so it'll show up very
+  // clearly and easily in crash dumps.
+  volatile char* addr = reinterpret_cast<volatile char*>(syscall);
+  *addr = '\0';
+  // In case we hit a mapped address, hit the null page with just the syscall,
+  // for paranoia.
+  syscall &= 0xfffUL;
+  addr = reinterpret_cast<volatile char*>(syscall);
+  *addr = '\0';
+  for (;;)
+    _exit(1);
+}
+
+// TODO(jln): refactor the reporting functions.
+
+intptr_t SIGSYSCloneFailure(const struct arch_seccomp_data& args, void* aux) {
+  static const char kSeccompCloneError[] =
+      __FILE__":**CRASHING**:" SECCOMP_MESSAGE_CLONE_CONTENT "\n";
+  WriteToStdErr(kSeccompCloneError, sizeof(kSeccompCloneError) - 1);
+  // "flags" is the first argument in the kernel's clone().
+  // Mark as volatile to be able to find the value on the stack in a minidump.
+  volatile uint64_t clone_flags = args.args[0];
+  volatile char* addr;
+  if (IsArchitectureX86_64()) {
+    addr = reinterpret_cast<volatile char*>(clone_flags & 0xFFFFFF);
+    *addr = '\0';
+  }
+  // Hit the NULL page if this fails to fault.
+  addr = reinterpret_cast<volatile char*>(clone_flags & 0xFFF);
+  *addr = '\0';
+  for (;;)
+    _exit(1);
+}
+
+intptr_t SIGSYSPrctlFailure(const struct arch_seccomp_data& args,
+                            void* /* aux */) {
+  static const char kSeccompPrctlError[] =
+      __FILE__":**CRASHING**:" SECCOMP_MESSAGE_PRCTL_CONTENT "\n";
+  WriteToStdErr(kSeccompPrctlError, sizeof(kSeccompPrctlError) - 1);
+  // Mark as volatile to be able to find the value on the stack in a minidump.
+  volatile uint64_t option = args.args[0];
+  volatile char* addr =
+      reinterpret_cast<volatile char*>(option & 0xFFF);
+  *addr = '\0';
+  for (;;)
+    _exit(1);
+}
+
+intptr_t SIGSYSIoctlFailure(const struct arch_seccomp_data& args,
+                            void* /* aux */) {
+  static const char kSeccompIoctlError[] =
+      __FILE__":**CRASHING**:" SECCOMP_MESSAGE_IOCTL_CONTENT "\n";
+  WriteToStdErr(kSeccompIoctlError, sizeof(kSeccompIoctlError) - 1);
+  // Make "request" volatile so that we can see it on the stack in a minidump.
+  volatile uint64_t request = args.args[1];
+  volatile char* addr = reinterpret_cast<volatile char*>(request & 0xFFFF);
+  *addr = '\0';
+  // Hit the NULL page if this fails.
+  addr = reinterpret_cast<volatile char*>(request & 0xFFF);
+  *addr = '\0';
+  for (;;)
+    _exit(1);
+}
+
+intptr_t SIGSYSKillFailure(const struct arch_seccomp_data& args,
+                           void* /* aux */) {
+   static const char kSeccompKillError[] =
+      __FILE__":**CRASHING**:" SECCOMP_MESSAGE_KILL_CONTENT "\n";
+  WriteToStdErr(kSeccompKillError, sizeof(kSeccompKillError) - 1);
+  // Make "pid" volatile so that we can see it on the stack in a minidump.
+  volatile uint64_t my_pid = sys_getpid();
+  volatile char* addr = reinterpret_cast<volatile char*>(my_pid & 0xFFF);
+  *addr = '\0';
+  for (;;)
+    _exit(1);
+}
+
+intptr_t SIGSYSFutexFailure(const struct arch_seccomp_data& args,
+                            void* /* aux */) {
+  static const char kSeccompFutexError[] =
+      __FILE__ ":**CRASHING**:" SECCOMP_MESSAGE_FUTEX_CONTENT "\n";
+  WriteToStdErr(kSeccompFutexError, sizeof(kSeccompFutexError) - 1);
+  volatile int futex_op = args.args[1];
+  volatile char* addr = reinterpret_cast<volatile char*>(futex_op & 0xFFF);
+  *addr = '\0';
+  for (;;)
+    _exit(1);
+}
+
+intptr_t SIGSYSSchedHandler(const struct arch_seccomp_data& args,
+                            void* aux) {
+  switch (args.nr) {
+    case __NR_sched_getaffinity:
+    case __NR_sched_getattr:
+    case __NR_sched_getparam:
+    case __NR_sched_getscheduler:
+    case __NR_sched_rr_get_interval:
+    case __NR_sched_setaffinity:
+    case __NR_sched_setattr:
+    case __NR_sched_setparam:
+    case __NR_sched_setscheduler:
+      const pid_t tid = sys_gettid();
+      // The first argument is the pid.  If is our thread id, then replace it
+      // with 0, which is equivalent and allowed by the policy.
+      if (args.args[0] == static_cast<uint64_t>(tid)) {
+        return Syscall::Call(args.nr,
+                             0,
+                             static_cast<intptr_t>(args.args[1]),
+                             static_cast<intptr_t>(args.args[2]),
+                             static_cast<intptr_t>(args.args[3]),
+                             static_cast<intptr_t>(args.args[4]),
+                             static_cast<intptr_t>(args.args[5]));
+      }
+      break;
+  }
+
+  CrashSIGSYS_Handler(args, aux);
+
+  // Should never be reached.
+  RAW_CHECK(false);
+  return -ENOSYS;
+}
+
+bpf_dsl::ResultExpr CrashSIGSYS() {
+  return bpf_dsl::Trap(CrashSIGSYS_Handler, NULL);
+}
+
+bpf_dsl::ResultExpr CrashSIGSYSClone() {
+  return bpf_dsl::Trap(SIGSYSCloneFailure, NULL);
+}
+
+bpf_dsl::ResultExpr CrashSIGSYSPrctl() {
+  return bpf_dsl::Trap(SIGSYSPrctlFailure, NULL);
+}
+
+bpf_dsl::ResultExpr CrashSIGSYSIoctl() {
+  return bpf_dsl::Trap(SIGSYSIoctlFailure, NULL);
+}
+
+bpf_dsl::ResultExpr CrashSIGSYSKill() {
+  return bpf_dsl::Trap(SIGSYSKillFailure, NULL);
+}
+
+bpf_dsl::ResultExpr CrashSIGSYSFutex() {
+  return bpf_dsl::Trap(SIGSYSFutexFailure, NULL);
+}
+
+bpf_dsl::ResultExpr RewriteSchedSIGSYS() {
+  return bpf_dsl::Trap(SIGSYSSchedHandler, NULL);
+}
+
+const char* GetErrorMessageContentForTests() {
+  return SECCOMP_MESSAGE_COMMON_CONTENT;
+}
+
+const char* GetCloneErrorMessageContentForTests() {
+  return SECCOMP_MESSAGE_CLONE_CONTENT;
+}
+
+const char* GetPrctlErrorMessageContentForTests() {
+  return SECCOMP_MESSAGE_PRCTL_CONTENT;
+}
+
+const char* GetIoctlErrorMessageContentForTests() {
+  return SECCOMP_MESSAGE_IOCTL_CONTENT;
+}
+
+const char* GetKillErrorMessageContentForTests() {
+  return SECCOMP_MESSAGE_KILL_CONTENT;
+}
+
+const char* GetFutexErrorMessageContentForTests() {
+  return SECCOMP_MESSAGE_FUTEX_CONTENT;
+}
+
+}  // namespace sandbox.