Add utility functions for forking new PID namespaces.

sandbox/linux/services/credentials.cc

Index: sandbox/linux/services/credentials.cc
diff --git a/sandbox/linux/services/credentials.cc b/sandbox/linux/services/credentials.cc
index 210a955531c4b8cc72379ce680821d03510bb44b..23e87eae1f5e735fdbdfe96b7510c5eac293e821 100644
--- a/sandbox/linux/services/credentials.cc
+++ b/sandbox/linux/services/credentials.cc
@@ -110,23 +110,24 @@ void CheckCloneNewUserErrno(int error) {
          error == ENOSYS);
 }
 
-// Converts a LinuxCapability to the corresponding Linux CAP_XXX value.
-int LinuxCapabilityToKernelValue(LinuxCapability cap) {
+// Converts a Capability to the corresponding Linux CAP_XXX value.
+int CapabilityToKernelValue(Credentials::Capability cap) {
   switch (cap) {
-    case LinuxCapability::kCapSysChroot:
+    case Credentials::Capability::SYS_CHROOT:
       return CAP_SYS_CHROOT;
-    case LinuxCapability::kCapSysAdmin:
+    case Credentials::Capability::SYS_ADMIN:
       return CAP_SYS_ADMIN;
   }
 
-  LOG(FATAL) << "Invalid LinuxCapability: " << static_cast<int>(cap);
+  LOG(FATAL) << "Invalid Capability: " << static_cast<int>(cap);
   return 0;
 }
 
 }  // namespace.
 
+// static
 bool Credentials::DropAllCapabilities(int proc_fd) {
-  if (!SetCapabilities(proc_fd, std::vector<LinuxCapability>())) {
+  if (!SetCapabilities(proc_fd, std::vector<Capability>())) {
     return false;
   }
 
@@ -134,30 +135,28 @@ bool Credentials::DropAllCapabilities(int proc_fd) {
   return true;
 }
 
+// static
 bool Credentials::DropAllCapabilities() {
   base::ScopedFD proc_fd(ProcUtil::OpenProc());
   return Credentials::DropAllCapabilities(proc_fd.get());
 }
 
 // static
-bool Credentials::SetCapabilities(int proc_fd,
-                                  const std::vector<LinuxCapability>& caps) {
-  DCHECK_LE(0, proc_fd);
-
-#if !defined(THREAD_SANITIZER)
-  // With TSAN, accept to break the security model as it is a testing
-  // configuration.
-  CHECK(ThreadHelpers::IsSingleThreaded(proc_fd));
-#endif
+bool Credentials::DropAllCapabilitiesOnCurrentThread() {
+  return SetCapabilitiesOnCurrentThread(std::vector<Capability>());
+}
 
+// static
+bool Credentials::SetCapabilitiesOnCurrentThread(
+    const std::vector<Capability>& caps) {
   struct cap_hdr hdr = {};
   hdr.version = _LINUX_CAPABILITY_VERSION_3;
   struct cap_data data[_LINUX_CAPABILITY_U32S_3] = {{}};
 
   // Initially, cap has no capability flags set. Enable the effective and
   // permitted flags only for the requested capabilities.
-  for (const LinuxCapability cap : caps) {
-    const int cap_num = LinuxCapabilityToKernelValue(cap);
+  for (const Capability cap : caps) {
+    const int cap_num = CapabilityToKernelValue(cap);
     const size_t index = CAP_TO_INDEX(cap_num);
     const uint32_t mask = CAP_TO_MASK(cap_num);
     data[index].effective |= mask;
@@ -167,6 +166,20 @@ bool Credentials::SetCapabilities(int proc_fd,
   return sys_capset(&hdr, data) == 0;
 }
 
+// static
+bool Credentials::SetCapabilities(int proc_fd,
+                                  const std::vector<Capability>& caps) {
+  DCHECK_LE(0, proc_fd);
+
+#if !defined(THREAD_SANITIZER)
+  // With TSAN, accept to break the security model as it is a testing
+  // configuration.
+  CHECK(ThreadHelpers::IsSingleThreaded(proc_fd));
+#endif
+
+  return SetCapabilitiesOnCurrentThread(caps);
+}
+
 bool Credentials::HasAnyCapability() {
   struct cap_hdr hdr = {};
   hdr.version = _LINUX_CAPABILITY_VERSION_3;
@@ -183,14 +196,14 @@ bool Credentials::HasAnyCapability() {
   return false;
 }
 
-bool Credentials::HasCapability(LinuxCapability cap) {
+bool Credentials::HasCapability(Capability cap) {
   struct cap_hdr hdr = {};
   hdr.version = _LINUX_CAPABILITY_VERSION_3;
   struct cap_data data[_LINUX_CAPABILITY_U32S_3] = {{}};
 
   PCHECK(sys_capget(&hdr, data) == 0);
 
-  const int cap_num = LinuxCapabilityToKernelValue(cap);
+  const int cap_num = CapabilityToKernelValue(cap);
   const size_t index = CAP_TO_INDEX(cap_num);
   const uint32_t mask = CAP_TO_MASK(cap_num);