Merge "Revert "Move seccomp policy logic to bionic""

core/jni/android_os_seccomp.cpp

@@ -14,11 +14,128 @@
  * limitations under the License.
  */
 
+#include "JNIHelp.h"
 #include "core_jni_helpers.h"
 #include "JniConstants.h"
 #include "utils/Log.h"
+#include "utils/misc.h"
+
+#if defined __arm__ || defined __aarch64__
+
+#include <vector>
+
+#include <sys/prctl.h>
+
+#include <linux/unistd.h>
+#include <linux/audit.h>
+#include <linux/filter.h>
+#include <linux/seccomp.h>
+
 #include "seccomp_policy.h"
 
+#define syscall_nr (offsetof(struct seccomp_data, nr))
+#define arch_nr (offsetof(struct seccomp_data, arch))
+
+typedef std::vector<sock_filter> filter;
+
+// We want to keep the below inline functions for debugging and future
+// development even though they are not all sed currently.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-function"
+
+static inline void Kill(filter& f) {
+    f.push_back(BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL));
+}
+
+static inline void Trap(filter& f) {
+    f.push_back(BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRAP));
+}
+
+static inline void Error(filter& f, __u16 retcode) {
+    f.push_back(BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO + retcode));
+}
+
+inline static void Trace(filter& f) {
+    f.push_back(BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_TRACE));
+}
+
+inline static void Allow(filter& f) {
+    f.push_back(BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW));
+}
+
+#pragma clang diagnostic pop
+
+inline static void ExamineSyscall(filter& f) {
+    f.push_back(BPF_STMT(BPF_LD|BPF_W|BPF_ABS, syscall_nr));
+}
+
+inline static int SetValidateArchitectureJumpTarget(size_t offset, filter& f) {
+    size_t jump_length = f.size() - offset - 1;
+    auto u8_jump_length = (__u8) jump_length;
+    if (u8_jump_length != jump_length) {
+        ALOGE("Can't set jump greater than 255 - actual jump is %zu",
+              jump_length);
+        return -1;
+    }
+    f[offset] = BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, AUDIT_ARCH_ARM, u8_jump_length, 0);
+    return 0;
+}
+
+inline static size_t ValidateArchitectureAndJumpIfNeeded(filter& f) {
+    f.push_back(BPF_STMT(BPF_LD|BPF_W|BPF_ABS, arch_nr));
+
+    f.push_back(BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, AUDIT_ARCH_AARCH64, 2, 0));
+    f.push_back(BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, AUDIT_ARCH_ARM, 1, 0));
+    Trap(f);
+    return f.size() - 2;
+}
+
+static bool install_filter(filter const& f) {
+    struct sock_fprog prog = {
+        (unsigned short) f.size(),
+        (struct sock_filter*) &f[0],
+    };
+
+    if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog) < 0) {
+        ALOGE("SECCOMP: Could not set seccomp filter of size %zu: %s", f.size(), strerror(errno));
+        return false;
+    }
+
+    ALOGI("SECCOMP: Global filter of size %zu installed", f.size());
+    return true;
+}
+
+bool set_seccomp_filter() {
+    filter f;
+
+    // Note that for mixed 64/32 bit architectures, ValidateArchitecture inserts a
+    // jump that must be changed to point to the start of the 32-bit policy
+    // 32 bit syscalls will not hit the policy between here and the call to SetJump
+    auto offset_to_32bit_filter =
+        ValidateArchitectureAndJumpIfNeeded(f);
+
+    // 64-bit filter
+    ExamineSyscall(f);
+
+    // arm64-only filter - autogenerated from bionic syscall usage
+    for (size_t i = 0; i < arm64_filter_size; ++i)
+        f.push_back(arm64_filter[i]);
+    Trap(f);
+
+    if (SetValidateArchitectureJumpTarget(offset_to_32bit_filter, f) != 0)
+        return -1;
+
+    // 32-bit filter
+    ExamineSyscall(f);
+
+    // arm32 filter - autogenerated from bionic syscall usage
+    for (size_t i = 0; i < arm_filter_size; ++i)
+        f.push_back(arm_filter[i]);
+    Trap(f);
+
+    return install_filter(f);
+}
+
 static void Seccomp_setPolicy(JNIEnv* /*env*/) {
     if (!set_seccomp_filter()) {
         ALOGE("Failed to set seccomp policy - killing");
@@ -26,6 +143,13 @@ static void Seccomp_setPolicy(JNIEnv* /*env*/) {
     }
 }
 
+#else // #if defined __arm__ || defined __aarch64__
+
+static void Seccomp_setPolicy(JNIEnv* /*env*/) {
+}
+
+#endif
+
 static const JNINativeMethod method_table[] = {
     NATIVE_METHOD(Seccomp, setPolicy, "()V"),
 };