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@@ -120,7 +120,7 @@ final class Seccomp {
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static final int PR_SET_NO_NEW_PRIVS = 38; // since Linux 3.5
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static final int PR_GET_SECCOMP = 21; // since Linux 2.6.23
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static final int PR_SET_SECCOMP = 22; // since Linux 2.6.23
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- static final int SECCOMP_MODE_FILTER = 2; // since Linux Linux 3.5
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+ static final long SECCOMP_MODE_FILTER = 2; // since Linux Linux 3.5
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/** corresponds to struct sock_filter */
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static final class SockFilter {
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@@ -209,9 +209,10 @@ final class Seccomp {
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static final int NR_SYSCALL_FORK = 57;
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static final int NR_SYSCALL_EXECVE = 59;
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static final int NR_SYSCALL_EXECVEAT = 322; // since Linux 3.19
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+ static final int NR_SYSCALL_TUXCALL = 184; // should return ENOSYS
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/** try to install our BPF filters via seccomp() or prctl() to block execution */
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- private static void linuxImpl() {
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+ private static int linuxImpl() {
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// first be defensive: we can give nice errors this way, at the very least.
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// also, some of these security features get backported to old versions, checking kernel version here is a big no-no!
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boolean supported = Constants.LINUX && "amd64".equals(Constants.OS_ARCH);
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@@ -224,24 +225,85 @@ final class Seccomp {
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throw new UnsupportedOperationException("seccomp unavailable: could not link methods. requires kernel 3.5+ with CONFIG_SECCOMP and CONFIG_SECCOMP_FILTER compiled in");
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}
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- // check for kernel version
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- if (linux_libc.prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0) < 0) {
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+ // pure paranoia:
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+
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+ // check that unimplemented syscalls actually return ENOSYS
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+ // you never know (e.g. https://code.google.com/p/chromium/issues/detail?id=439795)
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+ if (linux_libc.syscall(NR_SYSCALL_TUXCALL) >= 0 || Native.getLastError() != ENOSYS) {
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+ throw new UnsupportedOperationException("seccomp unavailable: your kernel is buggy and you should upgrade");
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+ }
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+
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+ // try to check system calls really are who they claim
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+ // you never know (e.g. https://chromium.googlesource.com/chromium/src.git/+/master/sandbox/linux/seccomp-bpf/sandbox_bpf.cc#57)
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+ final int bogusArg = 0xf7a46a5c;
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+
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+ // test seccomp(BOGUS)
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+ long ret = linux_libc.syscall(SECCOMP_SYSCALL_NR, bogusArg);
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+ if (ret != -1) {
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+ throw new UnsupportedOperationException("seccomp unavailable: seccomp(BOGUS_OPERATION) returned " + ret);
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+ } else {
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int errno = Native.getLastError();
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switch (errno) {
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- case ENOSYS: throw new UnsupportedOperationException("seccomp unavailable: requires kernel 3.5+ with CONFIG_SECCOMP and CONFIG_SECCOMP_FILTER compiled in");
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- default: throw new UnsupportedOperationException("prctl(PR_GET_NO_NEW_PRIVS): " + JNACLibrary.strerror(errno));
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+ case ENOSYS: break; // ok
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+ case EINVAL: break; // ok
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+ default: throw new UnsupportedOperationException("seccomp(BOGUS_OPERATION): " + JNACLibrary.strerror(errno));
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}
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}
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- // check for SECCOMP
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- if (linux_libc.prctl(PR_GET_SECCOMP, 0, 0, 0, 0) < 0) {
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+
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+ // test seccomp(VALID, BOGUS)
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+ ret = linux_libc.syscall(SECCOMP_SYSCALL_NR, SECCOMP_SET_MODE_FILTER, bogusArg);
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+ if (ret != -1) {
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+ throw new UnsupportedOperationException("seccomp unavailable: seccomp(SECCOMP_SET_MODE_FILTER, BOGUS_FLAG) returned " + ret);
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+ } else {
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int errno = Native.getLastError();
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switch (errno) {
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- case EINVAL: throw new UnsupportedOperationException("seccomp unavailable: CONFIG_SECCOMP not compiled into kernel, CONFIG_SECCOMP and CONFIG_SECCOMP_FILTER are needed");
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- default: throw new UnsupportedOperationException("prctl(PR_GET_SECCOMP): " + JNACLibrary.strerror(errno));
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+ case ENOSYS: break; // ok
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+ case EINVAL: break; // ok
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+ default: throw new UnsupportedOperationException("seccomp(SECCOMP_SET_MODE_FILTER, BOGUS_FLAG): " + JNACLibrary.strerror(errno));
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}
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}
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+
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+ // test prctl(BOGUS)
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+ ret = linux_libc.prctl(bogusArg, 0, 0, 0, 0);
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+ if (ret != -1) {
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+ throw new UnsupportedOperationException("seccomp unavailable: prctl(BOGUS_OPTION) returned " + ret);
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+ } else {
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+ int errno = Native.getLastError();
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+ switch (errno) {
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+ case ENOSYS: break; // ok
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+ case EINVAL: break; // ok
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+ default: throw new UnsupportedOperationException("prctl(BOGUS_OPTION): " + JNACLibrary.strerror(errno));
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+ }
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+ }
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+
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+ // now just normal defensive checks
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+
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+ // check for GET_NO_NEW_PRIVS
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+ switch (linux_libc.prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0)) {
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+ case 0: break; // not yet set
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+ case 1: break; // already set by caller
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+ default:
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+ int errno = Native.getLastError();
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+ if (errno == ENOSYS) {
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+ throw new UnsupportedOperationException("seccomp unavailable: requires kernel 3.5+ with CONFIG_SECCOMP and CONFIG_SECCOMP_FILTER compiled in");
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+ } else {
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+ throw new UnsupportedOperationException("prctl(PR_GET_NO_NEW_PRIVS): " + JNACLibrary.strerror(errno));
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+ }
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+ }
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+ // check for SECCOMP
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+ switch (linux_libc.prctl(PR_GET_SECCOMP, 0, 0, 0, 0)) {
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+ case 0: break; // not yet set
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+ case 2: break; // already in filter mode by caller
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+ default:
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+ int errno = Native.getLastError();
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+ if (errno == EINVAL) {
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+ throw new UnsupportedOperationException("seccomp unavailable: CONFIG_SECCOMP not compiled into kernel, CONFIG_SECCOMP and CONFIG_SECCOMP_FILTER are needed");
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+ } else {
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+ throw new UnsupportedOperationException("prctl(PR_GET_SECCOMP): " + JNACLibrary.strerror(errno));
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+ }
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+ }
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// check for SECCOMP_MODE_FILTER
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- if (linux_libc.prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, 0, 0, 0) < 0) {
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+ if (linux_libc.prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, 0, 0, 0) != 0) {
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int errno = Native.getLastError();
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switch (errno) {
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case EFAULT: break; // available
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@@ -251,10 +313,15 @@ final class Seccomp {
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}
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// ok, now set PR_SET_NO_NEW_PRIVS, needed to be able to set a seccomp filter as ordinary user
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- if (linux_libc.prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) < 0) {
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+ if (linux_libc.prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) != 0) {
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throw new UnsupportedOperationException("prctl(PR_SET_NO_NEW_PRIVS): " + JNACLibrary.strerror(Native.getLastError()));
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}
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+ // check it worked
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+ if (linux_libc.prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0) != 1) {
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+ throw new UnsupportedOperationException("seccomp filter did not really succeed: prctl(PR_GET_NO_NEW_PRIVS): " + JNACLibrary.strerror(Native.getLastError()));
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+ }
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+
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// BPF installed to check arch, then syscall range. See https://www.kernel.org/doc/Documentation/prctl/seccomp_filter.txt for details.
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SockFilter insns[] = {
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/* 1 */ BPF_STMT(BPF_LD + BPF_W + BPF_ABS, SECCOMP_DATA_ARCH_OFFSET), //
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@@ -272,14 +339,16 @@ final class Seccomp {
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prog.write();
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long pointer = Pointer.nativeValue(prog.getPointer());
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+ int method = 1;
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// install filter, if this works, after this there is no going back!
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// first try it with seccomp(SECCOMP_SET_MODE_FILTER), falling back to prctl()
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if (linux_libc.syscall(SECCOMP_SYSCALL_NR, SECCOMP_SET_MODE_FILTER, SECCOMP_FILTER_FLAG_TSYNC, pointer) != 0) {
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+ method = 0;
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int errno1 = Native.getLastError();
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if (logger.isDebugEnabled()) {
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logger.debug("seccomp(SECCOMP_SET_MODE_FILTER): " + JNACLibrary.strerror(errno1) + ", falling back to prctl(PR_SET_SECCOMP)...");
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}
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- if (linux_libc.prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, pointer, 0, 0) < 0) {
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+ if (linux_libc.prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, pointer, 0, 0) != 0) {
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int errno2 = Native.getLastError();
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throw new UnsupportedOperationException("seccomp(SECCOMP_SET_MODE_FILTER): " + JNACLibrary.strerror(errno1) +
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", prctl(PR_SET_SECCOMP): " + JNACLibrary.strerror(errno2));
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@@ -291,7 +360,8 @@ final class Seccomp {
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throw new UnsupportedOperationException("seccomp filter installation did not really succeed. seccomp(PR_GET_SECCOMP): " + JNACLibrary.strerror(Native.getLastError()));
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}
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- logger.debug("Linux seccomp filter installation successful");
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+ logger.debug("Linux seccomp filter installation successful, threads: [{}]", method == 1 ? "all" : "app" );
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+ return method;
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}
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// OS X implementation via sandbox(7)
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@@ -334,7 +404,7 @@ final class Seccomp {
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// first be defensive: we can give nice errors this way, at the very least.
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boolean supported = Constants.MAC_OS_X;
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if (supported == false) {
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- throw new IllegalStateException("bug: should not be trying to initialize seccomp for an unsupported OS");
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+ throw new IllegalStateException("bug: should not be trying to initialize seatbelt for an unsupported OS");
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}
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// we couldn't link methods, could be some really ancient OS X (< Leopard) or some bug
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@@ -372,12 +442,14 @@ final class Seccomp {
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* Attempt to drop the capability to execute for the process.
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* <p>
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* This is best effort and OS and architecture dependent. It may throw any Throwable.
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+ * @return 0 if we can do this for application threads, 1 for the entire process
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*/
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- static void init(Path tmpFile) throws Throwable {
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+ static int init(Path tmpFile) throws Throwable {
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if (Constants.LINUX) {
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- linuxImpl();
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+ return linuxImpl();
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} else if (Constants.MAC_OS_X) {
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macImpl(tmpFile);
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+ return 1;
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} else {
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throw new UnsupportedOperationException("syscall filtering not supported for OS: '" + Constants.OS_NAME + "'");
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}
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