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Merge pull request #13829 from rmuir/add_seatbelt 

improve seccomp syscall filtering
This commit is contained in:
Robert Muir 2015-09-29 08:54:06 -04:00
parent 8c7c7652f6 d7a087a41b
commit 94972bb39d
5 changed files with 184 additions and 65 deletions
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8
core/src/main/java/org/elasticsearch/bootstrap/Bootstrap.java
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@ -43,6 +43,7 @@ import org.elasticsearch.node.internal.InternalSettingsPreparer;
import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import java.nio.file.Path;
import java.util.Locale;
import java.util.concurrent.CountDownLatch;
@ -82,7 +83,7 @@ final class Bootstrap {
}
/** initialize native resources */
public static void initializeNatives(boolean mlockAll, boolean seccomp, boolean ctrlHandler) {
public static void initializeNatives(Path tmpFile, boolean mlockAll, boolean seccomp, boolean ctrlHandler) {
final ESLogger logger = Loggers.getLogger(Bootstrap.class);
// check if the user is running as root, and bail
@ -96,7 +97,7 @@ final class Bootstrap {
// enable secure computing mode
if (seccomp) {
Natives.trySeccomp();
Natives.trySeccomp(tmpFile);
}
// mlockall if requested
@ -141,7 +142,8 @@ final class Bootstrap {
}
private void setup(boolean addShutdownHook, Settings settings, Environment environment) throws Exception {
initializeNatives(settings.getAsBoolean("bootstrap.mlockall", false),
initializeNatives(environment.tmpFile(),
settings.getAsBoolean("bootstrap.mlockall", false),
settings.getAsBoolean("bootstrap.seccomp", true),
settings.getAsBoolean("bootstrap.ctrlhandler", true));

25
core/src/main/java/org/elasticsearch/bootstrap/JNANatives.java
View File

@ -21,11 +21,14 @@ package org.elasticsearch.bootstrap;
import com.sun.jna.Native;
import com.sun.jna.Pointer;
import org.apache.lucene.util.Constants;
import org.elasticsearch.common.logging.ESLogger;
import org.elasticsearch.common.logging.Loggers;
import org.elasticsearch.monitor.jvm.JvmInfo;
import java.nio.file.Path;
import static org.elasticsearch.bootstrap.JNAKernel32Library.SizeT;
/**
@ -172,19 +175,17 @@ class JNANatives {
}
}
static void trySeccomp() {
if (Constants.LINUX && "amd64".equals(Constants.OS_ARCH)) {
try {
Seccomp.installFilter();
LOCAL_SECCOMP = true;
} catch (Exception e) {
// this is likely to happen unless the kernel is newish, its a best effort at the moment
// so we log stacktrace at debug for now...
if (logger.isDebugEnabled()) {
logger.debug("unable to install seccomp filter", e);
}
logger.warn("unable to install seccomp filter: " + e.getMessage());
static void trySeccomp(Path tmpFile) {
try {
Seccomp.init(tmpFile);
LOCAL_SECCOMP = true;
} catch (Throwable t) {
// this is likely to happen unless the kernel is newish, its a best effort at the moment
// so we log stacktrace at debug for now...
if (logger.isDebugEnabled()) {
logger.debug("unable to install syscall filter", t);
}
logger.warn("unable to install syscall filter: " + t.getMessage());
}
}
}

8
core/src/main/java/org/elasticsearch/bootstrap/Natives.java
View File

@ -22,6 +22,8 @@ package org.elasticsearch.bootstrap;
import org.elasticsearch.common.logging.ESLogger;
import org.elasticsearch.common.logging.Loggers;
import java.nio.file.Path;
/**
* The Natives class is a wrapper class that checks if the classes necessary for calling native methods are available on
* startup. If they are not available, this class will avoid calling code that loads these classes.
@ -89,12 +91,12 @@ final class Natives {
return JNANatives.LOCAL_MLOCKALL;
}
static void trySeccomp() {
static void trySeccomp(Path tmpFile) {
if (!JNA_AVAILABLE) {
logger.warn("cannot install seccomp filters because JNA is not available");
logger.warn("cannot install syscall filters because JNA is not available");
return;
}
JNANatives.trySeccomp();
JNANatives.trySeccomp(tmpFile);
}
static boolean isSeccompInstalled() {

188
core/src/main/java/org/elasticsearch/bootstrap/Seccomp.java
View File

@ -24,46 +24,65 @@ import com.sun.jna.Memory;
import com.sun.jna.Native;
import com.sun.jna.Pointer;
import com.sun.jna.Structure;
import com.sun.jna.ptr.PointerByReference;
import org.apache.lucene.util.Constants;
import org.apache.lucene.util.IOUtils;
import org.elasticsearch.common.logging.ESLogger;
import org.elasticsearch.common.logging.Loggers;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
/**
* Installs a limited form of Linux secure computing mode (filter mode).
* This filters system calls to block process execution.
* Installs a limited form of secure computing mode,
* to filters system calls to block process execution.
* <p>
* This is only supported on the amd64 architecture, on Linux kernels 3.5 or above, and requires
* This is only supported on the Linux and Mac OS X operating systems.
* <p>
* On Linux it currently supports on the amd64 architecture, on Linux kernels 3.5 or above, and requires
* {@code CONFIG_SECCOMP} and {@code CONFIG_SECCOMP_FILTER} compiled into the kernel.
* <p>
* Filters are installed using either {@code seccomp(2)} (3.17+) or {@code prctl(2)} (3.5+). {@code seccomp(2)}
* On Linux BPF Filters are installed using either {@code seccomp(2)} (3.17+) or {@code prctl(2)} (3.5+). {@code seccomp(2)}
* is preferred, as it allows filters to be applied to any existing threads in the process, and one motivation
* here is to protect against bugs in the JVM. Otherwise, code will fall back to the {@code prctl(2)} method
* which will at least protect elasticsearch application threads.
* <p>
* The filters will return {@code EACCES} (Access Denied) for the following system calls:
* Linux BPF filters will return {@code EACCES} (Access Denied) for the following system calls:
* <ul>
* <li>{@code execve}</li>
* <li>{@code fork}</li>
* <li>{@code vfork}</li>
* <li>{@code execveat}</li>
* </ul>
* <p>
* On Mac OS X Leopard or above, a custom {@code sandbox(7)} ("Seatbelt") profile is installed that
* denies the following rules:
* <ul>
* <li>{@code process-fork}</li>
* <li>{@code process-exec}</li>
* </ul>
* <p>
* This is not intended as a sandbox. It is another level of security, mostly intended to annoy
* security researchers and make their lives more difficult in achieving "remote execution" exploits.
* @see <a href="http://www.kernel.org/doc/Documentation/prctl/seccomp_filter.txt">
* http://www.kernel.org/doc/Documentation/prctl/seccomp_filter.txt</a>
* @see <a href="https://reverse.put.as/wp-content/uploads/2011/06/The-Apple-Sandbox-BHDC2011-Paper.pdf">
* https://reverse.put.as/wp-content/uploads/2011/06/The-Apple-Sandbox-BHDC2011-Paper.pdf</a>
*/
// only supported on linux/amd64
// not an example of how to write code!!!
final class Seccomp {
private static final ESLogger logger = Loggers.getLogger(Seccomp.class);
/** we use an explicit interface for native methods, for varargs support */
// Linux implementation, based on seccomp(2) or prctl(2) with bpf filtering
/** Access to non-standard Linux libc methods */
static interface LinuxLibrary extends Library {
/**
* maps to prctl(2)
@ -76,17 +95,19 @@ final class Seccomp {
long syscall(long number, Object... args);
};
// null if something goes wrong.
static final LinuxLibrary libc;
// null if unavailable or something goes wrong.
static final LinuxLibrary linux_libc;
static {
LinuxLibrary lib = null;
try {
lib = (LinuxLibrary) Native.loadLibrary("c", LinuxLibrary.class);
} catch (UnsatisfiedLinkError e) {
logger.warn("unable to link C library. native methods (seccomp) will be disabled.", e);
if (Constants.LINUX) {
try {
lib = (LinuxLibrary) Native.loadLibrary("c", LinuxLibrary.class);
} catch (UnsatisfiedLinkError e) {
logger.warn("unable to link C library. native methods (seccomp) will be disabled.", e);
}
}
libc = lib;
linux_libc = lib;
}
/** the preferred method is seccomp(2), since we can apply to all threads of the process */
@ -176,34 +197,35 @@ final class Seccomp {
static final int SECCOMP_DATA_NR_OFFSET = 0x00;
static final int SECCOMP_DATA_ARCH_OFFSET = 0x04;
// currently this range is blocked (inclusive):
// currently these ranges are blocked (inclusive):
// execve is really the only one needed but why let someone fork a 30G heap? (not really what happens)
// ...
// 57: fork
// 58: vfork
// 59: execve
// ...
static final int BLACKLIST_START = 57;
static final int BLACKLIST_END = 59;
// TODO: execveat()? its less of a risk since the jvm does not use it...
// 322: execveat
// ...
static final int NR_SYSCALL_FORK = 57;
static final int NR_SYSCALL_EXECVE = 59;
static final int NR_SYSCALL_EXECVEAT = 322; // since Linux 3.19
/** try to install our filters */
static void installFilter() {
/** try to install our BPF filters via seccomp() or prctl() to block execution */
private static void linuxImpl() {
// first be defensive: we can give nice errors this way, at the very least.
// also, some of these security features get backported to old versions, checking kernel version here is a big no-no!
boolean supported = Constants.LINUX && "amd64".equals(Constants.OS_ARCH);
if (supported == false) {
throw new IllegalStateException("bug: should not be trying to initialize seccomp for an unsupported architecture");
throw new UnsupportedOperationException("seccomp unavailable: '" + Constants.OS_ARCH + "' architecture unsupported");
}
// we couldn't link methods, could be some really ancient kernel (e.g. < 2.1.57) or some bug
if (libc == null) {
if (linux_libc == null) {
throw new UnsupportedOperationException("seccomp unavailable: could not link methods. requires kernel 3.5+ with CONFIG_SECCOMP and CONFIG_SECCOMP_FILTER compiled in");
}
// check for kernel version
if (libc.prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0) < 0) {
if (linux_libc.prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0) < 0) {
int errno = Native.getLastError();
switch (errno) {
case ENOSYS: throw new UnsupportedOperationException("seccomp unavailable: requires kernel 3.5+ with CONFIG_SECCOMP and CONFIG_SECCOMP_FILTER compiled in");
@ -211,7 +233,7 @@ final class Seccomp {
}
}
// check for SECCOMP
if (libc.prctl(PR_GET_SECCOMP, 0, 0, 0, 0) < 0) {
if (linux_libc.prctl(PR_GET_SECCOMP, 0, 0, 0, 0) < 0) {
int errno = Native.getLastError();
switch (errno) {
case EINVAL: throw new UnsupportedOperationException("seccomp unavailable: CONFIG_SECCOMP not compiled into kernel, CONFIG_SECCOMP and CONFIG_SECCOMP_FILTER are needed");
@ -219,7 +241,7 @@ final class Seccomp {
}
}
// check for SECCOMP_MODE_FILTER
if (libc.prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, 0, 0, 0) < 0) {
if (linux_libc.prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, 0, 0, 0) < 0) {
int errno = Native.getLastError();
switch (errno) {
case EFAULT: break; // available
@ -229,19 +251,20 @@ final class Seccomp {
}
// ok, now set PR_SET_NO_NEW_PRIVS, needed to be able to set a seccomp filter as ordinary user
if (libc.prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) < 0) {
if (linux_libc.prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0) < 0) {
throw new UnsupportedOperationException("prctl(PR_SET_NO_NEW_PRIVS): " + JNACLibrary.strerror(Native.getLastError()));
}
// BPF installed to check arch, then syscall range. See https://www.kernel.org/doc/Documentation/prctl/seccomp_filter.txt for details.
SockFilter insns[] = {
/* 1 */ BPF_STMT(BPF_LD + BPF_W + BPF_ABS, SECCOMP_DATA_ARCH_OFFSET), // if (arch != amd64) goto fail;
/* 2 */ BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, AUDIT_ARCH_X86_64, 0, 3), //
/* 3 */ BPF_STMT(BPF_LD + BPF_W + BPF_ABS, SECCOMP_DATA_NR_OFFSET), // if (syscall < BLACKLIST_START) goto pass;
/* 4 */ BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, BLACKLIST_START, 0, 2), //
/* 5 */ BPF_JUMP(BPF_JMP + BPF_JGT + BPF_K, BLACKLIST_END, 1, 0), // if (syscall > BLACKLIST_END) goto pass;
/* 6 */ BPF_STMT(BPF_RET + BPF_K, SECCOMP_RET_ERRNO | (EACCES & SECCOMP_RET_DATA)), // fail: return EACCES;
/* 7 */ BPF_STMT(BPF_RET + BPF_K, SECCOMP_RET_ALLOW) // pass: return OK;
/* 1 */ BPF_STMT(BPF_LD + BPF_W + BPF_ABS, SECCOMP_DATA_ARCH_OFFSET), //
/* 2 */ BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, AUDIT_ARCH_X86_64, 0, 4), // if (arch != amd64) goto fail;
/* 3 */ BPF_STMT(BPF_LD + BPF_W + BPF_ABS, SECCOMP_DATA_NR_OFFSET), //
/* 4 */ BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, NR_SYSCALL_FORK, 0, 3), // if (syscall < SYSCALL_FORK) goto pass;
/* 5 */ BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, NR_SYSCALL_EXECVEAT, 1, 0), // if (syscall == SYSCALL_EXECVEAT) goto fail;
/* 6 */ BPF_JUMP(BPF_JMP + BPF_JGT + BPF_K, NR_SYSCALL_EXECVE, 1, 0), // if (syscall > SYSCALL_EXECVE) goto pass;
/* 7 */ BPF_STMT(BPF_RET + BPF_K, SECCOMP_RET_ERRNO | (EACCES & SECCOMP_RET_DATA)), // fail: return EACCES;
/* 8 */ BPF_STMT(BPF_RET + BPF_K, SECCOMP_RET_ALLOW) // pass: return OK;
};
// seccomp takes a long, so we pass it one explicitly to keep the JNA simple
@ -251,12 +274,12 @@ final class Seccomp {
// install filter, if this works, after this there is no going back!
// first try it with seccomp(SECCOMP_SET_MODE_FILTER), falling back to prctl()
if (libc.syscall(SECCOMP_SYSCALL_NR, SECCOMP_SET_MODE_FILTER, SECCOMP_FILTER_FLAG_TSYNC, pointer) != 0) {
if (linux_libc.syscall(SECCOMP_SYSCALL_NR, SECCOMP_SET_MODE_FILTER, SECCOMP_FILTER_FLAG_TSYNC, pointer) != 0) {
int errno1 = Native.getLastError();
if (logger.isDebugEnabled()) {
logger.debug("seccomp(SECCOMP_SET_MODE_FILTER): " + JNACLibrary.strerror(errno1) + ", falling back to prctl(PR_SET_SECCOMP)...");
}
if (libc.prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, pointer, 0, 0) < 0) {
if (linux_libc.prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, pointer, 0, 0) < 0) {
int errno2 = Native.getLastError();
throw new UnsupportedOperationException("seccomp(SECCOMP_SET_MODE_FILTER): " + JNACLibrary.strerror(errno1) +
", prctl(PR_SET_SECCOMP): " + JNACLibrary.strerror(errno2));
@ -264,8 +287,99 @@ final class Seccomp {
}
// now check that the filter was really installed, we should be in filter mode.
if (libc.prctl(PR_GET_SECCOMP, 0, 0, 0, 0) != 2) {
if (linux_libc.prctl(PR_GET_SECCOMP, 0, 0, 0, 0) != 2) {
throw new UnsupportedOperationException("seccomp filter installation did not really succeed. seccomp(PR_GET_SECCOMP): " + JNACLibrary.strerror(Native.getLastError()));
}
logger.debug("Linux seccomp filter installation successful");
}
// OS X implementation via sandbox(7)
/** Access to non-standard OS X libc methods */
static interface MacLibrary extends Library {
/**
* maps to sandbox_init(3), since Leopard
*/
int sandbox_init(String profile, long flags, PointerByReference errorbuf);
/**
* releases memory when an error occurs during initialization (e.g. syntax bug)
*/
void sandbox_free_error(Pointer errorbuf);
}
// null if unavailable, or something goes wrong.
static final MacLibrary libc_mac;
static {
MacLibrary lib = null;
if (Constants.MAC_OS_X) {
try {
lib = (MacLibrary) Native.loadLibrary("c", MacLibrary.class);
} catch (UnsatisfiedLinkError e) {
logger.warn("unable to link C library. native methods (seatbelt) will be disabled.", e);
}
}
libc_mac = lib;
}
/** The only supported flag... */
static final int SANDBOX_NAMED = 1;
/** Allow everything except process fork and execution */
static final String SANDBOX_RULES = "(version 1) (allow default) (deny process-fork) (deny process-exec)";
/** try to install our custom rule profile into sandbox_init() to block execution */
private static void macImpl(Path tmpFile) throws IOException {
// first be defensive: we can give nice errors this way, at the very least.
boolean supported = Constants.MAC_OS_X;
if (supported == false) {
throw new IllegalStateException("bug: should not be trying to initialize seccomp for an unsupported OS");
}
// we couldn't link methods, could be some really ancient OS X (< Leopard) or some bug
if (libc_mac == null) {
throw new UnsupportedOperationException("seatbelt unavailable: could not link methods. requires Leopard or above.");
}
// write rules to a temporary file, which will be passed to sandbox_init()
Path rules = Files.createTempFile(tmpFile, "es", "sb");
Files.write(rules, Collections.singleton(SANDBOX_RULES));
boolean success = false;
try {
PointerByReference errorRef = new PointerByReference();
int ret = libc_mac.sandbox_init(rules.toAbsolutePath().toString(), SANDBOX_NAMED, errorRef);
// if sandbox_init() fails, add the message from the OS (e.g. syntax error) and free the buffer
if (ret != 0) {
Pointer errorBuf = errorRef.getValue();
RuntimeException e = new UnsupportedOperationException("sandbox_init(): " + errorBuf.getString(0));
libc_mac.sandbox_free_error(errorBuf);
throw e;
}
logger.debug("OS X seatbelt initialization successful");
success = true;
} finally {
if (success) {
Files.delete(rules);
} else {
IOUtils.deleteFilesIgnoringExceptions(rules);
}
}
}
/**
* Attempt to drop the capability to execute for the process.
* <p>
* This is best effort and OS and architecture dependent. It may throw any Throwable.
*/
static void init(Path tmpFile) throws Throwable {
if (Constants.LINUX) {
linuxImpl();
} else if (Constants.MAC_OS_X) {
macImpl(tmpFile);
} else {
logger.debug("syscall filtering not supported for OS {}", Constants.OS_NAME);
}
}
}

20
core/src/test/java/org/elasticsearch/bootstrap/BootstrapForTesting.java
View File

@ -51,8 +51,17 @@ public class BootstrapForTesting {
// without making things complex???
static {
// make sure java.io.tmpdir exists always (in case code uses it in a static initializer)
Path javaTmpDir = PathUtils.get(Objects.requireNonNull(System.getProperty("java.io.tmpdir"),
"please set ${java.io.tmpdir} in pom.xml"));
try {
Security.ensureDirectoryExists(javaTmpDir);
} catch (Exception e) {
throw new RuntimeException("unable to create test temp directory", e);
}
// just like bootstrap, initialize natives, then SM
Bootstrap.initializeNatives(true, true, true);
Bootstrap.initializeNatives(javaTmpDir, true, true, true);
// initialize probes
Bootstrap.initializeProbes();
@ -64,15 +73,6 @@ public class BootstrapForTesting {
throw new RuntimeException("found jar hell in test classpath", e);
}
// make sure java.io.tmpdir exists always (in case code uses it in a static initializer)
Path javaTmpDir = PathUtils.get(Objects.requireNonNull(System.getProperty("java.io.tmpdir"),
"please set ${java.io.tmpdir} in pom.xml"));
try {
Security.ensureDirectoryExists(javaTmpDir);
} catch (Exception e) {
throw new RuntimeException("unable to create test temp directory", e);
}
// install security manager if requested
if (systemPropertyAsBoolean("tests.security.manager", true)) {
try {