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lgoldstein pushed a commit to branch master
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The following commit(s) were added to refs/heads/master by this push:
new e021a6f [SSHD-954] Improve validation of DH public key values
e021a6f is described below
commit e021a6f4597cb7259162169851bb9e4cb85e1a39
Author: Lyor Goldstein <lgoldst...@apache.org>
AuthorDate: Fri Oct 9 09:17:01 2020 +0300
[SSHD-954] Improve validation of DH public key values
---
CHANGES.md | 1 +
.../org/apache/sshd/common/util/buffer/Buffer.java | 14 ++--
.../sshd/common/util/buffer/BufferUtils.java | 13 ++++
.../java/org/apache/sshd/client/kex/DHGClient.java | 8 +-
.../org/apache/sshd/client/kex/DHGEXClient.java | 50 ++++++++++--
.../org/apache/sshd/common/kex/KeyExchange.java | 19 +++++
.../sshd/common/kex/dh/AbstractDHKeyExchange.java | 88 +++++++++++++++++++++-
.../org/apache/sshd/server/kex/DHGEXServer.java | 32 ++++++--
.../java/org/apache/sshd/server/kex/DHGServer.java | 6 +-
9 files changed, 202 insertions(+), 29 deletions(-)
diff --git a/CHANGES.md b/CHANGES.md
index c9d2864..001fc9e 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -37,6 +37,7 @@ or `-key-file` command line option.
## Behavioral changes and enhancements
* [SSHD-506](https://issues.apache.org/jira/browse/SSHD-506) Added support for
AES-GCM ciphers.
+* [SSHD-954](https://issues.apache.org/jira/browse/SSHD-954) Improve
validation of DH public key values.
* [SSHD-1004](https://issues.apache.org/jira/browse/SSHD-1004) Deprecate DES,
RC4 and Blowfish ciphers from default setup.
* [SSHD-1004](https://issues.apache.org/jira/browse/SSHD-1004) Deprecate SHA-1
based key exchanges and signatures from default setup.
* [SSHD-1004](https://issues.apache.org/jira/browse/SSHD-1004) Deprecate
MD5-based and truncated HMAC algorithms from default setup.
diff --git
a/sshd-common/src/main/java/org/apache/sshd/common/util/buffer/Buffer.java
b/sshd-common/src/main/java/org/apache/sshd/common/util/buffer/Buffer.java
index 8022df3..4a1bfeb 100644
--- a/sshd-common/src/main/java/org/apache/sshd/common/util/buffer/Buffer.java
+++ b/sshd-common/src/main/java/org/apache/sshd/common/util/buffer/Buffer.java
@@ -853,18 +853,18 @@ public abstract class Buffer implements Readable {
}
}
- public void putMPInt(BigInteger bi) {
- putMPInt(bi.toByteArray());
+ public void putMPInt(BigInteger bigint) {
+ putMPInt(bigint.toByteArray());
}
- public void putMPInt(byte[] foo) {
- if ((foo[0] & 0x80) != 0) {
- putInt(foo.length + 1 /* padding */);
+ public void putMPInt(byte[] mpInt) {
+ if ((mpInt[0] & 0x80) != 0) {
+ putInt(mpInt.length + 1 /* padding */);
putByte((byte) 0);
} else {
- putInt(foo.length);
+ putInt(mpInt.length);
}
- putRawBytes(foo);
+ putRawBytes(mpInt);
}
public void putRawBytes(byte[] d) {
diff --git
a/sshd-common/src/main/java/org/apache/sshd/common/util/buffer/BufferUtils.java
b/sshd-common/src/main/java/org/apache/sshd/common/util/buffer/BufferUtils.java
index be67be0..ad67a5f 100644
---
a/sshd-common/src/main/java/org/apache/sshd/common/util/buffer/BufferUtils.java
+++
b/sshd-common/src/main/java/org/apache/sshd/common/util/buffer/BufferUtils.java
@@ -22,6 +22,7 @@ import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.StreamCorruptedException;
+import java.math.BigInteger;
import java.util.function.IntUnaryOperator;
import java.util.logging.Level;
@@ -402,6 +403,18 @@ public final class BufferUtils {
return l;
}
+ public static BigInteger fromMPIntBytes(byte[] mpInt) {
+ if (NumberUtils.isEmpty(mpInt)) {
+ return null;
+ }
+
+ if ((mpInt[0] & 0x80) != 0) {
+ return new BigInteger(0, mpInt);
+ } else {
+ return new BigInteger(mpInt);
+ }
+ }
+
/**
* Writes a 32-bit value in network order (i.e., MSB 1st)
*
diff --git a/sshd-core/src/main/java/org/apache/sshd/client/kex/DHGClient.java
b/sshd-core/src/main/java/org/apache/sshd/client/kex/DHGClient.java
index 559206b..ec65ba1 100644
--- a/sshd-core/src/main/java/org/apache/sshd/client/kex/DHGClient.java
+++ b/sshd-core/src/main/java/org/apache/sshd/client/kex/DHGClient.java
@@ -95,7 +95,8 @@ public class DHGClient extends AbstractDHClientKeyExchange {
dh = getDH();
hash = dh.getHash();
hash.init();
- e = dh.getE();
+
+ byte[] e = updateE(dh.getE());
Session s = getSession();
if (log.isDebugEnabled()) {
@@ -127,8 +128,9 @@ public class DHGClient extends AbstractDHClientKeyExchange {
}
byte[] k_s = buffer.getBytes();
- f = buffer.getMPIntAsBytes();
+ byte[] f = updateF(buffer);
byte[] sig = buffer.getBytes();
+
dh.setF(f);
k = dh.getK();
@@ -166,7 +168,7 @@ public class DHGClient extends AbstractDHClientKeyExchange {
buffer.putBytes(i_c);
buffer.putBytes(i_s);
buffer.putBytes(k_s);
- buffer.putMPInt(e);
+ buffer.putMPInt(getE());
buffer.putMPInt(f);
buffer.putMPInt(k);
hash.update(buffer.array(), 0, buffer.available());
diff --git
a/sshd-core/src/main/java/org/apache/sshd/client/kex/DHGEXClient.java
b/sshd-core/src/main/java/org/apache/sshd/client/kex/DHGEXClient.java
index d02d7e6..6c7923c 100644
--- a/sshd-core/src/main/java/org/apache/sshd/client/kex/DHGEXClient.java
+++ b/sshd-core/src/main/java/org/apache/sshd/client/kex/DHGEXClient.java
@@ -37,6 +37,7 @@ import org.apache.sshd.common.signature.Signature;
import org.apache.sshd.common.util.GenericUtils;
import org.apache.sshd.common.util.ValidateUtils;
import org.apache.sshd.common.util.buffer.Buffer;
+import org.apache.sshd.common.util.buffer.BufferUtils;
import org.apache.sshd.common.util.buffer.ByteArrayBuffer;
import org.apache.sshd.common.util.security.SecurityUtils;
import org.apache.sshd.core.CoreModuleProperties;
@@ -52,9 +53,11 @@ public class DHGEXClient extends AbstractDHClientKeyExchange
{
protected int prf;
protected int max;
protected AbstractDH dh;
- protected byte[] p;
protected byte[] g;
+ private byte[] p;
+ private BigInteger pValue;
+
protected DHGEXClient(DHFactory factory, Session session) {
super(session);
this.factory = Objects.requireNonNull(factory, "No factory");
@@ -73,6 +76,34 @@ public class DHGEXClient extends AbstractDHClientKeyExchange
{
return factory.getName();
}
+ protected byte[] getP() {
+ return p;
+ }
+
+ protected BigInteger getPValue() {
+ if (pValue == null) {
+ pValue = BufferUtils.fromMPIntBytes(getP());
+ }
+
+ return pValue;
+ }
+
+ protected void setP(byte[] p) {
+ this.p = p;
+
+ if (pValue != null) {
+ pValue = null; // force lazy re-initialization
+ }
+ }
+
+ protected void validateEValue() throws Exception {
+ validateEValue(getPValue());
+ }
+
+ protected void validateFValue() throws Exception {
+ validateFValue(getPValue());
+ }
+
public static KeyExchangeFactory newFactory(DHFactory delegate) {
return new KeyExchangeFactory() {
@Override
@@ -137,13 +168,15 @@ public class DHGEXClient extends
AbstractDHClientKeyExchange {
}
if (cmd == SshConstants.SSH_MSG_KEX_DH_GEX_GROUP) {
- p = buffer.getMPIntAsBytes();
+ setP(buffer.getMPIntAsBytes());
g = buffer.getMPIntAsBytes();
- dh = getDH(new BigInteger(p), new BigInteger(g));
+ dh = getDH(getPValue(), new BigInteger(g));
hash = dh.getHash();
hash.init();
- e = dh.getE();
+
+ byte[] e = updateE(dh.getE());
+ validateEValue();
if (debugEnabled) {
log.debug("next({})[{}] Send SSH_MSG_KEX_DH_GEX_INIT", this,
session);
@@ -164,8 +197,11 @@ public class DHGEXClient extends
AbstractDHClientKeyExchange {
}
byte[] k_s = buffer.getBytes();
- f = buffer.getMPIntAsBytes();
+ byte[] f = updateF(buffer);
byte[] sig = buffer.getBytes();
+
+ validateFValue();
+
dh.setF(f);
k = dh.getK();
@@ -188,9 +224,9 @@ public class DHGEXClient extends
AbstractDHClientKeyExchange {
buffer.putInt(min);
buffer.putInt(prf);
buffer.putInt(max);
- buffer.putMPInt(p);
+ buffer.putMPInt(getP());
buffer.putMPInt(g);
- buffer.putMPInt(e);
+ buffer.putMPInt(getE());
buffer.putMPInt(f);
buffer.putMPInt(k);
hash.update(buffer.array(), 0, buffer.available());
diff --git
a/sshd-core/src/main/java/org/apache/sshd/common/kex/KeyExchange.java
b/sshd-core/src/main/java/org/apache/sshd/common/kex/KeyExchange.java
index a0ad22e..f50cd36 100644
--- a/sshd-core/src/main/java/org/apache/sshd/common/kex/KeyExchange.java
+++ b/sshd-core/src/main/java/org/apache/sshd/common/kex/KeyExchange.java
@@ -18,6 +18,7 @@
*/
package org.apache.sshd.common.kex;
+import java.math.BigInteger;
import java.util.Collections;
import java.util.NavigableMap;
@@ -101,4 +102,22 @@ public interface KeyExchange extends NamedResource,
SessionHolder<Session> {
return name;
}
}
+
+ // see https://tools.ietf.org/html/rfc8268#section-4
+ static boolean isValidDHValue(BigInteger value, BigInteger p) {
+ if ((value == null) || (p == null)) {
+ return false;
+ }
+
+ // 1 < value < p-1
+ if (value.compareTo(BigInteger.ONE) <= 0) {
+ return false;
+ }
+
+ if (value.compareTo(p.subtract(BigInteger.ONE)) >= 0) {
+ return false;
+ }
+
+ return true;
+ }
}
diff --git
a/sshd-core/src/main/java/org/apache/sshd/common/kex/dh/AbstractDHKeyExchange.java
b/sshd-core/src/main/java/org/apache/sshd/common/kex/dh/AbstractDHKeyExchange.java
index 7f29782..1e77c38 100644
---
a/sshd-core/src/main/java/org/apache/sshd/common/kex/dh/AbstractDHKeyExchange.java
+++
b/sshd-core/src/main/java/org/apache/sshd/common/kex/dh/AbstractDHKeyExchange.java
@@ -19,12 +19,17 @@
package org.apache.sshd.common.kex.dh;
+import java.math.BigInteger;
import java.util.Objects;
+import org.apache.sshd.common.SshConstants;
+import org.apache.sshd.common.SshException;
import org.apache.sshd.common.digest.Digest;
import org.apache.sshd.common.kex.KeyExchange;
import org.apache.sshd.common.session.Session;
import org.apache.sshd.common.util.ValidateUtils;
+import org.apache.sshd.common.util.buffer.Buffer;
+import org.apache.sshd.common.util.buffer.BufferUtils;
import org.apache.sshd.common.util.logging.AbstractLoggingBean;
/**
@@ -36,11 +41,14 @@ public abstract class AbstractDHKeyExchange extends
AbstractLoggingBean implemen
protected byte[] i_s;
protected byte[] i_c;
protected Digest hash;
- protected byte[] e;
- protected byte[] f;
protected byte[] k;
protected byte[] h;
+ private byte[] e;
+ private BigInteger eValue;
+ private byte[] f;
+ private BigInteger fValue;
+
private final Session session;
protected AbstractDHKeyExchange(Session session) {
@@ -75,6 +83,82 @@ public abstract class AbstractDHKeyExchange extends
AbstractLoggingBean implemen
return k;
}
+ protected byte[] getE() {
+ return e;
+ }
+
+ protected BigInteger getEValue() {
+ if (eValue == null) {
+ eValue = BufferUtils.fromMPIntBytes(getE());
+ }
+
+ return eValue;
+ }
+
+ protected byte[] updateE(Buffer buffer) {
+ return updateE(buffer.getMPIntAsBytes());
+ }
+
+ protected byte[] updateE(byte[] mpInt) {
+ setE(mpInt);
+ return mpInt;
+ }
+
+ protected void setE(byte[] e) {
+ this.e = e;
+
+ if (eValue != null) {
+ eValue = null; // force lazy re-initialization
+ }
+ }
+
+ protected void validateEValue(BigInteger pValue) throws Exception {
+ BigInteger value = Objects.requireNonNull(getEValue(), "No DH 'e'
value set");
+ if (!KeyExchange.isValidDHValue(value, pValue)) {
+ throw new SshException(
+ SshConstants.SSH2_DISCONNECT_KEY_EXCHANGE_FAILED,
+ "Protocol error: invalid DH 'e' value");
+ }
+ }
+
+ protected byte[] getF() {
+ return f;
+ }
+
+ protected BigInteger getFValue() {
+ if (fValue == null) {
+ fValue = BufferUtils.fromMPIntBytes(getF());
+ }
+
+ return fValue;
+ }
+
+ protected byte[] updateF(Buffer buffer) {
+ return updateF(buffer.getMPIntAsBytes());
+ }
+
+ protected byte[] updateF(byte[] mpInt) {
+ setF(mpInt);
+ return mpInt;
+ }
+
+ protected void setF(byte[] f) {
+ this.f = f;
+
+ if (fValue != null) {
+ fValue = null; // force lazy re-initialization
+ }
+ }
+
+ protected void validateFValue(BigInteger pValue) throws Exception {
+ BigInteger value = Objects.requireNonNull(getFValue(), "No DH 'f'
value set");
+ if (!KeyExchange.isValidDHValue(value, pValue)) {
+ throw new SshException(
+ SshConstants.SSH2_DISCONNECT_KEY_EXCHANGE_FAILED,
+ "Protocol error: invalid DH 'f' value");
+ }
+ }
+
@Override
public String toString() {
return getClass().getSimpleName() + "[" + getName() + "]";
diff --git
a/sshd-core/src/main/java/org/apache/sshd/server/kex/DHGEXServer.java
b/sshd-core/src/main/java/org/apache/sshd/server/kex/DHGEXServer.java
index f6f2c18..66fbf4a 100644
--- a/sshd-core/src/main/java/org/apache/sshd/server/kex/DHGEXServer.java
+++ b/sshd-core/src/main/java/org/apache/sshd/server/kex/DHGEXServer.java
@@ -126,7 +126,12 @@ public class DHGEXServer extends
AbstractDHServerKeyExchange {
}
dh = chooseDH(min, prf, max);
- f = dh.getE();
+
+ setF(dh.getE());
+
+ BigInteger pValue = dh.getP();
+ validateFValue(pValue);
+
hash = dh.getHash();
hash.init();
@@ -136,7 +141,7 @@ public class DHGEXServer extends
AbstractDHServerKeyExchange {
}
buffer =
session.createBuffer(SshConstants.SSH_MSG_KEX_DH_GEX_GROUP);
- buffer.putMPInt(dh.getP());
+ buffer.putMPInt(pValue);
buffer.putMPInt(dh.getG());
session.writePacket(buffer);
@@ -157,7 +162,12 @@ public class DHGEXServer extends
AbstractDHServerKeyExchange {
}
dh = chooseDH(min, prf, max);
- f = dh.getE();
+
+ setF(dh.getE());
+
+ BigInteger pValue = dh.getP();
+ validateFValue(pValue);
+
hash = dh.getHash();
hash.init();
@@ -166,7 +176,7 @@ public class DHGEXServer extends
AbstractDHServerKeyExchange {
this, session, min, prf, max);
}
buffer =
session.createBuffer(SshConstants.SSH_MSG_KEX_DH_GEX_GROUP);
- buffer.putMPInt(dh.getP());
+ buffer.putMPInt(pValue);
buffer.putMPInt(dh.getG());
session.writePacket(buffer);
@@ -182,11 +192,14 @@ public class DHGEXServer extends
AbstractDHServerKeyExchange {
}
if (cmd == SshConstants.SSH_MSG_KEX_DH_GEX_INIT) {
- e = buffer.getMPIntAsBytes();
+ byte[] e = updateE(buffer.getMPIntAsBytes());
+ BigInteger pValue = dh.getP();
+ validateEValue(pValue);
+
dh.setF(e);
+
k = dh.getK();
- byte[] k_s;
KeyPair kp = Objects.requireNonNull(session.getHostKey(), "No
server key pair available");
String algo =
session.getNegotiatedKexParameter(KexProposalOption.SERVERKEYS);
Signature sig = ValidateUtils.checkNotNull(
@@ -196,7 +209,8 @@ public class DHGEXServer extends
AbstractDHServerKeyExchange {
buffer = new ByteArrayBuffer();
buffer.putRawPublicKey(kp.getPublic());
- k_s = buffer.getCompactData();
+
+ byte[] k_s = buffer.getCompactData();
buffer.clear();
buffer.putBytes(v_c);
@@ -213,11 +227,13 @@ public class DHGEXServer extends
AbstractDHServerKeyExchange {
buffer.putInt(max);
}
- buffer.putMPInt(dh.getP());
+ buffer.putMPInt(pValue);
buffer.putMPInt(dh.getG());
buffer.putMPInt(e);
+ byte[] f = getF();
buffer.putMPInt(f);
buffer.putMPInt(k);
+
hash.update(buffer.array(), 0, buffer.available());
h = hash.digest();
sig.update(session, h);
diff --git a/sshd-core/src/main/java/org/apache/sshd/server/kex/DHGServer.java
b/sshd-core/src/main/java/org/apache/sshd/server/kex/DHGServer.java
index d911f2f..6ac9337 100644
--- a/sshd-core/src/main/java/org/apache/sshd/server/kex/DHGServer.java
+++ b/sshd-core/src/main/java/org/apache/sshd/server/kex/DHGServer.java
@@ -82,7 +82,7 @@ public class DHGServer extends AbstractDHServerKeyExchange {
dh = factory.create();
hash = dh.getHash();
hash.init();
- f = dh.getE();
+ setF(dh.getE());
}
@Override
@@ -99,7 +99,7 @@ public class DHGServer extends AbstractDHServerKeyExchange {
"Protocol error: expected packet SSH_MSG_KEXDH_INIT, got "
+ KeyExchange.getSimpleKexOpcodeName(cmd));
}
- e = buffer.getMPIntAsBytes();
+ byte[] e = updateE(buffer);
dh.setF(e);
k = dh.getK();
@@ -122,8 +122,10 @@ public class DHGServer extends AbstractDHServerKeyExchange
{
buffer.putBytes(i_s);
buffer.putBytes(k_s);
buffer.putMPInt(e);
+ byte[] f = getF();
buffer.putMPInt(f);
buffer.putMPInt(k);
+
hash.update(buffer.array(), 0, buffer.available());
h = hash.digest();
sig.update(session, h);
