[mina-sshd] 02/02: [SSHD-506] Guard against GCM IV reuse.

[lgoldstein]

This is an automated email from the ASF dual-hosted git repository.

lgoldstein pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/mina-sshd.git

commit c110ff837e1fcb638d76b38349216ab67fb2160e
Author: Jeremy Norris <jeremy.nor...@localbackhaul.com>
AuthorDate: Mon Oct 12 15:34:32 2020 -0500

    [SSHD-506] Guard against GCM IV reuse.
---
 .../main/java/org/apache/sshd/common/cipher/BaseGCMCipher.java    | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git 
a/sshd-common/src/main/java/org/apache/sshd/common/cipher/BaseGCMCipher.java 
b/sshd-common/src/main/java/org/apache/sshd/common/cipher/BaseGCMCipher.java
index 5e43336..d1b3191 100644
--- a/sshd-common/src/main/java/org/apache/sshd/common/cipher/BaseGCMCipher.java
+++ b/sshd-common/src/main/java/org/apache/sshd/common/cipher/BaseGCMCipher.java
@@ -78,6 +78,7 @@ public class BaseGCMCipher extends BaseCipher {
      */
     protected static class CounterGCMParameterSpec extends GCMParameterSpec {
         protected final byte[] iv;
+        protected final long initialCounter;
 
         protected CounterGCMParameterSpec(int tLen, byte[] src) {
             super(tLen, src);
@@ -85,12 +86,17 @@ public class BaseGCMCipher extends BaseCipher {
                 throw new IllegalArgumentException("GCM nonce must be 12 
bytes, but given len=" + src.length);
             }
             iv = src.clone();
+            initialCounter = BufferUtils.getLong(iv, iv.length - Long.BYTES, 
Long.BYTES);
         }
 
         protected void incrementCounter() {
             int off = iv.length - Long.BYTES;
             long counter = BufferUtils.getLong(iv, off, Long.BYTES);
-            BufferUtils.putLong(counter + 1L, iv, off, Long.BYTES);
+            long newCounter = counter + 1L;
+            if (newCounter == initialCounter) {
+                throw new IllegalStateException("GCM IV would be reused");
+            }
+            BufferUtils.putLong(newCounter, iv, off, Long.BYTES);
         }
 
         @Override