From 1a473d1cc67e04ae9fea517b36dc332143250cf5 Mon Sep 17 00:00:00 2001
From: Pauli <pauli@openssl.org>
Date: Wed, 22 Sep 2021 10:31:22 +1000
Subject: [PATCH] tls: reduce the strength of CCM_8 ciphers due to their short
 IV.

Fixes #16154

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/16652)
---
 CHANGES.md   |  5 +++++
 ssl/s3_lib.c | 44 ++++++++++++++++++++++----------------------
 2 files changed, 27 insertions(+), 22 deletions(-)

diff --git a/CHANGES.md b/CHANGES.md
index c9d3825eec..cfb6eb0821 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -24,6 +24,11 @@ OpenSSL 3.1
 
 ### Changes between 3.0 and 3.1 [xx XXX xxxx]
 
+ * CCM8 cipher suites in TLS have been downgraded to security level 1 because
+   they use a short tag which lowers their strength.
+
+   *Paul Dale*
+
  * Subject or issuer names in X.509 objects are now displayed as UTF-8 strings
    by default.
 
diff --git a/ssl/s3_lib.c b/ssl/s3_lib.c
index ef027d79e0..88565a7000 100644
--- a/ssl/s3_lib.c
+++ b/ssl/s3_lib.c
@@ -108,9 +108,9 @@ static SSL_CIPHER tls13_ciphers[] = {
         SSL_AEAD,
         TLS1_3_VERSION, TLS1_3_VERSION,
         0, 0,
-        SSL_NOT_DEFAULT | SSL_HIGH,
+        SSL_NOT_DEFAULT | SSL_MEDIUM,
         SSL_HANDSHAKE_MAC_SHA256,
-        128,
+        64, /* CCM8 uses a short tag, so we have a low security strength */
         128,
     }
 };
@@ -699,9 +699,9 @@ static SSL_CIPHER ssl3_ciphers[] = {
      SSL_AEAD,
      TLS1_2_VERSION, TLS1_2_VERSION,
      DTLS1_2_VERSION, DTLS1_2_VERSION,
-     SSL_NOT_DEFAULT | SSL_HIGH,
+     SSL_NOT_DEFAULT | SSL_MEDIUM,
      SSL_HANDSHAKE_MAC_SHA256 | TLS1_PRF_SHA256,
-     128,
+     64, /* CCM8 uses a short tag, so we have a low security strength */
      128,
      },
     {
@@ -715,9 +715,9 @@ static SSL_CIPHER ssl3_ciphers[] = {
      SSL_AEAD,
      TLS1_2_VERSION, TLS1_2_VERSION,
      DTLS1_2_VERSION, DTLS1_2_VERSION,
-     SSL_NOT_DEFAULT | SSL_HIGH,
+     SSL_NOT_DEFAULT | SSL_MEDIUM,
      SSL_HANDSHAKE_MAC_SHA256 | TLS1_PRF_SHA256,
-     256,
+     64, /* CCM8 uses a short tag, so we have a low security strength */
      256,
      },
     {
@@ -731,9 +731,9 @@ static SSL_CIPHER ssl3_ciphers[] = {
      SSL_AEAD,
      TLS1_2_VERSION, TLS1_2_VERSION,
      DTLS1_2_VERSION, DTLS1_2_VERSION,
-     SSL_NOT_DEFAULT | SSL_HIGH,
+     SSL_NOT_DEFAULT | SSL_MEDIUM,
      SSL_HANDSHAKE_MAC_SHA256 | TLS1_PRF_SHA256,
-     128,
+     64, /* CCM8 uses a short tag, so we have a low security strength */
      128,
      },
     {
@@ -747,9 +747,9 @@ static SSL_CIPHER ssl3_ciphers[] = {
      SSL_AEAD,
      TLS1_2_VERSION, TLS1_2_VERSION,
      DTLS1_2_VERSION, DTLS1_2_VERSION,
-     SSL_NOT_DEFAULT | SSL_HIGH,
+     SSL_NOT_DEFAULT | SSL_MEDIUM,
      SSL_HANDSHAKE_MAC_SHA256 | TLS1_PRF_SHA256,
-     256,
+     64, /* CCM8 uses a short tag, so we have a low security strength */
      256,
      },
     {
@@ -827,9 +827,9 @@ static SSL_CIPHER ssl3_ciphers[] = {
      SSL_AEAD,
      TLS1_2_VERSION, TLS1_2_VERSION,
      DTLS1_2_VERSION, DTLS1_2_VERSION,
-     SSL_NOT_DEFAULT | SSL_HIGH,
+     SSL_NOT_DEFAULT | SSL_MEDIUM,
      SSL_HANDSHAKE_MAC_SHA256 | TLS1_PRF_SHA256,
-     128,
+     64, /* CCM8 uses a short tag, so we have a low security strength */
      128,
      },
     {
@@ -843,9 +843,9 @@ static SSL_CIPHER ssl3_ciphers[] = {
      SSL_AEAD,
      TLS1_2_VERSION, TLS1_2_VERSION,
      DTLS1_2_VERSION, DTLS1_2_VERSION,
-     SSL_NOT_DEFAULT | SSL_HIGH,
+     SSL_NOT_DEFAULT | SSL_MEDIUM,
      SSL_HANDSHAKE_MAC_SHA256 | TLS1_PRF_SHA256,
-     256,
+     64, /* CCM8 uses a short tag, so we have a low security strength */
      256,
      },
     {
@@ -859,9 +859,9 @@ static SSL_CIPHER ssl3_ciphers[] = {
      SSL_AEAD,
      TLS1_2_VERSION, TLS1_2_VERSION,
      DTLS1_2_VERSION, DTLS1_2_VERSION,
-     SSL_NOT_DEFAULT | SSL_HIGH,
+     SSL_NOT_DEFAULT | SSL_MEDIUM,
      SSL_HANDSHAKE_MAC_SHA256 | TLS1_PRF_SHA256,
-     128,
+     64, /* CCM8 uses a short tag, so we have a low security strength */
      128,
      },
     {
@@ -875,9 +875,9 @@ static SSL_CIPHER ssl3_ciphers[] = {
      SSL_AEAD,
      TLS1_2_VERSION, TLS1_2_VERSION,
      DTLS1_2_VERSION, DTLS1_2_VERSION,
-     SSL_NOT_DEFAULT | SSL_HIGH,
+     SSL_NOT_DEFAULT | SSL_MEDIUM,
      SSL_HANDSHAKE_MAC_SHA256 | TLS1_PRF_SHA256,
-     256,
+     64, /* CCM8 uses a short tag, so we have a low security strength */
      256,
      },
     {
@@ -923,9 +923,9 @@ static SSL_CIPHER ssl3_ciphers[] = {
      SSL_AEAD,
      TLS1_2_VERSION, TLS1_2_VERSION,
      DTLS1_2_VERSION, DTLS1_2_VERSION,
-     SSL_NOT_DEFAULT | SSL_HIGH,
+     SSL_NOT_DEFAULT | SSL_MEDIUM,
      SSL_HANDSHAKE_MAC_SHA256 | TLS1_PRF_SHA256,
-     128,
+     64, /* CCM8 uses a short tag, so we have a low security strength */
      128,
      },
     {
@@ -939,9 +939,9 @@ static SSL_CIPHER ssl3_ciphers[] = {
      SSL_AEAD,
      TLS1_2_VERSION, TLS1_2_VERSION,
      DTLS1_2_VERSION, DTLS1_2_VERSION,
-     SSL_NOT_DEFAULT | SSL_HIGH,
+     SSL_NOT_DEFAULT | SSL_MEDIUM,
      SSL_HANDSHAKE_MAC_SHA256 | TLS1_PRF_SHA256,
-     256,
+     64, /* CCM8 uses a short tag, so we have a low security strength */
      256,
      },
     {
-- 
2.39.5