[Openvpn-devel,M] Change in openvpn[master]: Implement support for larger packet counter sizes

Message ID def1d1e58b22fe5c305eef8e1d776bc30c61d5ba-HTML@gerrit.openvpn.net
State New
Headers show
Series [Openvpn-devel,M] Change in openvpn[master]: Implement support for larger packet counter sizes | expand

Commit Message

its_Giaan (Code Review) Jan. 25, 2024, 12:38 p.m. UTC
Attention is currently required from: flichtenheld.

Hello flichtenheld,

I'd like you to do a code review.
Please visit

    http://gerrit.openvpn.net/c/openvpn/+/507?usp=email

to review the following change.


Change subject: Implement support for larger packet counter sizes
......................................................................

Implement support for larger packet counter sizes

With DCO and possible future hardware assisted OpenVPN acceleration we
are approaching the point where 32 bit IVs are not cutting it any more.

To illustrate the problem, some back of the envelope math here:

If we want to keep the current 3600s renegotiation interval and have
a safety margin of 25% (when we trigger renegotiation) we have about
3.2 million packets (2*32 * 0.7) to work with. That translates to
about 835k packets per second.

With 1300 Byte packets that translates into 8-9 Gbit/s. That is far
from unrealistic any more. Current DCO implementations are already in
spitting distance to that or might even reach (for a single client
connection) that if you have extremely fast
single core performance CPU.

This introduces the 64bit packet counters for AEAD data channel
ciphers in TLS mode ciphers. No effort has been made to support
larger packet counters in any scenario since the other scenarios
are all legacy.

While we still keep the old --secret logic around we use the same
weird unix timestamp + packet counter format to avoid refactoring the
code now and again when we remove --secret code but DCO
implementations are free to use just a single 64 bit counter. One
other small downside of this approach is that when rollover happens
and we get reordering all the older packets are thrown away since
the distance between the packet before and after the rollover is
quite large as we probably jump forward more than 1s (or more than
2^32 packet ids) forward. But this is an obscure edge that we can
(currently) live with.

Change-Id: I01e258e97351b5aa4b9e561f5b35ddc2318569e2
---
M src/openvpn/crypto.c
M src/openvpn/crypto.h
M src/openvpn/init.c
M src/openvpn/multi.c
M src/openvpn/options.c
M src/openvpn/push.c
M src/openvpn/ssl.c
M src/openvpn/ssl_common.h
M src/openvpn/ssl_ncp.c
M tests/unit_tests/openvpn/test_ssl.c
10 files changed, 105 insertions(+), 20 deletions(-)



  git pull ssh://gerrit.openvpn.net:29418/openvpn refs/changes/07/507/1

Patch

diff --git a/src/openvpn/crypto.c b/src/openvpn/crypto.c
index 9988ebe..81b33fe 100644
--- a/src/openvpn/crypto.c
+++ b/src/openvpn/crypto.c
@@ -68,6 +68,7 @@ 
     const struct key_ctx *ctx = &opt->key_ctx_bi.encrypt;
     uint8_t *mac_out = NULL;
     const int mac_len = OPENVPN_AEAD_TAG_LENGTH;
+    bool longiv = opt->flags & CO_64_BIT_PKT_ID;
 
     /* IV, packet-ID and implicit IV required for this mode. */
     ASSERT(ctx->cipher);
@@ -86,7 +87,7 @@ 
         buf_set_write(&iv_buffer, iv, iv_len);
 
         /* IV starts with packet id to make the IV unique for packet */
-        if (!packet_id_write(&opt->packet_id.send, &iv_buffer, false, false))
+        if (!packet_id_write(&opt->packet_id.send, &iv_buffer, longiv, false))
         {
             msg(D_CRYPT_ERRORS, "ENCRYPT ERROR: packet ID roll over");
             goto err;
@@ -384,6 +385,8 @@ 
     /* IV and Packet ID required for this mode */
     ASSERT(packet_id_initialized(&opt->packet_id));
 
+    bool longiv = opt->flags & CO_64_BIT_PKT_ID;
+
     /* Combine IV from explicit part from packet and implicit part from context */
     {
         uint8_t iv[OPENVPN_MAX_IV_LENGTH] = { 0 };
@@ -409,7 +412,7 @@ 
     }
 
     /* Read packet ID from packet */
-    if (!packet_id_read(&pin, buf, false))
+    if (!packet_id_read(&pin, buf, longiv))
     {
         CRYPT_ERROR("error reading packet-id");
     }
diff --git a/src/openvpn/crypto.h b/src/openvpn/crypto.h
index 95a5b31..0ef13e0 100644
--- a/src/openvpn/crypto.h
+++ b/src/openvpn/crypto.h
@@ -283,6 +283,11 @@ 
     /**< Bit-flag indicating that the AEAD tag is at the end of the
      *   packet.
      */
+#define CO_64_BIT_PKT_ID  (1<<9)
+    /**< Bit-flag indicating that we should use a 64 bit (8 byte) packet
+     * counter instead of the 32 bit that we normally use.
+     */
+
 
     unsigned int flags;         /**< Bit-flags determining behavior of
                                  *   security operation functions. */
diff --git a/src/openvpn/init.c b/src/openvpn/init.c
index cd37b36..7db8d06 100644
--- a/src/openvpn/init.c
+++ b/src/openvpn/init.c
@@ -2327,6 +2327,10 @@ 
         {
             buf_printf(&out, " aead-tag-end");
         }
+        if (o->imported_protocol_flags & CO_64_BIT_PKT_ID)
+        {
+            buf_printf(&out, " pkt-id-64-bit");
+        }
     }
 
     if (buf_len(&out) > strlen(header))
@@ -3297,6 +3301,16 @@ 
         to.push_peer_info_detail = 1;
     }
 
+    /* Check if the DCO drivers support the new 64bit packet counter and
+     * AEAD tag at the end */
+    if (dco_enabled(options))
+    {
+        to.data_v3_features_supported = false;
+    }
+    else
+    {
+        to.data_v3_features_supported = true;
+    }
 
     /* should we not xmit any packets until we get an initial
      * response from client? */
diff --git a/src/openvpn/multi.c b/src/openvpn/multi.c
index 4344126..a80b9f4 100644
--- a/src/openvpn/multi.c
+++ b/src/openvpn/multi.c
@@ -1851,6 +1851,13 @@ 
         o->imported_protocol_flags |= CO_USE_CC_EXIT_NOTIFY;
     }
 
+    if (tls_multi->session[TM_ACTIVE].opt->data_v3_features_supported
+        && (proto & IV_PROTO_DATA_V3))
+    {
+        o->imported_protocol_flags |= CO_AEAD_TAG_AT_THE_END;
+        o->imported_protocol_flags |= CO_64_BIT_PKT_ID;
+    }
+
     /* Select cipher if client supports Negotiable Crypto Parameters */
 
     /* if we have already created our key, we cannot *change* our own
diff --git a/src/openvpn/options.c b/src/openvpn/options.c
index 39f00c0..3f8fccf 100644
--- a/src/openvpn/options.c
+++ b/src/openvpn/options.c
@@ -8690,6 +8690,10 @@ 
             {
                 options->imported_protocol_flags |= CO_AEAD_TAG_AT_THE_END;
             }
+            else if (streq(p[j], "pkt-id-64-bit"))
+            {
+                options->imported_protocol_flags |= CO_64_BIT_PKT_ID;
+            }
             else
             {
                 msg(msglevel, "Unknown protocol-flags flag: %s", p[j]);
diff --git a/src/openvpn/push.c b/src/openvpn/push.c
index e4c122c..5766c97 100644
--- a/src/openvpn/push.c
+++ b/src/openvpn/push.c
@@ -691,6 +691,10 @@ 
     {
         buf_printf(&proto_flags, " aead-tag-end");
     }
+    if (o->imported_protocol_flags & CO_64_BIT_PKT_ID)
+    {
+        buf_printf(&proto_flags, " pkt-id-64-bit");
+    }
 
     if (buf_len(&proto_flags) > 0)
     {
diff --git a/src/openvpn/ssl.c b/src/openvpn/ssl.c
index 33c8670..6579ff9 100644
--- a/src/openvpn/ssl.c
+++ b/src/openvpn/ssl.c
@@ -105,9 +105,11 @@ 
  * @param ctx                   Encrypt/decrypt key context
  * @param key                   HMAC key, used to calculate implicit IV
  * @param key_len               HMAC key length
+ * @param long_pkt_id           64-bit packet counters are used
  */
 static void
-key_ctx_update_implicit_iv(struct key_ctx *ctx, uint8_t *key, size_t key_len);
+key_ctx_update_implicit_iv(struct key_ctx *ctx, uint8_t *key, size_t key_len,
+                           bool long_pkt_id);
 
 
 /**
@@ -1369,13 +1371,15 @@ 
     }
     else
     {
+        bool longiv = ks->crypto_options.flags & CO_64_BIT_PKT_ID;
         init_key_ctx_bi(key, key2, key_direction, key_type, "Data Channel");
         /* Initialize implicit IVs */
-        key_ctx_update_implicit_iv(&key->encrypt, key2->keys[(int)server].hmac,
-                                   MAX_HMAC_KEY_LENGTH);
+        key_ctx_update_implicit_iv(&key->encrypt,
+                                   key2->keys[(int)server].hmac,
+                                   MAX_HMAC_KEY_LENGTH, longiv);
         key_ctx_update_implicit_iv(&key->decrypt,
                                    key2->keys[1 - (int)server].hmac,
-                                   MAX_HMAC_KEY_LENGTH);
+                                   MAX_HMAC_KEY_LENGTH, longiv);
     }
 }
 
@@ -1513,14 +1517,15 @@ 
 }
 
 static void
-key_ctx_update_implicit_iv(struct key_ctx *ctx, uint8_t *key, size_t key_len)
+key_ctx_update_implicit_iv(struct key_ctx *ctx, uint8_t *key,
+                           size_t key_len, bool longiv)
 {
     /* Only use implicit IV in AEAD cipher mode, where HMAC key is not used */
     if (cipher_ctx_mode_aead(ctx->cipher))
     {
         size_t impl_iv_len = 0;
         ASSERT(cipher_ctx_iv_length(ctx->cipher) >= OPENVPN_AEAD_MIN_IV_LEN);
-        impl_iv_len = cipher_ctx_iv_length(ctx->cipher) - sizeof(packet_id_type);
+        impl_iv_len = cipher_ctx_iv_length(ctx->cipher) - packet_id_size(longiv);
         ASSERT(impl_iv_len <= OPENVPN_MAX_IV_LENGTH);
         ASSERT(impl_iv_len <= key_len);
         memcpy(ctx->implicit_iv, key, impl_iv_len);
@@ -1935,6 +1940,12 @@ 
         iv_proto |= IV_PROTO_DYN_TLS_CRYPT;
 #endif
 
+        /* support for AEAD tag at the end and 8 byte IV */
+        if (session->opt->data_v3_features_supported)
+        {
+            iv_proto |= IV_PROTO_DATA_V3;
+        }
+
         buf_printf(&out, "IV_PROTO=%d\n", iv_proto);
 
         if (session->opt->push_peer_info_detail > 1)
diff --git a/src/openvpn/ssl_common.h b/src/openvpn/ssl_common.h
index f085e0d..53bf763 100644
--- a/src/openvpn/ssl_common.h
+++ b/src/openvpn/ssl_common.h
@@ -311,7 +311,6 @@ 
 
     /* from command line */
     bool single_session;
-    bool disable_occ;
     int mode;
     bool pull;
     /**
@@ -361,6 +360,8 @@ 
     const char *config_ciphername;
     const char *config_ncp_ciphers;
 
+    bool data_v3_features_supported; /**< dco supports new data channel features */
+
     bool tls_crypt_v2;
     const char *tls_crypt_v2_verify_script;
 
@@ -490,8 +491,6 @@ 
      */
     int key_id;
 
-    int limit_next;             /* used for traffic shaping on the control channel */
-
     int verify_maxlevel;
 
     char *common_name;
diff --git a/src/openvpn/ssl_ncp.c b/src/openvpn/ssl_ncp.c
index 0ca6d42..0b4ad8a 100644
--- a/src/openvpn/ssl_ncp.c
+++ b/src/openvpn/ssl_ncp.c
@@ -430,6 +430,12 @@ 
         session->opt->crypto_flags |= CO_USE_CC_EXIT_NOTIFY;
     }
 
+    if (session->opt->data_v3_features_supported && (iv_proto_peer & IV_PROTO_DATA_V3))
+    {
+        session->opt->crypto_flags |= CO_AEAD_TAG_AT_THE_END;
+        session->opt->crypto_flags |= CO_64_BIT_PKT_ID;
+    }
+
 #if defined(HAVE_EXPORT_KEYING_MATERIAL)
     if (iv_proto_peer & IV_PROTO_TLS_KEY_EXPORT)
     {
diff --git a/tests/unit_tests/openvpn/test_ssl.c b/tests/unit_tests/openvpn/test_ssl.c
index 0ded052..125d24b 100644
--- a/tests/unit_tests/openvpn/test_ssl.c
+++ b/tests/unit_tests/openvpn/test_ssl.c
@@ -128,9 +128,12 @@ 
 {
     cipher_ctx_t *cipher = co->key_ctx_bi.encrypt.cipher;
 
+
     if (cipher_ctx_mode_aead(cipher))
     {
-        size_t impl_iv_len = cipher_ctx_iv_length(cipher) - sizeof(packet_id_type);
+        bool longiv = co->flags & CO_64_BIT_PKT_ID;
+
+        size_t impl_iv_len = cipher_ctx_iv_length(cipher) - packet_id_size(longiv);
         ASSERT(cipher_ctx_iv_length(cipher) <= OPENVPN_MAX_IV_LENGTH);
         ASSERT(cipher_ctx_iv_length(cipher) >= OPENVPN_AEAD_MIN_IV_LEN);
 
@@ -142,6 +145,11 @@ 
         memcpy(co->key_ctx_bi.decrypt.implicit_iv,
                co->key_ctx_bi.encrypt.implicit_iv, OPENVPN_MAX_IV_LENGTH);
         co->key_ctx_bi.decrypt.implicit_iv_len = impl_iv_len;
+
+        if (longiv)
+        {
+            co->flags |= CO_64_BIT_PKT_ID;
+        }
     }
 }
 
@@ -280,6 +288,25 @@ 
 }
 
 static void
+run_data_channel_with_cipher_end_and_long_pkt_counter(const char *cipher)
+{
+    struct crypto_options co = init_crypto_options(cipher, "none");
+    co.flags |= CO_AEAD_TAG_AT_THE_END;
+    do_data_channel_round_trip(&co);
+    uninit_crypto_options(&co);
+}
+
+static void
+run_data_channel_with_long_pkt_counter(const char *cipher)
+{
+    struct crypto_options co = init_crypto_options(cipher, "none");
+    co.flags |= CO_64_BIT_PKT_ID;
+    do_data_channel_round_trip(&co);
+    uninit_crypto_options(&co);
+}
+
+
+static void
 run_data_channel_with_cipher(const char *cipher, const char *auth)
 {
     struct crypto_options co = init_crypto_options(cipher, auth);
@@ -289,24 +316,30 @@ 
 
 
 static void
+run_aead_channel_tests(const char *cipher)
+{
+    run_data_channel_with_cipher_end(cipher);
+    run_data_channel_with_cipher(cipher, "none");
+    run_data_channel_with_cipher_end_and_long_pkt_counter(cipher);
+    run_data_channel_with_long_pkt_counter(cipher);
+}
+
+static void
 test_data_channel_roundtrip_aes_128_gcm(void **state)
 {
-    run_data_channel_with_cipher_end("AES-128-GCM");
-    run_data_channel_with_cipher("AES-128-GCM", "none");
+    run_aead_channel_tests("AES-128-GCM");
 }
 
 static void
 test_data_channel_roundtrip_aes_192_gcm(void **state)
 {
-    run_data_channel_with_cipher_end("AES-192-GCM");
-    run_data_channel_with_cipher("AES-192-GCM", "none");
+    run_aead_channel_tests("AES-192-GCM");
 }
 
 static void
 test_data_channel_roundtrip_aes_256_gcm(void **state)
 {
-    run_data_channel_with_cipher_end("AES-256-GCM");
-    run_data_channel_with_cipher("AES-256-GCM", "none");
+    run_aead_channel_tests("AES-256-GCM");
 }
 
 static void
@@ -336,8 +369,7 @@ 
         return;
     }
 
-    run_data_channel_with_cipher_end("ChaCha20-Poly1305");
-    run_data_channel_with_cipher("ChaCha20-Poly1305", "none");
+    run_aead_channel_tests("ChaCha20-Poly1305");
 }
 
 static void