From 0fe9cfef743a00fb38d62e95bbb012a523a8eb3e Mon Sep 17 00:00:00 2001
From: David Goulet <dgoulet@torproject.org>
Date: Mon, 22 Jan 2024 14:57:19 -0500
Subject: [PATCH] ntorv3: Adapt CC client extension to new code

Signed-off-by: David Goulet <dgoulet@torproject.org>
---
 src/core/crypto/onion_crypto.c          | 62 ++++++++++++++++++++++---
 src/core/or/congestion_control_common.c | 39 ++++++++++++++++
 src/core/or/congestion_control_common.h |  3 ++
 3 files changed, 98 insertions(+), 6 deletions(-)

diff --git a/src/core/crypto/onion_crypto.c b/src/core/crypto/onion_crypto.c
index 8c785a5c1a..8507f9f163 100644
--- a/src/core/crypto/onion_crypto.c
+++ b/src/core/crypto/onion_crypto.c
@@ -159,6 +159,59 @@ parse_ntor3_server_ext(const uint8_t *data, size_t data_len,
   return ret;
 }
 
+/** Parse all ntorv3 extensions and populate the params_out with the parsed
+ * values.
+ *
+ * If the extension is not present, the corresponding params_out values are
+ * untouched.
+ *
+ * The returned value in params_out are coherent but should not be considered
+ * valid. The caller must do a proper validation on them.
+ *
+ * Return true on success else false indicating a parsing error or incoherent
+ * values in an extension. */
+static bool
+parse_ntorv3_client_ext(const uint8_t *data, const size_t data_len,
+                        circuit_params_t *params_out)
+{
+  bool ret = false;
+  trn_extension_t *ext = NULL;
+
+  /* Parse extension from payload. */
+  if (trn_extension_parse(&ext, data, data_len) < 0) {
+    goto end;
+  }
+
+  for (size_t idx = 0; idx < trn_extension_get_num(ext); idx++) {
+    const trn_extension_field_t *field = trn_extension_get_fields(ext, idx);
+    if (field == NULL) {
+      ret = -1;
+      goto end;
+    }
+
+    switch (trn_extension_field_get_field_type(field)) {
+    case TRUNNEL_NTORV3_EXT_TYPE_CC_RESPONSE:
+      ret = congestion_control_ntor3_parse_ext_response(field, params_out);
+      break;
+    default:
+      /* Fail on unknown extensions. */
+      ret = false;
+      break;
+    }
+
+    if (!ret) {
+      goto end;
+    }
+  }
+
+  /* Success. */
+  ret = true;
+
+ end:
+  trn_extension_free(ext);
+  return ret;
+}
+
 /** Return a new server_onion_keys_t object with all of the keys
  * and other info we might need to do onion handshakes.  (We make a copy of
  * our keys for each cpuworker to avoid race conditions with the main thread,
@@ -608,10 +661,8 @@ negotiate_v3_ntor_client_circ_params(const uint8_t *param_response_msg,
                                      size_t param_response_len,
                                      circuit_params_t *params_out)
 {
-  int ret = congestion_control_parse_ext_response(param_response_msg,
-                                                  param_response_len,
-                                                  params_out);
-  if (ret < 0) {
+  if (!parse_ntorv3_client_ext(param_response_msg, param_response_len,
+                               params_out)) {
     return -1;
   }
 
@@ -626,10 +677,9 @@ negotiate_v3_ntor_client_circ_params(const uint8_t *param_response_msg,
    * In either case, we cannot proceed on this circuit, and must try a
    * new one.
    */
-  if (ret && !congestion_control_enabled()) {
+  if (params_out->cc_enabled && !congestion_control_enabled()) {
     return -1;
   }
-  params_out->cc_enabled = ret;
 
   return 0;
 }
diff --git a/src/core/or/congestion_control_common.c b/src/core/or/congestion_control_common.c
index 83a0afed30..841dea4eef 100644
--- a/src/core/or/congestion_control_common.c
+++ b/src/core/or/congestion_control_common.c
@@ -1088,6 +1088,45 @@ congestion_control_ntor3_build_ext_response(const circuit_params_t *our_params)
   return field;
 }
 
+/** Parse the given response in the extension field and populate the params_out
+ * with what we find in the extensions.
+ *
+ * Return true on success else false indicating an error. */
+bool
+congestion_control_ntor3_parse_ext_response(const trn_extension_field_t *field,
+                                            circuit_params_t *params_out)
+{
+  bool ret = false;
+  trn_ntorv3_ext_cc_response_t *cc_field = NULL;
+
+  tor_assert(field);
+  tor_assert(params_out);
+  tor_assert(trn_extension_field_get_field_type(field) ==
+             TRUNNEL_NTORV3_EXT_TYPE_CC_RESPONSE);
+
+  /* Parse the field into the congestion control field. */
+  if (trn_ntorv3_ext_cc_response_parse(&cc_field,
+                        trn_extension_field_getconstarray_field(field),
+                        trn_extension_field_getlen_field(field)) < 0) {
+    goto end;
+  }
+
+  uint8_t sendme_inc_cells =
+    trn_ntorv3_ext_cc_response_get_sendme_inc(cc_field);
+  if (!congestion_control_validate_sendme_increment(sendme_inc_cells)) {
+    goto end;
+  }
+
+  /* All good. Get value and break */
+  params_out->cc_enabled = true;
+  params_out->sendme_inc_cells = sendme_inc_cells;
+  ret = true;
+
+ end:
+  trn_ntorv3_ext_cc_response_free(cc_field);
+  return ret;
+}
+
 /** Return true iff the given sendme increment is within the acceptable
  * margins. */
 bool
diff --git a/src/core/or/congestion_control_common.h b/src/core/or/congestion_control_common.h
index a9454f493c..9f284a7ec2 100644
--- a/src/core/or/congestion_control_common.h
+++ b/src/core/or/congestion_control_common.h
@@ -71,6 +71,9 @@ bool congestion_control_enabled(void);
 bool congestion_control_ntor3_parse_ext_request(
                                     const trn_extension_field_t *ext,
                                     circuit_params_t *params_out);
+bool congestion_control_ntor3_parse_ext_response(
+                                    const trn_extension_field_t *field,
+                                    circuit_params_t *params_out);
 trn_extension_field_t *congestion_control_build_ext_request(void);
 trn_extension_field_t *congestion_control_ntor3_build_ext_response(
                                           const circuit_params_t *our_params);
-- 
2.47.3