Refactor the HS ntor key expansion to fit the e2e circuit API.

We want to use the circuit_init_cpath_crypto() function to setup our
cpath, and that function accepts a key array as input. So let's make our
HS ntor key expansion function also return a key array as output,
instead of a struct.

Also, we actually don't need KH from the key expansion, so the key
expansion output can be one DIGEST256_LEN shorter. See here for more
info: https://trac.torproject.org/projects/tor/ticket/22052#comment:3

1 files changed, 6 insertions, 17 deletions

diff --git a/src/or/hs_ntor.h b/src/or/hs_ntor.h
index cd75f46a4c..3a97e17acc 100644
--- a/src/or/hs_ntor.h
+++ b/src/or/hs_ntor.h
@@ -6,6 +6,10 @@
 
 #include "or.h"
 
+/* Output length of KDF for key expansion */
+#define HS_NTOR_KEY_EXPANSION_KDF_OUT_LEN \
+  (DIGEST256_LEN*2 + CIPHER256_KEY_LEN*2)
+
 /* Key material needed to encode/decode INTRODUCE1 cells */
 typedef struct {
   /* Key used for encryption of encrypted INTRODUCE1 blob */
@@ -23,21 +27,6 @@ typedef struct {
   uint8_t ntor_key_seed[DIGEST256_LEN];
 } hs_ntor_rend_cell_keys_t;
 
-/* Key material resulting from key expansion as detailed in section "4.2.1. Key
- * expansion" of rend-spec-ng.txt. */
-typedef struct {
-  /* Per-circuit key material used in ESTABLISH_INTRO cell */
-  uint8_t KH[DIGEST256_LEN];
-  /* Authentication key for outgoing RELAY cells */
-  uint8_t Df[DIGEST256_LEN];
-  /* Authentication key for incoming RELAY cells */
-  uint8_t Db[DIGEST256_LEN];
-  /* Encryption key for outgoing RELAY cells */
-  uint8_t Kf[CIPHER256_KEY_LEN];
-  /* Decryption key for incoming RELAY cells */
-  uint8_t Kb[CIPHER256_KEY_LEN];
-} hs_ntor_rend_circuit_keys_t;
-
 int hs_ntor_client_get_introduce1_keys(
                       const ed25519_public_key_t *intro_auth_pubkey,
                       const curve25519_public_key_t *intro_enc_pubkey,
@@ -66,8 +55,8 @@ int hs_ntor_service_get_rendezvous1_keys(
                   const curve25519_public_key_t *client_ephemeral_enc_pubkey,
                   hs_ntor_rend_cell_keys_t *hs_ntor_rend_cell_keys_out);
 
-hs_ntor_rend_circuit_keys_t *hs_ntor_circuit_key_expansion(
-                       const hs_ntor_rend_cell_keys_t *hs_ntor_rend_cell_keys);
+void hs_ntor_circuit_key_expansion(const uint8_t *ntor_key_seed,
+                                   uint8_t *keys_out);
 
 int hs_ntor_client_rendezvous2_mac_is_good(
                         const hs_ntor_rend_cell_keys_t *hs_ntor_rend_cell_keys,