prop224: API for the creation of blinded keys

Add a function for both the client and service side that is building a blinded
key from a keypair (service) and from a public key (client). Those two
functions uses the current time period information to build the key.

Signed-off-by: David Goulet <dgoulet@torproject.org>

1 files changed, 26 insertions, 1 deletions

diff --git a/src/or/hs_common.h b/src/or/hs_common.h
index a6c9994ef9..ae9c4e36a5 100644
--- a/src/or/hs_common.h
+++ b/src/or/hs_common.h
@@ -79,6 +79,22 @@
 #define HS_SERVICE_ADDR_LEN_BASE32 \
   (CEIL_DIV(HS_SERVICE_ADDR_LEN * 8, 5))
 
+/* The default HS time period length */
+#define HS_TIME_PERIOD_LENGTH_DEFAULT 1440 /* 1440 minutes == one day */
+/* The minimum time period length as seen in prop224 section [TIME-PERIODS] */
+#define HS_TIME_PERIOD_LENGTH_MIN 30 /* minutes */
+/* The minimum time period length as seen in prop224 section [TIME-PERIODS] */
+#define HS_TIME_PERIOD_LENGTH_MAX (60 * 24 * 10) /* 10 days or 14400 minutes */
+/* The time period rotation offset as seen in prop224 section [TIME-PERIODS] */
+#define HS_TIME_PERIOD_ROTATION_OFFSET (12 * 60) /* minutes */
+
+/* Keyblinding parameter construction is as follow:
+ *    "key-blind" || INT_8(period_num) || INT_8(start_period_sec) */
+#define HS_KEYBLIND_NONCE_PREFIX "key-blind"
+#define HS_KEYBLIND_NONCE_PREFIX_LEN (sizeof(HS_KEYBLIND_NONCE_PREFIX) - 1)
+#define HS_KEYBLIND_NONCE_LEN \
+  (HS_KEYBLIND_NONCE_PREFIX_LEN + sizeof(uint64_t) + sizeof(uint64_t))
+
 /* Type of authentication key used by an introduction point. */
 typedef enum {
   HS_AUTH_KEY_TYPE_LEGACY  = 1,
@@ -98,6 +114,15 @@ int hs_address_is_valid(const char *address);
 int hs_parse_address(const char *address, ed25519_public_key_t *key_out,
                      uint8_t *checksum_out, uint8_t *version_out);
 
+void hs_build_blinded_pubkey(const ed25519_public_key_t *pubkey,
+                             const uint8_t *secret, size_t secret_len,
+                             uint64_t time_period_num,
+                             ed25519_public_key_t *pubkey_out);
+void hs_build_blinded_keypair(const ed25519_keypair_t *kp,
+                              const uint8_t *secret, size_t secret_len,
+                              uint64_t time_period_num,
+                              ed25519_keypair_t *kp_out);
+
 void rend_data_free(rend_data_t *data);
 rend_data_t *rend_data_dup(const rend_data_t *data);
 rend_data_t *rend_data_client_create(const char *onion_address,
@@ -114,6 +139,7 @@ const char *rend_data_get_desc_id(const rend_data_t *rend_data,
 const uint8_t *rend_data_get_pk_digest(const rend_data_t *rend_data,
                                        size_t *len_out);
 
+uint64_t hs_get_time_period_num(time_t now);
 uint64_t hs_get_next_time_period_num(time_t now);
 
 link_specifier_t *hs_link_specifier_dup(const link_specifier_t *lspec);
@@ -123,7 +149,6 @@ link_specifier_t *hs_link_specifier_dup(const link_specifier_t *lspec);
 #ifdef TOR_UNIT_TESTS
 
 STATIC uint64_t get_time_period_length(void);
-STATIC uint64_t get_time_period_num(time_t now);
 
 #endif /* TOR_UNIT_TESTS */