prop250: Add memory and disk state in new files

This commit introduces two new files with their header.

"shared_random.c" contains basic functions to initialize the state and allow
commit decoding for the disk state to be able to parse them from disk.

"shared_random_state.c" contains everything that has to do with the state
for both our memory and disk. Lots of helper functions as well as a
mechanism to query the state in a synchronized way.

Signed-off-by: David Goulet <dgoulet@torproject.org>
Signed-off-by: George Kadianakis <desnacked@riseup.net>

1 files changed, 114 insertions, 0 deletions

diff --git a/src/or/shared_random.h b/src/or/shared_random.h
new file mode 100644
index 0000000000..447de0c4b5
--- /dev/null
+++ b/src/or/shared_random.h
@@ -0,0 +1,114 @@
+/* Copyright (c) 2016, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#ifndef TOR_SHARED_RANDOM_H
+#define TOR_SHARED_RANDOM_H
+
+/*
+ * This file contains ABI/API of the shared random protocol defined in
+ * proposal #250. Every public functions and data structure are namespaced
+ * with "sr_" which stands for shared random.
+ */
+
+#include "or.h"
+
+/* Protocol version */
+#define SR_PROTO_VERSION  1
+/* Default digest algorithm. */
+#define SR_DIGEST_ALG DIGEST_SHA3_256
+/* Invariant token in the SRV calculation. */
+#define SR_SRV_TOKEN "shared-random"
+/* Don't count the NUL terminated byte even though the TOKEN has it. */
+#define SR_SRV_TOKEN_LEN (sizeof(SR_SRV_TOKEN) - 1)
+
+/* Length of the random number (in bytes). */
+#define SR_RANDOM_NUMBER_LEN 32
+/* Size of a decoded commit value in a vote or state. It's a hash and a
+ * timestamp. It adds up to 40 bytes. */
+#define SR_COMMIT_LEN (sizeof(uint64_t) + DIGEST256_LEN)
+/* Size of a decoded reveal value from a vote or state. It's a 64 bit
+ * timestamp and the hashed random number. This adds up to 40 bytes. */
+#define SR_REVEAL_LEN (sizeof(uint64_t) + DIGEST256_LEN)
+/* Size of SRV message length. The construction is has follow:
+ *  "shared-random" | INT_8(reveal_num) | INT_8(version) | PREV_SRV */
+#define SR_SRV_MSG_LEN \
+  (SR_SRV_TOKEN_LEN + 1 + 1 + DIGEST256_LEN)
+
+/* Length of base64 encoded commit NOT including the NULL terminated byte.
+ * Formula is taken from base64_encode_size. */
+#define SR_COMMIT_BASE64_LEN \
+  (((SR_COMMIT_LEN - 1) / 3) * 4 + 4)
+/* Length of base64 encoded reveal NOT including the NULL terminated byte.
+ * Formula is taken from base64_encode_size. This adds up to 56 bytes. */
+#define SR_REVEAL_BASE64_LEN \
+  (((SR_REVEAL_LEN - 1) / 3) * 4 + 4)
+
+/* Protocol phase. */
+typedef enum {
+  /* Commitment phase */
+  SR_PHASE_COMMIT  = 1,
+  /* Reveal phase */
+  SR_PHASE_REVEAL  = 2,
+} sr_phase_t;
+
+/* A shared random value (SRV). */
+typedef struct sr_srv_t {
+  /* The number of reveal values used to derive this SRV. */
+  int num_reveals;
+  /* The actual value. This is the stored result of SHA3-256. */
+  uint8_t value[DIGEST256_LEN];
+} sr_srv_t;
+
+/* A commit (either ours or from another authority). */
+typedef struct sr_commit_t {
+  /* Hashing algorithm used. */
+  digest_algorithm_t alg;
+
+  /* Commit owner info */
+
+  /* The RSA identity fingerprint of the authority. */
+  char rsa_identity_fpr[FINGERPRINT_LEN + 1];
+
+  /* Commitment information */
+
+  /* Timestamp of reveal. Correspond to TIMESTAMP. */
+  time_t reveal_ts;
+  /* H(REVEAL) as found in COMMIT message. */
+  char hashed_reveal[DIGEST256_LEN];
+  /* Base64 encoded COMMIT. We use this to put it in our vote. */
+  char encoded_commit[SR_COMMIT_BASE64_LEN + 1];
+
+  /* Reveal information */
+
+  /* H(RN) which is what we used as the random value for this commit. We
+   * don't use the raw bytes since those are sent on the network thus
+   * avoiding possible information leaks of our PRNG. */
+  uint8_t random_number[SR_RANDOM_NUMBER_LEN];
+  /* Timestamp of commit. Correspond to TIMESTAMP. */
+  time_t commit_ts;
+  /* This is the whole reveal message. We use it during verification */
+  char encoded_reveal[SR_REVEAL_BASE64_LEN + 1];
+} sr_commit_t;
+
+/* API */
+
+/* Public methods: */
+
+int sr_init(int save_to_disk);
+void sr_save_and_cleanup(void);
+void sr_commit_free(sr_commit_t *commit);
+
+/* Private methods (only used by shared_random_state.c): */
+
+sr_commit_t *sr_parse_commit(const smartlist_t *args);
+sr_srv_t *sr_parse_srv(const smartlist_t *args);
+
+#ifdef SHARED_RANDOM_PRIVATE
+
+/* Decode. */
+STATIC int commit_decode(const char *encoded, sr_commit_t *commit);
+STATIC int reveal_decode(const char *encoded, sr_commit_t *commit);
+
+#endif /* SHARED_RANDOM_PRIVATE */
+
+#endif /* TOR_SHARED_RANDOM_H */