[taler-anastasis] branch master updated: use POW hash when hashing security answer, also deduplicate code

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grothoff pushed a commit to branch master
in repository anastasis.

The following commit(s) were added to refs/heads/master by this push:
     new cc9d5f9  use POW hash when hashing security answer, also deduplicate 
code
cc9d5f9 is described below

commit cc9d5f9f5cf1d4d98cbea28ab9a759be2d4e9d30
Author: Christian Grothoff <grothoff@gnunet.org>
AuthorDate: Fri Mar 19 18:14:10 2021 +0100

    use POW hash when hashing security answer, also deduplicate code
---
 src/include/anastasis_crypto_lib.h | 20 +++++++++++++++++++-
 src/lib/anastasis_backup.c         | 19 ++++---------------
 src/lib/anastasis_recovery.c       | 18 ++++--------------
 src/util/anastasis_crypto.c        | 28 ++++++++++++++++++++++++++++
 4 files changed, 55 insertions(+), 30 deletions(-)

diff --git a/src/include/anastasis_crypto_lib.h 
b/src/include/anastasis_crypto_lib.h
index 57f4841..97103fa 100644
--- a/src/include/anastasis_crypto_lib.h
+++ b/src/include/anastasis_crypto_lib.h
@@ -103,7 +103,8 @@ struct ANASTASIS_CRYPTO_MasterSaltP
  */
 struct ANASTASIS_CRYPTO_QuestionSaltP
 {
-  struct GNUNET_ShortHashCode salt GNUNET_PACKED;
+  struct GNUNET_ShortHashCode key GNUNET_PACKED;
+  // struct GNUNET_CRYPTO_PowSalt pow_salt;
 };
 
 
@@ -320,6 +321,23 @@ ANASTASIS_CRYPTO_account_private_key_derive (
   struct ANASTASIS_CRYPTO_AccountPrivateKeyP *priv_key);
 
 
+/**
+ * Hash @a answer to security question with @a salt and @a uuid to compute
+ * @a result that would be sent to the service for authorization.
+ *
+ * @param answer human answer to a security question
+ * @param uuid the truth UUID (known to the service)
+ * @param salt random salt value, unknown to the service
+ * @param[out] result where to write the resulting hash
+ */
+void
+ANASTASIS_CRYPTO_secure_answer_hash (
+  const char *answer,
+  const struct ANASTASIS_CRYPTO_TruthUUIDP *uuid,
+  const struct ANASTASIS_CRYPTO_QuestionSaltP *salt,
+  struct GNUNET_HashCode *result);
+
+
 /**
  * Encrypt and signs the recovery document with AES256, the recovery
  * document is encrypted with a derivation from the user identifier
diff --git a/src/lib/anastasis_backup.c b/src/lib/anastasis_backup.c
index bfd0b26..f5c0693 100644
--- a/src/lib/anastasis_backup.c
+++ b/src/lib/anastasis_backup.c
@@ -285,21 +285,10 @@ ANASTASIS_truth_upload3 (struct GNUNET_CURL_Context *ctx,
 
     answer = GNUNET_strndup (truth_data,
                              truth_data_size);
-    // FIXME: deduplicate this call with anastasis_recovery.c!
-    GNUNET_assert (GNUNET_YES ==
-                   GNUNET_CRYPTO_kdf (
-                     &nt,
-                     sizeof (nt),
-                     "Anastasis-secure-question-uuid-salting",
-                     strlen ("Anastasis-secure-question-uuid-salting"),
-                     answer,
-                     strlen (answer),
-                     &t->uuid,
-                     sizeof (t->uuid),
-                     &t->salt,
-                     sizeof (t->salt),
-                     NULL,
-                     0));
+    ANASTASIS_CRYPTO_secure_answer_hash (answer,
+                                         &t->uuid,
+                                         &t->salt,
+                                         &nt);
     GNUNET_free (answer);
     truth_data = &nt;
     truth_data_size = sizeof (nt);
diff --git a/src/lib/anastasis_recovery.c b/src/lib/anastasis_recovery.c
index c4a52e5..1104d4a 100644
--- a/src/lib/anastasis_recovery.c
+++ b/src/lib/anastasis_recovery.c
@@ -464,20 +464,10 @@ ANASTASIS_challenge_answer (
 {
   struct GNUNET_HashCode hashed_answer;
 
-  GNUNET_assert (GNUNET_YES ==
-                 GNUNET_CRYPTO_kdf (
-                   &hashed_answer,
-                   sizeof (hashed_answer),
-                   "Anastasis-secure-question-uuid-salting",
-                   strlen ("Anastasis-secure-question-uuid-salting"),
-                   answer_str,
-                   strlen (answer_str),
-                   &c->ci.uuid,
-                   sizeof (c->ci.uuid),
-                   &c->salt,
-                   sizeof (c->salt),
-                   NULL,
-                   0));
+  ANASTASIS_CRYPTO_secure_answer_hash (answer_str,
+                                       &c->ci.uuid,
+                                       &c->salt,
+                                       &hashed_answer);
   return ANASTASIS_challenge_start (c,
                                     psp,
                                     timeout,
diff --git a/src/util/anastasis_crypto.c b/src/util/anastasis_crypto.c
index 1b8b4b9..35e0761 100644
--- a/src/util/anastasis_crypto.c
+++ b/src/util/anastasis_crypto.c
@@ -52,6 +52,34 @@ ANASTASIS_hash_answer (uint64_t code,
 }
 
 
+void
+ANASTASIS_CRYPTO_secure_answer_hash (
+  const char *answer,
+  const struct ANASTASIS_CRYPTO_TruthUUIDP *uuid,
+  const struct ANASTASIS_CRYPTO_QuestionSaltP *salt,
+  struct GNUNET_HashCode *result)
+{
+  struct GNUNET_HashCode pow;
+
+  GNUNET_CRYPTO_pow_hash (&salt->pow_salt,
+                          answer,
+                          strlen (answer),
+                          &pow);
+  GNUNET_assert (GNUNET_YES ==
+                 GNUNET_CRYPTO_kdf (
+                   result,
+                   sizeof (*result),
+                   "Anastasis-secure-question-uuid-salting",
+                   strlen ("Anastasis-secure-question-uuid-salting"),
+                   &pow,
+                   sizeof (pow),
+                   uuid,
+                   sizeof (*uuid),
+                   NULL,
+                   0));
+}
+
+
 /**
  * Compute @a key and @a iv.
  *

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