[taler-anastasis] branch master updated: -improve docs on what truth is, make truth_mime optional

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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 71c6258  -improve docs on what truth is, make truth_mime optional
71c6258 is described below

commit 71c62583d81f149cef2bdbe13870da70b50f3cbd
Author: Christian Grothoff <christian@grothoff.org>
AuthorDate: Sat Aug 14 10:45:50 2021 +0200

    -improve docs on what truth is, make truth_mime optional
---
 doc/anastasis.texi                         | 65 ++++++++++++++++--------------
 src/backend/anastasis-httpd_truth_upload.c |  7 ++--
 src/restclient/anastasis_api_truth_store.c |  7 ++--
 3 files changed, 41 insertions(+), 38 deletions(-)

diff --git a/doc/anastasis.texi b/doc/anastasis.texi
index a5d8b11..c103f7a 100644
--- a/doc/anastasis.texi
+++ b/doc/anastasis.texi
@@ -424,27 +424,31 @@ to recover their core secret.
 @subsection The recovery document
 
 
-A @strong{recovery document} includes all of the information a user needs to
-recover access to their core secret.  It specifies a set of @strong{escrow
-methods}, which specify how the user should convince the Anastasis server
-that they are “real”.  Escrow methods can for example include SMS-based
-verification, video identification or a security question.  For each escrow
-method, the Anastasis server is provided with @strong{truth}, that is data the
-Anastasis operator may learn during the recovery process to authenticate the
-user.  Examples for truth would be a phone number (for SMS), a picture of the
-user (for video identification), or the (hash of) a security answer.  A strong
-adversary is assumed to be able to learn the truth, while weak adversaries
-must not.  In addition to a set of escrow methods and associated Anastasis
-server operators, the @strong{recovery document} also specifies 
@strong{policies}, which
-describe the combination(s) of the escrow methods that suffice to obtain
-access to the core secret.  For example, a @strong{policy} could say that the
-escrow methods (A and B) suffice, and a second policy may permit (A and C).  A
-different user may choose to use the policy that (A and B and C) are all
+A @strong{recovery document} includes all of the information a user
+needs to recover access to their core secret.  It specifies a set of
+@strong{escrow methods}, which specify how the user should convince
+the Anastasis server that they are “real”.  Escrow methods can for
+example include SMS-based verification, video identification or a
+security question.  For each escrow method, the Anastasis server is
+provided with @strong{truth}, that is data the Anastasis operator may
+learn during the recovery process. Truth always consists of an
+encrypted key share and associated data to authenticate the user.
+Examples for truth would be a phone number (for SMS), a picture of the
+user (for video identification), or the (hash of) a security answer.
+A strong adversary is assumed to be able to learn the truth, while
+weak adversaries must not.  In addition to a set of escrow methods and
+associated Anastasis server operators, the @strong{recovery document}
+also specifies @strong{policies}, which describe the combination(s) of
+the escrow methods that suffice to obtain access to the core secret.
+For example, a @strong{policy} could say that the escrow methods (A
+and B) suffice, and a second policy may permit (A and C).  A different
+user may choose to use the policy that (A and B and C) are all
 required.  Anastasis imposes no limit on the number of policies in a
-@strong{recovery document}, or the set of providers or escrow methods involved 
in
-guarding a user’s secret.  Weak adversaries must not be able to deduce
-information about a user’s @strong{recovery document} (except for its length, 
which
-may be exposed to an adversary which monitors the user’s network traffic).
+@strong{recovery document}, or the set of providers or escrow methods
+involved in guarding a user’s secret.  Weak adversaries must not be
+able to deduce information about a user’s @strong{recovery document}
+(except for its length, which may be exposed to an adversary which
+monitors the user’s network traffic).
 
 @c This file is part of Anastasis
 @c Copyright (C) 2019-2021 Anastasis SARL
@@ -2269,9 +2273,15 @@ interface DecryptionPolicy @{
 @anchor{rest managing-truth}@anchor{51}@anchor{rest truth}@anchor{52}
 @subsubsection Managing truth
 
+Truth always consists of an encrypted key share and encrypted
+authentication data.  The key share and the authentication data
+are encrypted using different keys. Additionally, truth includes
+the name of the authentication method, the mime-type of the
+authentication data, and an expiration time in
+cleartext.
 
-This API is used by the Anastasis client to deposit @strong{truth} or request 
a (encrypted) @strong{key share} with
-the escrow provider.
+This API is used by the Anastasis client to deposit @strong{truth} or
+request a (encrypted) @strong{key share} with the escrow provider.
 
 An @strong{escrow method} specifies an Anastasis provider and how the user 
should
 authorize themself.  The @strong{truth} API allows the user to provide the
@@ -2343,13 +2353,6 @@ interface TruthUploadRequest @{
   // Key share method, i.e. "security question", "SMS", "e-mail", ...
   type: string;
 
-  // Nonce used to compute the (iv,key) pair for encryption of the
-  // encrypted_truth.
-  nonce: [32]; //bytearray
-
-  // Authentication tag of `@w{`}encrypted_truth`@w{`}.
-  aes_gcm_tag: [16]; //bytearray
-
   // Variable-size truth. After decryption,
   // this contains the ground truth, i.e. H(challenge answer),
   // phone number, e-mail address, picture, fingerprint, ...
@@ -2357,10 +2360,10 @@ interface TruthUploadRequest @{
   //
   // The nonce of the HKDF for this encryption must include the
   // string "ECT".
-  encrypted_truth: [80]; //bytearray
+  encrypted_truth: []; //bytearray
 
   // MIME type of truth, i.e. text/ascii, image/jpeg, etc.
-  truth_mime: string;
+  truth_mime?: string;
 
   // For how many years from now would the client like us to
   // store the truth?
diff --git a/src/backend/anastasis-httpd_truth_upload.c 
b/src/backend/anastasis-httpd_truth_upload.c
index ada4d4c..451054f 100644
--- a/src/backend/anastasis-httpd_truth_upload.c
+++ b/src/backend/anastasis-httpd_truth_upload.c
@@ -522,7 +522,7 @@ AH_handler_truth_post (
   struct ANASTASIS_CRYPTO_EncryptedKeyShareP keyshare_data;
   void *encrypted_truth;
   size_t encrypted_truth_size;
-  const char *truth_mime;
+  const char *truth_mime = "";
   const char *type;
   enum GNUNET_DB_QueryStatus qs;
   uint32_t storage_years;
@@ -535,8 +535,9 @@ AH_handler_truth_post (
     GNUNET_JSON_spec_varsize ("encrypted_truth",
                               &encrypted_truth,
                               &encrypted_truth_size),
-    GNUNET_JSON_spec_string ("truth_mime",
-                             &truth_mime),
+    GNUNET_JSON_spec_mark_optional (
+      GNUNET_JSON_spec_string ("truth_mime",
+                               &truth_mime)),
     GNUNET_JSON_spec_uint32 ("storage_duration_years",
                              &storage_years),
     GNUNET_JSON_spec_end ()
diff --git a/src/restclient/anastasis_api_truth_store.c 
b/src/restclient/anastasis_api_truth_store.c
index 185e06b..74b9238 100644
--- a/src/restclient/anastasis_api_truth_store.c
+++ b/src/restclient/anastasis_api_truth_store.c
@@ -303,10 +303,9 @@ ANASTASIS_truth_store (
       GNUNET_JSON_pack_data_varsize ("encrypted_truth",
                                      encrypted_truth,
                                      encrypted_truth_size),
-      GNUNET_JSON_pack_string ("truth_mime",
-                               (NULL != truth_mime)
-                               ? truth_mime
-                               : ""),
+      GNUNET_JSON_pack_allow_null (
+        GNUNET_JSON_pack_string ("truth_mime",
+                                 truth_mime)),
       GNUNET_JSON_pack_uint64 ("storage_duration_years",
                                payment_years_requested));
     json_str = json_dumps (truth_data,

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