From d36c331137eb2016d044ce948cf0989c23fecab0 Mon Sep 17 00:00:00 2001
From: Vivien Kraus <vivien@planete-kraus.eu>
Date: Wed, 1 Jan 2020 00:00:00 +0100
Subject: Add a function to hash a public key for DPoP.

---
 src/jwk/ChangeLog          |  4 ++++
 src/jwk/generate-key.c     |  4 ++++
 src/jwk/libwebidoidc-jwk.c | 14 ++++++++++++++
 3 files changed, 22 insertions(+)

(limited to 'src/jwk')

diff --git a/src/jwk/ChangeLog b/src/jwk/ChangeLog
index ebd0873..88b04e0 100644
--- a/src/jwk/ChangeLog
+++ b/src/jwk/ChangeLog
@@ -6,6 +6,10 @@
 
 2020-11-25  Vivien Kraus  <vivien@planete-kraus.eu>
 
+	* libwebidoidc-jwk.c (jkt): Implement the jkt function.
+
+	* generate-key.c (run): display the hash of the key.
+
 	* libwebidoidc-jwk.c: new file.
 	Add the strip function.
 
diff --git a/src/jwk/generate-key.c b/src/jwk/generate-key.c
index ec8ce76..e875b24 100644
--- a/src/jwk/generate-key.c
+++ b/src/jwk/generate-key.c
@@ -10,6 +10,8 @@
 #define _(s) gettext (s)
 
 SCM webidoidc_generate_key_g (SCM args);
+SCM webidoidc_strip_key_g (SCM key);
+SCM webidoidc_jkt_g (SCM key);
 
 extern int init_webidoidc (void);
 
@@ -48,6 +50,8 @@ run (void *params, int argc, char *argv[])
 				  (scm_from_utf8_keyword ("n-size"),
 				   scm_from_size_t (n_size)));
     }
+  scm_display (webidoidc_jkt_g (data), scm_current_error_port ());
+  fprintf (stderr, "\n");
   scm_display (data, scm_current_output_port ());
 }
 
diff --git a/src/jwk/libwebidoidc-jwk.c b/src/jwk/libwebidoidc-jwk.c
index 84da5da..71cb71c 100644
--- a/src/jwk/libwebidoidc-jwk.c
+++ b/src/jwk/libwebidoidc-jwk.c
@@ -3,6 +3,7 @@
 #define _(s) dgettext (PACKAGE, s)
 
 void webid_oidc_random (size_t len, uint8_t * dst);
+SCM webidoidc_hash_g (SCM alg, SCM payload);
 
 /* Register "generate-key", a guile function to generate a keypair. */
 void init_webidoidc_jwk (void);
@@ -173,9 +174,22 @@ SCM_DEFINE (webidoidc_strip_key_g, "strip-key", 1, 0, 0, (SCM key),
   scm_throw (unsupported_kty, scm_list_1 (key));
 }
 
+static SCM scm_to_json_string;
+
+SCM_SYMBOL (sha256, "SHA-256");
+
+SCM_DEFINE (webidoidc_jkt_g, "jkt", 1, 0, 0, (SCM key), "Hash a public key.")
+{
+  SCM stripped = webidoidc_strip_key_g (key);
+  SCM as_json = scm_call_1 (scm_to_json_string, stripped);
+  SCM as_bytevector = scm_string_to_utf8 (as_json);
+  return webidoidc_hash_g (sha256, as_bytevector);
+}
+
 void
 init_webidoidc_jwk (void)
 {
+  scm_to_json_string = scm_c_public_ref ("json", "scm->json-string");
 #ifndef SCM_MAGIC_SNARFER
 #include "libwebidoidc-jwk.x"
 #endif /* not SCM_MAGIC_SNARFER */
-- 
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