From 3738b0a99a45c09fa5f66e80110dbdff185bbf7c Mon Sep 17 00:00:00 2001
From: Werner Koch <wk@gnupg.org>
Date: Fri, 7 Feb 2025 11:10:09 +0100
Subject: gpg: Store Link attributes for composite keys.

* g10/call-agent.c (agent_crosslink_keys): New.
* g10/keygen.c (common_gen): Store the Link attribute.
--

The Link attribute may be useful to quickly find the other part of a
composite private key.

GnuPG-bug-id: 6638
---
 g10/call-agent.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

(limited to 'g10/call-agent.c')

diff --git a/g10/call-agent.c b/g10/call-agent.c
index 54d8f62f1..bdde9b053 100644
--- a/g10/call-agent.c
+++ b/g10/call-agent.c
@@ -2673,6 +2673,30 @@ agent_genkey (ctrl_t ctrl, char **cache_nonce_addr, char **passwd_nonce_addr,
 }
 
 
+/* Add the Link attribute to both given keys.  */
+gpg_error_t
+agent_crosslink_keys (ctrl_t ctrl, const char *hexgrip1, const char *hexgrip2)
+{
+  gpg_error_t err;
+  char line[ASSUAN_LINELENGTH];
+
+  err = start_agent (ctrl, 0);
+  if (err)
+    goto leave;
+
+  snprintf (line, sizeof line, "KEYATTR %s Link: %s", hexgrip1, hexgrip2);
+  err = assuan_transact (agent_ctx, line, NULL, NULL, NULL, NULL, NULL, NULL);
+  if (err)
+    goto leave;
+
+  snprintf (line, sizeof line, "KEYATTR %s Link: %s", hexgrip2, hexgrip1);
+  err = assuan_transact (agent_ctx, line, NULL, NULL, NULL, NULL, NULL, NULL);
+
+ leave:
+  return err;
+}
+
+
 
 /* Call the agent to read the public key part for a given keygrip.
  * Values from FROMCARD:
-- 
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