gpg: Add accessor & utility functions for pk->keyid and pk->main_keyid.

* g10/keydb.h (keyid_cmp): New function.
* g10/keyid.c (pk_keyid): New function.
(pk_main_keyid): New function.
(keyid_copy): New function.
(pk_keyid_str): New function.
* g10/packet.h (PKT_public_key): Update comments for main_keyid and
keyid.

--
Signed-off-by: Neal H. Walfield <neal@g10code.com>

Before accessing pk->keyid, it is necessary to call keyid_from_pk (pk,
NULL) to ensure that pk->keyid is valid.  Because it is easy to forget
to do this, these accessor functions take care of it.

g10/keydb.h

@@ -1,7 +1,7 @@
 /* keydb.h - Key database
  * Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
  *               2006, 2010 Free Software Foundation, Inc.
- * Copyright (C) 2015 g10 Code GmbH
+ * Copyright (C) 2015, 2016 g10 Code GmbH
  *
  * This file is part of GnuPG.
  *
@@ -396,12 +396,44 @@ char *pubkey_string (PKT_public_key *pk, char *buffer, size_t bufsize);
 u32 v3_keyid (gcry_mpi_t a, u32 *ki);
 void hash_public_key( gcry_md_hd_t md, PKT_public_key *pk );
 char *format_keyid (u32 *keyid, int format, char *buffer, int len);
+
+/* Return PK's keyid.  The memory is owned by PK.  */
+u32 *pk_keyid (PKT_public_key *pk);
+
+/* Return the keyid of the primary key associated with PK.  The memory
+   is owned by PK.  */
+u32 *pk_main_keyid (PKT_public_key *pk);
+
+/* Order A and B.  If A < B then return -1, if A == B then return 0,
+   and if A > B then return 1.  */
+static int GPGRT_ATTR_UNUSED
+keyid_cmp (const u32 *a, const u32 *b)
+{
+  if (a[0] < b[0])
+    return -1;
+  if (a[0] > b[0])
+    return 1;
+  if (a[1] < b[1])
+    return -1;
+  if (a[1] > b[1])
+    return 1;
+  return 0;
+}
+
+/* Copy the keyid in SRC to DEST and return DEST.  */
+u32 *keyid_copy (u32 *dest, const u32 *src);
+
 size_t keystrlen(void);
 const char *keystr(u32 *keyid);
 const char *keystr_with_sub (u32 *main_kid, u32 *sub_kid);
 const char *keystr_from_pk(PKT_public_key *pk);
 const char *keystr_from_pk_with_sub (PKT_public_key *main_pk,
                                      PKT_public_key *sub_pk);
+
+/* Return PK's key id as a string using the default format.  PK owns
+   the storage.  */
+const char *pk_keyid_str (PKT_public_key *pk);
+
 const char *keystr_from_desc(KEYDB_SEARCH_DESC *desc);
 u32 keyid_from_pk( PKT_public_key *pk, u32 *keyid );
 u32 keyid_from_sig( PKT_signature *sig, u32 *keyid );

g10/keyid.c

@@ -2,6 +2,7 @@
  * Copyright (C) 1998, 1999, 2000, 2001, 2003,
  *               2004, 2006, 2010 Free Software Foundation, Inc.
  * Copyright (C) 2014 Werner Koch
+ * Copyright (C) 2016 g10 Code GmbH
  *
  * This file is part of GnuPG.
  *
@@ -274,6 +275,52 @@ v3_keyid (gcry_mpi_t a, u32 *ki)
 }
 
 
+/* Return PK's keyid.  The memory is owned by PK.  */
+u32 *
+pk_keyid (PKT_public_key *pk)
+{
+  keyid_from_pk (pk, NULL);
+
+  /* Uncomment this for help tracking down bugs related to keyid or
+     main_keyid not being set correctly.  */
+#if 0
+  if (! (pk->main_keyid[0] || pk->main_keyid[1]))
+    log_bug ("pk->main_keyid not set!\n");
+  if (keyid_cmp (pk->keyid, pk->main_keyid) == 0
+      && ! pk->flags.primary)
+    log_bug ("keyid and main_keyid are the same, but primary flag not set!\n");
+  if (keyid_cmp (pk->keyid, pk->main_keyid) != 0
+      && pk->flags.primary)
+    log_bug ("keyid and main_keyid are different, but primary flag set!\n");
+#endif
+
+  return pk->keyid;
+}
+
+/* Return the keyid of the primary key associated with PK.  The memory
+   is owned by PK.  */
+u32 *
+pk_main_keyid (PKT_public_key *pk)
+{
+  /* Uncomment this for help tracking down bugs related to keyid or
+     main_keyid not being set correctly.  */
+#if 0
+  if (! (pk->main_keyid[0] || pk->main_keyid[1]))
+    log_bug ("pk->main_keyid not set!\n");
+#endif
+
+  return pk->main_keyid;
+}
+
+/* Copy the keyid in SRC to DEST and return DEST.  */
+u32 *
+keyid_copy (u32 *dest, const u32 *src)
+{
+  dest[0] = src[0];
+  dest[1] = src[1];
+  return dest;
+}
+
 char *
 format_keyid (u32 *keyid, int format, char *buffer, int len)
 {
@@ -396,6 +443,14 @@ keystr_from_pk_with_sub (PKT_public_key *main_pk, PKT_public_key *sub_pk)
 }
 
 
+/* Return PK's key id as a string using the default format.  PK owns
+   the storage.  */
+const char *
+pk_keyid_str (PKT_public_key *pk)
+{
+  return keystr (pk_keyid (pk));
+}
+
 
 const char *
 keystr_from_desc(KEYDB_SEARCH_DESC *desc)

g10/packet.h

@@ -279,8 +279,12 @@ typedef struct
   byte    pubkey_usage;   /* for now only used to pass it to getkey() */
   byte    req_usage;      /* hack to pass a request to getkey() */
   u32     has_expired;    /* set to the expiration date if expired */
-  u32     main_keyid[2];  /* keyid of the primary key */
-  u32     keyid[2];	    /* calculated by keyid_from_pk() */
+  /* keyid of the primary key.  Never access this value directly.
+     Instead, use pk_main_keyid().  */
+  u32     main_keyid[2];
+  /* keyid of this key.  Never access this value directly!  Instead,
+     use pk_keyid().  */
+  u32     keyid[2];
   prefitem_t *prefs;      /* list of preferences (may be NULL) */
   struct
   {