[gmime] Improved gpg key lookup code

[Rico Tzschichholz <ricotz src gnome org>]

commit 9493bb491aebfd8cff1d8e4d5290ad810e600a78
Author: Jeffrey Stedfast <jestedfa microsoft com>
Date:   Mon Mar 9 19:47:48 2020 -0400

    Improved gpg key lookup code

 gmime/gmime-gpgme-utils.c | 95 ++++++++++++++++++++++++++++-------------------
 1 file changed, 56 insertions(+), 39 deletions(-)
---
diff --git a/gmime/gmime-gpgme-utils.c b/gmime/gmime-gpgme-utils.c
index 041dd020..08699dbc 100644
--- a/gmime/gmime-gpgme-utils.c
+++ b/gmime/gmime-gpgme-utils.c
@@ -97,18 +97,61 @@ g_mime_gpgme_passphrase_callback (void *hook, const char *uid_hint, const char *
 }
 
 
-#define KEY_IS_OK(k)   (!((k)->expired || (k)->revoked || (k)->disabled || (k)->invalid))
+static gboolean
+g_mime_gpgme_key_is_usable (gpgme_key_t key, gboolean secret, time_t now, gpgme_error_t *err)
+{
+       gpgme_subkey_t subkey;
+       
+       *err = GPG_ERR_NO_ERROR;
+       
+       /* first, check the state of the key itself... */
+       if (key->expired)
+               *err = GPG_ERR_KEY_EXPIRED;
+       else if (key->revoked)
+               *err = GPG_ERR_CERT_REVOKED;
+       else if (key->disabled)
+               *err = GPG_ERR_KEY_DISABLED;
+       else if (key->invalid)
+               *err = GPG_ERR_BAD_KEY;
+       
+       if (*err != GPG_ERR_NO_ERROR)
+               return FALSE;
+       
+       /* now check if there is a subkey that we can use */
+       subkey = key->subkeys;
+       
+       while (subkey) {
+               if ((secret && subkey->can_sign) || (!secret && subkey->can_encrypt)) {
+                       if (subkey->expired || (subkey->expires != 0 && subkey->expires <= now))
+                               *err = GPG_ERR_KEY_EXPIRED;
+                       else if (subkey->revoked)
+                               *err = GPG_ERR_CERT_REVOKED;
+                       else if (subkey->disabled)
+                               *err = GPG_ERR_KEY_DISABLED;
+                       else if (subkey->invalid)
+                               *err = GPG_ERR_BAD_KEY;
+                       else
+                               return TRUE;
+               }
+               
+               subkey = subkey->next;
+       }
+       
+       if (*err == GPG_ERR_NO_ERROR)
+               *err = GPG_ERR_BAD_KEY;
+       
+       return FALSE;
+}
 
 /* Note: this function based on code in Balsa written by Albrecht Dreß. */
 static gpgme_key_t
 g_mime_gpgme_get_key_by_name (gpgme_ctx_t ctx, const char *name, gboolean secret, GError **err)
 {
+       gpgme_error_t key_error = GPG_ERR_NO_ERROR;
        time_t now = time (NULL);
        gpgme_key_t key = NULL;
-       gpgme_subkey_t subkey;
-       gboolean bad = FALSE;
+       gboolean found = FALSE;
        gpgme_error_t error;
-       int errval = 0;
        
        if ((error = gpgme_op_keylist_start (ctx, name, secret)) != GPG_ERR_NO_ERROR) {
                if (secret) {
@@ -126,37 +169,11 @@ g_mime_gpgme_get_key_by_name (gpgme_ctx_t ctx, const char *name, gboolean secret
        
        while ((error = gpgme_op_keylist_next (ctx, &key)) == GPG_ERR_NO_ERROR) {
                /* check if this key and the relevant subkey are usable */
-               if (KEY_IS_OK (key)) {
-                       subkey = key->subkeys;
-                       
-                       while (subkey) {
-                               if ((secret && subkey->can_sign) || (!secret && subkey->can_encrypt)) {
-                                       if (KEY_IS_OK (subkey) && (subkey->expires == 0 || subkey->expires > 
now)) {
-                                               errval = GPG_ERR_NO_ERROR;
-                                               break;
-                                       }
-                                       
-                                       if (subkey->expired)
-                                               errval = GPG_ERR_KEY_EXPIRED;
-                               }
-                               
-                               subkey = subkey->next;
-                       }
-                       
-                       if (subkey)
-                               break;
-                       
-                       if (errval == GPG_ERR_NO_ERROR)
-                               errval = GPG_ERR_BAD_KEY;
-               } else {
-                       if (key->expired)
-                               errval = GPG_ERR_KEY_EXPIRED;
-                       else
-                               errval = GPG_ERR_BAD_KEY;
-               }
+               if (g_mime_gpgme_key_is_usable (key, secret, now, &key_error))
+                       break;
                
                gpgme_key_unref (key);
-               bad = TRUE;
+               found = TRUE;
                key = NULL;
        }
        
@@ -178,22 +195,22 @@ g_mime_gpgme_get_key_by_name (gpgme_ctx_t ctx, const char *name, gboolean secret
        
        if (!key) {
                if (strchr (name, '@')) {
-                       if (bad) {
-                               g_set_error (err, GMIME_GPGME_ERROR, errval,
+                       if (found && key_error != GPG_ERR_NO_ERROR) {
+                               g_set_error (err, GMIME_GPGME_ERROR, key_error,
                                             _("A key for %s is present, but it is expired, disabled, revoked 
or invalid"),
                                             name);
                        } else {
                                g_set_error (err, GMIME_GPGME_ERROR, GPG_ERR_NOT_FOUND,
-                                            _("Could not find a key for %s"), name);
+                                            _("Could not find a suitable key for %s"), name);
                        }
                } else {
-                       if (bad) {
-                               g_set_error (err, GMIME_GPGME_ERROR, errval,
+                       if (found && key_error != GPG_ERR_NO_ERROR) {
+                               g_set_error (err, GMIME_GPGME_ERROR, key_error,
                                             _("A key with id %s is present, but it is expired, disabled, 
revoked or invalid"),
                                             name);
                        } else {
                                g_set_error (err, GMIME_GPGME_ERROR, GPG_ERR_NOT_FOUND,
-                                            _("Could not find a key with id %s"), name);
+                                            _("Could not find a suitable key with id %s"), name);
                        }
                }