cli: new crypto structure to store crypto contexts and parameters, and functions to support it

This new structure, notmuch_crypto_t, keeps all relevant crypto
contexts and parameters together, and will make it easier to pass the
stuff around and clean it up.  The name of the crypto context inside
this new struct will change, to reflect that it is actually a GPG
context, which is a sub type of Crypto context.  There are other types
of Crypto contexts (Pkcs7 in particular, which we hope to support) so
we want to be clear.

The new crypto.c contains functions to return the proper context from
the struct for a given protocol (and initialize it if needed), and to
cleanup a struct by releasing the crypto contexts.

Makefile.local

@@ -292,6 +292,7 @@ notmuch_client_srcs =		\
 	notmuch-time.c		\
 	query-string.c		\
 	mime-node.c		\
+	crypto.c		\
 	json.c
 
 notmuch_client_modules = $(notmuch_client_srcs:.c=.o)

crypto.c

@@ -0,0 +1,71 @@
+/* notmuch - Not much of an email program, (just index and search)
+ *
+ * Copyright © 2012 Jameson Rollins
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see http://www.gnu.org/licenses/ .
+ *
+ * Authors: Jameson Rollins <jrollins@finestructure.net>
+ */
+
+#include "notmuch-client.h"
+
+/* for the specified protocol return the context pointer (initializing
+ * if needed) */
+notmuch_crypto_context_t *
+notmuch_crypto_get_context (notmuch_crypto_t *crypto, const char *protocol)
+{
+    notmuch_crypto_context_t *cryptoctx = NULL;
+
+    /* As per RFC 1847 section 2.1: "the [protocol] value token is
+     * comprised of the type and sub-type tokens of the Content-Type".
+     * As per RFC 1521 section 2: "Content-Type values, subtypes, and
+     * parameter names as defined in this document are
+     * case-insensitive."  Thus, we use strcasecmp for the protocol.
+     */
+    if ((strcasecmp (protocol, "application/pgp-signature") == 0)
+	|| (strcasecmp (protocol, "application/pgp-encrypted") == 0)) {
+	if (!crypto->gpgctx) {
+#ifdef GMIME_ATLEAST_26
+	    /* TODO: GMimePasswordRequestFunc */
+	    crypto->gpgctx = g_mime_gpg_context_new (NULL, "gpg");
+#else
+	    GMimeSession* session = g_object_new (g_mime_session_get_type(), NULL);
+	    crypto->gpgctx = g_mime_gpg_context_new (session, "gpg");
+	    g_object_unref (session);
+#endif
+	    if (crypto->gpgctx) {
+		g_mime_gpg_context_set_always_trust ((GMimeGpgContext*) crypto->gpgctx, FALSE);
+	    } else {
+		fprintf (stderr, "Failed to construct gpg context.\n");
+	    }
+	}
+	cryptoctx = crypto->gpgctx;
+
+    } else {
+	fprintf (stderr, "Unknown or unsupported cryptographic protocol.\n");
+    }
+
+    return cryptoctx;
+}
+
+int
+notmuch_crypto_cleanup (notmuch_crypto_t *crypto)
+{
+    if (crypto->gpgctx) {
+	g_object_unref (crypto->gpgctx);
+	crypto->gpgctx = NULL;
+    }
+
+    return 0;
+}

notmuch-client.h

@@ -77,6 +77,11 @@ typedef struct notmuch_show_format {
     const char *message_set_end;
 } notmuch_show_format_t;
 
+typedef struct notmuch_crypto {
+    notmuch_crypto_context_t* gpgctx;
+    notmuch_bool_t decrypt;
+} notmuch_crypto_t;
+
 typedef struct notmuch_show_params {
     notmuch_bool_t entire_thread;
     notmuch_bool_t omit_excluded;
@@ -112,6 +117,12 @@ chomp_newline (char *str)
 	str[strlen(str)-1] = '\0';
 }
 
+notmuch_crypto_context_t *
+notmuch_crypto_get_context (notmuch_crypto_t *crypto, const char *protocol);
+
+int
+notmuch_crypto_cleanup (notmuch_crypto_t *crypto);
+
 int
 notmuch_count_command (void *ctx, int argc, char *argv[]);