[PATCH 03/10] crypto: make shared crypto code behave library-like

[Daniel Kahn Gillmor <dkg@fifthhorseman.net>]

If we're going to reuse the crypto code across both the library and
the client, then it needs to report error states properly and not
write to stderr.
---
 lib/database.cc |  6 ++++
 lib/notmuch.h   | 17 +++++++++++
 mime-node.c     |  7 ++++-
 util/crypto.c   | 89 ++++++++++++++++++++++++++++-----------------------------
 util/crypto.h   |  6 ++--
 5 files changed, 76 insertions(+), 49 deletions(-)

diff --git a/lib/database.cc b/lib/database.cc
index 79eb3d69..82a3d463 100644
--- a/lib/database.cc
+++ b/lib/database.cc
@@ -413,6 +413,12 @@ notmuch_status_to_string (notmuch_status_t status)
 	return "Operation requires a database upgrade";
     case NOTMUCH_STATUS_PATH_ERROR:
 	return "Path supplied is illegal for this function";
+    case NOTMUCH_STATUS_MALFORMED_CRYPTO_PROTOCOL:
+	return "Crypto protocol missing, malformed, or unintelligible";
+    case NOTMUCH_STATUS_FAILED_CRYPTO_CONTEXT_CREATION:
+	return "Crypto engine initialization failure";
+    case NOTMUCH_STATUS_UNKNOWN_CRYPTO_PROTOCOL:
+	return "Unknown crypto protocol";
     default:
     case NOTMUCH_STATUS_LAST_STATUS:
 	return "Unknown error status value";
diff --git a/lib/notmuch.h b/lib/notmuch.h
index f26565f3..6c76fb40 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -191,6 +191,23 @@ typedef enum _notmuch_status {
      * function, in a way not covered by a more specific argument.
      */
     NOTMUCH_STATUS_ILLEGAL_ARGUMENT,
+    /**
+     * A MIME object claimed to have cryptographic protection which
+     * notmuch tried to handle, but the protocol was not specified in
+     * an intelligible way.
+     */
+    NOTMUCH_STATUS_MALFORMED_CRYPTO_PROTOCOL,
+    /**
+     * Notmuch attempted to do crypto processing, but could not
+     * initialize the engine needed to do so.
+     */
+    NOTMUCH_STATUS_FAILED_CRYPTO_CONTEXT_CREATION,
+    /**
+     * A MIME object claimed to have cryptographic protection, and
+     * notmuch attempted to process it, but the specific protocol was
+     * something that notmuch doesn't know how to handle.
+     */
+    NOTMUCH_STATUS_UNKNOWN_CRYPTO_PROTOCOL,
     /**
      * Not an actual status value. Just a way to find out how many
      * valid status values there are.
diff --git a/mime-node.c b/mime-node.c
index d9ff7de1..6cd7d2de 100644
--- a/mime-node.c
+++ b/mime-node.c
@@ -265,7 +265,12 @@ _mime_node_create (mime_node_t *parent, GMimeObject *part)
 	|| (GMIME_IS_MULTIPART_SIGNED (part) && node->ctx->crypto->verify)) {
 	GMimeContentType *content_type = g_mime_object_get_content_type (part);
 	const char *protocol = g_mime_content_type_get_parameter (content_type, "protocol");
-	cryptoctx = _notmuch_crypto_get_gmime_context (node->ctx->crypto, protocol);
+	notmuch_status_t status;
+	status = _notmuch_crypto_get_gmime_ctx_for_protocol (node->ctx->crypto,
+							     protocol, &cryptoctx);
+	if (status) /* this is a warning, not an error */
+	    fprintf (stderr, "Warning: %s (%s).\n", notmuch_status_to_string (status),
+		     protocol ? protocol : "(NULL)");
 	if (!cryptoctx)
 	    return NULL;
     }
diff --git a/util/crypto.c b/util/crypto.c
index 97e8c8f4..e7908197 100644
--- a/util/crypto.c
+++ b/util/crypto.c
@@ -27,86 +27,86 @@
 #define ARRAY_SIZE(arr) (sizeof (arr) / sizeof (arr[0]))
 
 #if (GMIME_MAJOR_VERSION < 3)
-/* Create a GPG context (GMime 2.6) */
-static GMimeCryptoContext*
-create_gpg_context (_notmuch_crypto_t *crypto)
+/* Create or pass on a GPG context (GMime 2.6) */
+static notmuch_status_t
+get_gpg_context (_notmuch_crypto_t *crypto, GMimeCryptoContext **ctx)
 {
-    GMimeCryptoContext *gpgctx;
+    if (ctx == NULL || crypto == NULL)
+	return NOTMUCH_STATUS_NULL_POINTER;
 
     if (crypto->gpgctx) {
-	return crypto->gpgctx;
+	*ctx = crypto->gpgctx;
+	return NOTMUCH_STATUS_SUCCESS;
     }
 
     /* TODO: GMimePasswordRequestFunc */
-    gpgctx = g_mime_gpg_context_new (NULL, crypto->gpgpath ? crypto->gpgpath : "gpg");
-    if (! gpgctx) {
-	fprintf (stderr, "Failed to construct gpg context.\n");
-	return NULL;
+    crypto->gpgctx = g_mime_gpg_context_new (NULL, crypto->gpgpath ? crypto->gpgpath : "gpg");
+    if (! crypto->gpgctx) {
+	return NOTMUCH_STATUS_FAILED_CRYPTO_CONTEXT_CREATION;
     }
-    crypto->gpgctx = gpgctx;
 
-    g_mime_gpg_context_set_use_agent ((GMimeGpgContext *) gpgctx, TRUE);
-    g_mime_gpg_context_set_always_trust ((GMimeGpgContext *) gpgctx, FALSE);
+    g_mime_gpg_context_set_use_agent ((GMimeGpgContext *) crypto->gpgctx, TRUE);
+    g_mime_gpg_context_set_always_trust ((GMimeGpgContext *) crypto->gpgctx, FALSE);
 
-    return crypto->gpgctx;
+    *ctx = crypto->gpgctx;
+    return NOTMUCH_STATUS_SUCCESS;
 }
 
-/* Create a PKCS7 context (GMime 2.6) */
-static GMimeCryptoContext*
-create_pkcs7_context (_notmuch_crypto_t *crypto)
+/* Create or pass on a PKCS7 context (GMime 2.6) */
+static notmuch_status_t 
+get_pkcs7_context (_notmuch_crypto_t *crypto, GMimeCryptoContext **ctx)
 {
-    GMimeCryptoContext *pkcs7ctx;
+    if (ctx == NULL || crypto == NULL)
+	return NOTMUCH_STATUS_NULL_POINTER;
 
-    if (crypto->pkcs7ctx)
-	return crypto->pkcs7ctx;
+    if (crypto->pkcs7ctx) {
+	*ctx = crypto->pkcs7ctx;
+	return NOTMUCH_STATUS_SUCCESS;
+    }
 
     /* TODO: GMimePasswordRequestFunc */
-    pkcs7ctx = g_mime_pkcs7_context_new (NULL);
-    if (! pkcs7ctx) {
-	fprintf (stderr, "Failed to construct pkcs7 context.\n");
-	return NULL;
+    crypto->pkcs7ctx = g_mime_pkcs7_context_new (NULL);
+    if (! crypto->pkcs7ctx) {
+	return NOTMUCH_STATUS_FAILED_CRYPTO_CONTEXT_CREATION;
     }
-    crypto->pkcs7ctx = pkcs7ctx;
 
-    g_mime_pkcs7_context_set_always_trust ((GMimePkcs7Context *) pkcs7ctx,
+    g_mime_pkcs7_context_set_always_trust ((GMimePkcs7Context *) crypto->pkcs7ctx,
 					   FALSE);
 
-    return crypto->pkcs7ctx;
+    *ctx = crypto->pkcs7ctx;
+    return NOTMUCH_STATUS_SUCCESS;
 }
 static const struct {
     const char *protocol;
-    GMimeCryptoContext *(*get_context) (_notmuch_crypto_t *crypto);
+    notmuch_status_t (*get_context) (_notmuch_crypto_t *crypto, GMimeCryptoContext **ctx);
 } protocols[] = {
     {
 	.protocol = "application/pgp-signature",
-	.get_context = create_gpg_context,
+	.get_context = get_gpg_context,
     },
     {
 	.protocol = "application/pgp-encrypted",
-	.get_context = create_gpg_context,
+	.get_context = get_gpg_context,
     },
     {
 	.protocol = "application/pkcs7-signature",
-	.get_context = create_pkcs7_context,
+	.get_context = get_pkcs7_context,
     },
     {
 	.protocol = "application/x-pkcs7-signature",
-	.get_context = create_pkcs7_context,
+	.get_context = get_pkcs7_context,
     },
 };
 
 /* for the specified protocol return the context pointer (initializing
  * if needed) */
-GMimeCryptoContext *
-_notmuch_crypto_get_gmime_context (_notmuch_crypto_t *crypto, const char *protocol)
+notmuch_status_t
+_notmuch_crypto_get_gmime_ctx_for_protocol (_notmuch_crypto_t *crypto,
+					    const char *protocol,
+					    GMimeCryptoContext **ctx)
 {
-    GMimeCryptoContext *cryptoctx = NULL;
-    size_t i;
-
-    if (! protocol) {
-	fprintf (stderr, "Cryptographic protocol is empty.\n");
-	return cryptoctx;
-    }
+    if (! protocol)
+	return NOTMUCH_STATUS_MALFORMED_CRYPTO_PROTOCOL;
 
     /* As per RFC 1847 section 2.1: "the [protocol] value token is
      * comprised of the type and sub-type tokens of the Content-Type".
@@ -114,15 +114,12 @@ _notmuch_crypto_get_gmime_context (_notmuch_crypto_t *crypto, const char *protoc
      * parameter names as defined in this document are
      * case-insensitive."  Thus, we use strcasecmp for the protocol.
      */
-    for (i = 0; i < ARRAY_SIZE (protocols); i++) {
+    for (size_t i = 0; i < ARRAY_SIZE (protocols); i++) {
 	if (strcasecmp (protocol, protocols[i].protocol) == 0)
-	    return protocols[i].get_context (crypto);
+	    return protocols[i].get_context (crypto, ctx);
     }
 
-    fprintf (stderr, "Unknown or unsupported cryptographic protocol %s.\n",
-	     protocol);
-
-    return NULL;
+    return NOTMUCH_STATUS_UNKNOWN_CRYPTO_PROTOCOL;
 }
 
 void
diff --git a/util/crypto.h b/util/crypto.h
index 6d15a6ae..d653ffb4 100644
--- a/util/crypto.h
+++ b/util/crypto.h
@@ -21,8 +21,10 @@ typedef struct _notmuch_crypto {
 
 
 #if (GMIME_MAJOR_VERSION < 3)
-GMimeCryptoContext *
-_notmuch_crypto_get_gmime_context (_notmuch_crypto_t *crypto, const char *protocol);
+notmuch_status_t
+_notmuch_crypto_get_gmime_ctx_for_protocol (_notmuch_crypto_t *crypto,
+					    const char *protocol,
+					    GMimeCryptoContext **ctx);
 #endif
 
 void
-- 
2.14.1