Introduce the crypto_backend API and provide support for... encrypted queue

using the new API. By default, OpenSMTPD does not provide queue encryption,
but it can be enabled with "queue encryption [args]" and will transparently
encrypt/decrypt envelopes/messages as they hit the queue.

By default, it will use Blowfish in CBC mode with a different random IV for
each envelope and message. User provided key is expanded using sha256 but a
different cipher and digest may be specified in smtpd.conf

Queue encryption is compatible with compression and if both options are set
it will do them in correct order and transparently.

tested by chl@, a few users and myself
ok chl@ and I

1 files changed, 38 insertions, 24 deletions

diff --git a/usr.sbin/smtpd/queue_backend.c b/usr.sbin/smtpd/queue_backend.c
index dcc4217f584..25f0137f0fc 100644
--- a/usr.sbin/smtpd/queue_backend.c
+++ b/usr.sbin/smtpd/queue_backend.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: queue_backend.c,v 1.34 2012/08/26 11:21:28 gilles Exp $	*/
+/*	$OpenBSD: queue_backend.c,v 1.35 2012/08/29 16:26:17 gilles Exp $	*/
 
 /*
  * Copyright (c) 2011 Gilles Chehade <gilles@openbsd.org>
@@ -103,6 +103,8 @@ queue_message_commit(uint32_t msgid)
 	char	msgpath[MAXPATHLEN];
 	char	tmppath[MAXPATHLEN];
 	int	fdin = -1, fdout = -1;
+	FILE	*ifp = NULL;
+	FILE	*ofp = NULL;
 
 	queue_message_incoming_path(msgid, msgpath, sizeof msgpath);
 	strlcat(msgpath, PATH_MESSAGE, sizeof(msgpath));
@@ -126,26 +128,27 @@ queue_message_commit(uint32_t msgid)
 		}
 	}
 
-#if 0
 	if (env->sc_queue_flags & QUEUE_ENCRYPT) {
 
 		bsnprintf(tmppath, sizeof tmppath, "%s.crypt", msgpath);
-		fdin = open(msgpath, O_RDONLY);
-		fdout = open(tmppath, O_RDWR | O_CREAT | O_EXCL, 0600);
-		if (fdin == -1 || fdout == -1)
+		ifp = fopen(msgpath, "r");
+		ofp = fopen(tmppath, "w+");
+		if (ifp == NULL || ofp == NULL)
 			goto err;
-		if (! encrypt_file(fdin, fdout))
+		if (! crypto_encrypt_file(ifp, ofp))
 			goto err;
-		close(fdin);
-		close(fdout);
+		fclose(ifp);
+		fclose(ofp);
+		ifp = NULL;
+		ofp = NULL;
 
+		log_debug("tmppath=%s, msgpath=%s", tmppath, msgpath);
 		if (rename(tmppath, msgpath) == -1) {
 			if (errno == ENOSPC)
 				return (0);
 			fatal("queue_message_commit: rename");
 		}
 	}
-#endif
 
 	return env->sc_queue->message(QOP_COMMIT, &msgid);
 
@@ -154,6 +157,10 @@ err:
 		close(fdin);
 	if (fdout != -1)
 		close(fdout);
+	if (ifp)
+		fclose(ifp);
+	if (ofp)
+		fclose(ofp);
 	return 0;
 }
 
@@ -167,18 +174,25 @@ int
 queue_message_fd_r(uint32_t msgid)
 {
 	int	fdin, fdout;
+	FILE	*ifp = NULL;
+	FILE	*ofp = NULL;
 
 	fdin = env->sc_queue->message(QOP_FD_R, &msgid);
 
-#if 0
 	if (env->sc_queue_flags & QUEUE_ENCRYPT) {
 		fdout = mktmpfile();
-		if (! decrypt_file(fdin, fdout))
+		ifp = fdopen(fdin, "r");
+		ofp = fdopen(fdout, "w+");
+		if (ifp == NULL || ofp == NULL)
 			goto err;
-		close(fdin);
-		fdin = fdout;
+		if (! crypto_decrypt_file(ifp, ofp))
+			goto err;
+		fseek(ofp, SEEK_SET, 0);
+		fdin = fileno(ofp);
+		fclose(ifp);
+		ifp = NULL;
+		ofp = NULL;
 	}
-#endif
 
 	if (env->sc_queue_flags & QUEUE_COMPRESS) {
 		fdout = mktmpfile();
@@ -195,6 +209,10 @@ err:
 		close(fdin);
 	if (fdout != -1)
 		close(fdout);
+	if (ifp)
+		fclose(ifp);
+	if (ofp)
+		fclose(ofp);
 	return -1;
 }
 
@@ -213,7 +231,7 @@ static int
 queue_envelope_dump_buffer(struct envelope *ep, char *evpbuf, size_t evpbufsize)
 {
 	char		 evpbufcom[sizeof(struct envelope)];
-/*	char		 evpbufenc[sizeof(struct envelope)];*/
+	char		 evpbufenc[sizeof(struct envelope)];
 	char		*evp;
 	size_t		 evplen;
 
@@ -228,16 +246,13 @@ queue_envelope_dump_buffer(struct envelope *ep, char *evpbuf, size_t evpbufsize)
 			return (0);
 		evp = evpbufcom;
 	}
-
-#if 0
 	if (env->sc_queue_flags & QUEUE_ENCRYPT) {
-		evplen = encrypt_buffer(evp, evplen, evpbufenc, sizeof evpbufenc);
+		evplen = crypto_encrypt_buffer(evp, evplen, evpbufenc,
+		    sizeof evpbufenc);
 		if (evplen == 0)
 			return (0);
 		evp = evpbufenc;
 	}
-#endif
-
 	memmove(evpbuf, evp, evplen);
 
 	return (evplen);
@@ -247,21 +262,20 @@ static int
 queue_envelope_load_buffer(struct envelope *ep, char *evpbuf, size_t evpbufsize)
 {
 	char		 evpbufcom[sizeof(struct envelope)];
-/*	char		 evpbufenc[sizeof(struct envelope)];*/
+	char		 evpbufenc[sizeof(struct envelope)];
 	char		*evp;
 	size_t		 evplen;
 
 	evp = evpbuf;
 	evplen = evpbufsize;
 
-#if 0
 	if (env->sc_queue_flags & QUEUE_ENCRYPT) {
-		evplen = decrypt_buffer(evp, evplen, evpbufenc, sizeof evpbufenc);
+		evplen = crypto_decrypt_buffer(evp, evplen, evpbufenc,
+		    sizeof evpbufenc);
 		if (evplen == 0)
 			return (0);
 		evp = evpbufenc;
 	}
-#endif
 
 	if (env->sc_queue_flags & QUEUE_COMPRESS) {
 		evplen = uncompress_buffer(evp, evplen, evpbufcom, sizeof evpbufcom);