New callback to handle multipart/signed parts. (decode_pgp): Update to

2000-12-15  Jeffrey Stedfast  <fejj@helixcode.com>

	* mail-format.c (handle_multipart_signed): New callback to handle
	multipart/signed parts.
	(decode_pgp): Update to account for the cipherlen argument needed
	for openpgp_decrypt.
	(is_rfc2015): Removed as we now have a better version in
	mail-crypto.
	(handle_multipart_encrypted): Updated to use the PGP/MIME utility
	functions.

	* mail-crypto.c (mail_crypto_openpgp_decrypt): Don't check
	(!*plaintext) as it could be a binary stream. Now also takes a
	cipherlen argument.
	(mail_crypto_openpgp_sign): New function.
	(pgp_mime_part_sign): New function to replace a mime part with the
	pgp signed equivalent.
	(pgp_mime_part_encrypt): New function to replace a mime part with
	the pgp encrypted equivalent.
	(pgp_mime_part_decrypt): New function to decrypt a pgp encrypted
	mime part (like from pgp_mime_part_encrypt) and replace it.
	(is_rfc2015_signed): New function to determine if a mime part is
	an rfc2015 signed part.
	(is_rfc2015_encrypted): New function to determine if a mime part
	is an rfc2015 encrypted part.
	(mail_crypto_openpgp_verify): New openpgp function to verify a
	signature.

svn path=/trunk/; revision=7056

1 files changed, 660 insertions, 14 deletions

diff --git a/mail/mail-crypto.c b/mail/mail-crypto.c
index de866bcda3..a013b72878 100644
--- a/mail/mail-crypto.c
+++ b/mail/mail-crypto.c
@@ -57,6 +57,8 @@
 #include <unistd.h>
 #include <signal.h>
 
+#include <camel/camel-mime-filter-from.h>
+
 static int
 cleanup_child (pid_t child)
 {
@@ -338,7 +340,8 @@ crypto_exec_with_passwd (const char *path, char *argv[], const char *input, int
  * the case that the cleartext is a binary stream.
  **/
 char *
-mail_crypto_openpgp_decrypt (const char *ciphertext, int *outlen, CamelException *ex)
+mail_crypto_openpgp_decrypt (const char *ciphertext, int cipherlen,
+			     int *outlen, CamelException *ex)
 {
 	int retval, i;
 	char *path, *argv[12];
@@ -398,14 +401,17 @@ mail_crypto_openpgp_decrypt (const char *ciphertext, int *outlen, CamelException
 	putenv (passwd_fd);
 #endif
 	argv[i++] = NULL;
-
+	
+	/* initialize outlen */
+	*outlen = 0;
+	
 	retval = crypto_exec_with_passwd (path, argv,
-					  ciphertext, strlen (ciphertext),
+					  ciphertext, cipherlen,
 					  passwd_fds, passphrase,
 					  &plaintext, outlen,
 					  &diagnostics);
 	
-	if (retval != 0 || !*plaintext) {
+	if (retval != 0 || *outlen == 0) {
 		camel_exception_setv (ex, CAMEL_EXCEPTION_SYSTEM,
 				      "%s", diagnostics);
 		g_free (plaintext);
@@ -599,15 +605,15 @@ mail_crypto_openpgp_encrypt (const char *in, int inlen,
  * @plaintext: text to sign
  * @userid: user id to sign with
  * @hash: Preferred hash function (md5 or sha1)
- * @detach: Specify whether or not to generate a detached clearsign.
  * @ex: a CamelException
  *
  * Clearsigns the plaintext using the user id
  **/
 
 char *
-mail_crypto_openpgp_clearsign (const char *plaintext, const char *userid,
-			       PgpHashType hash, gboolean detach,
+mail_crypto_openpgp_clearsign (const char *plaintext,
+			       const char *userid,
+			       PgpHashType hash,
 			       CamelException *ex)
 {
 	int retval;
@@ -661,9 +667,6 @@ mail_crypto_openpgp_clearsign (const char *plaintext, const char *userid,
 	
 	argv[i++] = "--clearsign";
 	
-	if (detach)
-		argv[i++] = "-b";
-	
 	if (hash_str) {
 		argv[i++] = "--digest-algo";
 		argv[i++] = hash_str;
@@ -692,9 +695,6 @@ mail_crypto_openpgp_clearsign (const char *plaintext, const char *userid,
 	
 	argv[i++] = "pgps";
 	
-	if (detach)
-		argv[i++] = "-b";
-	
 	if (userid) {
 		argv[i++] = "-u";
 		argv[i++] = (char *) userid;
@@ -710,7 +710,7 @@ mail_crypto_openpgp_clearsign (const char *plaintext, const char *userid,
 	sprintf (passwd_fd, "PGPPASSFD=%d", passwd_fds[0]);
 	putenv (passwd_fd);
 #else
-	/* FIXME: modify to respect hash and detach */
+	/* FIXME: modify to respect hash */
 	path = PGP_PATH;
 
 	argv[i++] = "pgp";
@@ -741,7 +741,653 @@ mail_crypto_openpgp_clearsign (const char *plaintext, const char *userid,
 	}
 	
 	g_free (diagnostics);
+	
 	return ciphertext;
 }
 
+
+/**
+ * mail_crypto_openpgp_sign:
+ * @in: input data to sign
+ * @inlen: length of input data
+ * @userid: userid to sign with
+ * @hash: preferred hash type (md5 or sha1)
+ * @ex: exception
+ *
+ * Returns an allocated string containing the detached signature using
+ * the preferred hash.
+ **/
+char *
+mail_crypto_openpgp_sign (const char *in, int inlen, const char *userid,
+			  PgpHashType hash, CamelException *ex)
+{
+	char *argv[20];
+	char *cyphertext = NULL;
+	char *diagnostics = NULL;
+	char *passphrase = NULL;
+	char *hash_str = NULL;
+	char *path;
+	int passwd_fds[2];
+	char passwd_fd[32];
+	int retval, i;
+	
+	
+#ifndef PGP_PROGRAM
+	camel_exception_setv (ex, CAMEL_EXCEPTION_SYSTEM,
+			      _("No GPG/PGP program available."));
+	return NULL;
+#endif
+	
+	passphrase = mail_session_request_dialog (_("Please enter your PGP/GPG passphrase."),
+						  TRUE, "pgp", FALSE);
+	if (!passphrase) {
+		camel_exception_set (ex, CAMEL_EXCEPTION_SYSTEM,
+				     _("No password provided."));
+		return NULL;
+	}
+	
+	if (pipe (passwd_fds) < 0) {
+		g_free (passphrase);
+		camel_exception_setv (ex, CAMEL_EXCEPTION_SYSTEM,
+				      _("Couldn't create pipe to GPG/PGP: %s"),
+				      g_strerror (errno));
+		return NULL;
+	}
+	
+	switch (hash) {
+	case PGP_HASH_TYPE_MD5:
+		hash_str = "MD5";
+		break;
+	case PGP_HASH_TYPE_SHA1:
+		hash_str = "SHA1";
+		break;
+	default:
+		hash_str = NULL;
+	}
+	
+	i = 0;
+#if defined(GPG_PATH)
+	path = GPG_PATH;
+	argv[i++] = "gpg";
+	
+	argv[i++] = "--sign";
+	argv[i++] = "-b";
+	if (hash_str) {
+		argv[i++] = "--digest-algo";
+		argv[i++] = hash_str;
+	}
+	
+	if (userid) {
+		argv[i++] = "-u";
+		argv[i++] = (char *) userid;
+	}
+	
+	argv[i++] = "--verbose";
+	argv[i++] = "--yes";
+	argv[i++] = "--batch";
+	
+	argv[i++] = "--armor";
+	
+	argv[i++] = "--output";
+	argv[i++] = "-";            /* output to stdout */
+	
+	argv[i++] = "--passphrase-fd";
+	sprintf (passwd_fd, "%d", passwd_fds[0]);
+	argv[i++] = passwd_fd;
+#elif defined(PGP5_PATH)
+	path = PGP5_PATH;
+	
+	/* FIXME: respect hash */
+	argv[i++] = "pgps";
+	
+	if (userid) {
+		argv[i++] = "-u";
+		argv[i++] = (char *) userid;
+	}
+	
+	argv[i++] = "-b";
+	argv[i++] = "-f";
+	argv[i++] = "-z";
+	argv[i++] = "-a";
+	argv[i++] = "-o";
+	argv[i++] = "-";        /* output to stdout */
+	
+	argv[i++] = "-s";	
+	sprintf (passwd_fd, "PGPPASSFD=%d", passwd_fds[0]);
+	putenv (passwd_fd);
+#else
+	path = PGP_PATH;
+	
+	/* FIXME: needs to respect hash and also return only the detached sig */
+	argv[i++] = "pgp";
+	
+	if (userid) {
+		argv[i++] = "-u";
+		argv[i++] = (char *) userid;
+	}
+	
+	argv[i++] = "-f";
+	argv[i++] = "-a";
+	argv[i++] = "-o";
+	argv[i++] = "-";
+	
+	argv[i++] = "-s";	
+	sprintf (passwd_fd, "PGPPASSFD=%d", passwd_fds[0]);
+	putenv (passwd_fd);
+#endif
+	
+	argv[i++] = NULL;
+	
+	retval = crypto_exec_with_passwd (path, argv,
+					  in, inlen,
+					  passwd_fds, passphrase,
+					  &cyphertext, NULL,
+					  &diagnostics);
+	
+	g_free (passphrase);
+	
+	if (retval != 0 || !*cyphertext) {
+		camel_exception_setv (ex, CAMEL_EXCEPTION_SYSTEM,
+				      "%s", diagnostics);
+		g_free (cyphertext);
+		cyphertext = NULL;
+	}
+	
+	g_free (diagnostics);
+	
+	return cyphertext;
+}
+
+gboolean
+mail_crypto_openpgp_verify (const char *in, int inlen, const char *sigin, int siglen, CamelException *ex)
+{
+	char *argv[20];
+	char *cleartext = NULL;
+	char *diagnostics = NULL;
+	char *path;
+	int passwd_fds[2];
+	char passwd_fd[32];
+	char *tmp = "/tmp/mail-crypto-XXXXXX";
+	int retval, i, clearlen;
+	gboolean valid = TRUE;
+	
+	
+#ifndef PGP_PROGRAM
+	camel_exception_setv (ex, CAMEL_EXCEPTION_SYSTEM,
+			      _("No GPG/PGP program available."));
+	return FALSE;
+#endif
+	
+	if (pipe (passwd_fds) < 0) {
+		camel_exception_setv (ex, CAMEL_EXCEPTION_SYSTEM,
+				      _("Couldn't create pipe to GPG/PGP: %s"),
+				      g_strerror (errno));
+		return FALSE;
+	}
+	
+	i = 0;
+#if defined(GPG_PATH)
+	path = GPG_PATH;
+	
+	argv[i++] = "gpg";
+	
+	argv[i++] = "--verify";
+	
+	if (sigin != NULL && siglen) {
+		/* We are going to verify a detached signature so save
+                   the signature to a temp file and write the data to
+                   verify to stdin */
+		int fd;
+		
+		fd = mkstemp (tmp);
+		if (fd == -1) {
+			camel_exception_setv (ex, CAMEL_EXCEPTION_SYSTEM,
+					      _("Couldn't create temp file: %s"),
+					      g_strerror (errno));
+			return FALSE;
+		}
+		
+		write (fd, sigin, siglen);
+		close (fd);
+		
+		argv[i++] = tmp;
+		argv[i++] = "-";
+	} else {
+		/* We are going to verify using stdin */
+		argv[i++] = "-";
+	}
+	
+	argv[i++] = "--verbose";
+	argv[i++] = "--yes";
+	argv[i++] = "--batch";
+	
+	argv[i++] = "--output";
+	argv[i++] = "-";            /* output to stdout */
+#elif defined (PGP5_PATH)
+	path = PGP5_PATH;
+	
+	argv[i++] = "pgpv";
+#else
+	path = PGP_PATH;
+	
+	argv[i++] = "pgp";
+#endif
+	
+	argv[i++] = NULL;
+	
+	clearlen = 0;
+	retval = crypto_exec_with_passwd (path, argv,
+					  in, inlen,
+					  passwd_fds, NULL,
+					  &cleartext, &clearlen,
+					  &diagnostics);
+	
+	/* FIXME: maybe we should always set an exception? */
+	if (retval != 0 || clearlen == 0) {
+		camel_exception_setv (ex, CAMEL_EXCEPTION_SYSTEM,
+				      "%s", diagnostics);
+		valid = FALSE;
+	}
+	
+	g_free (diagnostics);
+	g_free (cleartext);
+	
+	return valid;
+}
+
+/** rfc2015 stuff *******************************/
+
+gboolean
+is_rfc2015_signed (CamelMimePart *mime_part)
+{
+	CamelDataWrapper *wrapper;
+	CamelMultipart *mp;
+	CamelMimePart *part;
+	GMimeContentField *type;
+	const gchar *param;
+	int nparts;
+	
+	/* check that we have a multipart/signed */
+	type = camel_mime_part_get_content_type (mime_part);
+	if (!gmime_content_field_is_type (type, "multipart", "signed"))
+		return FALSE;
+	
+	/* check that we have a protocol param with the value: "application/pgp-signed" */
+	param = gmime_content_field_get_parameter (type, "protocol");
+	if (!param || g_strcasecmp (param, "\"application/pgp-signed\""))
+		return FALSE;
+	
+	/* check that we have exactly 2 subparts */
+	wrapper = camel_medium_get_content_object (CAMEL_MEDIUM (mime_part));
+	mp = CAMEL_MULTIPART (wrapper);
+	nparts = camel_multipart_get_number (mp);
+	if (nparts != 2)
+		return FALSE;
+	
+	/* The first part may be of any type except for 
+	 * application/pgp-signature - check it. */
+	part = camel_multipart_get_part (mp, 0);
+	type = camel_mime_part_get_content_type (part);
+	if (gmime_content_field_is_type (type, "application","pgp-signature"))
+		return FALSE;
+	
+	/* The second part should be application/pgp-signature. */
+	part = camel_multipart_get_part (mp, 1);
+	type = camel_mime_part_get_content_type (part);
+	if (!gmime_content_field_is_type (type, "application","pgp-siganture"))
+		return FALSE;
+	
+	/* FIXME: Implement multisig stuff */	
+	
+	return TRUE;
+}
+
+gboolean
+is_rfc2015_encrypted (CamelMimePart *mime_part)
+{
+	CamelDataWrapper *wrapper;
+	CamelMultipart *mp;
+	CamelMimePart *part;
+	GMimeContentField *type;
+	const gchar *param;
+	int nparts;
+	
+	/* check that we have a multipart/encrypted */
+	type = camel_mime_part_get_content_type (mime_part);
+	if (!gmime_content_field_is_type (type, "multipart", "encrypted"))
+		return FALSE;
+	
+	/* check that we have a protocol param with the value: "application/pgp-encrypted" */
+	param = gmime_content_field_get_parameter (type, "protocol");
+	if (!param || g_strcasecmp (param, "\"application/pgp-encrypted\""))
+		return FALSE;
+	
+	/* check that we have at least 2 subparts */
+	wrapper = camel_medium_get_content_object (CAMEL_MEDIUM (mime_part));
+	mp = CAMEL_MULTIPART (wrapper);
+	nparts = camel_multipart_get_number (mp);
+	if (nparts < 2)
+		return FALSE;
+	
+	/* The first part should be application/pgp-encrypted */
+	part = camel_multipart_get_part (mp, 0);
+	type = camel_mime_part_get_content_type (part);
+	if (!gmime_content_field_is_type (type, "application","pgp-encrypted"))
+		return FALSE;
+	
+	/* The second part should be application/octet-stream - this
+           is the one we care most about */
+	part = camel_multipart_get_part (mp, 1);
+	type = camel_mime_part_get_content_type (part);
+	if (!gmime_content_field_is_type (type, "application","octet-stream"))
+		return FALSE;
+	
+	return TRUE;
+}
+
+/**
+ * pgp_mime_part_sign:
+ * @mime_part: a MIME part that will be replaced by a pgp signed part
+ * @userid: userid to sign with
+ * @hash: one of PGP_HASH_TYPE_MD5 or PGP_HASH_TYPE_SHA1
+ * @ex: exception which will be set if there are any errors.
+ *
+ * Constructs a PGP/MIME multipart in compliance with rfc2015 and
+ * replaces #part with the generated multipart/signed. On failure,
+ * #ex will be set and #part will remain untouched.
+ **/
+void
+pgp_mime_part_sign (CamelMimePart **mime_part, const gchar *userid, PgpHashType hash, CamelException *ex)
+{
+	CamelMimePart *part, *signed_part;
+	CamelMultipart *multipart;
+	CamelMimePartEncodingType encoding;
+	GMimeContentField *mime_type;
+	CamelStreamFilter *filtered_stream;
+	CamelMimeFilter *crlf_filter, *from_filter;
+	CamelStream *stream;
+	GByteArray *array;
+	gchar *cleartext, *signature;
+	gchar *hash_type;
+	gint clearlen;
+	
+	g_return_if_fail (*mime_part != NULL);
+	g_return_if_fail (userid != NULL);
+	g_return_if_fail (hash != PGP_HASH_TYPE_NONE);
+	
+	part = *mime_part;
+	encoding = camel_mime_part_get_encoding (part);
+	
+	/* the encoding should really be QP or Base64 */
+	if (encoding != CAMEL_MIME_PART_ENCODING_BASE64)
+		camel_mime_part_set_encoding (part, CAMEL_MIME_PART_ENCODING_QUOTEDPRINTABLE);
+	
+	/* get the cleartext */
+	array = g_byte_array_new ();
+	stream = camel_stream_mem_new_with_byte_array (array);
+	crlf_filter = camel_mime_filter_crlf_new (CAMEL_MIME_FILTER_CRLF_ENCODE,
+						  CAMEL_MIME_FILTER_CRLF_MODE_CRLF_ONLY);
+	from_filter = CAMEL_MIME_FILTER (camel_mime_filter_from_new ());
+	filtered_stream = camel_stream_filter_new_with_stream (stream);
+	camel_stream_filter_add (filtered_stream, CAMEL_MIME_FILTER (crlf_filter));
+	camel_stream_filter_add (filtered_stream, CAMEL_MIME_FILTER (from_filter));
+	camel_data_wrapper_write_to_stream (CAMEL_DATA_WRAPPER (part), CAMEL_STREAM (filtered_stream));
+	camel_object_unref (CAMEL_OBJECT (filtered_stream));
+	camel_object_unref (CAMEL_OBJECT (stream));
+	cleartext = array->data;
+	clearlen = array->len;
+	
+	/* get the signature */
+	signature = mail_crypto_openpgp_sign (cleartext, clearlen, userid, hash, ex);
+	g_byte_array_free (array, TRUE);
+	if (camel_exception_is_set (ex)) {
+		/* restore the original encoding */
+		camel_mime_part_set_encoding (part, encoding);
+		return;
+	}
+	
+	/* construct the pgp-signature mime part */
+	fprintf (stderr, "signature:\n%s\n", signature);
+	signed_part = camel_mime_part_new ();
+	camel_mime_part_set_content (signed_part, signature, strlen (signature),
+				     "application/pgp-signature");
+	g_free (signature);
+	camel_mime_part_set_encoding (signed_part, CAMEL_MIME_PART_ENCODING_DEFAULT);
+	
+	/* construct the container multipart/signed */
+	multipart = camel_multipart_new ();
+	camel_data_wrapper_set_mime_type (CAMEL_DATA_WRAPPER (multipart),
+					  "multipart/signed");
+	switch (hash) {
+	case PGP_HASH_TYPE_MD5:
+		hash_type = "pgp-md5";
+		break;
+	case PGP_HASH_TYPE_SHA1:
+		hash_type = "pgp-sha1";
+		break;
+	default:
+		hash_type = NULL;
+	}
+	mime_type = camel_data_wrapper_get_mime_type_field (CAMEL_DATA_WRAPPER (multipart));
+	gmime_content_field_set_parameter (mime_type, "micalg", hash_type);
+	gmime_content_field_set_parameter (mime_type, "protocol", "application/pgp-signature");
+	camel_multipart_set_boundary (multipart, NULL);
+	
+	/* add the parts to the multipart */
+	camel_multipart_add_part (multipart, part);
+	camel_object_unref (CAMEL_OBJECT (part));
+	camel_multipart_add_part (multipart, signed_part);
+	camel_object_unref (CAMEL_OBJECT (signed_part));
+	
+	/* replace the input part with the output part */
+	*mime_part = camel_mime_part_new ();
+	camel_medium_set_content_object (CAMEL_MEDIUM (*mime_part),
+					 CAMEL_DATA_WRAPPER (multipart));
+	camel_object_unref (CAMEL_OBJECT (multipart));
+}
+
+
+/**
+ * pgp_mime_part_verify:
+ * @mime_part: a multipart/signed MIME Part
+ * @ex: exception
+ *
+ * Returns TRUE if the signature is valid otherwise returns
+ * FALSE. Note: you may want to check the exception if it fails as
+ * there may be useful information to give to the user; example:
+ * verification may have failed merely because the user doesn't have
+ * the sender's key on her system.
+ **/
+gboolean
+pgp_mime_part_verify (CamelMimePart *mime_part, CamelException *ex)
+{
+	CamelDataWrapper *wrapper;
+	CamelMultipart *multipart;
+	CamelMimePart *part, *sigpart;
+	GByteArray *content, *sig;
+	CamelStreamFilter *filtered_stream;
+	CamelMimeFilter *crlf_filter;
+	CamelStream *stream;
+	gboolean valid = FALSE;
+	
+	g_return_val_if_fail (mime_part != NULL, FALSE);
+	
+	if (!is_rfc2015_signed (mime_part))
+		return FALSE;
+	
+	wrapper = camel_medium_get_content_object (CAMEL_MEDIUM (mime_part));
+	multipart = CAMEL_MULTIPART (wrapper);
+	
+	/* get the plain part */
+	part = camel_multipart_get_part (multipart, 0);
+	content = g_byte_array_new ();
+	stream = camel_stream_mem_new_with_byte_array (content);
+	crlf_filter = camel_mime_filter_crlf_new (CAMEL_MIME_FILTER_CRLF_ENCODE,
+						  CAMEL_MIME_FILTER_CRLF_MODE_CRLF_ONLY);
+	filtered_stream = camel_stream_filter_new_with_stream (stream);
+	camel_stream_filter_add (filtered_stream, CAMEL_MIME_FILTER (crlf_filter));
+	camel_data_wrapper_write_to_stream (CAMEL_DATA_WRAPPER (part), CAMEL_STREAM (filtered_stream));
+	camel_object_unref (CAMEL_OBJECT (filtered_stream));
+	camel_object_unref (CAMEL_OBJECT (stream));
+	
+	/* get the signed part */
+	sigpart = camel_multipart_get_part (multipart, 1);
+	sig = g_byte_array_new ();
+	stream = camel_stream_mem_new_with_byte_array (sig);
+	camel_data_wrapper_write_to_stream (camel_medium_get_content_object (CAMEL_MEDIUM (sigpart)), stream);
+	camel_object_unref (CAMEL_OBJECT (stream));
+	
+	/* verify */
+	valid = mail_crypto_openpgp_verify (content->data, content->len,
+					    sig->data, sig->len, ex);
+	
+	g_byte_array_free (content, TRUE);
+	g_byte_array_free (sig, TRUE);
+	
+	return valid;
+}
+
+
+/**
+ * pgp_mime_part_encrypt:
+ * @mime_part: a MIME part that will be replaced by a pgp encrypted part
+ * @recipients: list of recipient PGP Key IDs
+ * @ex: exception which will be set if there are any errors.
+ *
+ * Constructs a PGP/MIME multipart in compliance with rfc2015 and
+ * replaces #mime_part with the generated multipart/signed. On failure,
+ * #ex will be set and #part will remain untouched.
+ **/
+void
+pgp_mime_part_encrypt (CamelMimePart **mime_part, const GPtrArray *recipients, CamelException *ex)
+{
+	CamelMultipart *multipart;
+	CamelMimePart *part, *version_part, *encrypted_part;
+	GMimeContentField *mime_type;
+	CamelStream *stream;
+	GByteArray *contents;
+	gchar *ciphertext;
+	
+	g_return_if_fail (*mime_part != NULL);
+	g_return_if_fail (recipients != NULL);
+	
+	part = *mime_part;
+	
+	/* get the contents */
+	contents = g_byte_array_new ();
+	stream = camel_stream_mem_new_with_byte_array (contents);
+	camel_data_wrapper_write_to_stream (CAMEL_DATA_WRAPPER (part), stream);
+	camel_object_unref (CAMEL_OBJECT (stream));
+	
+	/* pgp encrypt */
+	ciphertext = mail_crypto_openpgp_encrypt (contents->data,
+						  contents->len,
+						  recipients, FALSE, NULL, ex);
+	if (camel_exception_is_set (ex))
+		return;
+	
+	/* construct the version part */
+	version_part = camel_mime_part_new ();
+	camel_mime_part_set_encoding (version_part, CAMEL_MIME_PART_ENCODING_7BIT);
+	camel_mime_part_set_content (version_part, "Version: 1", strlen ("Version: 1"),
+				     "application/pgp-encrypted");
+	
+	/* construct the pgp-encrypted mime part */
+	encrypted_part = camel_mime_part_new ();
+	camel_mime_part_set_encoding (encrypted_part, CAMEL_MIME_PART_ENCODING_7BIT);
+	camel_mime_part_set_content (encrypted_part, ciphertext, strlen (ciphertext),
+				     "application/octet-stream");
+	g_free (ciphertext);
+	
+	/* construct the container multipart/signed */
+	multipart = camel_multipart_new ();
+	camel_data_wrapper_set_mime_type (CAMEL_DATA_WRAPPER (multipart),
+					  "multipart/encrypted");
+	camel_multipart_set_boundary (multipart, NULL);
+	mime_type = camel_data_wrapper_get_mime_type_field (CAMEL_DATA_WRAPPER (multipart));
+	gmime_content_field_set_parameter (mime_type, "protocol", "application/pgp-encrypted");
+	
+	/* add the parts to the multipart */
+	camel_multipart_add_part (multipart, version_part);
+	camel_object_unref (CAMEL_OBJECT (version_part));
+	camel_multipart_add_part (multipart, encrypted_part);
+	camel_object_unref (CAMEL_OBJECT (encrypted_part));
+	
+	/* replace the input part with the output part */
+	*mime_part = camel_mime_part_new ();
+	camel_medium_set_content_object (CAMEL_MEDIUM (*mime_part),
+					 CAMEL_DATA_WRAPPER (multipart));
+	camel_object_unref (CAMEL_OBJECT (multipart));
+	
+	/* destroy the original part */
+	camel_object_unref (CAMEL_OBJECT (part));
+}
+
+
+/**
+ * pgp_mime_part_decrypt:
+ * @mime_part: a multipart/encrypted MIME Part
+ * @ex: exception
+ *
+ * Returns the decrypted MIME Part on success or NULL on fail.
+ **/
+CamelMimePart *
+pgp_mime_part_decrypt (CamelMimePart *mime_part, CamelException *ex)
+{
+	CamelDataWrapper *wrapper;
+	CamelMultipart *multipart;
+	CamelMimeParser *parser;
+	CamelMimePart *encrypted_part, *part;
+	GMimeContentField *mime_type;
+	CamelStream *stream;
+	GByteArray *content;
+	gchar *cleartext, *ciphertext = NULL;
+	int cipherlen, clearlen;
+	
+	g_return_val_if_fail (mime_part != NULL, NULL);
+	
+	/* make sure the mime part is a multipart/encrypted */
+	if (!is_rfc2015_encrypted (mime_part))
+		return NULL;
+	
+	wrapper = camel_medium_get_content_object (CAMEL_MEDIUM (mime_part));
+	multipart = CAMEL_MULTIPART (wrapper);
+	
+	/* get the encrypted part (second part) */
+	encrypted_part = camel_multipart_get_part (multipart, 1 /* second part starting at 0 */);
+	mime_type = camel_mime_part_get_content_type (encrypted_part);
+	if (!gmime_content_field_is_type (mime_type, "application", "octet-stream"))
+		return NULL;
+	
+	/* get the ciphertext */
+	content = g_byte_array_new ();
+	stream = camel_stream_mem_new_with_byte_array (content);
+	camel_data_wrapper_write_to_stream (CAMEL_DATA_WRAPPER (encrypted_part), stream);
+	camel_object_unref (CAMEL_OBJECT (stream));
+	ciphertext = content->data;
+	cipherlen = content->len;
+	
+	/* get the cleartext */
+	cleartext = mail_crypto_openpgp_decrypt (ciphertext, cipherlen, &clearlen, ex);
+	g_byte_array_free (content, TRUE);
+	if (camel_exception_is_set (ex))
+		return NULL;
+	
+	/* create a stream based on the returned cleartext */
+	stream = camel_stream_mem_new ();
+	camel_stream_write (stream, cleartext, clearlen);
+	camel_stream_reset (stream);
+	g_free (cleartext);
+	
+	/* construct the new decrypted mime part from the stream */
+	part = camel_mime_part_new ();
+	parser = camel_mime_parser_new ();
+	camel_mime_parser_init_with_stream (parser, stream);
+	camel_mime_part_construct_from_parser (part, parser);
+	camel_object_unref (CAMEL_OBJECT (parser));
+	camel_object_unref (CAMEL_OBJECT (stream));
+	
+	return part;
+}
+
 #endif /* PGP_PROGRAM */