From 530c1e950a1bb46ff4e4a7c8e4b7cd945ff28916 Mon Sep 17 00:00:00 2001

From: Timo Sirainen <timo.sirainen@open-xchange.com>

Date: Wed, 18 Nov 2020 18:55:34 +0200

Subject: [PATCH] lib-imap: Fix writing BODYSTRUCTURE for truncated

 message/rfc822 part

If the max nesting limit is reached, write the last part out as

application/octet-stream instead of dummy message/rfc822.

Fixes error while parsing BODYSTRUCTURE:

message_part message/rfc822 flag doesn't match BODYSTRUCTURE

---

 src/lib-imap/imap-bodystructure.c      | 54 +++++++++----------

 src/lib-imap/test-imap-bodystructure.c | 73 ++++++++++++++++++++++++--

 2 files changed, 96 insertions(+), 31 deletions(-)

diff --git a/src/lib-imap/imap-bodystructure.c b/src/lib-imap/imap-bodystructure.c

index e3da1090b4..ab422c00d2 100644

--- a/src/lib-imap/imap-bodystructure.c

+++ b/src/lib-imap/imap-bodystructure.c

@@ -142,31 +142,42 @@ static void part_write_body_multipart(const struct message_part *part,

 	part_write_bodystructure_common(data, str);

 }

+static bool part_is_truncated(const struct message_part *part)

+{

+	const struct message_part_data *data = part->data;

+

+	i_assert((part->flags & MESSAGE_PART_FLAG_MESSAGE_RFC822) == 0);

+

+	if (data->content_type != NULL) {

+		if (strcasecmp(data->content_type, "message") == 0 &&

+		    strcasecmp(data->content_subtype, "rfc822") == 0) {

+			/* It's message/rfc822, but without

+			   MESSAGE_PART_FLAG_MESSAGE_RFC822. */

+			return TRUE;

+		}

+	}

+	return FALSE;

+}

+

 static void part_write_body(const struct message_part *part,

 			    string_t *str, bool extended)

 {

 	const struct message_part_data *data = part->data;

-	bool text, message_rfc822;

+	bool text;

 	i_assert(part->data != NULL);

-	if ((part->flags & MESSAGE_PART_FLAG_MESSAGE_RFC822) != 0)

-		message_rfc822 = TRUE;

-	else if (data->content_type != NULL &&

-		 strcasecmp(data->content_type, "message") == 0 &&

-		 strcasecmp(data->content_subtype, "rfc822") == 0) {

-		/* It's message/rfc822, but without

-		   MESSAGE_PART_FLAG_MESSAGE_RFC822. That likely means maximum

-		   MIME part count was reached while parsing the mail. Write

-		   the missing child mail's ENVELOPE and BODY as empty dummy

-		   values. */

-		message_rfc822 = TRUE;

-	} else

-		message_rfc822 = FALSE;

-

-	if (message_rfc822) {

+	if ((part->flags & MESSAGE_PART_FLAG_MESSAGE_RFC822) != 0) {

 		str_append(str, "\"message\" \"rfc822\"");

 		text = FALSE;

+	} else if (part_is_truncated(part)) {

+		/* Maximum MIME part count was reached while parsing the mail.

+		   Write this part out as application/octet-stream instead.

+		   We're not using text/plain, because it would require

+		   message-parser to use MESSAGE_PART_FLAG_TEXT for this part

+		   to avoid losing line count in message_part serialization. */

+		str_append(str, "\"application\" \"octet-stream\"");

+		text = FALSE;

 	} else {

 		/* "content type" "subtype" */

 		if (data->content_type == NULL) {

@@ -214,17 +225,6 @@ static void part_write_body(const struct message_part *part,

 		part_write_bodystructure_siblings(part->children, str, extended);

 		str_printfa(str, " %u", part->body_size.lines);

-	} else if (message_rfc822) {

-		/* truncated MIME part - write out dummy values */

-		i_assert(part->children == NULL);

-

-		str_append(str, " (NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL) ");

-

-		if (!extended)

-			str_append(str, EMPTY_BODY);

-		else

-			str_append(str, EMPTY_BODYSTRUCTURE);

-		str_printfa(str, " %u", part->body_size.lines);

 	}

 	if (!extended)

diff --git a/src/lib-imap/test-imap-bodystructure.c b/src/lib-imap/test-imap-bodystructure.c

index dfc9957488..6cb699e126 100644

--- a/src/lib-imap/test-imap-bodystructure.c

+++ b/src/lib-imap/test-imap-bodystructure.c

@@ -4,6 +4,7 @@

 #include "istream.h"

 #include "str.h"

 #include "message-part-data.h"

+#include "message-part-serialize.h"

 #include "message-parser.h"

 #include "imap-bodystructure.h"

 #include "test-common.h"

@@ -379,12 +380,14 @@ struct normalize_test normalize_tests[] = {

 static const unsigned int normalize_tests_count = N_ELEMENTS(normalize_tests);

 static struct message_part *

-msg_parse(pool_t pool, const char *message, bool parse_bodystructure)

+msg_parse(pool_t pool, const char *message, unsigned int max_nested_mime_parts,

+	  bool parse_bodystructure)

 {

 	const struct message_parser_settings parser_set = {

 		.hdr_flags = MESSAGE_HEADER_PARSER_FLAG_SKIP_INITIAL_LWSP |

 			MESSAGE_HEADER_PARSER_FLAG_DROP_CR,

 		.flags = MESSAGE_PARSER_FLAG_SKIP_BODY_BLOCK,

+		.max_nested_mime_parts = max_nested_mime_parts,

 	};

 	struct message_parser_ctx *parser;

 	struct istream *input;

@@ -418,7 +421,7 @@ static void test_imap_bodystructure_write(void)

 		pool_t pool = pool_alloconly_create("imap bodystructure write", 1024);

 		test_begin(t_strdup_printf("imap bodystructure write [%u]", i));

-		parts = msg_parse(pool, test->message, TRUE);

+		parts = msg_parse(pool, test->message, 0, TRUE);

 		imap_bodystructure_write(parts, str, TRUE);

 		test_assert(strcmp(str_c(str), test->bodystructure) == 0);

@@ -445,7 +448,7 @@ static void test_imap_bodystructure_parse(void)

 		pool_t pool = pool_alloconly_create("imap bodystructure parse", 1024);

 		test_begin(t_strdup_printf("imap bodystructure parser [%u]", i));

-		parts = msg_parse(pool, test->message, FALSE);

+		parts = msg_parse(pool, test->message, 0, FALSE);

 		test_assert(imap_body_parse_from_bodystructure(test->bodystructure,

 								     str, &error) == 0);

@@ -512,7 +515,7 @@ static void test_imap_bodystructure_normalize(void)

 		pool_t pool = pool_alloconly_create("imap bodystructure parse", 1024);

 		test_begin(t_strdup_printf("imap bodystructure normalize [%u]", i));

-		parts = msg_parse(pool, test->message, FALSE);

+		parts = msg_parse(pool, test->message, 0, FALSE);

 		ret = imap_bodystructure_parse(test->input,

 							   pool, parts, &error);

@@ -531,6 +534,67 @@ static void test_imap_bodystructure_normalize(void)

 	} T_END;

 }

+static const struct {

+	const char *input;

+	const char *bodystructure;

+	unsigned int max_depth;

+} truncation_tests[] = {

+	{

+		.input = "Content-Type: message/rfc822\n"

+			"\n"

+			"Content-Type: message/rfc822\n"

+			"Header2: value2\n"

+			"\n"

+			"Subject: hello world\n"

+			"Header2: value2\n"

+			"Header3: value3\n"

+			"\n"

+			"body line 1\n"

+			"body line 2\n"

+			"body line 4\n"

+			"body line 3\n",

+		.bodystructure = "\"message\" \"rfc822\" NIL NIL NIL \"7bit\" 159 (NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL) (\"application\" \"octet-stream\" NIL NIL NIL \"7bit\" 110 NIL NIL NIL NIL) 11 NIL NIL NIL NIL",

+		.max_depth = 2,

+	},

+};

+

+static void test_imap_bodystructure_truncation(void)

+{

+	struct message_part *parts;

+	const char *error;

+	string_t *str_body = t_str_new(128);

+	string_t *str_parts = t_str_new(128);

+	pool_t pool = pool_alloconly_create("imap bodystructure parse", 1024);

+

+	test_begin("imap bodystructure truncation");

+

+	for (unsigned int i = 0; i < N_ELEMENTS(truncation_tests); i++) {

+		p_clear(pool);

+		str_truncate(str_body, 0);

+		str_truncate(str_parts, 0);

+

+		parts = msg_parse(pool, truncation_tests[i].input,

+				  truncation_tests[i].max_depth,

+				  TRUE);

+

+		/* write out BODYSTRUCTURE and serialize message_parts */

+		imap_bodystructure_write(parts, str_body, TRUE);

+		message_part_serialize(parts, str_parts);

+

+		/* now deserialize message_parts and make sure they can be used

+		   to parse BODYSTRUCTURE */

+		parts = message_part_deserialize(pool, str_data(str_parts),

+						 str_len(str_parts), &error);

+		test_assert(parts != NULL);

+		test_assert(imap_bodystructure_parse(str_c(str_body), pool,

+						     parts, &error) == 0);

+		test_assert_strcmp(str_c(str_body),

+				   truncation_tests[i].bodystructure);

+	}

+	pool_unref(&pool);

+	test_end();

+}

+

 int main(void)

 {

 	static void (*const test_functions[])(void) = {

@@ -538,6 +602,7 @@ int main(void)

 		test_imap_bodystructure_parse,

 		test_imap_bodystructure_normalize,

 		test_imap_bodystructure_parse_full,

+		test_imap_bodystructure_truncation,

 		NULL

 	};

 	return test_run(test_functions);