From: Timo Sirainen <timo.sirainen@open-xchange.com>
Date: Mon, 13 Jan 2025 13:58:29 +0000 (+0200)
Subject: lib-mail: message_skip_virtual() - Fix handling plain CRs in message body
X-Git-Tag: 2.4.0~1361
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=fc88314aa45ca751d7d83d1307d46e11cfbe263c;p=thirdparty%2Fdovecot%2Fcore.git

lib-mail: message_skip_virtual() - Fix handling plain CRs in message body

The plain CRs should be handled like any other character, not returning
last_cr_r=TRUE.

This fixes partial IMAP FETCHes where body contains e.g. "\rfoo" and
doing a partial FETCH BODY[TEXT]<1> to skip over the CR.

Fixes errors like:
Deleting corrupted cache record: Broken virtual size in mailbox .. FETCH BODY[]<1> got too little data: 2 vs 3
---

diff --git a/src/lib-mail/message-size.c b/src/lib-mail/message-size.c
index 472abeb7c2..309d0b4428 100644
--- a/src/lib-mail/message-size.c
+++ b/src/lib-mail/message-size.c
@@ -128,14 +128,14 @@ void message_size_add(struct message_size *dest,
 }
 
 int message_skip_virtual(struct istream *input, uoff_t virtual_skip,
-			 bool *last_cr_r)
+			 bool *last_virtual_cr_r)
 {
 	const unsigned char *msg;
 	size_t i, size;
 	bool cr_skipped = FALSE;
 	int ret;
 
-	*last_cr_r = FALSE;
+	*last_virtual_cr_r = FALSE;
 	if (virtual_skip == 0)
 		return 0;
 
@@ -143,17 +143,13 @@ int message_skip_virtual(struct istream *input, uoff_t virtual_skip,
 		for (i = 0; i < size && virtual_skip > 0; i++) {
 			virtual_skip--;
 
-			if (msg[i] == '\r') {
-				/* CR */
-				if (virtual_skip == 0)
-					*last_cr_r = TRUE;
-			} else if (msg[i] == '\n') {
+			if (msg[i] == '\n') {
 				/* LF */
 				if ((i == 0 && !cr_skipped) ||
 				    (i > 0 && msg[i-1] != '\r')) {
 					if (virtual_skip == 0) {
 						/* CR/LF boundary */
-						*last_cr_r = TRUE;
+						*last_virtual_cr_r = TRUE;
 						break;
 					}
 
diff --git a/src/lib-mail/message-size.h b/src/lib-mail/message-size.h
index 5fe6b8a9d5..c5be99b8d4 100644
--- a/src/lib-mail/message-size.h
+++ b/src/lib-mail/message-size.h
@@ -19,10 +19,12 @@ int message_get_body_size(struct istream *input, struct message_size *body,
 void message_size_add(struct message_size *dest,
 		      const struct message_size *src);
 
-/* Skip number of virtual bytes from buffer. last_cr_r is set to TRUE if the
-   last character we skipped was '\r', meaning that the next character should
-   be '\n', which shouldn't be treated as "\r\n". */
+/* Skip a number of bytes in the input stream, counting LFs as CRLFs.
+   last_virtual_cr_r is set to TRUE if the last character we skipped was a
+   virtual (nonexistent in istream) '\r', meaning that the next character in
+   the input stream is "\n", which means be treated as plain "\n",
+   not "\r\n". */
 int message_skip_virtual(struct istream *input, uoff_t virtual_skip,
-			 bool *last_cr_r);
+			 bool *last_virtual_cr_r);
 
 #endif
diff --git a/src/lib-mail/test-message-size.c b/src/lib-mail/test-message-size.c
index 4342c27a28..cd49056363 100644
--- a/src/lib-mail/test-message-size.c
+++ b/src/lib-mail/test-message-size.c
@@ -149,10 +149,58 @@ static void test_message_size(void)
 	}
 }
 
+static void test_message_skip_virtual(void)
+{
+	struct {
+		const char *input;
+		uoff_t virtual_skip;
+
+		const char *output;
+		bool last_virtual_cr;
+	} tests[] = {
+		{ "\r\nfoo", 1, "\nfoo", FALSE },
+		{ "\r\nfoo", 2, "foo", FALSE },
+		{ "foo\r\nbar", 3, "\r\nbar", FALSE },
+		{ "foo\r\nbar", 4, "\nbar", FALSE },
+		{ "foo\r\nbar", 5, "bar", FALSE },
+		{ "foo\r\n", 5, "", FALSE },
+		{ "foo\r\nbar\r\nbaz", 8, "\r\nbaz", FALSE },
+		{ "foo\r\nbar\r\nbaz", 9, "\nbaz", FALSE },
+		{ "foo\r\nbar\r\nbaz", 10, "baz", FALSE },
+
+		{ "\nfoo", 1, "\nfoo", TRUE },
+		{ "\nfoo", 2, "foo", FALSE },
+		{ "foo\nbar", 3, "\nbar", FALSE },
+		{ "foo\nbar", 4, "\nbar", TRUE },
+		{ "foo\nbar", 5, "bar", FALSE },
+		{ "foo\n", 5, "", FALSE },
+		{ "foo\nbar\nbaz", 8, "\nbaz", FALSE },
+		{ "foo\nbar\nbaz", 9, "\nbaz", TRUE },
+		{ "foo\nbar\nbaz", 10, "baz", FALSE },
+	};
+	test_begin("message_skip_virtual()");
+	for (unsigned int i = 0; i < N_ELEMENTS(tests); i++) {
+		struct istream *input =
+			i_stream_create_from_data(tests[i].input,
+						  strlen(tests[i].input));
+		bool last_virtual_cr;
+		test_assert_idx(message_skip_virtual(input, tests[i].virtual_skip,
+						     &last_virtual_cr) == 0, i);
+		size_t size;
+		const unsigned char *output =
+			i_stream_get_data(input, &size);
+		test_assert_strcmp_idx(t_strndup(output, size), tests[i].output, i);
+		test_assert_idx(last_virtual_cr == tests[i].last_virtual_cr, i);
+		i_stream_unref(&input);
+	}
+	test_end();
+}
+
 int main(void)
 {
 	static void (*const test_functions[])(void) = {
 		test_message_size,
+		test_message_skip_virtual,
 		NULL
 	};
 	return test_run(test_functions);