Subject: multipart: Fix read out of buffer bounds under soup_multipart_new_from_message()
From: Milan Crha <[email-masked]>
Date: Tue, 15 Apr 2025 09:03:00 +0200

This is CVE-2025-32914, special crafted input can cause read out of buffer bounds
of the body argument.

Closes #436

(cherry picked from commit 5bfcf8157597f2d327050114fb37ff600004dbcf)

Upstream-Status: Backport [import from debian https://salsa.debian.org/gnome-team/libsoup/-/blob/debian/bullseye/debian/patches/CVE-2025-32914.patch?ref_type=heads
Upstream commit https://gitlab.gnome.org/GNOME/libsoup/-/commit/5bfcf8157597f2d327050114fb37ff600004dbcf]
CVE: CVE-2025-32914
Signed-off-by: Vijay Anusuri <[email-masked]>
---
 libsoup/soup-multipart.c |  2 +-
 tests/multipart-test.c   | 85 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 86 insertions(+), 1 deletion(-)

diff --git a/libsoup/soup-multipart.c b/libsoup/soup-multipart.c
index a7e550f..dd93973 100644
--- a/libsoup/soup-multipart.c
+++ b/libsoup/soup-multipart.c
@@ -181,7 +181,7 @@ soup_multipart_new_from_message (SoupMessageHeaders *headers,
 			return NULL;
 		}
 
-		split = strstr (start, "\r\n\r\n");
+		split = g_strstr_len (start, body_end - start, "\r\n\r\n");
 		if (!split || split > end) {
 			soup_multipart_free (multipart);
 			soup_buffer_free (flattened);
diff --git a/tests/multipart-test.c b/tests/multipart-test.c
index 64a5ebf..834b181 100644
--- a/tests/multipart-test.c
+++ b/tests/multipart-test.c
@@ -479,6 +479,89 @@ test_multipart (gconstpointer data)
 	g_main_loop_unref (loop);
 }
 
+static void
+test_multipart_bounds_good (void)
+{
+	#define TEXT "line1\r\nline2"
+	SoupMultipart *multipart;
+	SoupMessageHeaders *headers, *set_headers = NULL;
+	//GBytes *bytes, *set_bytes = NULL;
+	GBytes *bytes;
+	const char *raw_data = "--123\r\nContent-Type: text/plain;\r\n\r\n" TEXT "\r\n--123--\r\n";
+	gboolean success;
+	SoupMessageBody *body = soup_message_body_new ();
+	SoupBuffer *set_buffer = NULL;
+	gconstpointer data;
+	gsize size;
+
+	headers = soup_message_headers_new (SOUP_MESSAGE_HEADERS_MULTIPART);
+	soup_message_headers_append (headers, "Content-Type", "multipart/mixed; boundary=\"123\"");
+
+	bytes = g_bytes_new (raw_data, strlen (raw_data));
+
+	data = g_bytes_get_data(bytes, NULL);
+	size = g_bytes_get_size(bytes);
+
+	soup_message_body_append(body, SOUP_MEMORY_STATIC, data, size);
+
+	//multipart = soup_multipart_new_from_message (headers, bytes);
+	multipart = soup_multipart_new_from_message (headers, body);
+
+	soup_message_body_free (body);
+
+	g_assert_nonnull (multipart);
+	g_assert_cmpint (soup_multipart_get_length (multipart), ==, 1);
+	success = soup_multipart_get_part (multipart, 0, &set_headers, &set_buffer);
+	g_assert_true (success);
+	g_assert_nonnull (set_headers);
+	//g_assert_nonnull (set_bytes);
+	g_assert_nonnull (set_buffer);
+	//g_assert_cmpint (strlen (TEXT), ==, g_bytes_get_size (set_bytes));
+	g_assert_cmpint (strlen (TEXT), ==, set_buffer->length);
+	g_assert_cmpstr ("text/plain", ==, soup_message_headers_get_content_type (set_headers, NULL));
+	//g_assert_cmpmem (TEXT, strlen (TEXT), g_bytes_get_data (set_bytes, NULL), g_bytes_get_size (set_bytes));
+	g_assert_cmpmem(TEXT, strlen(TEXT), set_buffer->data, set_buffer->length);
+
+	soup_message_headers_free (headers);
+	g_bytes_unref (bytes);
+
+	soup_multipart_free (multipart);
+
+	#undef TEXT
+}
+
+static void
+test_multipart_bounds_bad (void)
+{
+	SoupMultipart *multipart;
+	SoupMessageHeaders *headers;
+	GBytes *bytes;
+	const char *raw_data = "--123\r\nContent-Type: text/plain;\r\nline1\r\nline2\r\n--123--\r\n";
+	SoupMessageBody *body = soup_message_body_new ();
+	gconstpointer data;
+	gsize size;
+
+	headers = soup_message_headers_new (SOUP_MESSAGE_HEADERS_MULTIPART);
+	soup_message_headers_append (headers, "Content-Type", "multipart/mixed; boundary=\"123\"");
+
+	bytes = g_bytes_new (raw_data, strlen (raw_data));
+
+	data = g_bytes_get_data(bytes, NULL);
+	size = g_bytes_get_size(bytes);
+
+	soup_message_body_append(body, SOUP_MEMORY_STATIC, data, size);
+
+	/* it did read out of raw_data/bytes bounds */
+	//multipart = soup_multipart_new_from_message (headers, bytes);
+	multipart = soup_multipart_new_from_message (headers, body);
+	g_assert_null (multipart);
+
+	soup_message_body_free (body);
+
+	soup_message_headers_free (headers);
+	g_bytes_unref (bytes);
+}
+
 int
 main (int argc, char **argv)
 {
@@ -508,6 +591,8 @@ main (int argc, char **argv)
 	g_test_add_data_func ("/multipart/sync", GINT_TO_POINTER (SYNC_MULTIPART), test_multipart);
 	g_test_add_data_func ("/multipart/async", GINT_TO_POINTER (ASYNC_MULTIPART), test_multipart);
 	g_test_add_data_func ("/multipart/async-small-reads", GINT_TO_POINTER (ASYNC_MULTIPART_SMALL_READS), test_multipart);
+	g_test_add_func ("/multipart/bounds-good", test_multipart_bounds_good);
+	g_test_add_func ("/multipart/bounds-bad", test_multipart_bounds_bad);
 
 	ret = g_test_run ();