src: fix printing of XML/JSON event wrapper header/footer

Use the nft_fprintf() helper. The helper handles \0 properly.

Before this patch, we get trash in the output due to the buffer being
printed without any \0.

Signed-off-by: Arturo Borrero Gonzalez <arturo.borrero.glez@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 18 insertions, 16 deletions

diff --git a/src/common.c b/src/common.c
index 3ceb811..a6f2508 100644
--- a/src/common.c
+++ b/src/common.c
@@ -114,14 +114,15 @@ int nft_event_header_snprintf(char *buf, size_t size, uint32_t type,
 	return ret;
 }
 
-int nft_event_header_fprintf(FILE *fp, uint32_t type, uint32_t flags)
+static int nft_event_header_fprintf_cb(char *buf, size_t size, void *unused,
+				       uint32_t type, uint32_t flags)
 {
-	char buf[64]; /* enough for the maximum string length above */
-
-	nft_event_header_snprintf(buf, sizeof(buf), type, flags);
-	buf[sizeof(buf) - 1] = '\0';
+	return nft_event_header_snprintf(buf, size, type, flags);
+}
 
-	return fprintf(fp, "%s", buf);
+int nft_event_header_fprintf(FILE *fp, uint32_t type, uint32_t flags)
+{
+	return nft_fprintf(fp, NULL, type, flags, nft_event_header_fprintf_cb);
 }
 
 int nft_event_footer_snprintf(char *buf, size_t size, uint32_t type,
@@ -140,6 +141,17 @@ int nft_event_footer_snprintf(char *buf, size_t size, uint32_t type,
 	}
 }
 
+static int nft_event_footer_fprintf_cb(char *buf, size_t size, void *unused,
+				       uint32_t type, uint32_t flags)
+{
+	return nft_event_footer_snprintf(buf, size, type, flags);
+}
+
+int nft_event_footer_fprintf(FILE *fp, uint32_t type, uint32_t flags)
+{
+	return nft_fprintf(fp, NULL, type, flags, nft_event_footer_fprintf_cb);
+}
+
 static void nft_batch_build_hdr(char *buf, uint16_t type, uint32_t seq)
 {
 	struct nlmsghdr *nlh;
@@ -168,16 +180,6 @@ void nft_batch_end(char *buf, uint32_t seq)
 }
 EXPORT_SYMBOL(nft_batch_end);
 
-int nft_event_footer_fprintf(FILE *fp, uint32_t type, uint32_t flags)
-{
-	char buf[32]; /* enough for the maximum string length above */
-
-	nft_event_footer_snprintf(buf, sizeof(buf), type, flags);
-	buf[sizeof(buf) - 1] = '\0';
-
-	return fprintf(fp, "%s", buf);
-}
-
 int nft_batch_is_supported(void)
 {
 	struct mnl_socket *nl;