output: DBI: improve mapping of DB columns to input-keys

Currently, we copy the column-name to a buffer, iterate over it to
replace the underscores with full-stops, using `strchr` from the start
of the buffer on each iteration, iterate over it a second time to
lower-case all letters, and finally copy the buffer to the input-key's
`name` member.

In addition to being inefficient, `strncpy` is used to do the copies,
which leads gcc to complain:

  ulogd_output_DBI.c:160:17: warning: `strncpy` output may be truncated copying 31 bytes from a string of length 31

Furthermore, the buffer is not initialized, which means that there is
also a possible buffer overrun if the column-name is too long, since
`strncpy` will not append a NUL.

Instead, copy the column-name directly to the input-key using
`snprintf`, and then iterate over it once to replace underscores and
lower-case letters.

Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 13 insertions, 21 deletions

diff --git a/output/dbi/ulogd_output_DBI.c b/output/dbi/ulogd_output_DBI.c
index b4a5bac..fff9abc 100644
--- a/output/dbi/ulogd_output_DBI.c
+++ b/output/dbi/ulogd_output_DBI.c
@@ -91,15 +91,6 @@ static struct config_keyset dbi_kset = {
 #define dbtype_ce(x)	(x->ces[DB_CE_NUM+6])
 
 
-/* lower-cases s in place */
-static void str_tolower(char *s)
-{
-	while(*s) {
-		*s = tolower(*s);
-		s++;
-	}
-}
-
 /* find out which columns the table has */
 static int get_columns_dbi(struct ulogd_pluginstance *upi)
 {
@@ -140,24 +131,25 @@ static int get_columns_dbi(struct ulogd_pluginstance *upi)
 	}
 
 	for (ui=1; ui<=upi->input.num_keys; ui++) {
-		char buf[ULOGD_MAX_KEYLEN+1];
-		char *underscore;
-		const char* field_name = dbi_result_get_field_name(pi->result, ui);
+		const char *field_name = dbi_result_get_field_name(pi->result, ui);
+		char *cp;
 
 		if (!field_name)
 			break;
 
-		/* replace all underscores with dots */
-		strncpy(buf, field_name, ULOGD_MAX_KEYLEN);
-		while ((underscore = strchr(buf, '_')))
-			*underscore = '.';
-
-		str_tolower(buf);
+		snprintf(upi->input.keys[ui - 1].name,
+			 sizeof(upi->input.keys[ui - 1].name),
+			 "%s", field_name);
 
-		DEBUGP("field '%s' found: ", buf);
+		/* down-case and replace all underscores with dots */
+		for (cp = upi->input.keys[ui - 1].name; *cp; cp++) {
+			if (*cp == '_')
+				*cp = '.';
+			else
+				*cp = tolower(*cp);
+		}
 
-		/* add it to list of input keys */
-		strncpy(upi->input.keys[ui-1].name, buf, ULOGD_MAX_KEYLEN);
+		DEBUGP("field '%s' found: ", upi->input.keys[ui - 1].name);
 	}
 
 	/* ID is a sequence */