output: MYSQL: 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, then copy the buffer to the input-key's
`name` member.

Apart from the inefficiency, `strncpy` is used to do the copies, which
leads gcc to complain:

  ulogd_output_MYSQL.c:149:17: 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 run `strchr` from the last underscore on each iteration.

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

diff --git a/output/mysql/ulogd_output_MYSQL.c b/output/mysql/ulogd_output_MYSQL.c
index 66151feb4939af96e6d9e6f977fa303c966f3f0f..9727e303f2c585b1f9987315c9a5a7082d2e2aec 100644 (file)
--- a/output/mysql/ulogd_output_MYSQL.c
+++ b/output/mysql/ulogd_output_MYSQL.c
@@ -135,18 +135,18 @@ static int get_columns_mysql(struct ulogd_pluginstance *upi)
        }
 
        for (i = 0; (field = mysql_fetch_field(result)); i++) {
-               char buf[ULOGD_MAX_KEYLEN+1];
                char *underscore;
 
+               snprintf(upi->input.keys[i].name,
+                        sizeof(upi->input.keys[i].name),
+                        "%s", field->name);
+
                /* replace all underscores with dots */
-               strncpy(buf, field->name, ULOGD_MAX_KEYLEN);
-               while ((underscore = strchr(buf, '_')))
+               for (underscore = upi->input.keys[i].name;
+                    (underscore = strchr(underscore, '_')); )
                        *underscore = '.';
 
-               DEBUGP("field '%s' found\n", buf);
-
-               /* add it to list of input keys */
-               strncpy(upi->input.keys[i].name, buf, ULOGD_MAX_KEYLEN);
+               DEBUGP("field '%s' found\n", upi->input.keys[i].name);
        }
        /* MySQL Auto increment ... ID :) */
        upi->input.keys[0].flags |= ULOGD_KEYF_INACTIVE;