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List:       netfilter-devel
Subject:    [ulogd2 PATCH v4 25/32] db: improve mapping of input-keys to DB columns
From:       Jeremy Sowden <jeremy () azazel ! net>
Date:       2021-11-30 10:55:53
Message-ID: 20211130105600.3103609-26-jeremy () azazel ! net
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Currently, we copy the key-name to a buffer, iterate over it to replace
the full-stops with underscores, using `strchr` from the start of the
buffer on each iteration, then append the buffer to the SQL statement.

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

  ../../util/db.c:118:25: warning: `strncpy` output may be truncated copying 31 bytes \
from a string of length 31

Furthermore, the buffer is one character too short and so there is the
possibility of overruns.

Instead, append the key-name directly to the statement using `sprintf`,
and run `strchr` from the last underscore on each iteration.

Signed-off-by: Jeremy Sowden <jeremy@azazel.net>
---
 util/db.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/util/db.c b/util/db.c
index 2dbe0db2fbfe..339e39ef4797 100644
--- a/util/db.c
+++ b/util/db.c
@@ -96,8 +96,6 @@ static int sql_createstmt(struct ulogd_pluginstance *upi)
 	    (procedure[strlen("INSERT")] == '\0' ||
 			procedure[strlen("INSERT")] == ' ')) {
 		char *stmt_val = mi->stmt;
-		char buf[ULOGD_MAX_KEYLEN];
-		char *underscore;
 
 		if(procedure[6] == '\0') {
 			/* procedure == "INSERT" */
@@ -112,13 +110,18 @@ static int sql_createstmt(struct ulogd_pluginstance *upi)
 			stmt_val += sprintf(stmt_val, "%s (", procedure);
 
 		for (i = 0; i < upi->input.num_keys; i++) {
+			char *underscore;
+
 			if (upi->input.keys[i].flags & ULOGD_KEYF_INACTIVE)
 				continue;
 
-			strncpy(buf, upi->input.keys[i].name, ULOGD_MAX_KEYLEN);	
-			while ((underscore = strchr(buf, '.')))
+			underscore = stmt_val;
+
+			stmt_val += sprintf(stmt_val, "%s,",
+					    upi->input.keys[i].name);
+
+			while ((underscore = strchr(underscore, '.')))
 				*underscore = '_';
-			stmt_val += sprintf(stmt_val, "%s,", buf);
 		}
 		*(stmt_val - 1) = ')';
 
-- 
2.33.0


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