whois: fix a possible out-of-bounds stack access

If fgets() returns incomplete string, we replace NUL with
'\n', and then trim() runs on a non-NUL-terminated buffer.
Prevent that.

While at it, bump buffer from 1k to 2k.

function                                             old     new   delta
query                                                519     524      +5

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/networking/whois.c b/networking/whois.c
index f0ec86301..f3da32b4e 100644
--- a/networking/whois.c
+++ b/networking/whois.c
@@ -39,20 +39,26 @@ static char *query(const char *host, int port, const char *domain)
 	bool success;
 	char *redir = NULL;
 	const char *pfx = "";
-	char linebuf[1024];
+	/* some .io domains reported to have very long strings in whois
+	 * responses, 1k was not enough:
+	 */
+	char linebuf[2 * 1024];
 	char *buf = NULL;
 	unsigned bufpos = 0;
 
  again:
 	printf("[Querying %s:%d '%s%s']\n", host, port, pfx, domain);
 	fd = create_and_connect_stream_or_die(host, port);
-	success = 0;
 	fdprintf(fd, "%s%s\r\n", pfx, domain);
 	fp = xfdopen_for_read(fd);
 
-	while (fgets(linebuf, sizeof(linebuf), fp)) {
-		unsigned len = strcspn(linebuf, "\r\n");
+	success = 0;
+	while (fgets(linebuf, sizeof(linebuf)-1, fp)) {
+		unsigned len;
+
+		len = strcspn(linebuf, "\r\n");
 		linebuf[len++] = '\n';
+		linebuf[len] = '\0';
 
 		buf = xrealloc(buf, bufpos + len + 1);
 		memcpy(buf + bufpos, linebuf, len);