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);