[PATCH] telnet: Use memove for overlapping memory instead of strncpy

[Tim Rühsen]

---
 ChangeLog         | 14 ++++++++++++++
 telnet/commands.c |  6 +++---
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 96490b50..4fa4640b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,17 @@
+2020-04-27  Tim Rühsen  <address@hidden>
+
+       telnet: Use memove for overlapping memory instead of strncpy.
+
+       Overlapping source and destination buffers are not supported
+       by strncpy and give undefined results.
+
+       7.24.2.3 of ISO/IEC 9899:201x:
+       "If  copying  takes  place  between  objects  thatoverlap,
+       the behavior is undefined."
+
+       * telnet/commands.c (cmds): Use memove for overlapping memory
+       instead of strncpy.
+
 2020-04-12  Mats Erik Andersson  <address@hidden>

        whois: Delegation of IP and AS.
diff --git a/telnet/commands.c b/telnet/commands.c
index 29b2bfd4..ca3010bf 100644
--- a/telnet/commands.c
+++ b/telnet/commands.c
@@ -3108,11 +3108,11 @@ cmdrc (char *m1, char *m2)
          if (isspace (line[0]))
            continue;
          if (strncasecmp (line, m1, l1) == 0)
-           strncpy (line, &line[l1], sizeof (line) - l1);
+           memmove (line, &line[l1], strlen(&line[l1]) + 1);
          else if (strncasecmp (line, m2, l2) == 0)
-           strncpy (line, &line[l2], sizeof (line) - l2);
+           memmove (line, &line[l2], strlen(&line[l2]) + 1);
          else if (strncasecmp (line, "DEFAULT", 7) == 0)
-           strncpy (line, &line[7], sizeof (line) - 7);
+           memmove (line, &line[7], strlen(&line[7]) + 1);
          else
            continue;
          if (line[0] != ' ' && line[0] != '\t' && line[0] != '\n')
--
2.26.2