upstream/opnsense-src
1
0
Fork 0
mirror of https://github.com/opnsense/src.git synced 2026-06-04 22:32:43 -04:00
Code Issues Projects Releases Packages Wiki Activity Actions

telnet: Prevent buffer overflow in the user prompt for SRA

Browse source 
The Secure RPC authenticator for telnet prompts the local user for the
username to use for authentication.  Previously it was using sprintf()
into a buffer of 256 bytes, but the username received over the wire
can be up to 255 bytes long which would overflow the prompt buffer.
Fix this in two ways: First, use snprintf() and check for overflow.
If the prompt buffer overflows, fail authentication without prompting
the user.  Second, add 10 bytes to the buffer size to account for the
overhead of the prompt so that a maximally sized username fits.

While here, replace a bare 255 in the subsequent telnet_gets call with
an expression using sizeof() the relevant buffer.

PR:		270263
Reported by:	Robert Morris <rtm@lcs.mit.edu>
Tested on:	CHERI
Reviewed by:	emaste
Differential Revision:	https://reviews.freebsd.org/D49832
This commit is contained in:
John Baldwin 2025-04-16 09:41:03 -04:00
parent b836c229aa
commit 5737c2ae06
1 changed files with 12 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

16
contrib/telnet/libtelnet/sra.c
View file

@ -241,9 +241,10 @@ bad:
void
sra_reply(Authenticator *ap, unsigned char *data, int cnt)
{
char uprompt[256],tuser[256];
char uprompt[256 + 10]; /* +10 for "User (): " */
char tuser[256];
Session_Key skey;
size_t i;
size_t i, len;
if (cnt-- < 1)
return;
@ -266,8 +267,15 @@ sra_reply(Authenticator *ap, unsigned char *data, int cnt)
/* encode user */
memset(tuser,0,sizeof(tuser));
sprintf(uprompt,"User (%s): ",UserNameRequested);
telnet_gets(uprompt,tuser,255,1);
len = snprintf(uprompt, sizeof(uprompt), "User (%s): ",
UserNameRequested);
if (len >= sizeof(uprompt)) {
if (auth_debug_mode) {
printf("SRA user name too long\r\n");
}
return;
}
telnet_gets(uprompt, tuser, sizeof(tuser) - 1, 1);
if (tuser[0] == '\n' || tuser[0] == '\r' )
strcpy(user,UserNameRequested);
else {