220b352b70
- Since strncpy(3) is not designed to write strings, but rather
(null-padded) character sequences (a.k.a. unterminated strings), we
had to manually append a '\0'. strlcpy(3) creates strings, so they
are always terminated. This removes dependencies between lines, and
also removes chances of accidents.
- Repurposing strncpy(3) to create strings requires calculating the
location of the terminating null byte, which involves a '-1'
calculation. This is a source of off-by-one bugs. The new code has
no '-1' calculations, so there's almost-zero chance of these bugs.
- strlcpy(3) doesn't padd with null bytes. Padding is relevant when
writing fixed-width buffers to binary files, when interfacing certain
APIs (I believe utmpx requires null padding at lease in some
systems), or when sending them to other processes or through the
network. This is not the case, so padding is effectively ignored.
- strlcpy(3) requires that the input string is really a string;
otherwise it crashes (SIGSEGV). Let's check if the input strings are
really strings:
- lib/fields.c:
- 'cp' was assigned from 'newft', and 'newft' comes from fgets(3).
- lib/gshadow.c:
- strlen(string) is calculated a few lines above.
- libmisc/console.c:
- 'cons' comes from getdef_str, which is a bit cryptic, but seems
to generate strings, I guess.1
- libmisc/date_to_str.c:
- It receives a string literal. :)
- libmisc/utmp.c:
- 'tname' comes from ttyname(3), which returns a string.
- src/su.c:
- 'tmp_name' has been passed to strcmp(3) a few lines above.
Signed-off-by: Alejandro Colomar <alx@kernel.org>
108 lines
2.3 KiB
C
108 lines
2.3 KiB
C
/*
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* SPDX-FileCopyrightText: 1991 , Julianne Frances Haugh
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* SPDX-FileCopyrightText: 1991 , Chip Rosenthal
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* SPDX-FileCopyrightText: 1996 - 1998, Marek Michałkiewicz
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* SPDX-FileCopyrightText: 2003 - 2005, Tomasz Kłoczko
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* SPDX-FileCopyrightText: 2007 - 2010, Nicolas François
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#include <config.h>
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#include "defines.h"
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#include <stdio.h>
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#include "getdef.h"
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#include "prototypes.h"
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#ident "$Id$"
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/*
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* This is now rather generic function which decides if "tty" is listed
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* under "cfgin" in config (directly or indirectly). Fallback to default if
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* something is bad.
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*/
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static bool is_listed (const char *cfgin, const char *tty, bool def)
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{
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FILE *fp;
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char buf[1024], *s;
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const char *cons;
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/*
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* If the CONSOLE configuration definition isn't given,
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* fallback to default.
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*/
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cons = getdef_str (cfgin);
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if (NULL == cons) {
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return def;
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}
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/*
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* If this isn't a filename, then it is a ":" delimited list of
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* console devices upon which root logins are allowed.
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*/
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if (*cons != '/') {
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char *pbuf;
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strlcpy (buf, cons, sizeof (buf));
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pbuf = &buf[0];
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while ((s = strtok (pbuf, ":")) != NULL) {
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if (strcmp (s, tty) == 0) {
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return true;
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}
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pbuf = NULL;
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}
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return false;
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}
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/*
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* If we can't open the console list, then call everything a
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* console - otherwise root will never be allowed to login.
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*/
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fp = fopen (cons, "r");
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if (NULL == fp) {
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return def;
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}
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/*
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* See if this tty is listed in the console file.
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*/
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while (fgets (buf, (int) sizeof (buf), fp) != NULL) {
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buf[strlen (buf) - 1] = '\0';
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if (strcmp (buf, tty) == 0) {
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(void) fclose (fp);
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return true;
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}
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}
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/*
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* This tty isn't a console.
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*/
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(void) fclose (fp);
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return false;
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}
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/*
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* console - return 1 if the "tty" is a console device, else 0.
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*
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* Note - we need to take extreme care here to avoid locking out root logins
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* if something goes awry. That's why we do things like call everything a
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* console if the consoles file can't be opened. Because of this, we must
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* warn the user to protect against the remove of the consoles file since
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* that would allow an unauthorized root login.
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*/
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bool console (const char *tty)
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{
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if (strncmp (tty, "/dev/", 5) == 0) {
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tty += 5;
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}
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return is_listed ("CONSOLE", tty, true);
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}
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