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Merge pull request #2776 from swaywm/swaylock-setuid

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Fix swaylock w/shadow on glibc, improve security
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emersion 2018-10-06 18:47:34 +02:00 committed by GitHub
commit 176832fe30
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3 changed files with 31 additions and 0 deletions
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1
meson.build
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@ -44,6 +44,7 @@ gdk_pixbuf = dependency('gdk-pixbuf-2.0', required: false)
pixman = dependency('pixman-1')
libinput = dependency('libinput', version: '>=1.6.0')
libpam = cc.find_library('pam', required: false)
crypt = cc.find_library('crypt', required: false)
systemd = dependency('libsystemd', required: false)
elogind = dependency('libelogind', required: false)
math = cc.find_library('m')

3
swaylock/meson.build
View file

@ -26,6 +26,9 @@ else
warning('The swaylock binary must be setuid when compiled without libpam')
warning('You must do this manually post-install: chmod a+s /path/to/swaylock')
sources += ['shadow.c']
if crypt.found()
dependencies += [crypt]
endif
endif
executable('swaylock',

27
swaylock/shadow.c
View file

@ -6,9 +6,21 @@
#include <unistd.h>
#include <wlr/util/log.h>
#include "swaylock/swaylock.h"
#ifdef __GLIBC__
// GNU, you damn slimy bastard
#include <crypt.h>
#endif
static int comm[2][2];
static void clear_buffer(void *buf, size_t bytes) {
volatile char *buffer = buf;
volatile char zero = '\0';
for (size_t i = 0; i < bytes; ++i) {
buffer[i] = zero;
}
}
void run_child(void) {
/* This code runs as root */
struct passwd *pwent = getpwuid(getuid());
@ -25,6 +37,17 @@ void run_child(void) {
}
encpw = swent->sp_pwdp;
}
/* We don't need any additional logging here because the parent process will
* also fail here and will handle logging for us. */
if (setgid(getgid()) != 0) {
exit(EXIT_FAILURE);
}
if (setuid(getuid()) != 0) {
exit(EXIT_FAILURE);
}
/* This code does not run as root */
wlr_log(WLR_DEBUG, "prepared to authorize user %s", pwent->pw_name);
size_t size;
@ -60,10 +83,14 @@ void run_child(void) {
result = strcmp(c, encpw) == 0;
if (write(comm[1][1], &result, sizeof(result)) != sizeof(result)) {
wlr_log_errno(WLR_ERROR, "failed to write pw check result");
clear_buffer(buf, size);
exit(EXIT_FAILURE);
}
clear_buffer(buf, size);
free(buf);
}
clear_buffer(encpw, strlen(encpw));
exit(EXIT_SUCCESS);
}