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-rw-r--r--config.def.h4
-rw-r--r--config.mk2
-rw-r--r--slock.c30
3 files changed, 30 insertions, 6 deletions
diff --git a/config.def.h b/config.def.h
index eae2d9a..6fba2b6 100644
--- a/config.def.h
+++ b/config.def.h
@@ -1,3 +1,7 @@
+/* user and group to drop privileges to */
+static const char *user = "nobody";
+static const char *group = "nogroup";
+
static const char *colorname[NUMCOLS] = {
"black", /* after initialization */
"#005577", /* during input */
diff --git a/config.mk b/config.mk
index 049305c..11357a7 100644
--- a/config.mk
+++ b/config.mk
@@ -15,7 +15,7 @@ INCS = -I. -I/usr/include -I${X11INC}
LIBS = -L/usr/lib -lc -lcrypt -L${X11LIB} -lX11 -lXext -lXrandr
# flags
-CPPFLAGS = -DVERSION=\"${VERSION}\" -DHAVE_SHADOW_H
+CPPFLAGS = -DVERSION=\"${VERSION}\" -D_DEFAULT_SOURCE -DHAVE_SHADOW_H
CFLAGS = -std=c99 -pedantic -Wall -Os ${INCS} ${CPPFLAGS}
LDFLAGS = -s ${LIBS}
COMPATSRC = explicit_bzero.c
diff --git a/slock.c b/slock.c
index da4b099..7127ebe 100644
--- a/slock.c
+++ b/slock.c
@@ -6,6 +6,7 @@
#include <ctype.h>
#include <errno.h>
+#include <grp.h>
#include <pwd.h>
#include <stdarg.h>
#include <stdlib.h>
@@ -83,7 +84,6 @@ dontkillme(void)
}
#endif
-/* only run as root */
static const char *
getpw(void)
{
@@ -119,10 +119,6 @@ getpw(void)
}
#endif /* HAVE_SHADOW_H */
- /* drop privileges */
- if (geteuid() == 0 &&
- ((getegid() != pw->pw_gid && setgid(pw->pw_gid) < 0) || setuid(pw->pw_uid) < 0))
- die("slock: cannot drop privileges\n");
return rval;
}
@@ -316,6 +312,10 @@ usage(void)
int
main(int argc, char **argv) {
+ struct passwd *pwd;
+ struct group *grp;
+ uid_t duid;
+ gid_t dgid;
const char *pws;
Display *dpy;
int s, nlocks;
@@ -328,6 +328,18 @@ main(int argc, char **argv) {
usage();
} ARGEND
+ /* validate drop-user and -group */
+ errno = 0;
+ if (!(pwd = getpwnam(user)))
+ die("slock: getpwnam %s: %s\n", user, errno ?
+ strerror(errno) : "user entry not found");
+ duid = pwd->pw_uid;
+ errno = 0;
+ if (!(grp = getgrnam(group)))
+ die("slock: getgrnam %s: %s\n", group, errno ?
+ strerror(errno) : "group entry not found");
+ dgid = grp->gr_gid;
+
#ifdef __linux__
dontkillme();
#endif
@@ -339,6 +351,14 @@ main(int argc, char **argv) {
if (!(dpy = XOpenDisplay(NULL)))
die("slock: cannot open display\n");
+ /* drop privileges */
+ if (setgroups(0, NULL) < 0)
+ die("slock: setgroups: %s\n", strerror(errno));
+ if (setgid(dgid) < 0)
+ die("slock: setgid: %s\n", strerror(errno));
+ if (setuid(duid) < 0)
+ die("slock: setuid: %s\n", strerror(errno));
+
/* check for Xrandr support */
rr = XRRQueryExtension(dpy, &rrevbase, &rrerrbase);