1 /* $OpenBSD: setresgid.c,v 1.3 2021/12/15 18:42:38 anton Exp $ */ 2 /* 3 * Written by Bret Stephen Lambert <blambert@openbsd.org> 2014 4 * Public Domain. 5 */ 6 7 #include <sys/types.h> 8 #include <sys/signal.h> 9 #include <sys/proc.h> 10 #include <sys/sysctl.h> 11 #include <sys/wait.h> 12 13 #include <err.h> 14 #include <stdio.h> 15 #include <stdlib.h> 16 #include <pwd.h> 17 #include <unistd.h> 18 19 #include "setuid_regress.h" 20 21 int 22 main(int argc, const char *argv[]) 23 { 24 struct kinfo_proc kproc; 25 struct passwd *pw; 26 gid_t gid; 27 28 if ((pw = getpwnam(_SETUID_REGRESS_USER)) == NULL) 29 err(1, "unknown user \"%s\"", _SETUID_REGRESS_USER); 30 31 gid = getgid(); 32 33 if (setresgid(pw->pw_gid, -1, -1) == -1) 34 err(1, "setgid 0"); 35 checkgids(pw->pw_gid, gid, gid, "0"); 36 37 /* should only respond to setgid upon exec */ 38 if (issetugid()) 39 errx(1, "process incorrectly marked as issetugid()"); 40 41 if (read_kproc_pid(&kproc, getpid()) == -1) 42 err(1, "kproc read failed"); 43 44 if (!(kproc.p_psflags & PS_SUGID)) 45 errx(1, "PS_SUGID not set"); 46 if (kproc.p_psflags & PS_SUGIDEXEC) 47 errx(1, "PS_SUGIDEXEC incorrectly set"); 48 49 /* we should be able to roll back our gids for now */ 50 if (setresgid(gid, -1, -1) == -1) 51 err(1, "setgid 1"); 52 checkgids(gid, gid, gid, "1"); 53 54 if (setresgid(-1, pw->pw_gid, -1) == -1) 55 err(1, "setgid 2"); 56 checkgids(gid, pw->pw_gid, gid, "2"); 57 58 /* we should be able to roll back our gids for now */ 59 if (setresgid(-1, gid, -1) == -1) 60 err(1, "setgid 3"); 61 checkgids(gid, gid, gid, "3"); 62 63 /* 64 * after changing our saved gid and dropping superuser privs, 65 * we should be able to change our real and effective gids to 66 * that of our saved gid, but not to anything else 67 */ 68 69 if (setresgid(-1, -1, pw->pw_gid) == -1) 70 err(1, "setgid 4"); 71 checkgids(gid, gid, pw->pw_gid, "4"); 72 73 if (setresuid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1) 74 err(1, "setresuid 4"); 75 76 if (setresgid(pw->pw_gid, -1, -1) == -1) 77 err(1, "setgid 5"); 78 checkgids(pw->pw_gid, gid, pw->pw_gid, "5"); 79 80 if (setresgid(-1, pw->pw_gid, -1) == -1) 81 err(1, "setgid 6"); 82 checkgids(pw->pw_gid, pw->pw_gid, pw->pw_gid, "6"); 83 84 if (setresgid(gid, -1, -1) != -1) 85 errx(1, "incorrectly capable of setting real gid"); 86 checkgids(pw->pw_gid, pw->pw_gid, pw->pw_gid, "7"); 87 88 if (setresgid(-1, gid, -1) != -1) 89 errx(1, "incorrectly capable of setting effective gid"); 90 checkgids(pw->pw_gid, pw->pw_gid, pw->pw_gid, "9"); 91 92 if (setresgid(-1, -1, gid) != -1) 93 errx(1, "incorrectly capable of setting saved gid"); 94 checkgids(pw->pw_gid, pw->pw_gid, pw->pw_gid, "9"); 95 96 /* sanity-check use of -1 as noop */ 97 if (setresgid(-1, -1, -1) == -1) 98 errx(1, "-1 not properly recognized as noop"); 99 checkgids(pw->pw_gid, pw->pw_gid, pw->pw_gid, "9"); 100 101 exit(0); 102 } 103