2 * privs.h - header for privileged operations
3 * Copyright (C) 1993 Thomas Koenig
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37 /* Relinquish privileges temporarily for a setuid or setgid program
38 * with the option of getting them back later. This is done by swapping
39 * the real and effective userid BSD style. Call RELINQUISH_PRIVS once
40 * at the beginning of the main program. This will cause all operatons
41 * to be executed with the real userid. When you need the privileges
42 * of the setuid/setgid invocation, call PRIV_START; when you no longer
43 * need it, call PRIV_END. Note that it is an error to call PRIV_START
44 * and not PRIV_END within the same function.
46 * Use RELINQUISH_PRIVS_ROOT(a,b) if your program started out running
47 * as root, and you want to drop back the effective userid to a
48 * and the effective group id to b, with the option to get them back
51 * If you no longer need root privileges, but those of some other
52 * userid/groupid, you can call REDUCE_PRIV(a,b) when your effective
55 * Problems: Do not use return between PRIV_START and PRIV_END; this
56 * will cause the program to continue running in an unprivileged
59 * It is NOT safe to call exec(), system() or popen() with a user-
60 * supplied program (i.e. without carefully checking PATH and any
61 * library load paths) with relinquished privileges; the called program
62 * can aquire them just as easily. Set both effective and real userid
63 * to the real userid before calling any of them.
69 uid_t real_uid, effective_uid;
74 gid_t real_gid, effective_gid;
76 #define RELINQUISH_PRIVS { \
77 real_uid = getuid(); \
78 effective_uid = geteuid(); \
79 real_gid = getgid(); \
80 effective_gid = getegid(); \
81 setreuid(effective_uid, real_uid); \
82 setregid(effective_gid, real_gid); \
85 #define RELINQUISH_PRIVS_ROOT(a,b) { \
87 effective_uid = geteuid(); \
89 effective_gid = getegid(); \
90 setregid(effective_gid, real_gid); \
91 setreuid(effective_uid, real_uid); \
95 setreuid(real_uid, effective_uid); \
96 setregid(real_gid, effective_gid);
99 setregid(effective_gid, real_gid); \
100 setreuid(effective_uid, real_uid); \
103 #define REDUCE_PRIV(a,b) {\
104 setreuid(real_uid, effective_uid); \
105 setregid(real_gid, effective_gid); \
106 effective_uid = (a); \
107 effective_gid = (b); \
108 setregid(effective_gid, real_gid); \
109 setreuid(effective_uid, real_uid); \