# module Process::GID

The `Process::GID` module contains a collection of module functions which can be used to portably get, set, and switch the current process's real, effective, and saved group IDs.

### Public Class Methods

Process::GID.change_privilege(group) → integer click to toggle source

Change the current process's real and effective group ID to that specified by group. Returns the new group ID. Not available on all platforms.

    [Process.gid, Process.egid]          #=> [0, 0]
    Process::GID.change_privilege(33)    #=> 33
    [Process.gid, Process.egid]          #=> [33, 33]

    static VALUE
    p_gid_change_privilege(VALUE obj, VALUE id)
    {
        rb_gid_t gid;

        check_gid_switch();

        gid = OBJ2GID(id);

        if (geteuid() == 0) { /* root-user */
    #if defined(HAVE_SETRESGID)
            if (setresgid(gid, gid, gid) < 0) rb_sys_fail(0);
            SAVED_GROUP_ID = gid;
    #elif defined HAVE_SETGID
            if (setgid(gid) < 0) rb_sys_fail(0);
            SAVED_GROUP_ID = gid;
    #elif defined(HAVE_SETREGID) && !defined(OBSOLETE_SETREGID)
            if (getgid() == gid) {
                if (SAVED_GROUP_ID == gid) {
                    if (setregid(-1, gid) < 0) rb_sys_fail(0);
                }
                else {
                    if (gid == 0) { /* (r,e,s) == (root, y, x) */
                        if (setregid(-1, SAVED_GROUP_ID) < 0) rb_sys_fail(0);
                        if (setregid(SAVED_GROUP_ID, 0) < 0) rb_sys_fail(0);
                        SAVED_GROUP_ID = 0; /* (r,e,s) == (x, root, root) */
                        if (setregid(gid, gid) < 0) rb_sys_fail(0);
                        SAVED_GROUP_ID = gid;
                    }
                    else { /* (r,e,s) == (z, y, x) */
                        if (setregid(0, 0) < 0) rb_sys_fail(0);
                        SAVED_GROUP_ID = 0;
                        if (setregid(gid, gid) < 0) rb_sys_fail(0);
                        SAVED_GROUP_ID = gid;
                    }
                }
            }
            else {
                if (setregid(gid, gid) < 0) rb_sys_fail(0);
                SAVED_GROUP_ID = gid;
            }
    #elif defined(HAVE_SETRGID) && defined (HAVE_SETEGID)
            if (getgid() == gid) {
                if (SAVED_GROUP_ID == gid) {
                    if (setegid(gid) < 0) rb_sys_fail(0);
                }
                else {
                    if (gid == 0) {
                        if (setegid(gid) < 0) rb_sys_fail(0);
                        if (setrgid(SAVED_GROUP_ID) < 0) rb_sys_fail(0);
                        SAVED_GROUP_ID = 0;
                        if (setrgid(0) < 0) rb_sys_fail(0);
                    }
                    else {
                        if (setrgid(0) < 0) rb_sys_fail(0);
                        SAVED_GROUP_ID = 0;
                        if (setegid(gid) < 0) rb_sys_fail(0);
                        if (setrgid(gid) < 0) rb_sys_fail(0);
                        SAVED_GROUP_ID = gid;
                    }
                }
            }
            else {
                if (setegid(gid) < 0) rb_sys_fail(0);
                if (setrgid(gid) < 0) rb_sys_fail(0);
                SAVED_GROUP_ID = gid;
            }
    #else
            rb_notimplement();
    #endif
        }
        else { /* unprivileged user */
    #if defined(HAVE_SETRESGID)
            if (setresgid((getgid() == gid)? (rb_gid_t)-1: gid,
                          (getegid() == gid)? (rb_gid_t)-1: gid,
                          (SAVED_GROUP_ID == gid)? (rb_gid_t)-1: gid) < 0) rb_sys_fail(0);
            SAVED_GROUP_ID = gid;
    #elif defined(HAVE_SETREGID) && !defined(OBSOLETE_SETREGID)
            if (SAVED_GROUP_ID == gid) {
                if (setregid((getgid() == gid)? (rb_uid_t)-1: gid,
                             (getegid() == gid)? (rb_uid_t)-1: gid) < 0)
                    rb_sys_fail(0);
            }
            else if (getgid() != gid) {
                if (setregid(gid, (getegid() == gid)? (rb_uid_t)-1: gid) < 0)
                    rb_sys_fail(0);
                SAVED_GROUP_ID = gid;
            }
            else if (/* getgid() == gid && */ getegid() != gid) {
                if (setregid(getegid(), gid) < 0) rb_sys_fail(0);
                SAVED_GROUP_ID = gid;
                if (setregid(gid, -1) < 0) rb_sys_fail(0);
            }
            else { /* getgid() == gid && getegid() == gid */
                if (setregid(-1, SAVED_GROUP_ID) < 0) rb_sys_fail(0);
                if (setregid(SAVED_GROUP_ID, gid) < 0) rb_sys_fail(0);
                SAVED_GROUP_ID = gid;
                if (setregid(gid, -1) < 0) rb_sys_fail(0);
            }
    #elif defined(HAVE_SETRGID) && defined(HAVE_SETEGID)
            if (SAVED_GROUP_ID == gid) {
                if (getegid() != gid && setegid(gid) < 0) rb_sys_fail(0);
                if (getgid() != gid && setrgid(gid) < 0) rb_sys_fail(0);
            }
            else if (/* SAVED_GROUP_ID != gid && */ getegid() == gid) {
                if (getgid() != gid) {
                    if (setrgid(gid) < 0) rb_sys_fail(0);
                    SAVED_GROUP_ID = gid;
                }
                else {
                    if (setrgid(SAVED_GROUP_ID) < 0) rb_sys_fail(0);
                    SAVED_GROUP_ID = gid;
                    if (setrgid(gid) < 0) rb_sys_fail(0);
                }
            }
            else if (/* getegid() != gid && */ getgid() == gid) {
                if (setegid(gid) < 0) rb_sys_fail(0);
                if (setrgid(SAVED_GROUP_ID) < 0) rb_sys_fail(0);
                SAVED_GROUP_ID = gid;
                if (setrgid(gid) < 0) rb_sys_fail(0);
            }
            else {
                rb_syserr_fail(EPERM, 0);
            }
    #elif defined HAVE_44BSD_SETGID
            if (getgid() == gid) {
                /* (r,e,s)==(gid,?,?) ==> (gid,gid,gid) */
                if (setgid(gid) < 0) rb_sys_fail(0);
                SAVED_GROUP_ID = gid;
            }
            else {
                rb_syserr_fail(EPERM, 0);
            }
    #elif defined HAVE_SETEGID
            if (getgid() == gid && SAVED_GROUP_ID == gid) {
                if (setegid(gid) < 0) rb_sys_fail(0);
            }
            else {
                rb_syserr_fail(EPERM, 0);
            }
    #elif defined HAVE_SETGID
            if (getgid() == gid && SAVED_GROUP_ID == gid) {
                if (setgid(gid) < 0) rb_sys_fail(0);
            }
            else {
                rb_syserr_fail(EPERM, 0);
            }
    #else
            (void)gid;
            rb_notimplement();
    #endif
        }
        return id;
    }

egid → integer click to toggle source
Process::GID.eid → integer
Process::Sys.geteid → integer

Returns the effective group ID for this process. Not available on all platforms.

    Process.egid   #=> 500

    static VALUE
    proc_getegid(VALUE obj)
    {
        rb_gid_t egid = getegid();

        return GIDT2NUM(egid);
    }

Process::GID.from_name(name) → gid click to toggle source

Get the group ID by the name. If the group is not found, `ArgumentError` will be raised.

    Process::GID.from_name("wheel") #=> 0
    Process::GID.from_name("nosuchgroup") #=> can't find group for nosuchgroup (ArgumentError)

    static VALUE
    p_gid_from_name(VALUE self, VALUE id)
    {
        return GIDT2NUM(OBJ2GID(id));
    }

Process::GID.grant_privilege(group) → integer click to toggle source
Process::GID.eid = group → integer

Set the effective group ID, and if possible, the saved group ID of the process to the given group. Returns the new effective group ID. Not available on all platforms.

    [Process.gid, Process.egid]          #=> [0, 0]
    Process::GID.grant_privilege(31)     #=> 33
    [Process.gid, Process.egid]          #=> [0, 33]

    static VALUE
    p_gid_grant_privilege(VALUE obj, VALUE id)
    {
        rb_setegid_core(OBJ2GID(id));
        return id;
    }

Process::GID.re_exchange → integer click to toggle source

Exchange real and effective group IDs and return the new effective group ID. Not available on all platforms.

    [Process.gid, Process.egid]   #=> [0, 33]
    Process::GID.re_exchange      #=> 0
    [Process.gid, Process.egid]   #=> [33, 0]

    static VALUE
    p_gid_exchange(VALUE obj)
    {
        rb_gid_t gid;
    #if defined(HAVE_SETRESGID) || (defined(HAVE_SETREGID) && !defined(OBSOLETE_SETREGID))
        rb_gid_t egid;
    #endif

        check_gid_switch();

        gid = getgid();
    #if defined(HAVE_SETRESGID) || (defined(HAVE_SETREGID) && !defined(OBSOLETE_SETREGID))
        egid = getegid();
    #endif

    #if defined(HAVE_SETRESGID)
        if (setresgid(egid, gid, gid) < 0) rb_sys_fail(0);
        SAVED_GROUP_ID = gid;
    #elif defined(HAVE_SETREGID) && !defined(OBSOLETE_SETREGID)
        if (setregid(egid,gid) < 0) rb_sys_fail(0);
        SAVED_GROUP_ID = gid;
    #else
        rb_notimplement();
    #endif
        return GIDT2NUM(gid);
    }

Process::GID.re_exchangeable? → true or false click to toggle source

Returns `true` if the real and effective group IDs of a process may be exchanged on the current platform.

    static VALUE
    p_gid_exchangeable(void)
    {
    #if defined(HAVE_SETRESGID)
        return Qtrue;
    #elif defined(HAVE_SETREGID) && !defined(OBSOLETE_SETREGID)
        return Qtrue;
    #else
        return Qfalse;
    #endif
    }

gid → integer click to toggle source
Process::GID.rid → integer
Process::Sys.getgid → integer

Returns the (real) group ID for this process.

    Process.gid   #=> 500

    static VALUE
    proc_getgid(VALUE obj)
    {
        rb_gid_t gid = getgid();
        return GIDT2NUM(gid);
    }

Process::GID.sid_available? → true or false click to toggle source

Returns `true` if the current platform has saved group ID functionality.

    static VALUE
    p_gid_have_saved_id(void)
    {
    #if defined(HAVE_SETRESGID) || defined(HAVE_SETEGID) || defined(_POSIX_SAVED_IDS)
        return Qtrue;
    #else
        return Qfalse;
    #endif
    }

Process::GID.switch → integer click to toggle source
Process::GID.switch {|| block} → object

Switch the effective and real group IDs of the current process. If a block is given, the group IDs will be switched back after the block is executed. Returns the new effective group ID if called without a block, and the return value of the block if one is given.

    static VALUE
    p_gid_switch(VALUE obj)
    {
        rb_gid_t gid, egid;

        check_gid_switch();

        gid = getgid();
        egid = getegid();

        if (gid != egid) {
            proc_setegid(obj, GIDT2NUM(gid));
            if (rb_block_given_p()) {
                under_gid_switch = 1;
                return rb_ensure(rb_yield, Qnil, p_gid_sw_ensure, SAVED_GROUP_ID);
            }
            else {
                return GIDT2NUM(egid);
            }
        }
        else if (egid != SAVED_GROUP_ID) {
            proc_setegid(obj, GIDT2NUM(SAVED_GROUP_ID));
            if (rb_block_given_p()) {
                under_gid_switch = 1;
                return rb_ensure(rb_yield, Qnil, p_gid_sw_ensure, egid);
            }
            else {
                return GIDT2NUM(gid);
            }
        }
        else {
            rb_syserr_fail(EPERM, 0);
        }

        UNREACHABLE;
    }