capng_change_id(3) [debian man page]
CAPNG_CHANGE_ID(3) Libcap-ng API CAPNG_CHANGE_ID(3) NAME
capng_change_id - change the credentials retaining capabilities SYNOPSIS
#include <cap-ng.h> int capng_change_id(int uid, int gid, capng_flags_t flag); DESCRIPTION
This function will change uid and gid to the ones given while retaining the capabilities previously specified in capng_update. It is not necessary and perhaps better if capng_apply has not been called prior to this function so that all necessary privileges are still intact. The caller is required to have CAP_SETPCAP capability still active before calling this function. This function also takes a flag parameter that helps to tailor the exact actions performed by the function to secure the environment. The option may be or'ed together. The legal values are: CAPNG_NO_FLAG Simply change uid and retain specified capabilities and that's all. CAPNG_DROP_SUPP_GRP After changing id, remove and supplement groups that may come with the account. CAPNG_CLEAR_BOUNDING After changing the uid and gid, clear the bounding set regardless to the internal representation already setup. RETURN VALUE
This returns 0 on success and a negative number on failure. -1 means capng has not been initted properly, -2 means a failure requesting to keep capabilities across the uid change, -3 means that applying the intermediate capabilities failed, -4 means changing gid failed, -5 means dropping supplemental groups failed, -6 means changing the uid failed, -7 means dropping the ability to retain caps across a uid change failed, -8 means clearing the bounding set failed, -9 means dropping CAP_SETPCAP failed. Note: the only safe action to do upon failure of this function is to probably exit. This is because you are likely in a situation with par- tial permissions and not what you intended. SEE ALSO
capng_update(3), capng_apply(3), prctl(2), capabilities(7) AUTHOR
Steve Grubb Red Hat June 2009 CAPNG_CHANGE_ID(3)
Check Out this Related Man Page
CAPSH(1) User Commands CAPSH(1) NAME
capsh - capability shell wrapper SYNOPSIS
capsh [OPTION]... DESCRIPTION
Linux capability support and use can be explored and constrained with this tool. This tool provides a handy wrapper for certain types of capability testing and environment creation. It also provides some debugging features useful for summarizing capability state. OPTIONS
The tool takes a number of optional arguments, acting on them in the order they are provided. They are as follows: --print Display prevailing capability and related state. -- [args] Execute /bin/bash with trailing arguments. Note, you can use -c 'command to execute' for specific commands. == Execute capsh again with remaining arguments. Useful for testing exec() behavior. --caps=cap-set Set the prevailing process capabilities to those specified by cap-set. Where cap-set is a text-representation of capability state as per cap_from_text(3). --drop=cap-list Remove the listed capabilities from the prevailing bounding set. The capabilities are a comma separated list of capa- bilities as recognized by the cap_from_name(3) function. Use of this feature requires that the capsh program is oper- ating with CAP_SETPCAP in its effective set. --inh=cap-list Set the inheritable set of capabilities for the current process to equal those provided in the comma separated list. For this action to succeed, the prevailing process should already have each of these capabilities in the union of the current inheritable and permitted capability sets, or the capsh program is operating with CAP_SETPCAP in its effec- tive set. --user=username Assume the identity of the named user. That is, look up the user's uid and gid with getpwuid(3) and their group mem- berships with getgrouplist(3) and set them all. --uid=id Force all uid values to equal id using the setuid(2) system call. --gid=<id> Force all gid values to equal id using the setgid(2) system call. --groups=<id-list> Set the supplementary groups to the numerical list provided. The groups are set with the setgroups(2) system call. --keep=<0|1> In a non-pure capability mode, the kernel provides liberal privilege to the super-user. However, it is normally the case that when the super-user changes uid to some lesser user, then capabilities are dropped. For these situations, the kernel can permit the process to retain its capabilities after a setuid(2) system call. This feature is known as keep-caps support. The way to activate it using this script is with this argument. Setting the value to 1 will cause keep-caps to be active. Setting it to 0 will cause keep-caps to deactivate for the current process. In all cases, keep-caps is deactivated when an exec() is performed. See --secbits for ways to disable this feature. --secbits=N XXX - need to document this feature. --chroot=path Execute the chroot(2) system call with the new root-directory (/) equal to path. This operation requires CAP_SYS_CHROOT to be in effect. --forkfor=sec --killit=sig --decode=N This is a convenience feature. If you look at /proc/1/status there are some capability related fields of the follow- ing form: CapInh: 0000000000000000 CapPrm: ffffffffffffffff CapEff: fffffffffffffeff CapBnd: ffffffffffffffff This option provides a quick way to decode a capability vector represented in this form. For example, the missing capability from this effective set is 0x0100. By running: capsh --decode=0x0100 we observe that the missing capability is: cap_setpcap. --supports=xxx As the kernel evolves, more capabilities are added. This option can be used to verify the existence of a capability on the system. For example, --supports=cap_syslog will cause capsh to promptly exit with a status of 1 when run on kernel 2.6.27. However, when run on kernel 2.6.38 it will silently succeed. EXIT STATUS Following successful execution the tool exits with status 0. Following an error, the tool immediately exits with status 1. AUTHOR
Written by Andrew G. Morgan <morgan@kernel.org>. REPORTING BUGS
Please report bugs to the author. SEE ALSO
libcap(3), getcap(8),setcap(8) and capabilities(7). libcap 2 2011-04-24 CAPSH(1)