Closes#635
newuidmap and newgidmap currently take an integner pid as
the first argument, determining the process id on which to
act. Accept also "fd:N", where N must be an open file
descriptor to the /proc/pid directory for the process to
act upon. This way, if you
exec 10</proc/99
newuidmap fd:10 100000 0 65536
and pid 99 dies and a new process happens to take pid 99 before
newuidmap happens to do its work, then since newuidmap will use
openat() using fd 10, it won't change the mapping for the new
process.
Example:
// terminal 1:
serge@jerom ~/src/nsexec$ ./nsexec -W -s 0 -S 0 -U
about to unshare with 10000000
Press any key to exec (I am 129176)
// terminal 2:
serge@jerom ~/src/shadow$ exec 10</proc/129176
serge@jerom ~/src/shadow$ sudo chown root src/newuidmap src/newgidmap
serge@jerom ~/src/shadow$ sudo chmod u+s src/newuidmap
serge@jerom ~/src/shadow$ sudo chmod u+s src/newgidmap
serge@jerom ~/src/shadow$ ./src/newuidmap fd:10 0 100000 10
serge@jerom ~/src/shadow$ ./src/newgidmap fd:10 0 100000 10
// Terminal 1:
uid=0(root) gid=0(root) groups=0(root)
Signed-off-by: Serge Hallyn <serge@hallyn.com>
Following the discussion https://github.com/shadow-maint/shadow/pull/345
I have changed the documentation to clarify the behaviour of subid
delegation when any subid source except files is configured.
Clarify that the subid delegation can only come from one source.
Moreover, add an example of what might happen if the subid source is NSS
and useradd is executed.
Related: https://github.com/shadow-maint/shadow/issues/331
Users may otherwise be confused and think that because the kernel
does not restrict uid mappings to the root user (within his
current uid mappings), newuidmap will ignore /etc/subuid for the
root user. It will not.
Reported-by: Philippe Grégoire <gregoirep@hotmail.com>
Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
* libmisc/idmapping.h: Document what the upper and lower fields
are in struct map_range.
* man/newgidmap.1.xml: Document when the gid, gidlower and count
argument are.
* man/newuidmap.1.xml: Likewise for uid, uidlower and count.
