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nss-mymachines: map userns users of containers to real user names

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Given a container "foo", that maps user id $UID to container user, using
user namespaces, this NSS module extenstion will now map the $UID to a
name "vu-foo-$TUID" for the translated UID $UID.

Similar, userns groups are mapped to "vg-foo-$TGID" for translated GIDs
of $GID.

This simple change should make userns users more discoverable. Also,
given that many tools like "adduser" check NSS before allocating a UID,
should lower the chance of UID range conflicts between tools.
This commit is contained in:
Lennart Poettering
2015-07-09 14:46:20 -03:00
parent 43694a8cc7
commit c01ff965b4
8 changed files with 635 additions and 19 deletions
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src/shared/nss-util.h
+31 -2
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@@ -24,6 +24,9 @@
#include <nss.h>
#include <netdb.h>
#include <resolv.h>
#include <pwd.h>
#include <grp.h>
#define NSS_GETHOSTBYNAME_PROTOTYPES(module) \
enum nss_status _nss_##module##_gethostbyname4_r( \
@@ -109,7 +112,8 @@ enum nss_status _nss_##module##_gethostbyname_r( \
NULL, \
NULL); \
return ret; \
}
} \
struct __useless_struct_to_allow_trailing_semicolon__
#define NSS_GETHOSTBYADDR_FALLBACKS(module) \
enum nss_status _nss_##module##_gethostbyaddr_r( \
@@ -125,4 +129,29 @@ enum nss_status _nss_##module##_gethostbyaddr_r( \
buffer, buflen, \
errnop, h_errnop, \
NULL); \
}
} \
struct __useless_struct_to_allow_trailing_semicolon__
#define NSS_GETPW_PROTOTYPES(module) \
enum nss_status _nss_##module##_getpwnam_r( \
const char *name, \
struct passwd *pwd, \
char *buffer, size_t buflen, \
int *errnop) _public_; \
enum nss_status _nss_mymachines_getpwuid_r( \
uid_t uid, \
struct passwd *pwd, \
char *buffer, size_t buflen, \
int *errnop) _public_
#define NSS_GETGR_PROTOTYPES(module) \
enum nss_status _nss_##module##_getgrnam_r( \
const char *name, \
struct group *gr, \
char *buffer, size_t buflen, \
int *errnop) _public_; \
enum nss_status _nss_##module##_getgrgid_r( \
gid_t gid, \
struct group *gr, \
char *buffer, size_t buflen, \
int *errnop) _public_