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subids: support nsswitch

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Closes #154

When starting any operation to do with subuid delegation, check
nsswitch for a module to use.  If none is specified, then use
the traditional /etc/subuid and /etc/subgid files.

Currently only one module is supported, and there is no fallback
to the files on errors.  Several possibilities could be considered:

1. in case of connection error, fall back to files
2. in case of unknown user, also fall back to files

etc...

When non-files nss module is used, functions to edit the range
are not supported.  It may make sense to support it, but it also
may make sense to require another tool to be used.

libsubordinateio also uses the nss_ helpers.  This is how for instance
lxc could easily be converted to supporting nsswitch.

Add a set of test cases, including a dummy libsubid_zzz module.  This
hardcodes values such that:

'ubuntu' gets 200000 - 300000
'user1' gets 100000 - 165536
'error' emulates an nss module error
'unknown' emulates a user unknown to the nss module
'conn' emulates a connection error ot the nss module

Changes to libsubid:

Change the list_owner_ranges api: return a count instead of making the array
null terminated.

This is a breaking change, so bump the libsubid abi major number.

Rename free_subuid_range and free_subgid_range to ungrant_subuid_range,
because otherwise it's confusing with free_subid_ranges which frees
    memory.

Run libsubid tests in jenkins

Switch argument order in find_subid_owners

Move the db locking into subordinateio.c

Signed-off-by: Serge Hallyn <serge@hallyn.com>
This commit is contained in:
Serge Hallyn
2021-01-31 17:38:20 -06:00
parent 514c1328b6
commit 8492dee663
26 changed files with 935 additions and 205 deletions
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6
lib/subordinateio.h
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@@ -25,11 +25,11 @@ extern int sub_uid_unlock (void);
extern int sub_uid_add (const char *owner, uid_t start, unsigned long count);
extern int sub_uid_remove (const char *owner, uid_t start, unsigned long count);
extern uid_t sub_uid_find_free_range(uid_t min, uid_t max, unsigned long count);
extern struct subordinate_range **list_owner_ranges(const char *owner, enum subid_type id_type);
extern int list_owner_ranges(const char *owner, enum subid_type id_type, struct subordinate_range ***ranges);
extern bool new_subid_range(struct subordinate_range *range, enum subid_type id_type, bool reuse);
extern bool release_subid_range(struct subordinate_range *range, enum subid_type id_type);
extern int find_subid_owners(unsigned long id, uid_t **uids, enum subid_type id_type);
extern void free_subordinate_ranges(struct subordinate_range **ranges);
extern int find_subid_owners(unsigned long id, enum subid_type id_type, uid_t **uids);
extern void free_subordinate_ranges(struct subordinate_range **ranges, int count);
extern int sub_gid_close(void);
extern bool have_sub_gids(const char *owner, gid_t start, unsigned long count);