[CRIU] [PATCH] security: check additional groups,v4
Ruslan Kuprieiev
kupruser at gmail.com
Thu Jul 10 08:05:46 PDT 2014
On 10.07.2014 18:05, Andrew Vagin wrote:
> On Tue, Jul 08, 2014 at 05:18:01PM +0400, Ruslan Kuprieiev wrote:
>> Currently, we only check if process gids match primary gid of user.
>> But process and user have additional groups too. So lets:
>> 1) check that process rgid,egid and sgid are in the user's grouplist.
>> 2) on restore check that user has all groups from the images.
> offtopic: do we restore a group list?
Yes, we do. As a part of creds.
>> Signed-off-by: Ruslan Kuprieiev <kupruser at gmail.com>
>> ---
>> cr-service.c | 3 +-
>> crtools.c | 3 +-
>> include/crtools.h | 2 +-
>> security.c | 99 ++++++++++++++++++++++++++++++++++++++++++++++++++++---
>> 4 files changed, 99 insertions(+), 8 deletions(-)
>>
>> diff --git a/cr-service.c b/cr-service.c
>> index 64ce751..9504c14 100644
>> --- a/cr-service.c
>> +++ b/cr-service.c
>> @@ -178,7 +178,8 @@ static int setup_opts_from_req(int sk, CriuOpts *req)
>> return -1;
>> }
>>
>> - restrict_uid(ids.uid, ids.gid);
>> + if (restrict_uid(ids.uid, ids.gid))
>> + return -1;
>>
>> if (fstat(sk, &st)) {
>> pr_perror("Can't get socket stat");
>> diff --git a/crtools.c b/crtools.c
>> index b662fff..28d343e 100644
>> --- a/crtools.c
>> +++ b/crtools.c
>> @@ -173,7 +173,8 @@ int main(int argc, char *argv[])
>> BUILD_BUG_ON(PAGE_SIZE != PAGE_IMAGE_SIZE);
>>
>> cr_pb_init();
>> - restrict_uid(getuid(), getgid());
>> + if (restrict_uid(getuid(), getgid()))
>> + return 1;
>>
>> if (argc < 2)
>> goto usage;
>> diff --git a/include/crtools.h b/include/crtools.h
>> index c4ae580..75047fc 100644
>> --- a/include/crtools.h
>> +++ b/include/crtools.h
>> @@ -24,7 +24,7 @@ extern int cr_check(void);
>> extern int cr_exec(int pid, char **opts);
>> extern int cr_dedup(void);
>>
>> -extern void restrict_uid(unsigned int uid, unsigned int gid);
>> +extern int restrict_uid(unsigned int uid, unsigned int gid);
>> struct proc_status_creds;
>> extern bool may_dump(struct proc_status_creds *);
>> struct _CredsEntry;
>> diff --git a/security.c b/security.c
>> index d4b4230..d17c726 100644
>> --- a/security.c
>> +++ b/security.c
>> @@ -1,14 +1,22 @@
>> #include <unistd.h>
>> +#include <pwd.h>
>> +#include <grp.h>
>> +#include <limits.h>
>> +#include <stdlib.h>
>> +#include <string.h>
>> +
>> #include "crtools.h"
>> #include "proc_parse.h"
>> #include "log.h"
>> +#include "xmalloc.h"
>>
>> #include "protobuf/creds.pb-c.h"
>>
>> /*
>> - * UID and GID of user requesting for C/R
>> + * UID, GID and groups of user requesting for C/R
>> */
>> static unsigned int cr_uid, cr_gid;
>> +static unsigned int cr_ngroups, *cr_groups;
>>
>> /*
>> * Setup what user is requesting for dump (via rpc or using
>> @@ -17,11 +25,36 @@ static unsigned int cr_uid, cr_gid;
>> * access to. (Or implement some trickier security policy).
>> */
>>
>> -void restrict_uid(unsigned int uid, unsigned int gid)
>> +int restrict_uid(unsigned int uid, unsigned int gid)
>> {
>> - pr_info("Restrict C/R with %u:%u uid\n", uid, gid);
>> + struct passwd *pwd;
>> + unsigned int buf[NGROUPS_MAX];
>> + int nbuf;
>> +
>> + pr_info("Restrict C/R with %u:%u uid:gid\n", uid, gid);
>> cr_uid = uid;
>> cr_gid = gid;
>> +
>> + pwd = getpwuid(uid);
>> + if (!pwd) {
>> + pr_perror("Can't get password file entry");
>> + return -1;
>> + }
>> +
>> + nbuf = NGROUPS_MAX;
>> + if (getgrouplist(pwd->pw_name, pwd->pw_gid, buf, &nbuf) < 0) {
>> + pr_perror("Can't get group list");
>> + return -1;
>> + }
>> +
>> + cr_ngroups = nbuf;
>> + cr_groups = xmalloc(cr_ngroups*sizeof(*cr_groups));
>> + if (!cr_groups)
>> + return -1;
>> +
>> + memcpy(cr_groups, buf, cr_ngroups*sizeof(*cr_groups));
>> +
>> + return 0;
>> }
>>
>> static bool check_ids(unsigned int crid, unsigned int rid, unsigned int eid, unsigned int sid)
>> @@ -35,6 +68,61 @@ static bool check_ids(unsigned int crid, unsigned int rid, unsigned int eid, uns
>> return false;
>> }
>>
>> +static bool contains(unsigned int *crgids, unsigned int crgids_num, unsigned int gid)
>> +{
>> + int i;
>> +
>> + for (i = 0; i < crgids_num; ++i) {
>> + if (crgids[i] == gid)
>> + return true;
>> + }
>> +
>> + return false;
>> +}
>> +
>> +static bool check_gids(unsigned int rid, unsigned int eid, unsigned int sid)
>> +{
>> + if (cr_gid == 0)
>> + return true;
>> +
>> + if (!(contains(cr_groups, cr_ngroups, rid) &&
>> + contains(cr_groups, cr_ngroups, eid) &&
>> + contains(cr_groups, cr_ngroups, sid))) {
>> + pr_err("GID mismatch. User is absent in (%u,%u,%u)",
>> + rid, eid, sid);
>> + return false;
>> + }
>> +
>> + return true;
>> +}
>> +
>> +/*
>> + * There is no need to check groups on dump, because if uids and gids match
>> + * then groups will match too. Btw, getting groups on dump is problematic.
>> + * We can't parse proc, as it contains only first 32 groups. And we can't use
>> + * getgrouplist, as it reads /etc/group which depends on the namespace.
>> + *
>> + * On restore we're getting groups from imgs and can check if user didn't add
>> + * wrong groups by modifying images.
>> + */
>> +static bool check_groups(unsigned int *groups, unsigned int ngroups)
>> +{
>> + int i;
>> +
>> + if (cr_gid == 0)
>> + return true;
>> +
>> + for (i = 0; i < ngroups; ++i) {
>> + if (!contains(cr_groups, cr_ngroups, groups[i])) {
>> + pr_err("GID mismatch. User is absent in %u group\n",
>> + groups[i]);
>> + return false;
>> + }
>> + }
>> +
>> + return true;
>> +}
>> +
>> static bool check_caps(u32 *inh, u32 *eff, u32 *prm)
>> {
>> int i;
>> @@ -62,13 +150,14 @@ static bool check_caps(u32 *inh, u32 *eff, u32 *prm)
>> bool may_dump(struct proc_status_creds *creds)
>> {
>> return check_ids(cr_uid, creds->uids[0], creds->uids[1], creds->uids[2]) &&
>> - check_ids(cr_gid, creds->gids[0], creds->gids[1], creds->gids[2]) &&
>> + check_gids(creds->gids[0], creds->gids[1], creds->gids[2]) &&
>> check_caps(creds->cap_inh, creds->cap_eff, creds->cap_prm);
>> }
>>
>> bool may_restore(CredsEntry *creds)
>> {
>> return check_ids(cr_uid, creds->uid, creds->euid, creds->suid) &&
>> - check_ids(cr_gid, creds->gid, creds->egid, creds->sgid) &&
>> + check_gids(creds->gid, creds->egid, creds->sgid) &&
>> + check_groups(creds->groups, creds->n_groups) &&
>> check_caps(creds->cap_inh, creds->cap_eff, creds->cap_prm);
>> }
>> --
>> 1.8.3.2
>>
>> _______________________________________________
>> CRIU mailing list
>> CRIU at openvz.org
>> https://lists.openvz.org/mailman/listinfo/criu
More information about the CRIU
mailing list