[CRIU] [PATCH] security: check additional groups
Pavel Emelyanov
xemul at parallels.com
Fri Jul 4 05:08:31 PDT 2014
On 06/30/2014 06:35 PM, 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) check that user has all groups from the process grouplist.
>
> Signed-off-by: Ruslan Kuprieiev <kupruser at gmail.com>
> ---
> cr-service.c | 3 +-
> crtools.c | 3 +-
> include/crtools.h | 2 +-
> include/proc_parse.h | 2 ++
> proc_parse.c | 34 +++++++++++++++++--
> security.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++------
> 6 files changed, 122 insertions(+), 16 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 c3a2e27..c184dba 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/include/proc_parse.h b/include/proc_parse.h
> index b153328..a13ec14 100644
> --- a/include/proc_parse.h
> +++ b/include/proc_parse.h
> @@ -83,6 +83,8 @@ struct proc_pid_stat {
> struct proc_status_creds {
> unsigned int uids[4];
> unsigned int gids[4];
> + unsigned int *groups;
> + unsigned int ngroups;
>
> u32 cap_inh[PROC_CAP_SIZE];
> u32 cap_prm[PROC_CAP_SIZE];
> diff --git a/proc_parse.c b/proc_parse.c
> index f2ea897..2712432 100644
> --- a/proc_parse.c
> +++ b/proc_parse.c
> @@ -689,6 +689,29 @@ static int ids_parse(char *str, unsigned int *arr)
> return 0;
> }
>
> +static int groups_parse(char *str, unsigned int **arr, unsigned int *arr_size)
> +{
> + char *end;
> + unsigned int size = 0;
> + unsigned int *buf = NULL;
> +
> + end = str - 1;
> + /* "Groups:" string has a space before '\n' */
> + while (*end != ' ' && *(end+1) != '\n') {
> + size++;
> + buf = xrealloc(buf, size*sizeof(*buf));
> + if (!buf)
> + return -1;
> +
> + buf[size-1] = strtol(end + 1, &end, 10);
> + }
> +
> + *arr = buf;
> + *arr_size = size;
> +
> + return 0;
> +}
> +
> static int cap_parse(char *str, unsigned int *res)
> {
> int i, ret;
> @@ -715,7 +738,7 @@ int parse_pid_status(pid_t pid, struct proc_status_creds *cr)
> return -1;
> }
>
> - while (done < 6 && fgets(str, sizeof(str), f)) {
> + while (done < 7 && fgets(str, sizeof(str), f)) {
> if (!strncmp(str, "Uid:", 4)) {
> if (ids_parse(str + 5, cr->uids))
> goto err_parse;
> @@ -730,6 +753,13 @@ int parse_pid_status(pid_t pid, struct proc_status_creds *cr)
> done++;
> }
>
> + if (!strncmp(str, "Groups:", 7)) {
> + if (groups_parse(str + 8, &cr->groups, &cr->ngroups))
> + goto err_parse;
> +
> + done++;
> + }
> +
> if (!strncmp(str, "CapInh:", 7)) {
> if (cap_parse(str + 8, cr->cap_inh))
> goto err_parse;
> @@ -759,7 +789,7 @@ int parse_pid_status(pid_t pid, struct proc_status_creds *cr)
> }
> }
>
> - if (done != 6) {
> + if (done != 7) {
> err_parse:
> pr_err("Error parsing proc status file\n");
> fclose(f);
> diff --git a/security.c b/security.c
> index d4b4230..bbda294 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
> @@ -17,24 +25,88 @@ 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)
> +static bool check_uids(unsigned int rid, unsigned int eid, unsigned int sid)
This routine just changes its name. Plz, rename with separate patch.
> {
> - if (crid == 0)
> + if (cr_uid == 0)
> return true;
> - if (crid == rid && crid == eid && crid == sid)
> + if (cr_uid == rid && cr_uid == eid && cr_uid == sid)
> return true;
>
> - pr_err("UID/GID mismatch %u != (%u,%u,%u)\n", crid, rid, eid, sid);
> + pr_err("UID mismatch %u != (%u,%u,%u)\n", cr_uid, rid, eid, sid);
> 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,
> + unsigned int *groups, unsigned int ngroups)
> +{
> + int i;
> +
> + if (cr_gid == 0)
> + return true;
If cr_gid != 0 it should be "included" into cr_groups too.
> +
> + 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;
> + }
> +
> + 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;
> @@ -61,14 +133,14 @@ 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]) &&
> + return check_uids(creds->uids[0], creds->uids[1], creds->uids[2]) &&
> + check_gids(creds->gids[0], creds->gids[1], creds->gids[2], creds->groups, creds->ngroups) &&
> 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) &&
> + return check_uids(creds->uid, creds->euid, creds->suid) &&
> + check_gids(creds->gid, creds->egid, creds->sgid, creds->groups, creds->n_groups) &&
> check_caps(creds->cap_inh, creds->cap_eff, creds->cap_prm);
> }
>
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