3b11a1dece
Differentiate the objective and real subjective credentials from the effective subjective credentials on a task by introducing a second credentials pointer into the task_struct. task_struct::real_cred then refers to the objective and apparent real subjective credentials of a task, as perceived by the other tasks in the system. task_struct::cred then refers to the effective subjective credentials of a task, as used by that task when it's actually running. These are not visible to the other tasks in the system. __task_cred(task) then refers to the objective/real credentials of the task in question. current_cred() refers to the effective subjective credentials of the current task. prepare_creds() uses the objective creds as a base and commit_creds() changes both pointers in the task_struct (indeed commit_creds() requires them to be the same). override_creds() and revert_creds() change the subjective creds pointer only, and the former returns the old subjective creds. These are used by NFSD, faccessat() and do_coredump(), and will by used by CacheFiles. In SELinux, current_has_perm() is provided as an alternative to task_has_perm(). This uses the effective subjective context of current, whereas task_has_perm() uses the objective/real context of the subject. Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: James Morris <jmorris@namei.org>
96 lines
2 KiB
C
96 lines
2 KiB
C
/*
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* linux/fs/nfsd/auth.c
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*
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* Copyright (C) 1995, 1996 Olaf Kirch <okir@monad.swb.de>
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*/
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#include <linux/types.h>
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#include <linux/sched.h>
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#include <linux/sunrpc/svc.h>
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#include <linux/sunrpc/svcauth.h>
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#include <linux/nfsd/nfsd.h>
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#include <linux/nfsd/export.h>
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#include "auth.h"
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int nfsexp_flags(struct svc_rqst *rqstp, struct svc_export *exp)
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{
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struct exp_flavor_info *f;
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struct exp_flavor_info *end = exp->ex_flavors + exp->ex_nflavors;
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for (f = exp->ex_flavors; f < end; f++) {
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if (f->pseudoflavor == rqstp->rq_flavor)
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return f->flags;
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}
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return exp->ex_flags;
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}
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int nfsd_setuser(struct svc_rqst *rqstp, struct svc_export *exp)
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{
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struct group_info *rqgi;
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struct group_info *gi;
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struct cred *new;
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int i;
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int flags = nfsexp_flags(rqstp, exp);
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int ret;
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/* discard any old override before preparing the new set */
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revert_creds(get_cred(current->real_cred));
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new = prepare_creds();
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if (!new)
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return -ENOMEM;
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new->fsuid = rqstp->rq_cred.cr_uid;
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new->fsgid = rqstp->rq_cred.cr_gid;
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rqgi = rqstp->rq_cred.cr_group_info;
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if (flags & NFSEXP_ALLSQUASH) {
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new->fsuid = exp->ex_anon_uid;
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new->fsgid = exp->ex_anon_gid;
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gi = groups_alloc(0);
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} else if (flags & NFSEXP_ROOTSQUASH) {
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if (!new->fsuid)
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new->fsuid = exp->ex_anon_uid;
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if (!new->fsgid)
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new->fsgid = exp->ex_anon_gid;
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gi = groups_alloc(rqgi->ngroups);
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if (!gi)
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goto oom;
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for (i = 0; i < rqgi->ngroups; i++) {
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if (!GROUP_AT(rqgi, i))
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GROUP_AT(gi, i) = exp->ex_anon_gid;
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else
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GROUP_AT(gi, i) = GROUP_AT(rqgi, i);
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}
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} else {
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gi = get_group_info(rqgi);
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}
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if (new->fsuid == (uid_t) -1)
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new->fsuid = exp->ex_anon_uid;
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if (new->fsgid == (gid_t) -1)
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new->fsgid = exp->ex_anon_gid;
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ret = set_groups(new, gi);
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put_group_info(gi);
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if (!ret)
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goto error;
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if (new->uid)
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new->cap_effective = cap_drop_nfsd_set(new->cap_effective);
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else
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new->cap_effective = cap_raise_nfsd_set(new->cap_effective,
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new->cap_permitted);
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put_cred(override_creds(new));
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return 0;
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oom:
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ret = -ENOMEM;
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error:
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abort_creds(new);
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return ret;
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}
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