security/apparmor/capability.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * AppArmor security module
   4  *
   5  * This file contains AppArmor capability mediation functions
   6  *
   7  * Copyright (C) 1998-2008 Novell/SUSE
   8  * Copyright 2009-2010 Canonical Ltd.
   9  */
  10
  11 #include <linux/capability.h>
  12 #include <linux/errno.h>
  13 #include <linux/gfp.h>
  14 #include <linux/security.h>
  15 #include <linux/timekeeping.h>
  16
  17 #include "include/apparmor.h"
  18 #include "include/capability.h"
  19 #include "include/cred.h"
  20 #include "include/policy.h"
  21 #include "include/audit.h"
  22
  23 /*
  24  * Table of capability names: we generate it from capabilities.h.
  25  */
  26 #include "capability_names.h"
  27
  28 struct aa_sfs_entry aa_sfs_entry_caps[] = {
  29         AA_SFS_FILE_STRING("mask", AA_SFS_CAPS_MASK),
  30         { }
  31 };
  32
  33 struct audit_cache {
  34         const struct cred *ad_subj_cred;
  35         /* Capabilities go from 0 to CAP_LAST_CAP */
  36         u64 ktime_ns_expiration[CAP_LAST_CAP+1];
  37 };
  38
  39 static DEFINE_PER_CPU(struct audit_cache, audit_cache);
  40
  41 /**
  42  * audit_cb - call back for capability components of audit struct
  43  * @ab: audit buffer   (NOT NULL)
  44  * @va: audit struct to audit data from  (NOT NULL)
  45  */
  46 static void audit_cb(struct audit_buffer *ab, void *va)
  47 {
  48         struct common_audit_data *sa = va;
  49
  50         audit_log_format(ab, " capname=");
  51         audit_log_untrustedstring(ab, capability_names[sa->u.cap]);
  52 }
  53
  54 /**
  55  * audit_caps - audit a capability
  56  * @ad: audit data
  57  * @profile: profile being tested for confinement (NOT NULL)
  58  * @cap: capability tested
  59  * @error: error code returned by test
  60  *
  61  * Do auditing of capability and handle, audit/complain/kill modes switching
  62  * and duplicate message elimination.
  63  *
  64  * Returns: 0 or ad->error on success,  error code on failure
  65  */
  66 static int audit_caps(struct apparmor_audit_data *ad, struct aa_profile *profile,
  67                       int cap, int error)
  68 {
  69         const u64 AUDIT_CACHE_TIMEOUT_NS = 1000*1000*1000; /* 1 second */
  70
  71         struct aa_ruleset *rules = list_first_entry(&profile->rules,
  72                                                     typeof(*rules), list);
  73         struct audit_cache *ent;
  74         int type = AUDIT_APPARMOR_AUTO;
  75
  76         ad->error = error;
  77
  78         if (likely(!error)) {
  79                 /* test if auditing is being forced */
  80                 if (likely((AUDIT_MODE(profile) != AUDIT_ALL) &&
  81                            !cap_raised(rules->caps.audit, cap)))
  82                         return 0;
  83                 type = AUDIT_APPARMOR_AUDIT;
  84         } else if (KILL_MODE(profile) ||
  85                    cap_raised(rules->caps.kill, cap)) {
  86                 type = AUDIT_APPARMOR_KILL;
  87         } else if (cap_raised(rules->caps.quiet, cap) &&
  88                    AUDIT_MODE(profile) != AUDIT_NOQUIET &&
  89                    AUDIT_MODE(profile) != AUDIT_ALL) {
  90                 /* quiet auditing */
  91                 return error;
  92         }
  93
  94         /* Do simple duplicate message elimination */
  95         ent = &get_cpu_var(audit_cache);
  96         /* If the capability was never raised the timestamp check would also catch that */
  97         if (ad->subj_cred == ent->ad_subj_cred && ktime_get_ns() <= ent->ktime_ns_expiration[cap]) {
  98                 put_cpu_var(audit_cache);
  99                 if (COMPLAIN_MODE(profile))
 100                         return complain_error(error);
 101                 return error;
 102         } else {
 103                 put_cred(ent->ad_subj_cred);
 104                 ent->ad_subj_cred = get_cred(ad->subj_cred);
 105                 ent->ktime_ns_expiration[cap] = ktime_get_ns() + AUDIT_CACHE_TIMEOUT_NS;
 106         }
 107         put_cpu_var(audit_cache);
 108
 109         return aa_audit(type, profile, ad, audit_cb);
 110 }
 111
 112 /**
 113  * profile_capable - test if profile allows use of capability @cap
 114  * @profile: profile being enforced    (NOT NULL, NOT unconfined)
 115  * @cap: capability to test if allowed
 116  * @opts: CAP_OPT_NOAUDIT bit determines whether audit record is generated
 117  * @ad: audit data (NOT NULL)
 118  *
 119  * Returns: 0 if allowed else -EPERM
 120  */
 121 static int profile_capable(struct aa_profile *profile, int cap,
 122                            unsigned int opts, struct apparmor_audit_data *ad)
 123 {
 124         struct aa_ruleset *rules = list_first_entry(&profile->rules,
 125                                                     typeof(*rules), list);
 126         int error;
 127
 128         if (cap_raised(rules->caps.allow, cap) &&
 129             !cap_raised(rules->caps.denied, cap))
 130                 error = 0;
 131         else
 132                 error = -EPERM;
 133
 134         if (opts & CAP_OPT_NOAUDIT) {
 135                 if (!COMPLAIN_MODE(profile))
 136                         return error;
 137                 /* audit the cap request in complain mode but note that it
 138                  * should be optional.
 139                  */
 140                 ad->info = "optional: no audit";
 141         }
 142
 143         return audit_caps(ad, profile, cap, error);
 144 }
 145
 146 /**
 147  * aa_capable - test permission to use capability
 148  * @subj_cred: cred we are testing capability against
 149  * @label: label being tested for capability (NOT NULL)
 150  * @cap: capability to be tested
 151  * @opts: CAP_OPT_NOAUDIT bit determines whether audit record is generated
 152  *
 153  * Look up capability in profile capability set.
 154  *
 155  * Returns: 0 on success, or else an error code.
 156  */
 157 int aa_capable(const struct cred *subj_cred, struct aa_label *label,
 158                int cap, unsigned int opts)
 159 {
 160         struct aa_profile *profile;
 161         int error = 0;
 162         DEFINE_AUDIT_DATA(ad, LSM_AUDIT_DATA_CAP, AA_CLASS_CAP, OP_CAPABLE);
 163
 164         ad.subj_cred = subj_cred;
 165         ad.common.u.cap = cap;
 166         error = fn_for_each_confined(label, profile,
 167                         profile_capable(profile, cap, opts, &ad));
 168
 169         return error;
 170 }