security/apparmor/lib.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * AppArmor security module
   4  *
   5  * This file contains basic common functions used in AppArmor
   6  *
   7  * Copyright (C) 1998-2008 Novell/SUSE
   8  * Copyright 2009-2010 Canonical Ltd.
   9  */
  10
  11 #include <linux/ctype.h>
  12 #include <linux/mm.h>
  13 #include <linux/slab.h>
  14 #include <linux/string.h>
  15 #include <linux/vmalloc.h>
  16
  17 #include "include/audit.h"
  18 #include "include/apparmor.h"
  19 #include "include/lib.h"
  20 #include "include/perms.h"
  21 #include "include/policy.h"
  22
  23 struct aa_perms nullperms;
  24 struct aa_perms allperms = { .allow = ALL_PERMS_MASK,
  25                              .quiet = ALL_PERMS_MASK,
  26                              .hide = ALL_PERMS_MASK };
  27
  28 /**
  29  * aa_split_fqname - split a fqname into a profile and namespace name
  30  * @fqname: a full qualified name in namespace profile format (NOT NULL)
  31  * @ns_name: pointer to portion of the string containing the ns name (NOT NULL)
  32  *
  33  * Returns: profile name or NULL if one is not specified
  34  *
  35  * Split a namespace name from a profile name (see policy.c for naming
  36  * description).  If a portion of the name is missing it returns NULL for
  37  * that portion.
  38  *
  39  * NOTE: may modify the @fqname string.  The pointers returned point
  40  *       into the @fqname string.
  41  */
  42 char *aa_split_fqname(char *fqname, char **ns_name)
  43 {
  44         char *name = strim(fqname);
  45
  46         *ns_name = NULL;
  47         if (name[0] == ':') {
  48                 char *split = strchr(&name[1], ':');
  49                 *ns_name = skip_spaces(&name[1]);
  50                 if (split) {
  51                         /* overwrite ':' with \0 */
  52                         *split++ = 0;
  53                         if (strncmp(split, "//", 2) == 0)
  54                                 split += 2;
  55                         name = skip_spaces(split);
  56                 } else
  57                         /* a ns name without a following profile is allowed */
  58                         name = NULL;
  59         }
  60         if (name && *name == 0)
  61                 name = NULL;
  62
  63         return name;
  64 }
  65
  66 /**
  67  * skipn_spaces - Removes leading whitespace from @str.
  68  * @str: The string to be stripped.
  69  *
  70  * Returns a pointer to the first non-whitespace character in @str.
  71  * if all whitespace will return NULL
  72  */
  73
  74 const char *skipn_spaces(const char *str, size_t n)
  75 {
  76         for (; n && isspace(*str); --n)
  77                 ++str;
  78         if (n)
  79                 return (char *)str;
  80         return NULL;
  81 }
  82
  83 const char *aa_splitn_fqname(const char *fqname, size_t n, const char **ns_name,
  84                              size_t *ns_len)
  85 {
  86         const char *end = fqname + n;
  87         const char *name = skipn_spaces(fqname, n);
  88
  89         *ns_name = NULL;
  90         *ns_len = 0;
  91
  92         if (!name)
  93                 return NULL;
  94
  95         if (name[0] == ':') {
  96                 char *split = strnchr(&name[1], end - &name[1], ':');
  97                 *ns_name = skipn_spaces(&name[1], end - &name[1]);
  98                 if (!*ns_name)
  99                         return NULL;
 100                 if (split) {
 101                         *ns_len = split - *ns_name;
 102                         if (*ns_len == 0)
 103                                 *ns_name = NULL;
 104                         split++;
 105                         if (end - split > 1 && strncmp(split, "//", 2) == 0)
 106                                 split += 2;
 107                         name = skipn_spaces(split, end - split);
 108                 } else {
 109                         /* a ns name without a following profile is allowed */
 110                         name = NULL;
 111                         *ns_len = end - *ns_name;
 112                 }
 113         }
 114         if (name && *name == 0)
 115                 name = NULL;
 116
 117         return name;
 118 }
 119
 120 /**
 121  * aa_info_message - log a none profile related status message
 122  * @str: message to log
 123  */
 124 void aa_info_message(const char *str)
 125 {
 126         if (audit_enabled) {
 127                 DEFINE_AUDIT_DATA(sa, LSM_AUDIT_DATA_NONE, NULL);
 128
 129                 aad(&sa)->info = str;
 130                 aa_audit_msg(AUDIT_APPARMOR_STATUS, &sa, NULL);
 131         }
 132         printk(KERN_INFO "AppArmor: %s\n", str);
 133 }
 134
 135 __counted char *aa_str_alloc(int size, gfp_t gfp)
 136 {
 137         struct counted_str *str;
 138
 139         str = kmalloc(sizeof(struct counted_str) + size, gfp);
 140         if (!str)
 141                 return NULL;
 142
 143         kref_init(&str->count);
 144         return str->name;
 145 }
 146
 147 void aa_str_kref(struct kref *kref)
 148 {
 149         kfree(container_of(kref, struct counted_str, count));
 150 }
 151
 152
 153 const char aa_file_perm_chrs[] = "xwracd         km l     ";
 154 const char *aa_file_perm_names[] = {
 155         "exec",
 156         "write",
 157         "read",
 158         "append",
 159
 160         "create",
 161         "delete",
 162         "open",
 163         "rename",
 164
 165         "setattr",
 166         "getattr",
 167         "setcred",
 168         "getcred",
 169
 170         "chmod",
 171         "chown",
 172         "chgrp",
 173         "lock",
 174
 175         "mmap",
 176         "mprot",
 177         "link",
 178         "snapshot",
 179
 180         "unknown",
 181         "unknown",
 182         "unknown",
 183         "unknown",
 184
 185         "unknown",
 186         "unknown",
 187         "unknown",
 188         "unknown",
 189
 190         "stack",
 191         "change_onexec",
 192         "change_profile",
 193         "change_hat",
 194 };
 195
 196 /**
 197  * aa_perm_mask_to_str - convert a perm mask to its short string
 198  * @str: character buffer to store string in (at least 10 characters)
 199  * @str_size: size of the @str buffer
 200  * @chrs: NUL-terminated character buffer of permission characters
 201  * @mask: permission mask to convert
 202  */
 203 void aa_perm_mask_to_str(char *str, size_t str_size, const char *chrs, u32 mask)
 204 {
 205         unsigned int i, perm = 1;
 206         size_t num_chrs = strlen(chrs);
 207
 208         for (i = 0; i < num_chrs; perm <<= 1, i++) {
 209                 if (mask & perm) {
 210                         /* Ensure that one byte is left for NUL-termination */
 211                         if (WARN_ON_ONCE(str_size <= 1))
 212                                 break;
 213
 214                         *str++ = chrs[i];
 215                         str_size--;
 216                 }
 217         }
 218         *str = '\0';
 219 }
 220
 221 void aa_audit_perm_names(struct audit_buffer *ab, const char * const *names,
 222                          u32 mask)
 223 {
 224         const char *fmt = "%s";
 225         unsigned int i, perm = 1;
 226         bool prev = false;
 227
 228         for (i = 0; i < 32; perm <<= 1, i++) {
 229                 if (mask & perm) {
 230                         audit_log_format(ab, fmt, names[i]);
 231                         if (!prev) {
 232                                 prev = true;
 233                                 fmt = " %s";
 234                         }
 235                 }
 236         }
 237 }
 238
 239 void aa_audit_perm_mask(struct audit_buffer *ab, u32 mask, const char *chrs,
 240                         u32 chrsmask, const char * const *names, u32 namesmask)
 241 {
 242         char str[33];
 243
 244         audit_log_format(ab, "\"");
 245         if ((mask & chrsmask) && chrs) {
 246                 aa_perm_mask_to_str(str, sizeof(str), chrs, mask & chrsmask);
 247                 mask &= ~chrsmask;
 248                 audit_log_format(ab, "%s", str);
 249                 if (mask & namesmask)
 250                         audit_log_format(ab, " ");
 251         }
 252         if ((mask & namesmask) && names)
 253                 aa_audit_perm_names(ab, names, mask & namesmask);
 254         audit_log_format(ab, "\"");
 255 }
 256
 257 /**
 258  * aa_audit_perms_cb - generic callback fn for auditing perms
 259  * @ab: audit buffer (NOT NULL)
 260  * @va: audit struct to audit values of (NOT NULL)
 261  */
 262 static void aa_audit_perms_cb(struct audit_buffer *ab, void *va)
 263 {
 264         struct common_audit_data *sa = va;
 265
 266         if (aad(sa)->request) {
 267                 audit_log_format(ab, " requested_mask=");
 268                 aa_audit_perm_mask(ab, aad(sa)->request, aa_file_perm_chrs,
 269                                    PERMS_CHRS_MASK, aa_file_perm_names,
 270                                    PERMS_NAMES_MASK);
 271         }
 272         if (aad(sa)->denied) {
 273                 audit_log_format(ab, "denied_mask=");
 274                 aa_audit_perm_mask(ab, aad(sa)->denied, aa_file_perm_chrs,
 275                                    PERMS_CHRS_MASK, aa_file_perm_names,
 276                                    PERMS_NAMES_MASK);
 277         }
 278         audit_log_format(ab, " peer=");
 279         aa_label_xaudit(ab, labels_ns(aad(sa)->label), aad(sa)->peer,
 280                                       FLAGS_NONE, GFP_ATOMIC);
 281 }
 282
 283 /**
 284  * aa_apply_modes_to_perms - apply namespace and profile flags to perms
 285  * @profile: that perms where computed from
 286  * @perms: perms to apply mode modifiers to
 287  *
 288  * TODO: split into profile and ns based flags for when accumulating perms
 289  */
 290 void aa_apply_modes_to_perms(struct aa_profile *profile, struct aa_perms *perms)
 291 {
 292         switch (AUDIT_MODE(profile)) {
 293         case AUDIT_ALL:
 294                 perms->audit = ALL_PERMS_MASK;
 295                 /* fall through */
 296         case AUDIT_NOQUIET:
 297                 perms->quiet = 0;
 298                 break;
 299         case AUDIT_QUIET:
 300                 perms->audit = 0;
 301                 /* fall through */
 302         case AUDIT_QUIET_DENIED:
 303                 perms->quiet = ALL_PERMS_MASK;
 304                 break;
 305         }
 306
 307         if (KILL_MODE(profile))
 308                 perms->kill = ALL_PERMS_MASK;
 309         else if (COMPLAIN_MODE(profile))
 310                 perms->complain = ALL_PERMS_MASK;
 311 /*
 312  *  TODO:
 313  *      else if (PROMPT_MODE(profile))
 314  *              perms->prompt = ALL_PERMS_MASK;
 315  */
 316 }
 317
 318 static u32 map_other(u32 x)
 319 {
 320         return ((x & 0x3) << 8) |       /* SETATTR/GETATTR */
 321                 ((x & 0x1c) << 18) |    /* ACCEPT/BIND/LISTEN */
 322                 ((x & 0x60) << 19);     /* SETOPT/GETOPT */
 323 }
 324
 325 void aa_compute_perms(struct aa_dfa *dfa, unsigned int state,
 326                       struct aa_perms *perms)
 327 {
 328         *perms = (struct aa_perms) {
 329                 .allow = dfa_user_allow(dfa, state),
 330                 .audit = dfa_user_audit(dfa, state),
 331                 .quiet = dfa_user_quiet(dfa, state),
 332         };
 333
 334         /* for v5 perm mapping in the policydb, the other set is used
 335          * to extend the general perm set
 336          */
 337         perms->allow |= map_other(dfa_other_allow(dfa, state));
 338         perms->audit |= map_other(dfa_other_audit(dfa, state));
 339         perms->quiet |= map_other(dfa_other_quiet(dfa, state));
 340 //      perms->xindex = dfa_user_xindex(dfa, state);
 341 }
 342
 343 /**
 344  * aa_perms_accum_raw - accumulate perms with out masking off overlapping perms
 345  * @accum - perms struct to accumulate into
 346  * @addend - perms struct to add to @accum
 347  */
 348 void aa_perms_accum_raw(struct aa_perms *accum, struct aa_perms *addend)
 349 {
 350         accum->deny |= addend->deny;
 351         accum->allow &= addend->allow & ~addend->deny;
 352         accum->audit |= addend->audit & addend->allow;
 353         accum->quiet &= addend->quiet & ~addend->allow;
 354         accum->kill |= addend->kill & ~addend->allow;
 355         accum->stop |= addend->stop & ~addend->allow;
 356         accum->complain |= addend->complain & ~addend->allow & ~addend->deny;
 357         accum->cond |= addend->cond & ~addend->allow & ~addend->deny;
 358         accum->hide &= addend->hide & ~addend->allow;
 359         accum->prompt |= addend->prompt & ~addend->allow & ~addend->deny;
 360 }
 361
 362 /**
 363  * aa_perms_accum - accumulate perms, masking off overlapping perms
 364  * @accum - perms struct to accumulate into
 365  * @addend - perms struct to add to @accum
 366  */
 367 void aa_perms_accum(struct aa_perms *accum, struct aa_perms *addend)
 368 {
 369         accum->deny |= addend->deny;
 370         accum->allow &= addend->allow & ~accum->deny;
 371         accum->audit |= addend->audit & accum->allow;
 372         accum->quiet &= addend->quiet & ~accum->allow;
 373         accum->kill |= addend->kill & ~accum->allow;
 374         accum->stop |= addend->stop & ~accum->allow;
 375         accum->complain |= addend->complain & ~accum->allow & ~accum->deny;
 376         accum->cond |= addend->cond & ~accum->allow & ~accum->deny;
 377         accum->hide &= addend->hide & ~accum->allow;
 378         accum->prompt |= addend->prompt & ~accum->allow & ~accum->deny;
 379 }
 380
 381 void aa_profile_match_label(struct aa_profile *profile, struct aa_label *label,
 382                             int type, u32 request, struct aa_perms *perms)
 383 {
 384         /* TODO: doesn't yet handle extended types */
 385         unsigned int state;
 386
 387         state = aa_dfa_next(profile->policy.dfa,
 388                             profile->policy.start[AA_CLASS_LABEL],
 389                             type);
 390         aa_label_match(profile, label, state, false, request, perms);
 391 }
 392
 393
 394 /* currently unused */
 395 int aa_profile_label_perm(struct aa_profile *profile, struct aa_profile *target,
 396                           u32 request, int type, u32 *deny,
 397                           struct common_audit_data *sa)
 398 {
 399         struct aa_perms perms;
 400
 401         aad(sa)->label = &profile->label;
 402         aad(sa)->peer = &target->label;
 403         aad(sa)->request = request;
 404
 405         aa_profile_match_label(profile, &target->label, type, request, &perms);
 406         aa_apply_modes_to_perms(profile, &perms);
 407         *deny |= request & perms.deny;
 408         return aa_check_perms(profile, &perms, request, sa, aa_audit_perms_cb);
 409 }
 410
 411 /**
 412  * aa_check_perms - do audit mode selection based on perms set
 413  * @profile: profile being checked
 414  * @perms: perms computed for the request
 415  * @request: requested perms
 416  * @deny: Returns: explicit deny set
 417  * @sa: initialized audit structure (MAY BE NULL if not auditing)
 418  * @cb: callback fn for type specific fields (MAY BE NULL)
 419  *
 420  * Returns: 0 if permission else error code
 421  *
 422  * Note: profile audit modes need to be set before calling by setting the
 423  *       perm masks appropriately.
 424  *
 425  *       If not auditing then complain mode is not enabled and the
 426  *       error code will indicate whether there was an explicit deny
 427  *       with a positive value.
 428  */
 429 int aa_check_perms(struct aa_profile *profile, struct aa_perms *perms,
 430                    u32 request, struct common_audit_data *sa,
 431                    void (*cb)(struct audit_buffer *, void *))
 432 {
 433         int type, error;
 434         u32 denied = request & (~perms->allow | perms->deny);
 435
 436         if (likely(!denied)) {
 437                 /* mask off perms that are not being force audited */
 438                 request &= perms->audit;
 439                 if (!request || !sa)
 440                         return 0;
 441
 442                 type = AUDIT_APPARMOR_AUDIT;
 443                 error = 0;
 444         } else {
 445                 error = -EACCES;
 446
 447                 if (denied & perms->kill)
 448                         type = AUDIT_APPARMOR_KILL;
 449                 else if (denied == (denied & perms->complain))
 450                         type = AUDIT_APPARMOR_ALLOWED;
 451                 else
 452                         type = AUDIT_APPARMOR_DENIED;
 453
 454                 if (denied == (denied & perms->hide))
 455                         error = -ENOENT;
 456
 457                 denied &= ~perms->quiet;
 458                 if (!sa || !denied)
 459                         return error;
 460         }
 461
 462         if (sa) {
 463                 aad(sa)->label = &profile->label;
 464                 aad(sa)->request = request;
 465                 aad(sa)->denied = denied;
 466                 aad(sa)->error = error;
 467                 aa_audit_msg(type, sa, cb);
 468         }
 469
 470         if (type == AUDIT_APPARMOR_ALLOWED)
 471                 error = 0;
 472
 473         return error;
 474 }
 475
 476
 477 /**
 478  * aa_policy_init - initialize a policy structure
 479  * @policy: policy to initialize  (NOT NULL)
 480  * @prefix: prefix name if any is required.  (MAYBE NULL)
 481  * @name: name of the policy, init will make a copy of it  (NOT NULL)
 482  * @gfp: allocation mode
 483  *
 484  * Note: this fn creates a copy of strings passed in
 485  *
 486  * Returns: true if policy init successful
 487  */
 488 bool aa_policy_init(struct aa_policy *policy, const char *prefix,
 489                     const char *name, gfp_t gfp)
 490 {
 491         char *hname;
 492
 493         /* freed by policy_free */
 494         if (prefix) {
 495                 hname = aa_str_alloc(strlen(prefix) + strlen(name) + 3, gfp);
 496                 if (hname)
 497                         sprintf(hname, "%s//%s", prefix, name);
 498         } else {
 499                 hname = aa_str_alloc(strlen(name) + 1, gfp);
 500                 if (hname)
 501                         strcpy(hname, name);
 502         }
 503         if (!hname)
 504                 return false;
 505         policy->hname = hname;
 506         /* base.name is a substring of fqname */
 507         policy->name = basename(policy->hname);
 508         INIT_LIST_HEAD(&policy->list);
 509         INIT_LIST_HEAD(&policy->profiles);
 510
 511         return true;
 512 }
 513
 514 /**
 515  * aa_policy_destroy - free the elements referenced by @policy
 516  * @policy: policy that is to have its elements freed  (NOT NULL)
 517  */
 518 void aa_policy_destroy(struct aa_policy *policy)
 519 {
 520         AA_BUG(on_list_rcu(&policy->profiles));
 521         AA_BUG(on_list_rcu(&policy->list));
 522
 523         /* don't free name as its a subset of hname */
 524         aa_put_str(policy->hname);
 525 }