1/* Credentials management - see Documentation/security/credentials.txt 2 * 3 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. 4 * Written by David Howells (dhowells@redhat.com) 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public Licence 8 * as published by the Free Software Foundation; either version 9 * 2 of the Licence, or (at your option) any later version. 10 */ 11 12#ifndef _LINUX_CRED_H 13#define _LINUX_CRED_H 14 15#include <linux/capability.h> 16#include <linux/init.h> 17#include <linux/key.h> 18#include <linux/selinux.h> 19#include <linux/atomic.h> 20#include <linux/uidgid.h> 21 22struct user_struct; 23struct cred; 24struct inode; 25 26/* 27 * COW Supplementary groups list 28 */ 29#define NGROUPS_SMALL 32 30#define NGROUPS_PER_BLOCK ((unsigned int)(PAGE_SIZE / sizeof(kgid_t))) 31 32struct group_info { 33 atomic_t usage; 34 int ngroups; 35 int nblocks; 36 kgid_t small_block[NGROUPS_SMALL]; 37 kgid_t *blocks[0]; 38}; 39 40/** 41 * get_group_info - Get a reference to a group info structure 42 * @group_info: The group info to reference 43 * 44 * This gets a reference to a set of supplementary groups. 45 * 46 * If the caller is accessing a task's credentials, they must hold the RCU read 47 * lock when reading. 48 */ 49static inline struct group_info *get_group_info(struct group_info *gi) 50{ 51 atomic_inc(&gi->usage); 52 return gi; 53} 54 55/** 56 * put_group_info - Release a reference to a group info structure 57 * @group_info: The group info to release 58 */ 59#define put_group_info(group_info) \ 60do { \ 61 if (atomic_dec_and_test(&(group_info)->usage)) \ 62 groups_free(group_info); \ 63} while (0) 64 65extern struct group_info init_groups; 66#ifdef CONFIG_MULTIUSER 67extern struct group_info *groups_alloc(int); 68extern void groups_free(struct group_info *); 69 70extern int in_group_p(kgid_t); 71extern int in_egroup_p(kgid_t); 72#else 73static inline void groups_free(struct group_info *group_info) 74{ 75} 76 77static inline int in_group_p(kgid_t grp) 78{ 79 return 1; 80} 81static inline int in_egroup_p(kgid_t grp) 82{ 83 return 1; 84} 85#endif 86extern int set_current_groups(struct group_info *); 87extern void set_groups(struct cred *, struct group_info *); 88extern int groups_search(const struct group_info *, kgid_t); 89extern bool may_setgroups(void); 90 91/* access the groups "array" with this macro */ 92#define GROUP_AT(gi, i) \ 93 ((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK]) 94 95/* 96 * The security context of a task 97 * 98 * The parts of the context break down into two categories: 99 * 100 * (1) The objective context of a task. These parts are used when some other 101 * task is attempting to affect this one. 102 * 103 * (2) The subjective context. These details are used when the task is acting 104 * upon another object, be that a file, a task, a key or whatever. 105 * 106 * Note that some members of this structure belong to both categories - the 107 * LSM security pointer for instance. 108 * 109 * A task has two security pointers. task->real_cred points to the objective 110 * context that defines that task's actual details. The objective part of this 111 * context is used whenever that task is acted upon. 112 * 113 * task->cred points to the subjective context that defines the details of how 114 * that task is going to act upon another object. This may be overridden 115 * temporarily to point to another security context, but normally points to the 116 * same context as task->real_cred. 117 */ 118struct cred { 119 atomic_t usage; 120#ifdef CONFIG_DEBUG_CREDENTIALS 121 atomic_t subscribers; /* number of processes subscribed */ 122 void *put_addr; 123 unsigned magic; 124#define CRED_MAGIC 0x43736564 125#define CRED_MAGIC_DEAD 0x44656144 126#endif 127 kuid_t uid; /* real UID of the task */ 128 kgid_t gid; /* real GID of the task */ 129 kuid_t suid; /* saved UID of the task */ 130 kgid_t sgid; /* saved GID of the task */ 131 kuid_t euid; /* effective UID of the task */ 132 kgid_t egid; /* effective GID of the task */ 133 kuid_t fsuid; /* UID for VFS ops */ 134 kgid_t fsgid; /* GID for VFS ops */ 135 unsigned securebits; /* SUID-less security management */ 136 kernel_cap_t cap_inheritable; /* caps our children can inherit */ 137 kernel_cap_t cap_permitted; /* caps we're permitted */ 138 kernel_cap_t cap_effective; /* caps we can actually use */ 139 kernel_cap_t cap_bset; /* capability bounding set */ 140#ifdef CONFIG_KEYS 141 unsigned char jit_keyring; /* default keyring to attach requested 142 * keys to */ 143 struct key __rcu *session_keyring; /* keyring inherited over fork */ 144 struct key *process_keyring; /* keyring private to this process */ 145 struct key *thread_keyring; /* keyring private to this thread */ 146 struct key *request_key_auth; /* assumed request_key authority */ 147#endif 148#ifdef CONFIG_SECURITY 149 void *security; /* subjective LSM security */ 150#endif 151 struct user_struct *user; /* real user ID subscription */ 152 struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */ 153 struct group_info *group_info; /* supplementary groups for euid/fsgid */ 154 struct rcu_head rcu; /* RCU deletion hook */ 155}; 156 157extern void __put_cred(struct cred *); 158extern void exit_creds(struct task_struct *); 159extern int copy_creds(struct task_struct *, unsigned long); 160extern const struct cred *get_task_cred(struct task_struct *); 161extern struct cred *cred_alloc_blank(void); 162extern struct cred *prepare_creds(void); 163extern struct cred *prepare_exec_creds(void); 164extern int commit_creds(struct cred *); 165extern void abort_creds(struct cred *); 166extern const struct cred *override_creds(const struct cred *); 167extern void revert_creds(const struct cred *); 168extern struct cred *prepare_kernel_cred(struct task_struct *); 169extern int change_create_files_as(struct cred *, struct inode *); 170extern int set_security_override(struct cred *, u32); 171extern int set_security_override_from_ctx(struct cred *, const char *); 172extern int set_create_files_as(struct cred *, struct inode *); 173extern void __init cred_init(void); 174 175/* 176 * check for validity of credentials 177 */ 178#ifdef CONFIG_DEBUG_CREDENTIALS 179extern void __invalid_creds(const struct cred *, const char *, unsigned); 180extern void __validate_process_creds(struct task_struct *, 181 const char *, unsigned); 182 183extern bool creds_are_invalid(const struct cred *cred); 184 185static inline void __validate_creds(const struct cred *cred, 186 const char *file, unsigned line) 187{ 188 if (unlikely(creds_are_invalid(cred))) 189 __invalid_creds(cred, file, line); 190} 191 192#define validate_creds(cred) \ 193do { \ 194 __validate_creds((cred), __FILE__, __LINE__); \ 195} while(0) 196 197#define validate_process_creds() \ 198do { \ 199 __validate_process_creds(current, __FILE__, __LINE__); \ 200} while(0) 201 202extern void validate_creds_for_do_exit(struct task_struct *); 203#else 204static inline void validate_creds(const struct cred *cred) 205{ 206} 207static inline void validate_creds_for_do_exit(struct task_struct *tsk) 208{ 209} 210static inline void validate_process_creds(void) 211{ 212} 213#endif 214 215/** 216 * get_new_cred - Get a reference on a new set of credentials 217 * @cred: The new credentials to reference 218 * 219 * Get a reference on the specified set of new credentials. The caller must 220 * release the reference. 221 */ 222static inline struct cred *get_new_cred(struct cred *cred) 223{ 224 atomic_inc(&cred->usage); 225 return cred; 226} 227 228/** 229 * get_cred - Get a reference on a set of credentials 230 * @cred: The credentials to reference 231 * 232 * Get a reference on the specified set of credentials. The caller must 233 * release the reference. 234 * 235 * This is used to deal with a committed set of credentials. Although the 236 * pointer is const, this will temporarily discard the const and increment the 237 * usage count. The purpose of this is to attempt to catch at compile time the 238 * accidental alteration of a set of credentials that should be considered 239 * immutable. 240 */ 241static inline const struct cred *get_cred(const struct cred *cred) 242{ 243 struct cred *nonconst_cred = (struct cred *) cred; 244 validate_creds(cred); 245 return get_new_cred(nonconst_cred); 246} 247 248/** 249 * put_cred - Release a reference to a set of credentials 250 * @cred: The credentials to release 251 * 252 * Release a reference to a set of credentials, deleting them when the last ref 253 * is released. 254 * 255 * This takes a const pointer to a set of credentials because the credentials 256 * on task_struct are attached by const pointers to prevent accidental 257 * alteration of otherwise immutable credential sets. 258 */ 259static inline void put_cred(const struct cred *_cred) 260{ 261 struct cred *cred = (struct cred *) _cred; 262 263 validate_creds(cred); 264 if (atomic_dec_and_test(&(cred)->usage)) 265 __put_cred(cred); 266} 267 268/** 269 * current_cred - Access the current task's subjective credentials 270 * 271 * Access the subjective credentials of the current task. RCU-safe, 272 * since nobody else can modify it. 273 */ 274#define current_cred() \ 275 rcu_dereference_protected(current->cred, 1) 276 277/** 278 * current_real_cred - Access the current task's objective credentials 279 * 280 * Access the objective credentials of the current task. RCU-safe, 281 * since nobody else can modify it. 282 */ 283#define current_real_cred() \ 284 rcu_dereference_protected(current->real_cred, 1) 285 286/** 287 * __task_cred - Access a task's objective credentials 288 * @task: The task to query 289 * 290 * Access the objective credentials of a task. The caller must hold the RCU 291 * readlock. 292 * 293 * The result of this function should not be passed directly to get_cred(); 294 * rather get_task_cred() should be used instead. 295 */ 296#define __task_cred(task) \ 297 rcu_dereference((task)->real_cred) 298 299/** 300 * get_current_cred - Get the current task's subjective credentials 301 * 302 * Get the subjective credentials of the current task, pinning them so that 303 * they can't go away. Accessing the current task's credentials directly is 304 * not permitted. 305 */ 306#define get_current_cred() \ 307 (get_cred(current_cred())) 308 309/** 310 * get_current_user - Get the current task's user_struct 311 * 312 * Get the user record of the current task, pinning it so that it can't go 313 * away. 314 */ 315#define get_current_user() \ 316({ \ 317 struct user_struct *__u; \ 318 const struct cred *__cred; \ 319 __cred = current_cred(); \ 320 __u = get_uid(__cred->user); \ 321 __u; \ 322}) 323 324/** 325 * get_current_groups - Get the current task's supplementary group list 326 * 327 * Get the supplementary group list of the current task, pinning it so that it 328 * can't go away. 329 */ 330#define get_current_groups() \ 331({ \ 332 struct group_info *__groups; \ 333 const struct cred *__cred; \ 334 __cred = current_cred(); \ 335 __groups = get_group_info(__cred->group_info); \ 336 __groups; \ 337}) 338 339#define task_cred_xxx(task, xxx) \ 340({ \ 341 __typeof__(((struct cred *)NULL)->xxx) ___val; \ 342 rcu_read_lock(); \ 343 ___val = __task_cred((task))->xxx; \ 344 rcu_read_unlock(); \ 345 ___val; \ 346}) 347 348#define task_uid(task) (task_cred_xxx((task), uid)) 349#define task_euid(task) (task_cred_xxx((task), euid)) 350 351#define current_cred_xxx(xxx) \ 352({ \ 353 current_cred()->xxx; \ 354}) 355 356#define current_uid() (current_cred_xxx(uid)) 357#define current_gid() (current_cred_xxx(gid)) 358#define current_euid() (current_cred_xxx(euid)) 359#define current_egid() (current_cred_xxx(egid)) 360#define current_suid() (current_cred_xxx(suid)) 361#define current_sgid() (current_cred_xxx(sgid)) 362#define current_fsuid() (current_cred_xxx(fsuid)) 363#define current_fsgid() (current_cred_xxx(fsgid)) 364#define current_cap() (current_cred_xxx(cap_effective)) 365#define current_user() (current_cred_xxx(user)) 366#define current_security() (current_cred_xxx(security)) 367 368extern struct user_namespace init_user_ns; 369#ifdef CONFIG_USER_NS 370#define current_user_ns() (current_cred_xxx(user_ns)) 371#else 372#define current_user_ns() (&init_user_ns) 373#endif 374 375 376#define current_uid_gid(_uid, _gid) \ 377do { \ 378 const struct cred *__cred; \ 379 __cred = current_cred(); \ 380 *(_uid) = __cred->uid; \ 381 *(_gid) = __cred->gid; \ 382} while(0) 383 384#define current_euid_egid(_euid, _egid) \ 385do { \ 386 const struct cred *__cred; \ 387 __cred = current_cred(); \ 388 *(_euid) = __cred->euid; \ 389 *(_egid) = __cred->egid; \ 390} while(0) 391 392#define current_fsuid_fsgid(_fsuid, _fsgid) \ 393do { \ 394 const struct cred *__cred; \ 395 __cred = current_cred(); \ 396 *(_fsuid) = __cred->fsuid; \ 397 *(_fsgid) = __cred->fsgid; \ 398} while(0) 399 400#endif /* _LINUX_CRED_H */ 401