include/linux/cred.h

   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
  22 struct user_struct;
  23 struct cred;
  24 struct 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
  32 struct 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  */
  49 static 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)                      \
  60 do {                                                    \
  61         if (atomic_dec_and_test(&(group_info)->usage))  \
  62                 groups_free(group_info);                \
  63 } while (0)
  64
  65 extern struct group_info init_groups;
  66 #ifdef CONFIG_MULTIUSER
  67 extern struct group_info *groups_alloc(int);
  68 extern void groups_free(struct group_info *);
  69
  70 extern int in_group_p(kgid_t);
  71 extern int in_egroup_p(kgid_t);
  72 #else
  73 static inline void groups_free(struct group_info *group_info)
  74 {
  75 }
  76
  77 static inline int in_group_p(kgid_t grp)
  78 {
  79         return 1;
  80 }
  81 static inline int in_egroup_p(kgid_t grp)
  82 {
  83         return 1;
  84 }
  85 #endif
  86 extern int set_current_groups(struct group_info *);
  87 extern void set_groups(struct cred *, struct group_info *);
  88 extern int groups_search(const struct group_info *, kgid_t);
  89 extern 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  */
 118 struct 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         kernel_cap_t    cap_ambient;    /* Ambient capability set */
 141 #ifdef CONFIG_KEYS
 142         unsigned char   jit_keyring;    /* default keyring to attach requested
 143                                          * keys to */
 144         struct key __rcu *session_keyring; /* keyring inherited over fork */
 145         struct key      *process_keyring; /* keyring private to this process */
 146         struct key      *thread_keyring; /* keyring private to this thread */
 147         struct key      *request_key_auth; /* assumed request_key authority */
 148 #endif
 149 #ifdef CONFIG_SECURITY
 150         void            *security;      /* subjective LSM security */
 151 #endif
 152         struct user_struct *user;       /* real user ID subscription */
 153         struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
 154         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 155         struct rcu_head rcu;            /* RCU deletion hook */
 156 };
 157
 158 extern void __put_cred(struct cred *);
 159 extern void exit_creds(struct task_struct *);
 160 extern int copy_creds(struct task_struct *, unsigned long);
 161 extern const struct cred *get_task_cred(struct task_struct *);
 162 extern struct cred *cred_alloc_blank(void);
 163 extern struct cred *prepare_creds(void);
 164 extern struct cred *prepare_exec_creds(void);
 165 extern int commit_creds(struct cred *);
 166 extern void abort_creds(struct cred *);
 167 extern const struct cred *override_creds(const struct cred *);
 168 extern void revert_creds(const struct cred *);
 169 extern struct cred *prepare_kernel_cred(struct task_struct *);
 170 extern int change_create_files_as(struct cred *, struct inode *);
 171 extern int set_security_override(struct cred *, u32);
 172 extern int set_security_override_from_ctx(struct cred *, const char *);
 173 extern int set_create_files_as(struct cred *, struct inode *);
 174 extern void __init cred_init(void);
 175
 176 /*
 177  * check for validity of credentials
 178  */
 179 #ifdef CONFIG_DEBUG_CREDENTIALS
 180 extern void __invalid_creds(const struct cred *, const char *, unsigned);
 181 extern void __validate_process_creds(struct task_struct *,
 182                                      const char *, unsigned);
 183
 184 extern bool creds_are_invalid(const struct cred *cred);
 185
 186 static inline void __validate_creds(const struct cred *cred,
 187                                     const char *file, unsigned line)
 188 {
 189         if (unlikely(creds_are_invalid(cred)))
 190                 __invalid_creds(cred, file, line);
 191 }
 192
 193 #define validate_creds(cred)                            \
 194 do {                                                    \
 195         __validate_creds((cred), __FILE__, __LINE__);   \
 196 } while(0)
 197
 198 #define validate_process_creds()                                \
 199 do {                                                            \
 200         __validate_process_creds(current, __FILE__, __LINE__);  \
 201 } while(0)
 202
 203 extern void validate_creds_for_do_exit(struct task_struct *);
 204 #else
 205 static inline void validate_creds(const struct cred *cred)
 206 {
 207 }
 208 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
 209 {
 210 }
 211 static inline void validate_process_creds(void)
 212 {
 213 }
 214 #endif
 215
 216 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
 217 {
 218         return cap_issubset(cred->cap_ambient,
 219                             cap_intersect(cred->cap_permitted,
 220                                           cred->cap_inheritable));
 221 }
 222
 223 /**
 224  * get_new_cred - Get a reference on a new set of credentials
 225  * @cred: The new credentials to reference
 226  *
 227  * Get a reference on the specified set of new credentials.  The caller must
 228  * release the reference.
 229  */
 230 static inline struct cred *get_new_cred(struct cred *cred)
 231 {
 232         atomic_inc(&cred->usage);
 233         return cred;
 234 }
 235
 236 /**
 237  * get_cred - Get a reference on a set of credentials
 238  * @cred: The credentials to reference
 239  *
 240  * Get a reference on the specified set of credentials.  The caller must
 241  * release the reference.
 242  *
 243  * This is used to deal with a committed set of credentials.  Although the
 244  * pointer is const, this will temporarily discard the const and increment the
 245  * usage count.  The purpose of this is to attempt to catch at compile time the
 246  * accidental alteration of a set of credentials that should be considered
 247  * immutable.
 248  */
 249 static inline const struct cred *get_cred(const struct cred *cred)
 250 {
 251         struct cred *nonconst_cred = (struct cred *) cred;
 252         validate_creds(cred);
 253         return get_new_cred(nonconst_cred);
 254 }
 255
 256 /**
 257  * put_cred - Release a reference to a set of credentials
 258  * @cred: The credentials to release
 259  *
 260  * Release a reference to a set of credentials, deleting them when the last ref
 261  * is released.
 262  *
 263  * This takes a const pointer to a set of credentials because the credentials
 264  * on task_struct are attached by const pointers to prevent accidental
 265  * alteration of otherwise immutable credential sets.
 266  */
 267 static inline void put_cred(const struct cred *_cred)
 268 {
 269         struct cred *cred = (struct cred *) _cred;
 270
 271         validate_creds(cred);
 272         if (atomic_dec_and_test(&(cred)->usage))
 273                 __put_cred(cred);
 274 }
 275
 276 /**
 277  * current_cred - Access the current task's subjective credentials
 278  *
 279  * Access the subjective credentials of the current task.  RCU-safe,
 280  * since nobody else can modify it.
 281  */
 282 #define current_cred() \
 283         rcu_dereference_protected(current->cred, 1)
 284
 285 /**
 286  * current_real_cred - Access the current task's objective credentials
 287  *
 288  * Access the objective credentials of the current task.  RCU-safe,
 289  * since nobody else can modify it.
 290  */
 291 #define current_real_cred() \
 292         rcu_dereference_protected(current->real_cred, 1)
 293
 294 /**
 295  * __task_cred - Access a task's objective credentials
 296  * @task: The task to query
 297  *
 298  * Access the objective credentials of a task.  The caller must hold the RCU
 299  * readlock.
 300  *
 301  * The result of this function should not be passed directly to get_cred();
 302  * rather get_task_cred() should be used instead.
 303  */
 304 #define __task_cred(task)       \
 305         rcu_dereference((task)->real_cred)
 306
 307 /**
 308  * get_current_cred - Get the current task's subjective credentials
 309  *
 310  * Get the subjective credentials of the current task, pinning them so that
 311  * they can't go away.  Accessing the current task's credentials directly is
 312  * not permitted.
 313  */
 314 #define get_current_cred()                              \
 315         (get_cred(current_cred()))
 316
 317 /**
 318  * get_current_user - Get the current task's user_struct
 319  *
 320  * Get the user record of the current task, pinning it so that it can't go
 321  * away.
 322  */
 323 #define get_current_user()                              \
 324 ({                                                      \
 325         struct user_struct *__u;                        \
 326         const struct cred *__cred;                      \
 327         __cred = current_cred();                        \
 328         __u = get_uid(__cred->user);                    \
 329         __u;                                            \
 330 })
 331
 332 /**
 333  * get_current_groups - Get the current task's supplementary group list
 334  *
 335  * Get the supplementary group list of the current task, pinning it so that it
 336  * can't go away.
 337  */
 338 #define get_current_groups()                            \
 339 ({                                                      \
 340         struct group_info *__groups;                    \
 341         const struct cred *__cred;                      \
 342         __cred = current_cred();                        \
 343         __groups = get_group_info(__cred->group_info);  \
 344         __groups;                                       \
 345 })
 346
 347 #define task_cred_xxx(task, xxx)                        \
 348 ({                                                      \
 349         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 350         rcu_read_lock();                                \
 351         ___val = __task_cred((task))->xxx;              \
 352         rcu_read_unlock();                              \
 353         ___val;                                         \
 354 })
 355
 356 #define task_uid(task)          (task_cred_xxx((task), uid))
 357 #define task_euid(task)         (task_cred_xxx((task), euid))
 358
 359 #define current_cred_xxx(xxx)                   \
 360 ({                                              \
 361         current_cred()->xxx;                    \
 362 })
 363
 364 #define current_uid()           (current_cred_xxx(uid))
 365 #define current_gid()           (current_cred_xxx(gid))
 366 #define current_euid()          (current_cred_xxx(euid))
 367 #define current_egid()          (current_cred_xxx(egid))
 368 #define current_suid()          (current_cred_xxx(suid))
 369 #define current_sgid()          (current_cred_xxx(sgid))
 370 #define current_fsuid()         (current_cred_xxx(fsuid))
 371 #define current_fsgid()         (current_cred_xxx(fsgid))
 372 #define current_cap()           (current_cred_xxx(cap_effective))
 373 #define current_user()          (current_cred_xxx(user))
 374 #define current_security()      (current_cred_xxx(security))
 375
 376 extern struct user_namespace init_user_ns;
 377 #ifdef CONFIG_USER_NS
 378 #define current_user_ns()       (current_cred_xxx(user_ns))
 379 #else
 380 #define current_user_ns()       (&init_user_ns)
 381 #endif
 382
 383
 384 #define current_uid_gid(_uid, _gid)             \
 385 do {                                            \
 386         const struct cred *__cred;              \
 387         __cred = current_cred();                \
 388         *(_uid) = __cred->uid;                  \
 389         *(_gid) = __cred->gid;                  \
 390 } while(0)
 391
 392 #define current_euid_egid(_euid, _egid)         \
 393 do {                                            \
 394         const struct cred *__cred;              \
 395         __cred = current_cred();                \
 396         *(_euid) = __cred->euid;                \
 397         *(_egid) = __cred->egid;                \
 398 } while(0)
 399
 400 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 401 do {                                            \
 402         const struct cred *__cred;              \
 403         __cred = current_cred();                \
 404         *(_fsuid) = __cred->fsuid;              \
 405         *(_fsgid) = __cred->fsgid;              \
 406 } while(0)
 407
 408 #endif /* _LINUX_CRED_H */