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 #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
 157 extern void __put_cred(struct cred *);
 158 extern void exit_creds(struct task_struct *);
 159 extern int copy_creds(struct task_struct *, unsigned long);
 160 extern const struct cred *get_task_cred(struct task_struct *);
 161 extern struct cred *cred_alloc_blank(void);
 162 extern struct cred *prepare_creds(void);
 163 extern struct cred *prepare_exec_creds(void);
 164 extern int commit_creds(struct cred *);
 165 extern void abort_creds(struct cred *);
 166 extern const struct cred *override_creds(const struct cred *);
 167 extern void revert_creds(const struct cred *);
 168 extern struct cred *prepare_kernel_cred(struct task_struct *);
 169 extern int change_create_files_as(struct cred *, struct inode *);
 170 extern int set_security_override(struct cred *, u32);
 171 extern int set_security_override_from_ctx(struct cred *, const char *);
 172 extern int set_create_files_as(struct cred *, struct inode *);
 173 extern void __init cred_init(void);
 174
 175 /*
 176  * check for validity of credentials
 177  */
 178 #ifdef CONFIG_DEBUG_CREDENTIALS
 179 extern void __invalid_creds(const struct cred *, const char *, unsigned);
 180 extern void __validate_process_creds(struct task_struct *,
 181                                      const char *, unsigned);
 182
 183 extern bool creds_are_invalid(const struct cred *cred);
 184
 185 static 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)                            \
 193 do {                                                    \
 194         __validate_creds((cred), __FILE__, __LINE__);   \
 195 } while(0)
 196
 197 #define validate_process_creds()                                \
 198 do {                                                            \
 199         __validate_process_creds(current, __FILE__, __LINE__);  \
 200 } while(0)
 201
 202 extern void validate_creds_for_do_exit(struct task_struct *);
 203 #else
 204 static inline void validate_creds(const struct cred *cred)
 205 {
 206 }
 207 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
 208 {
 209 }
 210 static 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  */
 222 static 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  */
 241 static 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  */
 259 static 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
 368 extern 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)             \
 377 do {                                            \
 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)         \
 385 do {                                            \
 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)     \
 393 do {                                            \
 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 */