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