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 struct group_info {
  30         atomic_t        usage;
  31         int             ngroups;
  32         kgid_t          gid[0];
  33 };
  34
  35 /**
  36  * get_group_info - Get a reference to a group info structure
  37  * @group_info: The group info to reference
  38  *
  39  * This gets a reference to a set of supplementary groups.
  40  *
  41  * If the caller is accessing a task's credentials, they must hold the RCU read
  42  * lock when reading.
  43  */
  44 static inline struct group_info *get_group_info(struct group_info *gi)
  45 {
  46         atomic_inc(&gi->usage);
  47         return gi;
  48 }
  49
  50 /**
  51  * put_group_info - Release a reference to a group info structure
  52  * @group_info: The group info to release
  53  */
  54 #define put_group_info(group_info)                      \
  55 do {                                                    \
  56         if (atomic_dec_and_test(&(group_info)->usage))  \
  57                 groups_free(group_info);                \
  58 } while (0)
  59
  60 extern struct group_info init_groups;
  61 #ifdef CONFIG_MULTIUSER
  62 extern struct group_info *groups_alloc(int);
  63 extern void groups_free(struct group_info *);
  64
  65 extern int in_group_p(kgid_t);
  66 extern int in_egroup_p(kgid_t);
  67 #else
  68 static inline void groups_free(struct group_info *group_info)
  69 {
  70 }
  71
  72 static inline int in_group_p(kgid_t grp)
  73 {
  74         return 1;
  75 }
  76 static inline int in_egroup_p(kgid_t grp)
  77 {
  78         return 1;
  79 }
  80 #endif
  81 extern int set_current_groups(struct group_info *);
  82 extern void set_groups(struct cred *, struct group_info *);
  83 extern int groups_search(const struct group_info *, kgid_t);
  84 extern bool may_setgroups(void);
  85 extern void groups_sort(struct group_info *);
  86
  87 /*
  88  * The security context of a task
  89  *
  90  * The parts of the context break down into two categories:
  91  *
  92  *  (1) The objective context of a task.  These parts are used when some other
  93  *      task is attempting to affect this one.
  94  *
  95  *  (2) The subjective context.  These details are used when the task is acting
  96  *      upon another object, be that a file, a task, a key or whatever.
  97  *
  98  * Note that some members of this structure belong to both categories - the
  99  * LSM security pointer for instance.
 100  *
 101  * A task has two security pointers.  task->real_cred points to the objective
 102  * context that defines that task's actual details.  The objective part of this
 103  * context is used whenever that task is acted upon.
 104  *
 105  * task->cred points to the subjective context that defines the details of how
 106  * that task is going to act upon another object.  This may be overridden
 107  * temporarily to point to another security context, but normally points to the
 108  * same context as task->real_cred.
 109  */
 110 struct cred {
 111         atomic_t        usage;
 112 #ifdef CONFIG_DEBUG_CREDENTIALS
 113         atomic_t        subscribers;    /* number of processes subscribed */
 114         void            *put_addr;
 115         unsigned        magic;
 116 #define CRED_MAGIC      0x43736564
 117 #define CRED_MAGIC_DEAD 0x44656144
 118 #endif
 119         kuid_t          uid;            /* real UID of the task */
 120         kgid_t          gid;            /* real GID of the task */
 121         kuid_t          suid;           /* saved UID of the task */
 122         kgid_t          sgid;           /* saved GID of the task */
 123         kuid_t          euid;           /* effective UID of the task */
 124         kgid_t          egid;           /* effective GID of the task */
 125         kuid_t          fsuid;          /* UID for VFS ops */
 126         kgid_t          fsgid;          /* GID for VFS ops */
 127         unsigned        securebits;     /* SUID-less security management */
 128         kernel_cap_t    cap_inheritable; /* caps our children can inherit */
 129         kernel_cap_t    cap_permitted;  /* caps we're permitted */
 130         kernel_cap_t    cap_effective;  /* caps we can actually use */
 131         kernel_cap_t    cap_bset;       /* capability bounding set */
 132         kernel_cap_t    cap_ambient;    /* Ambient capability set */
 133 #ifdef CONFIG_KEYS
 134         unsigned char   jit_keyring;    /* default keyring to attach requested
 135                                          * keys to */
 136         struct key __rcu *session_keyring; /* keyring inherited over fork */
 137         struct key      *process_keyring; /* keyring private to this process */
 138         struct key      *thread_keyring; /* keyring private to this thread */
 139         struct key      *request_key_auth; /* assumed request_key authority */
 140 #endif
 141 #ifdef CONFIG_SECURITY
 142         void            *security;      /* subjective LSM security */
 143 #endif
 144         struct user_struct *user;       /* real user ID subscription */
 145         struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
 146         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 147         /* RCU deletion */
 148         union {
 149                 int non_rcu;                    /* Can we skip RCU deletion? */
 150                 struct rcu_head rcu;            /* RCU deletion hook */
 151         };
 152 };
 153
 154 extern void __put_cred(struct cred *);
 155 extern void exit_creds(struct task_struct *);
 156 extern int copy_creds(struct task_struct *, unsigned long);
 157 extern const struct cred *get_task_cred(struct task_struct *);
 158 extern struct cred *cred_alloc_blank(void);
 159 extern struct cred *prepare_creds(void);
 160 extern struct cred *prepare_exec_creds(void);
 161 extern int commit_creds(struct cred *);
 162 extern void abort_creds(struct cred *);
 163 extern const struct cred *override_creds(const struct cred *);
 164 extern void revert_creds(const struct cred *);
 165 extern struct cred *prepare_kernel_cred(struct task_struct *);
 166 extern int change_create_files_as(struct cred *, struct inode *);
 167 extern int set_security_override(struct cred *, u32);
 168 extern int set_security_override_from_ctx(struct cred *, const char *);
 169 extern int set_create_files_as(struct cred *, struct inode *);
 170 extern void __init cred_init(void);
 171
 172 /*
 173  * check for validity of credentials
 174  */
 175 #ifdef CONFIG_DEBUG_CREDENTIALS
 176 extern void __invalid_creds(const struct cred *, const char *, unsigned);
 177 extern void __validate_process_creds(struct task_struct *,
 178                                      const char *, unsigned);
 179
 180 extern bool creds_are_invalid(const struct cred *cred);
 181
 182 static inline void __validate_creds(const struct cred *cred,
 183                                     const char *file, unsigned line)
 184 {
 185         if (unlikely(creds_are_invalid(cred)))
 186                 __invalid_creds(cred, file, line);
 187 }
 188
 189 #define validate_creds(cred)                            \
 190 do {                                                    \
 191         __validate_creds((cred), __FILE__, __LINE__);   \
 192 } while(0)
 193
 194 #define validate_process_creds()                                \
 195 do {                                                            \
 196         __validate_process_creds(current, __FILE__, __LINE__);  \
 197 } while(0)
 198
 199 extern void validate_creds_for_do_exit(struct task_struct *);
 200 #else
 201 static inline void validate_creds(const struct cred *cred)
 202 {
 203 }
 204 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
 205 {
 206 }
 207 static inline void validate_process_creds(void)
 208 {
 209 }
 210 #endif
 211
 212 static inline bool cap_ambient_invariant_ok(const struct cred *cred)
 213 {
 214         return cap_issubset(cred->cap_ambient,
 215                             cap_intersect(cred->cap_permitted,
 216                                           cred->cap_inheritable));
 217 }
 218
 219 /**
 220  * get_new_cred - Get a reference on a new set of credentials
 221  * @cred: The new credentials to reference
 222  *
 223  * Get a reference on the specified set of new credentials.  The caller must
 224  * release the reference.
 225  */
 226 static inline struct cred *get_new_cred(struct cred *cred)
 227 {
 228         atomic_inc(&cred->usage);
 229         return cred;
 230 }
 231
 232 /**
 233  * get_cred - Get a reference on a set of credentials
 234  * @cred: The credentials to reference
 235  *
 236  * Get a reference on the specified set of credentials.  The caller must
 237  * release the reference.  If %NULL is passed, it is returned with no action.
 238  *
 239  * This is used to deal with a committed set of credentials.  Although the
 240  * pointer is const, this will temporarily discard the const and increment the
 241  * usage count.  The purpose of this is to attempt to catch at compile time the
 242  * accidental alteration of a set of credentials that should be considered
 243  * immutable.
 244  */
 245 static inline const struct cred *get_cred(const struct cred *cred)
 246 {
 247         struct cred *nonconst_cred = (struct cred *) cred;
 248         if (!cred)
 249                 return cred;
 250         validate_creds(cred);
 251         nonconst_cred->non_rcu = 0;
 252         return get_new_cred(nonconst_cred);
 253 }
 254
 255 /**
 256  * put_cred - Release a reference to a set of credentials
 257  * @cred: The credentials to release
 258  *
 259  * Release a reference to a set of credentials, deleting them when the last ref
 260  * is released.  If %NULL is passed, nothing is done.
 261  *
 262  * This takes a const pointer to a set of credentials because the credentials
 263  * on task_struct are attached by const pointers to prevent accidental
 264  * alteration of otherwise immutable credential sets.
 265  */
 266 static inline void put_cred(const struct cred *_cred)
 267 {
 268         struct cred *cred = (struct cred *) _cred;
 269
 270         if (cred) {
 271                 validate_creds(cred);
 272                 if (atomic_dec_and_test(&(cred)->usage))
 273                         __put_cred(cred);
 274         }
 275 }
 276
 277 /**
 278  * current_cred - Access the current task's subjective credentials
 279  *
 280  * Access the subjective credentials of the current task.  RCU-safe,
 281  * since nobody else can modify it.
 282  */
 283 #define current_cred() \
 284         rcu_dereference_protected(current->cred, 1)
 285
 286 /**
 287  * current_real_cred - Access the current task's objective credentials
 288  *
 289  * Access the objective credentials of the current task.  RCU-safe,
 290  * since nobody else can modify it.
 291  */
 292 #define current_real_cred() \
 293         rcu_dereference_protected(current->real_cred, 1)
 294
 295 /**
 296  * __task_cred - Access a task's objective credentials
 297  * @task: The task to query
 298  *
 299  * Access the objective credentials of a task.  The caller must hold the RCU
 300  * readlock.
 301  *
 302  * The result of this function should not be passed directly to get_cred();
 303  * rather get_task_cred() should be used instead.
 304  */
 305 #define __task_cred(task)       \
 306         rcu_dereference((task)->real_cred)
 307
 308 /**
 309  * get_current_cred - Get the current task's subjective credentials
 310  *
 311  * Get the subjective credentials of the current task, pinning them so that
 312  * they can't go away.  Accessing the current task's credentials directly is
 313  * not permitted.
 314  */
 315 #define get_current_cred()                              \
 316         (get_cred(current_cred()))
 317
 318 /**
 319  * get_current_user - Get the current task's user_struct
 320  *
 321  * Get the user record of the current task, pinning it so that it can't go
 322  * away.
 323  */
 324 #define get_current_user()                              \
 325 ({                                                      \
 326         struct user_struct *__u;                        \
 327         const struct cred *__cred;                      \
 328         __cred = current_cred();                        \
 329         __u = get_uid(__cred->user);                    \
 330         __u;                                            \
 331 })
 332
 333 /**
 334  * get_current_groups - Get the current task's supplementary group list
 335  *
 336  * Get the supplementary group list of the current task, pinning it so that it
 337  * can't go away.
 338  */
 339 #define get_current_groups()                            \
 340 ({                                                      \
 341         struct group_info *__groups;                    \
 342         const struct cred *__cred;                      \
 343         __cred = current_cred();                        \
 344         __groups = get_group_info(__cred->group_info);  \
 345         __groups;                                       \
 346 })
 347
 348 #define task_cred_xxx(task, xxx)                        \
 349 ({                                                      \
 350         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 351         rcu_read_lock();                                \
 352         ___val = __task_cred((task))->xxx;              \
 353         rcu_read_unlock();                              \
 354         ___val;                                         \
 355 })
 356
 357 #define task_uid(task)          (task_cred_xxx((task), uid))
 358 #define task_euid(task)         (task_cred_xxx((task), euid))
 359
 360 #define current_cred_xxx(xxx)                   \
 361 ({                                              \
 362         current_cred()->xxx;                    \
 363 })
 364
 365 #define current_uid()           (current_cred_xxx(uid))
 366 #define current_gid()           (current_cred_xxx(gid))
 367 #define current_euid()          (current_cred_xxx(euid))
 368 #define current_egid()          (current_cred_xxx(egid))
 369 #define current_suid()          (current_cred_xxx(suid))
 370 #define current_sgid()          (current_cred_xxx(sgid))
 371 #define current_fsuid()         (current_cred_xxx(fsuid))
 372 #define current_fsgid()         (current_cred_xxx(fsgid))
 373 #define current_cap()           (current_cred_xxx(cap_effective))
 374 #define current_user()          (current_cred_xxx(user))
 375 #define current_security()      (current_cred_xxx(security))
 376
 377 extern struct user_namespace init_user_ns;
 378 #ifdef CONFIG_USER_NS
 379 #define current_user_ns()       (current_cred_xxx(user_ns))
 380 #else
 381 static inline struct user_namespace *current_user_ns(void)
 382 {
 383         return &init_user_ns;
 384 }
 385 #endif
 386
 387
 388 #define current_uid_gid(_uid, _gid)             \
 389 do {                                            \
 390         const struct cred *__cred;              \
 391         __cred = current_cred();                \
 392         *(_uid) = __cred->uid;                  \
 393         *(_gid) = __cred->gid;                  \
 394 } while(0)
 395
 396 #define current_euid_egid(_euid, _egid)         \
 397 do {                                            \
 398         const struct cred *__cred;              \
 399         __cred = current_cred();                \
 400         *(_euid) = __cred->euid;                \
 401         *(_egid) = __cred->egid;                \
 402 } while(0)
 403
 404 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 405 do {                                            \
 406         const struct cred *__cred;              \
 407         __cred = current_cred();                \
 408         *(_fsuid) = __cred->fsuid;              \
 409         *(_fsgid) = __cred->fsgid;              \
 410 } while(0)
 411
 412 #endif /* _LINUX_CRED_H */