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 int 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         struct thread_group_cred *tgcred; /* thread-group shared credentials */
 132 #endif
 133 #ifdef CONFIG_SECURITY
 134         void            *security;      /* subjective LSM security */
 135 #endif
 136         struct user_struct *user;       /* real user ID subscription */
 137         struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
 138         struct group_info *group_info;  /* supplementary groups for euid/fsgid */
 139         struct rcu_head rcu;            /* RCU deletion hook */
 140 };
 141
 142 extern void __put_cred(struct cred *);
 143 extern void exit_creds(struct task_struct *);
 144 extern int copy_creds(struct task_struct *, unsigned long);
 145 extern const struct cred *get_task_cred(struct task_struct *);
 146 extern struct cred *cred_alloc_blank(void);
 147 extern struct cred *prepare_creds(void);
 148 extern struct cred *prepare_exec_creds(void);
 149 extern int commit_creds(struct cred *);
 150 extern void abort_creds(struct cred *);
 151 extern const struct cred *override_creds(const struct cred *);
 152 extern void revert_creds(const struct cred *);
 153 extern struct cred *prepare_kernel_cred(struct task_struct *);
 154 extern int change_create_files_as(struct cred *, struct inode *);
 155 extern int set_security_override(struct cred *, u32);
 156 extern int set_security_override_from_ctx(struct cred *, const char *);
 157 extern int set_create_files_as(struct cred *, struct inode *);
 158 extern void __init cred_init(void);
 159
 160 /*
 161  * check for validity of credentials
 162  */
 163 #ifdef CONFIG_DEBUG_CREDENTIALS
 164 extern void __invalid_creds(const struct cred *, const char *, unsigned);
 165 extern void __validate_process_creds(struct task_struct *,
 166                                      const char *, unsigned);
 167
 168 extern bool creds_are_invalid(const struct cred *cred);
 169
 170 static inline void __validate_creds(const struct cred *cred,
 171                                     const char *file, unsigned line)
 172 {
 173         if (unlikely(creds_are_invalid(cred)))
 174                 __invalid_creds(cred, file, line);
 175 }
 176
 177 #define validate_creds(cred)                            \
 178 do {                                                    \
 179         __validate_creds((cred), __FILE__, __LINE__);   \
 180 } while(0)
 181
 182 #define validate_process_creds()                                \
 183 do {                                                            \
 184         __validate_process_creds(current, __FILE__, __LINE__);  \
 185 } while(0)
 186
 187 extern void validate_creds_for_do_exit(struct task_struct *);
 188 #else
 189 static inline void validate_creds(const struct cred *cred)
 190 {
 191 }
 192 static inline void validate_creds_for_do_exit(struct task_struct *tsk)
 193 {
 194 }
 195 static inline void validate_process_creds(void)
 196 {
 197 }
 198 #endif
 199
 200 /**
 201  * get_new_cred - Get a reference on a new set of credentials
 202  * @cred: The new credentials to reference
 203  *
 204  * Get a reference on the specified set of new credentials.  The caller must
 205  * release the reference.
 206  */
 207 static inline struct cred *get_new_cred(struct cred *cred)
 208 {
 209         atomic_inc(&cred->usage);
 210         return cred;
 211 }
 212
 213 /**
 214  * get_cred - Get a reference on a set of credentials
 215  * @cred: The credentials to reference
 216  *
 217  * Get a reference on the specified set of credentials.  The caller must
 218  * release the reference.
 219  *
 220  * This is used to deal with a committed set of credentials.  Although the
 221  * pointer is const, this will temporarily discard the const and increment the
 222  * usage count.  The purpose of this is to attempt to catch at compile time the
 223  * accidental alteration of a set of credentials that should be considered
 224  * immutable.
 225  */
 226 static inline const struct cred *get_cred(const struct cred *cred)
 227 {
 228         struct cred *nonconst_cred = (struct cred *) cred;
 229         validate_creds(cred);
 230         return get_new_cred(nonconst_cred);
 231 }
 232
 233 /**
 234  * put_cred - Release a reference to a set of credentials
 235  * @cred: The credentials to release
 236  *
 237  * Release a reference to a set of credentials, deleting them when the last ref
 238  * is released.
 239  *
 240  * This takes a const pointer to a set of credentials because the credentials
 241  * on task_struct are attached by const pointers to prevent accidental
 242  * alteration of otherwise immutable credential sets.
 243  */
 244 static inline void put_cred(const struct cred *_cred)
 245 {
 246         struct cred *cred = (struct cred *) _cred;
 247
 248         validate_creds(cred);
 249         if (atomic_dec_and_test(&(cred)->usage))
 250                 __put_cred(cred);
 251 }
 252
 253 /**
 254  * current_cred - Access the current task's subjective credentials
 255  *
 256  * Access the subjective credentials of the current task.  RCU-safe,
 257  * since nobody else can modify it.
 258  */
 259 #define current_cred() \
 260         rcu_dereference_protected(current->cred, 1)
 261
 262 /**
 263  * __task_cred - Access a task's objective credentials
 264  * @task: The task to query
 265  *
 266  * Access the objective credentials of a task.  The caller must hold the RCU
 267  * readlock.
 268  *
 269  * The result of this function should not be passed directly to get_cred();
 270  * rather get_task_cred() should be used instead.
 271  */
 272 #define __task_cred(task)       \
 273         rcu_dereference((task)->real_cred)
 274
 275 /**
 276  * get_current_cred - Get the current task's subjective credentials
 277  *
 278  * Get the subjective credentials of the current task, pinning them so that
 279  * they can't go away.  Accessing the current task's credentials directly is
 280  * not permitted.
 281  */
 282 #define get_current_cred()                              \
 283         (get_cred(current_cred()))
 284
 285 /**
 286  * get_current_user - Get the current task's user_struct
 287  *
 288  * Get the user record of the current task, pinning it so that it can't go
 289  * away.
 290  */
 291 #define get_current_user()                              \
 292 ({                                                      \
 293         struct user_struct *__u;                        \
 294         const struct cred *__cred;                      \
 295         __cred = current_cred();                        \
 296         __u = get_uid(__cred->user);                    \
 297         __u;                                            \
 298 })
 299
 300 /**
 301  * get_current_groups - Get the current task's supplementary group list
 302  *
 303  * Get the supplementary group list of the current task, pinning it so that it
 304  * can't go away.
 305  */
 306 #define get_current_groups()                            \
 307 ({                                                      \
 308         struct group_info *__groups;                    \
 309         const struct cred *__cred;                      \
 310         __cred = current_cred();                        \
 311         __groups = get_group_info(__cred->group_info);  \
 312         __groups;                                       \
 313 })
 314
 315 #define task_cred_xxx(task, xxx)                        \
 316 ({                                                      \
 317         __typeof__(((struct cred *)NULL)->xxx) ___val;  \
 318         rcu_read_lock();                                \
 319         ___val = __task_cred((task))->xxx;              \
 320         rcu_read_unlock();                              \
 321         ___val;                                         \
 322 })
 323
 324 #define task_uid(task)          (task_cred_xxx((task), uid))
 325 #define task_euid(task)         (task_cred_xxx((task), euid))
 326
 327 #define current_cred_xxx(xxx)                   \
 328 ({                                              \
 329         current_cred()->xxx;                    \
 330 })
 331
 332 #define current_uid()           (current_cred_xxx(uid))
 333 #define current_gid()           (current_cred_xxx(gid))
 334 #define current_euid()          (current_cred_xxx(euid))
 335 #define current_egid()          (current_cred_xxx(egid))
 336 #define current_suid()          (current_cred_xxx(suid))
 337 #define current_sgid()          (current_cred_xxx(sgid))
 338 #define current_fsuid()         (current_cred_xxx(fsuid))
 339 #define current_fsgid()         (current_cred_xxx(fsgid))
 340 #define current_cap()           (current_cred_xxx(cap_effective))
 341 #define current_user()          (current_cred_xxx(user))
 342 #define current_security()      (current_cred_xxx(security))
 343
 344 extern struct user_namespace init_user_ns;
 345 #ifdef CONFIG_USER_NS
 346 #define current_user_ns()       (current_cred_xxx(user_ns))
 347 #else
 348 #define current_user_ns()       (&init_user_ns)
 349 #endif
 350
 351
 352 #define current_uid_gid(_uid, _gid)             \
 353 do {                                            \
 354         const struct cred *__cred;              \
 355         __cred = current_cred();                \
 356         *(_uid) = __cred->uid;                  \
 357         *(_gid) = __cred->gid;                  \
 358 } while(0)
 359
 360 #define current_euid_egid(_euid, _egid)         \
 361 do {                                            \
 362         const struct cred *__cred;              \
 363         __cred = current_cred();                \
 364         *(_euid) = __cred->euid;                \
 365         *(_egid) = __cred->egid;                \
 366 } while(0)
 367
 368 #define current_fsuid_fsgid(_fsuid, _fsgid)     \
 369 do {                                            \
 370         const struct cred *__cred;              \
 371         __cred = current_cred();                \
 372         *(_fsuid) = __cred->fsuid;              \
 373         *(_fsgid) = __cred->fsgid;              \
 374 } while(0)
 375
 376 #endif /* _LINUX_CRED_H */