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