/* Credentials management - see Documentation/security/credentials.txt
   *
   * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public Licence
   * as published by the Free Software Foundation; either version
   * 2 of the Licence, or (at your option) any later version.
   */
  
  #ifndef _LINUX_CRED_H
  #define _LINUX_CRED_H
  
  #include <linux/capability.h>
  #include <linux/init.h>
  #include <linux/key.h>
  #include <linux/selinux.h>
  #include <linux/atomic.h>
  #include <linux/uidgid.h>
  
  struct user_struct;
  struct cred;
  struct inode;
  
  /*
   * COW Supplementary groups list
   */
  #define NGROUPS_SMALL		32
  #define NGROUPS_PER_BLOCK	((unsigned int)(PAGE_SIZE / sizeof(kgid_t)))
  
  struct group_info {
  	atomic_t	usage;
  	int		ngroups;
  	int		nblocks;
  	kgid_t		small_block[NGROUPS_SMALL];
  	kgid_t		*blocks[0];
  };
  
  /**
   * get_group_info - Get a reference to a group info structure
   * @group_info: The group info to reference
   *
   * This gets a reference to a set of supplementary groups.
   *
   * If the caller is accessing a task's credentials, they must hold the RCU read
   * lock when reading.
   */
  static inline struct group_info *get_group_info(struct group_info *gi)
  {
  	atomic_inc(&gi->usage);
  	return gi;
  }
  
  /**
   * put_group_info - Release a reference to a group info structure
   * @group_info: The group info to release
   */
  #define put_group_info(group_info)			\
  do {							\
  	if (atomic_dec_and_test(&(group_info)->usage))	\
  		groups_free(group_info);		\
  } while (0)
  
  extern struct group_info *groups_alloc(int);
  extern struct group_info init_groups;
  extern void groups_free(struct group_info *);
  extern int set_current_groups(struct group_info *);
  extern int set_groups(struct cred *, struct group_info *);
  extern int groups_search(const struct group_info *, kgid_t);
  extern bool may_setgroups(void);
  
  /* access the groups "array" with this macro */
  #define GROUP_AT(gi, i) \
  	((gi)->blocks[(i) / NGROUPS_PER_BLOCK][(i) % NGROUPS_PER_BLOCK])
  
  extern int in_group_p(kgid_t);
  extern int in_egroup_p(kgid_t);
  
  /*
   * The security context of a task
   *
   * The parts of the context break down into two categories:
   *
   *  (1) The objective context of a task.  These parts are used when some other
   *	task is attempting to affect this one.
   *
   *  (2) The subjective context.  These details are used when the task is acting
   *	upon another object, be that a file, a task, a key or whatever.
   *
   * Note that some members of this structure belong to both categories - the
   * LSM security pointer for instance.
   *
   * A task has two security pointers.  task->real_cred points to the objective
   * context that defines that task's actual details.  The objective part of this
   * context is used whenever that task is acted upon.
   *
   * task->cred points to the subjective context that defines the details of how
   * that task is going to act upon another object.  This may be overridden
   * temporarily to point to another security context, but normally points to the
   * same context as task->real_cred.
   */
  struct cred {
  	atomic_t	usage;
  #ifdef CONFIG_DEBUG_CREDENTIALS
  	atomic_t	subscribers;	/* number of processes subscribed */
  	void		*put_addr;
  	unsigned	magic;
  #define CRED_MAGIC	0x43736564
  #define CRED_MAGIC_DEAD	0x44656144
  #endif
  	kuid_t		uid;		/* real UID of the task */
  	kgid_t		gid;		/* real GID of the task */
  	kuid_t		suid;		/* saved UID of the task */
  	kgid_t		sgid;		/* saved GID of the task */
  	kuid_t		euid;		/* effective UID of the task */
  	kgid_t		egid;		/* effective GID of the task */
  	kuid_t		fsuid;		/* UID for VFS ops */
  	kgid_t		fsgid;		/* GID for VFS ops */
  	unsigned	securebits;	/* SUID-less security management */
  	kernel_cap_t	cap_inheritable; /* caps our children can inherit */
  	kernel_cap_t	cap_permitted;	/* caps we're permitted */
  	kernel_cap_t	cap_effective;	/* caps we can actually use */
  	kernel_cap_t	cap_bset;	/* capability bounding set */
  #ifdef CONFIG_KEYS
  	unsigned char	jit_keyring;	/* default keyring to attach requested
  					 * keys to */
  	struct key __rcu *session_keyring; /* keyring inherited over fork */
  	struct key	*process_keyring; /* keyring private to this process */
  	struct key	*thread_keyring; /* keyring private to this thread */
  	struct key	*request_key_auth; /* assumed request_key authority */
  #endif
  #ifdef CONFIG_SECURITY
  	void		*security;	/* subjective LSM security */
  #endif
  	struct user_struct *user;	/* real user ID subscription */
  	struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
  	struct group_info *group_info;	/* supplementary groups for euid/fsgid */
  	struct rcu_head	rcu;		/* RCU deletion hook */
  };
  
  extern void __put_cred(struct cred *);
  extern void exit_creds(struct task_struct *);
  extern int copy_creds(struct task_struct *, unsigned long);
  extern const struct cred *get_task_cred(struct task_struct *);
  extern struct cred *cred_alloc_blank(void);
  extern struct cred *prepare_creds(void);
  extern struct cred *prepare_exec_creds(void);
  extern int commit_creds(struct cred *);
  extern void abort_creds(struct cred *);
  extern const struct cred *override_creds(const struct cred *);
  extern void revert_creds(const struct cred *);
  extern struct cred *prepare_kernel_cred(struct task_struct *);
  extern int change_create_files_as(struct cred *, struct inode *);
  extern int set_security_override(struct cred *, u32);
  extern int set_security_override_from_ctx(struct cred *, const char *);
  extern int set_create_files_as(struct cred *, struct inode *);
  extern void __init cred_init(void);
  
  /*
   * check for validity of credentials
   */
  #ifdef CONFIG_DEBUG_CREDENTIALS
  extern void __invalid_creds(const struct cred *, const char *, unsigned);
  extern void __validate_process_creds(struct task_struct *,
  				     const char *, unsigned);
  
  extern bool creds_are_invalid(const struct cred *cred);
  
  static inline void __validate_creds(const struct cred *cred,
  				    const char *file, unsigned line)
  {
  	if (unlikely(creds_are_invalid(cred)))
  		__invalid_creds(cred, file, line);
  }
  
  #define validate_creds(cred)				\
  do {							\
  	__validate_creds((cred), __FILE__, __LINE__);	\
  } while(0)
  
  #define validate_process_creds()				\
  do {								\
  	__validate_process_creds(current, __FILE__, __LINE__);	\
  } while(0)
  
  extern void validate_creds_for_do_exit(struct task_struct *);
  #else
  static inline void validate_creds(const struct cred *cred)
  {
  }
  static inline void validate_creds_for_do_exit(struct task_struct *tsk)
  {
  }
  static inline void validate_process_creds(void)
  {
  }
  #endif
  
  /**
   * get_new_cred - Get a reference on a new set of credentials
   * @cred: The new credentials to reference
   *
   * Get a reference on the specified set of new credentials.  The caller must
   * release the reference.
   */
  static inline struct cred *get_new_cred(struct cred *cred)
  {
  	atomic_inc(&cred->usage);
  	return cred;
  }
  
  /**
   * get_cred - Get a reference on a set of credentials
   * @cred: The credentials to reference
   *
   * Get a reference on the specified set of credentials.  The caller must
   * release the reference.
   *
   * This is used to deal with a committed set of credentials.  Although the
   * pointer is const, this will temporarily discard the const and increment the
   * usage count.  The purpose of this is to attempt to catch at compile time the
   * accidental alteration of a set of credentials that should be considered
   * immutable.
   */
  static inline const struct cred *get_cred(const struct cred *cred)
  {
  	struct cred *nonconst_cred = (struct cred *) cred;
  	validate_creds(cred);
  	return get_new_cred(nonconst_cred);
  }
  
  /**
   * put_cred - Release a reference to a set of credentials
   * @cred: The credentials to release
   *
   * Release a reference to a set of credentials, deleting them when the last ref
   * is released.
   *
   * This takes a const pointer to a set of credentials because the credentials
   * on task_struct are attached by const pointers to prevent accidental
   * alteration of otherwise immutable credential sets.
   */
  static inline void put_cred(const struct cred *_cred)
  {
  	struct cred *cred = (struct cred *) _cred;
  
  	validate_creds(cred);
  	if (atomic_dec_and_test(&(cred)->usage))
  		__put_cred(cred);
  }
  
  /**
   * current_cred - Access the current task's subjective credentials
   *
   * Access the subjective credentials of the current task.  RCU-safe,
   * since nobody else can modify it.
   */
  #define current_cred() \
  	rcu_dereference_protected(current->cred, 1)
  
  /**
   * __task_cred - Access a task's objective credentials
   * @task: The task to query
   *
   * Access the objective credentials of a task.  The caller must hold the RCU
   * readlock.
   *
   * The result of this function should not be passed directly to get_cred();
   * rather get_task_cred() should be used instead.
   */
  #define __task_cred(task)	\
  	rcu_dereference((task)->real_cred)
  
  /**
   * get_current_cred - Get the current task's subjective credentials
   *
   * Get the subjective credentials of the current task, pinning them so that
   * they can't go away.  Accessing the current task's credentials directly is
   * not permitted.
   */
  #define get_current_cred()				\
  	(get_cred(current_cred()))
  
  /**
   * get_current_user - Get the current task's user_struct
   *
   * Get the user record of the current task, pinning it so that it can't go
   * away.
   */
  #define get_current_user()				\
  ({							\
  	struct user_struct *__u;			\
  	const struct cred *__cred;			\
  	__cred = current_cred();			\
  	__u = get_uid(__cred->user);			\
  	__u;						\
  })
  
  /**
   * get_current_groups - Get the current task's supplementary group list
   *
   * Get the supplementary group list of the current task, pinning it so that it
   * can't go away.
   */
  #define get_current_groups()				\
  ({							\
  	struct group_info *__groups;			\
  	const struct cred *__cred;			\
  	__cred = current_cred();			\
  	__groups = get_group_info(__cred->group_info);	\
  	__groups;					\
  })
  
  #define task_cred_xxx(task, xxx)			\
  ({							\
  	__typeof__(((struct cred *)NULL)->xxx) ___val;	\
  	rcu_read_lock();				\
  	___val = __task_cred((task))->xxx;		\
  	rcu_read_unlock();				\
  	___val;						\
  })
  
  #define task_uid(task)		(task_cred_xxx((task), uid))
  #define task_euid(task)		(task_cred_xxx((task), euid))
  
  #define current_cred_xxx(xxx)			\
  ({						\
  	current_cred()->xxx;			\
  })
  
  #define current_uid()		(current_cred_xxx(uid))
  #define current_gid()		(current_cred_xxx(gid))
  #define current_euid()		(current_cred_xxx(euid))
  #define current_egid()		(current_cred_xxx(egid))
  #define current_suid()		(current_cred_xxx(suid))
  #define current_sgid()		(current_cred_xxx(sgid))
  #define current_fsuid() 	(current_cred_xxx(fsuid))
  #define current_fsgid() 	(current_cred_xxx(fsgid))
  #define current_cap()		(current_cred_xxx(cap_effective))
  #define current_user()		(current_cred_xxx(user))
  #define current_security()	(current_cred_xxx(security))
  
  extern struct user_namespace init_user_ns;
  #ifdef CONFIG_USER_NS
  #define current_user_ns()	(current_cred_xxx(user_ns))
  #else
  #define current_user_ns()	(&init_user_ns)
  #endif
  
  
  #define current_uid_gid(_uid, _gid)		\
  do {						\
  	const struct cred *__cred;		\
  	__cred = current_cred();		\
  	*(_uid) = __cred->uid;			\
  	*(_gid) = __cred->gid;			\
  } while(0)
  
  #define current_euid_egid(_euid, _egid)		\
  do {						\
  	const struct cred *__cred;		\
  	__cred = current_cred();		\
  	*(_euid) = __cred->euid;		\
  	*(_egid) = __cred->egid;		\
  } while(0)
  
  #define current_fsuid_fsgid(_fsuid, _fsgid)	\
  do {						\
  	const struct cred *__cred;		\
  	__cred = current_cred();		\
  	*(_fsuid) = __cred->fsuid;		\
  	*(_fsgid) = __cred->fsgid;		\
  } while(0)
  
  #endif /* _LINUX_CRED_H */