diff options
Diffstat (limited to 'security/commoncap.c')
| -rw-r--r-- | security/commoncap.c | 300 |
1 files changed, 248 insertions, 52 deletions
diff --git a/security/commoncap.c b/security/commoncap.c index 51dfa11e8e5..19cb398431e 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -40,14 +40,21 @@ int cap_netlink_recv(struct sk_buff *skb, int cap) return -EPERM; return 0; } - EXPORT_SYMBOL(cap_netlink_recv); -/* +/** + * cap_capable - Determine whether a task has a particular effective capability + * @tsk: The task to query + * @cap: The capability to check for + * @audit: Whether to write an audit message or not + * + * Determine whether the nominated task has the specified capability amongst + * its effective set, returning 0 if it does, -ve if it does not. + * * NOTE WELL: cap_capable() cannot be used like the kernel's capable() - * function. That is, it has the reverse semantics: cap_capable() - * returns 0 when a task has a capability, but the kernel's capable() - * returns 1 for this case. + * function. That is, it has the reverse semantics: cap_capable() returns 0 + * when a task has a capability, but the kernel's capable() returns 1 for this + * case. */ int cap_capable(struct task_struct *tsk, int cap, int audit) { @@ -60,6 +67,14 @@ int cap_capable(struct task_struct *tsk, int cap, int audit) return cap_raised ? 0 : -EPERM; } +/** + * cap_settime - Determine whether the current process may set the system clock + * @ts: The time to set + * @tz: The timezone to set + * + * Determine whether the current process may set the system clock and timezone + * information, returning 0 if permission granted, -ve if denied. + */ int cap_settime(struct timespec *ts, struct timezone *tz) { if (!capable(CAP_SYS_TIME)) @@ -67,6 +82,15 @@ int cap_settime(struct timespec *ts, struct timezone *tz) return 0; } +/** + * cap_ptrace_may_access - Determine whether the current process may access + * another + * @child: The process to be accessed + * @mode: The mode of attachment. + * + * Determine whether a process may access another, returning 0 if permission + * granted, -ve if denied. + */ int cap_ptrace_may_access(struct task_struct *child, unsigned int mode) { int ret = 0; @@ -80,6 +104,13 @@ int cap_ptrace_may_access(struct task_struct *child, unsigned int mode) return ret; } +/** + * cap_ptrace_traceme - Determine whether another process may trace the current + * @parent: The task proposed to be the tracer + * + * Determine whether the nominated task is permitted to trace the current + * process, returning 0 if permission is granted, -ve if denied. + */ int cap_ptrace_traceme(struct task_struct *parent) { int ret = 0; @@ -93,8 +124,18 @@ int cap_ptrace_traceme(struct task_struct *parent) return ret; } -int cap_capget (struct task_struct *target, kernel_cap_t *effective, - kernel_cap_t *inheritable, kernel_cap_t *permitted) +/** + * cap_capget - Retrieve a task's capability sets + * @target: The task from which to retrieve the capability sets + * @effective: The place to record the effective set + * @inheritable: The place to record the inheritable set + * @permitted: The place to record the permitted set + * + * This function retrieves the capabilities of the nominated task and returns + * them to the caller. + */ +int cap_capget(struct task_struct *target, kernel_cap_t *effective, + kernel_cap_t *inheritable, kernel_cap_t *permitted) { const struct cred *cred; @@ -108,30 +149,35 @@ int cap_capget (struct task_struct *target, kernel_cap_t *effective, return 0; } -#ifdef CONFIG_SECURITY_FILE_CAPABILITIES - +/* + * Determine whether the inheritable capabilities are limited to the old + * permitted set. Returns 1 if they are limited, 0 if they are not. + */ static inline int cap_inh_is_capped(void) { - /* - * Return 1 if changes to the inheritable set are limited - * to the old permitted set. That is, if the current task - * does *not* possess the CAP_SETPCAP capability. - */ - return cap_capable(current, CAP_SETPCAP, SECURITY_CAP_AUDIT) != 0; -} - -static inline int cap_limit_ptraced_target(void) { return 1; } - -#else /* ie., ndef CONFIG_SECURITY_FILE_CAPABILITIES */ +#ifdef CONFIG_SECURITY_FILE_CAPABILITIES -static inline int cap_inh_is_capped(void) { return 1; } -static inline int cap_limit_ptraced_target(void) -{ - return !capable(CAP_SETPCAP); + /* they are so limited unless the current task has the CAP_SETPCAP + * capability + */ + if (cap_capable(current, CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0) + return 0; +#endif + return 1; } -#endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */ - +/** + * cap_capset - Validate and apply proposed changes to current's capabilities + * @new: The proposed new credentials; alterations should be made here + * @old: The current task's current credentials + * @effective: A pointer to the proposed new effective capabilities set + * @inheritable: A pointer to the proposed new inheritable capabilities set + * @permitted: A pointer to the proposed new permitted capabilities set + * + * This function validates and applies a proposed mass change to the current + * process's capability sets. The changes are made to the proposed new + * credentials, and assuming no error, will be committed by the caller of LSM. + */ int cap_capset(struct cred *new, const struct cred *old, const kernel_cap_t *effective, @@ -165,6 +211,9 @@ int cap_capset(struct cred *new, return 0; } +/* + * Clear proposed capability sets for execve(). + */ static inline void bprm_clear_caps(struct linux_binprm *bprm) { cap_clear(bprm->cred->cap_permitted); @@ -173,6 +222,17 @@ static inline void bprm_clear_caps(struct linux_binprm *bprm) #ifdef CONFIG_SECURITY_FILE_CAPABILITIES +/** + * cap_inode_need_killpriv - Determine if inode change affects privileges + * @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV + * + * Determine if an inode having a change applied that's marked ATTR_KILL_PRIV + * affects the security markings on that inode, and if it is, should + * inode_killpriv() be invoked or the change rejected? + * + * Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and + * -ve to deny the change. + */ int cap_inode_need_killpriv(struct dentry *dentry) { struct inode *inode = dentry->d_inode; @@ -187,6 +247,14 @@ int cap_inode_need_killpriv(struct dentry *dentry) return 1; } +/** + * cap_inode_killpriv - Erase the security markings on an inode + * @dentry: The inode/dentry to alter + * + * Erase the privilege-enhancing security markings on an inode. + * + * Returns 0 if successful, -ve on error. + */ int cap_inode_killpriv(struct dentry *dentry) { struct inode *inode = dentry->d_inode; @@ -197,6 +265,10 @@ int cap_inode_killpriv(struct dentry *dentry) return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS); } +/* + * Calculate the new process capability sets from the capability sets attached + * to a file. + */ static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, struct linux_binprm *bprm, bool *effective) @@ -232,6 +304,9 @@ static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps, return *effective ? ret : 0; } +/* + * Extract the on-exec-apply capability sets for an executable file. + */ int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) { struct inode *inode = dentry->d_inode; @@ -283,7 +358,11 @@ int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data return 0; } -/* Locate any VFS capabilities: */ +/* + * Attempt to get the on-exec apply capability sets for an executable file from + * its xattrs and, if present, apply them to the proposed credentials being + * constructed by execve(). + */ static int get_file_caps(struct linux_binprm *bprm, bool *effective) { struct dentry *dentry; @@ -342,7 +421,31 @@ static inline int get_file_caps(struct linux_binprm *bprm, bool *effective) #endif /* - * set up the new credentials for an exec'd task + * Determine whether a exec'ing process's new permitted capabilities should be + * limited to just what it already has. + * + * This prevents processes that are being ptraced from gaining access to + * CAP_SETPCAP, unless the process they're tracing already has it, and the + * binary they're executing has filecaps that elevate it. + * + * Returns 1 if they should be limited, 0 if they are not. + */ +static inline int cap_limit_ptraced_target(void) +{ +#ifndef CONFIG_SECURITY_FILE_CAPABILITIES + if (capable(CAP_SETPCAP)) + return 0; +#endif + return 1; +} + +/** + * cap_bprm_set_creds - Set up the proposed credentials for execve(). + * @bprm: The execution parameters, including the proposed creds + * + * Set up the proposed credentials for a new execution context being + * constructed by execve(). The proposed creds in @bprm->cred is altered, + * which won't take effect immediately. Returns 0 if successful, -ve on error. */ int cap_bprm_set_creds(struct linux_binprm *bprm) { @@ -430,10 +533,15 @@ int cap_bprm_set_creds(struct linux_binprm *bprm) return 0; } -/* - * determine whether a secure execution is required - * - the creds have been committed at this point, and are no longer available - * through bprm +/** + * cap_bprm_secureexec - Determine whether a secure execution is required + * @bprm: The execution parameters + * + * Determine whether a secure execution is required, return 1 if it is, and 0 + * if it is not. + * + * The credentials have been committed by this point, and so are no longer + * available through @bprm->cred. */ int cap_bprm_secureexec(struct linux_binprm *bprm) { @@ -450,6 +558,20 @@ int cap_bprm_secureexec(struct linux_binprm *bprm) cred->egid != cred->gid); } +/** + * cap_inode_setxattr - Determine whether an xattr may be altered + * @dentry: The inode/dentry being altered + * @name: The name of the xattr to be changed + * @value: The value that the xattr will be changed to + * @size: The size of value + * @flags: The replacement flag + * + * Determine whether an xattr may be altered or set on an inode, returning 0 if + * permission is granted, -ve if denied. + * + * This is used to make sure security xattrs don't get updated or set by those + * who aren't privileged to do so. + */ int cap_inode_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags) { @@ -457,27 +579,41 @@ int cap_inode_setxattr(struct dentry *dentry, const char *name, if (!capable(CAP_SETFCAP)) return -EPERM; return 0; - } else if (!strncmp(name, XATTR_SECURITY_PREFIX, + } + + if (!strncmp(name, XATTR_SECURITY_PREFIX, sizeof(XATTR_SECURITY_PREFIX) - 1) && !capable(CAP_SYS_ADMIN)) return -EPERM; return 0; } +/** + * cap_inode_removexattr - Determine whether an xattr may be removed + * @dentry: The inode/dentry being altered + * @name: The name of the xattr to be changed + * + * Determine whether an xattr may be removed from an inode, returning 0 if + * permission is granted, -ve if denied. + * + * This is used to make sure security xattrs don't get removed by those who + * aren't privileged to remove them. + */ int cap_inode_removexattr(struct dentry *dentry, const char *name) { if (!strcmp(name, XATTR_NAME_CAPS)) { if (!capable(CAP_SETFCAP)) return -EPERM; return 0; - } else if (!strncmp(name, XATTR_SECURITY_PREFIX, + } + + if (!strncmp(name, XATTR_SECURITY_PREFIX, sizeof(XATTR_SECURITY_PREFIX) - 1) && !capable(CAP_SYS_ADMIN)) return -EPERM; return 0; } -/* moved from kernel/sys.c. */ /* * cap_emulate_setxuid() fixes the effective / permitted capabilities of * a process after a call to setuid, setreuid, or setresuid. @@ -521,35 +657,46 @@ static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) new->cap_effective = new->cap_permitted; } +/** + * cap_task_fix_setuid - Fix up the results of setuid() call + * @new: The proposed credentials + * @old: The current task's current credentials + * @flags: Indications of what has changed + * + * Fix up the results of setuid() call before the credential changes are + * actually applied, returning 0 to grant the changes, -ve to deny them. + */ int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags) { switch (flags) { case LSM_SETID_RE: case LSM_SETID_ID: case LSM_SETID_RES: - /* Copied from kernel/sys.c:setreuid/setuid/setresuid. */ + /* juggle the capabilities to follow [RES]UID changes unless + * otherwise suppressed */ if (!issecure(SECURE_NO_SETUID_FIXUP)) cap_emulate_setxuid(new, old); break; - case LSM_SETID_FS: - /* Copied from kernel/sys.c:setfsuid. */ - /* + case LSM_SETID_FS: + /* juggle the capabilties to follow FSUID changes, unless + * otherwise suppressed + * * FIXME - is fsuser used for all CAP_FS_MASK capabilities? * if not, we might be a bit too harsh here. */ if (!issecure(SECURE_NO_SETUID_FIXUP)) { - if (old->fsuid == 0 && new->fsuid != 0) { + if (old->fsuid == 0 && new->fsuid != 0) new->cap_effective = cap_drop_fs_set(new->cap_effective); - } - if (old->fsuid != 0 && new->fsuid == 0) { + + if (old->fsuid != 0 && new->fsuid == 0) new->cap_effective = cap_raise_fs_set(new->cap_effective, new->cap_permitted); - } } break; + default: return -EINVAL; } @@ -582,28 +729,50 @@ static int cap_safe_nice(struct task_struct *p) return 0; } -int cap_task_setscheduler (struct task_struct *p, int policy, +/** + * cap_task_setscheduler - Detemine if scheduler policy change is permitted + * @p: The task to affect + * @policy: The policy to effect + * @lp: The parameters to the scheduling policy + * + * Detemine if the requested scheduler policy change is permitted for the + * specified task, returning 0 if permission is granted, -ve if denied. + */ +int cap_task_setscheduler(struct task_struct *p, int policy, struct sched_param *lp) { return cap_safe_nice(p); } -int cap_task_setioprio (struct task_struct *p, int ioprio) +/** + * cap_task_ioprio - Detemine if I/O priority change is permitted + * @p: The task to affect + * @ioprio: The I/O priority to set + * + * Detemine if the requested I/O priority change is permitted for the specified + * task, returning 0 if permission is granted, -ve if denied. + */ +int cap_task_setioprio(struct task_struct *p, int ioprio) { return cap_safe_nice(p); } -int cap_task_setnice (struct task_struct *p, int nice) +/** + * cap_task_ioprio - Detemine if task priority change is permitted + * @p: The task to affect + * @nice: The nice value to set + * + * Detemine if the requested task priority change is permitted for the + * specified task, returning 0 if permission is granted, -ve if denied. + */ +int cap_task_setnice(struct task_struct *p, int nice) { return cap_safe_nice(p); } /* - * called from kernel/sys.c for prctl(PR_CABSET_DROP) - * done without task_capability_lock() because it introduces - * no new races - i.e. only another task doing capget() on - * this task could get inconsistent info. There can be no - * racing writer bc a task can only change its own caps. + * Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from + * the current task's bounding set. Returns 0 on success, -ve on error. */ static long cap_prctl_drop(struct cred *new, unsigned long cap) { @@ -632,6 +801,18 @@ int cap_task_setnice (struct task_struct *p, int nice) } #endif +/** + * cap_task_prctl - Implement process control functions for this security module + * @option: The process control function requested + * @arg2, @arg3, @arg4, @arg5: The argument data for this function + * + * Allow process control functions (sys_prctl()) to alter capabilities; may + * also deny access to other functions not otherwise implemented here. + * + * Returns 0 or +ve on success, -ENOSYS if this function is not implemented + * here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM + * modules will consider performing the function. + */ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3, unsigned long arg4, unsigned long arg5) { @@ -737,13 +918,28 @@ error: return error; } -int cap_syslog (int type) +/** + * cap_syslog - Determine whether syslog function is permitted + * @type: Function requested + * + * Determine whether the current process is permitted to use a particular + * syslog function, returning 0 if permission is granted, -ve if not. + */ +int cap_syslog(int type) { if ((type != 3 && type != 10) && !capable(CAP_SYS_ADMIN)) return -EPERM; return 0; } +/** + * cap_vm_enough_memory - Determine whether a new virtual mapping is permitted + * @mm: The VM space in which the new mapping is to be made + * @pages: The size of the mapping + * + * Determine whether the allocation of a new virtual mapping by the current + * task is permitted, returning 0 if permission is granted, -ve if not. + */ int cap_vm_enough_memory(struct mm_struct *mm, long pages) { int cap_sys_admin = 0; |