diff options
Diffstat (limited to 'security/commoncap.c')
| -rw-r--r-- | security/commoncap.c | 988 |
1 files changed, 988 insertions, 0 deletions
diff --git a/security/commoncap.c b/security/commoncap.c new file mode 100644 index 00000000..ccfe568b --- /dev/null +++ b/security/commoncap.c @@ -0,0 +1,988 @@ +/* Common capabilities, needed by capability.o. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + */ + +#include <linux/capability.h> +#include <linux/audit.h> +#include <linux/module.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/security.h> +#include <linux/file.h> +#include <linux/mm.h> +#include <linux/mman.h> +#include <linux/pagemap.h> +#include <linux/swap.h> +#include <linux/skbuff.h> +#include <linux/netlink.h> +#include <linux/ptrace.h> +#include <linux/xattr.h> +#include <linux/hugetlb.h> +#include <linux/mount.h> +#include <linux/sched.h> +#include <linux/prctl.h> +#include <linux/securebits.h> +#include <linux/user_namespace.h> +#include <linux/personality.h> + +#ifdef CONFIG_ANDROID_PARANOID_NETWORK +#include <linux/android_aid.h> +#endif + +/* + * If a non-root user executes a setuid-root binary in + * !secure(SECURE_NOROOT) mode, then we raise capabilities. + * However if fE is also set, then the intent is for only + * the file capabilities to be applied, and the setuid-root + * bit is left on either to change the uid (plausible) or + * to get full privilege on a kernel without file capabilities + * support. So in that case we do not raise capabilities. + * + * Warn if that happens, once per boot. + */ +static void warn_setuid_and_fcaps_mixed(const char *fname) +{ + static int warned; + if (!warned) { + printk(KERN_INFO "warning: `%s' has both setuid-root and" + " effective capabilities. Therefore not raising all" + " capabilities.\n", fname); + warned = 1; + } +} + +int cap_netlink_send(struct sock *sk, struct sk_buff *skb) +{ + return 0; +} + +int cap_netlink_recv(struct sk_buff *skb, int cap) +{ + if (!cap_raised(current_cap(), 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 + * @cred: The credentials to use + * @ns: The user namespace in which we need the capability + * @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_has_capability() cannot be used like the kernel's capable() + * and has_capability() functions. That is, it has the reverse semantics: + * cap_has_capability() returns 0 when a task has a capability, but the + * kernel's capable() and has_capability() returns 1 for this case. + */ +int cap_capable(struct task_struct *tsk, const struct cred *cred, + struct user_namespace *targ_ns, int cap, int audit) +{ + if (cap == CAP_NET_RAW && in_egroup_p(AID_NET_RAW)) + return 0; + if (cap == CAP_NET_ADMIN && in_egroup_p(AID_NET_ADMIN)) + return 0; + + for (;;) { + /* The creator of the user namespace has all caps. */ + if (targ_ns != &init_user_ns && targ_ns->creator == cred->user) + return 0; + + /* Do we have the necessary capabilities? */ + if (targ_ns == cred->user->user_ns) + return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM; + + /* Have we tried all of the parent namespaces? */ + if (targ_ns == &init_user_ns) + return -EPERM; + + /* + *If you have a capability in a parent user ns, then you have + * it over all children user namespaces as well. + */ + targ_ns = targ_ns->creator->user_ns; + } + + /* We never get here */ +} + +/** + * 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(const struct timespec *ts, const struct timezone *tz) +{ + if (!capable(CAP_SYS_TIME)) + return -EPERM; + return 0; +} + +/** + * cap_ptrace_access_check - Determine whether the current process may access + * another + * @child: The process to be accessed + * @mode: The mode of attachment. + * + * If we are in the same or an ancestor user_ns and have all the target + * task's capabilities, then ptrace access is allowed. + * If we have the ptrace capability to the target user_ns, then ptrace + * access is allowed. + * Else denied. + * + * Determine whether a process may access another, returning 0 if permission + * granted, -ve if denied. + */ +int cap_ptrace_access_check(struct task_struct *child, unsigned int mode) +{ + int ret = 0; + const struct cred *cred, *child_cred; + + rcu_read_lock(); + cred = current_cred(); + child_cred = __task_cred(child); + if (cred->user->user_ns == child_cred->user->user_ns && + cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) + goto out; + if (ns_capable(child_cred->user->user_ns, CAP_SYS_PTRACE)) + goto out; + ret = -EPERM; +out: + rcu_read_unlock(); + return ret; +} + +/** + * cap_ptrace_traceme - Determine whether another process may trace the current + * @parent: The task proposed to be the tracer + * + * If parent is in the same or an ancestor user_ns and has all current's + * capabilities, then ptrace access is allowed. + * If parent has the ptrace capability to current's user_ns, then ptrace + * access is allowed. + * Else denied. + * + * 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; + const struct cred *cred, *child_cred; + + rcu_read_lock(); + cred = __task_cred(parent); + child_cred = current_cred(); + if (cred->user->user_ns == child_cred->user->user_ns && + cap_issubset(child_cred->cap_permitted, cred->cap_permitted)) + goto out; + if (has_ns_capability(parent, child_cred->user->user_ns, CAP_SYS_PTRACE)) + goto out; + ret = -EPERM; +out: + rcu_read_unlock(); + return ret; +} + +/** + * 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; + + /* Derived from kernel/capability.c:sys_capget. */ + rcu_read_lock(); + cred = __task_cred(target); + *effective = cred->cap_effective; + *inheritable = cred->cap_inheritable; + *permitted = cred->cap_permitted; + rcu_read_unlock(); + return 0; +} + +/* + * 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) +{ + + /* they are so limited unless the current task has the CAP_SETPCAP + * capability + */ + if (cap_capable(current, current_cred(), + current_cred()->user->user_ns, CAP_SETPCAP, + SECURITY_CAP_AUDIT) == 0) + return 0; + return 1; +} + +/** + * 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, + const kernel_cap_t *inheritable, + const kernel_cap_t *permitted) +{ + if (cap_inh_is_capped() && + !cap_issubset(*inheritable, + cap_combine(old->cap_inheritable, + old->cap_permitted))) + /* incapable of using this inheritable set */ + return -EPERM; + + if (!cap_issubset(*inheritable, + cap_combine(old->cap_inheritable, + old->cap_bset))) + /* no new pI capabilities outside bounding set */ + return -EPERM; + + /* verify restrictions on target's new Permitted set */ + if (!cap_issubset(*permitted, old->cap_permitted)) + return -EPERM; + + /* verify the _new_Effective_ is a subset of the _new_Permitted_ */ + if (!cap_issubset(*effective, *permitted)) + return -EPERM; + + new->cap_effective = *effective; + new->cap_inheritable = *inheritable; + new->cap_permitted = *permitted; + return 0; +} + +/* + * Clear proposed capability sets for execve(). + */ +static inline void bprm_clear_caps(struct linux_binprm *bprm) +{ + cap_clear(bprm->cred->cap_permitted); + bprm->cap_effective = false; +} + +/** + * 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; + int error; + + if (!inode->i_op->getxattr) + return 0; + + error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0); + if (error <= 0) + return 0; + 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; + + if (!inode->i_op->removexattr) + return 0; + + 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) +{ + struct cred *new = bprm->cred; + unsigned i; + int ret = 0; + + if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE) + *effective = true; + + CAP_FOR_EACH_U32(i) { + __u32 permitted = caps->permitted.cap[i]; + __u32 inheritable = caps->inheritable.cap[i]; + + /* + * pP' = (X & fP) | (pI & fI) + */ + new->cap_permitted.cap[i] = + (new->cap_bset.cap[i] & permitted) | + (new->cap_inheritable.cap[i] & inheritable); + + if (permitted & ~new->cap_permitted.cap[i]) + /* insufficient to execute correctly */ + ret = -EPERM; + } + + /* + * For legacy apps, with no internal support for recognizing they + * do not have enough capabilities, we return an error if they are + * missing some "forced" (aka file-permitted) capabilities. + */ + 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; + __u32 magic_etc; + unsigned tocopy, i; + int size; + struct vfs_cap_data caps; + + memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); + + if (!inode || !inode->i_op->getxattr) + return -ENODATA; + + size = inode->i_op->getxattr((struct dentry *)dentry, XATTR_NAME_CAPS, &caps, + XATTR_CAPS_SZ); + if (size == -ENODATA || size == -EOPNOTSUPP) + /* no data, that's ok */ + return -ENODATA; + if (size < 0) + return size; + + if (size < sizeof(magic_etc)) + return -EINVAL; + + cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc); + + switch (magic_etc & VFS_CAP_REVISION_MASK) { + case VFS_CAP_REVISION_1: + if (size != XATTR_CAPS_SZ_1) + return -EINVAL; + tocopy = VFS_CAP_U32_1; + break; + case VFS_CAP_REVISION_2: + if (size != XATTR_CAPS_SZ_2) + return -EINVAL; + tocopy = VFS_CAP_U32_2; + break; + default: + return -EINVAL; + } + + CAP_FOR_EACH_U32(i) { + if (i >= tocopy) + break; + cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted); + cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable); + } + + return 0; +} + +/* + * 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; + int rc = 0; + struct cpu_vfs_cap_data vcaps; + + bprm_clear_caps(bprm); + + if (!file_caps_enabled) + return 0; + + if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) + return 0; + + dentry = dget(bprm->file->f_dentry); + + rc = get_vfs_caps_from_disk(dentry, &vcaps); + if (rc < 0) { + if (rc == -EINVAL) + printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n", + __func__, rc, bprm->filename); + else if (rc == -ENODATA) + rc = 0; + goto out; + } + + rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective); + if (rc == -EINVAL) + printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", + __func__, rc, bprm->filename); + +out: + dput(dentry); + if (rc) + bprm_clear_caps(bprm); + + return rc; +} + +/** + * 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) +{ + const struct cred *old = current_cred(); + struct cred *new = bprm->cred; + bool effective; + int ret; + + effective = false; + ret = get_file_caps(bprm, &effective); + if (ret < 0) + return ret; + + if (!issecure(SECURE_NOROOT)) { + /* + * If the legacy file capability is set, then don't set privs + * for a setuid root binary run by a non-root user. Do set it + * for a root user just to cause least surprise to an admin. + */ + if (effective && new->uid != 0 && new->euid == 0) { + warn_setuid_and_fcaps_mixed(bprm->filename); + goto skip; + } + /* + * To support inheritance of root-permissions and suid-root + * executables under compatibility mode, we override the + * capability sets for the file. + * + * If only the real uid is 0, we do not set the effective bit. + */ + if (new->euid == 0 || new->uid == 0) { + /* pP' = (cap_bset & ~0) | (pI & ~0) */ + new->cap_permitted = cap_combine(old->cap_bset, + old->cap_inheritable); + } + if (new->euid == 0) + effective = true; + } +skip: + + /* if we have fs caps, clear dangerous personality flags */ + if (!cap_issubset(new->cap_permitted, old->cap_permitted)) + bprm->per_clear |= PER_CLEAR_ON_SETID; + + + /* Don't let someone trace a set[ug]id/setpcap binary with the revised + * credentials unless they have the appropriate permit + */ + if ((new->euid != old->uid || + new->egid != old->gid || + !cap_issubset(new->cap_permitted, old->cap_permitted)) && + bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) { + /* downgrade; they get no more than they had, and maybe less */ + if (!capable(CAP_SETUID)) { + new->euid = new->uid; + new->egid = new->gid; + } + new->cap_permitted = cap_intersect(new->cap_permitted, + old->cap_permitted); + } + + new->suid = new->fsuid = new->euid; + new->sgid = new->fsgid = new->egid; + + if (effective) + new->cap_effective = new->cap_permitted; + else + cap_clear(new->cap_effective); + bprm->cap_effective = effective; + + /* + * Audit candidate if current->cap_effective is set + * + * We do not bother to audit if 3 things are true: + * 1) cap_effective has all caps + * 2) we are root + * 3) root is supposed to have all caps (SECURE_NOROOT) + * Since this is just a normal root execing a process. + * + * Number 1 above might fail if you don't have a full bset, but I think + * that is interesting information to audit. + */ + if (!cap_isclear(new->cap_effective)) { + if (!cap_issubset(CAP_FULL_SET, new->cap_effective) || + new->euid != 0 || new->uid != 0 || + issecure(SECURE_NOROOT)) { + ret = audit_log_bprm_fcaps(bprm, new, old); + if (ret < 0) + return ret; + } + } + + new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); + return 0; +} + +/** + * 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) +{ + const struct cred *cred = current_cred(); + + if (cred->uid != 0) { + if (bprm->cap_effective) + return 1; + if (!cap_isclear(cred->cap_permitted)) + return 1; + } + + return (cred->euid != cred->uid || + 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) +{ + if (!strcmp(name, XATTR_NAME_CAPS)) { + if (!capable(CAP_SETFCAP)) + return -EPERM; + return 0; + } + + 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; + } + + if (!strncmp(name, XATTR_SECURITY_PREFIX, + sizeof(XATTR_SECURITY_PREFIX) - 1) && + !capable(CAP_SYS_ADMIN)) + return -EPERM; + return 0; +} + +/* + * cap_emulate_setxuid() fixes the effective / permitted capabilities of + * a process after a call to setuid, setreuid, or setresuid. + * + * 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of + * {r,e,s}uid != 0, the permitted and effective capabilities are + * cleared. + * + * 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective + * capabilities of the process are cleared. + * + * 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective + * capabilities are set to the permitted capabilities. + * + * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should + * never happen. + * + * -astor + * + * cevans - New behaviour, Oct '99 + * A process may, via prctl(), elect to keep its capabilities when it + * calls setuid() and switches away from uid==0. Both permitted and + * effective sets will be retained. + * Without this change, it was impossible for a daemon to drop only some + * of its privilege. The call to setuid(!=0) would drop all privileges! + * Keeping uid 0 is not an option because uid 0 owns too many vital + * files.. + * Thanks to Olaf Kirch and Peter Benie for spotting this. + */ +static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old) +{ + if ((old->uid == 0 || old->euid == 0 || old->suid == 0) && + (new->uid != 0 && new->euid != 0 && new->suid != 0) && + !issecure(SECURE_KEEP_CAPS)) { + cap_clear(new->cap_permitted); + cap_clear(new->cap_effective); + } + if (old->euid == 0 && new->euid != 0) + cap_clear(new->cap_effective); + if (old->euid != 0 && new->euid == 0) + 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: + /* 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: + /* 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) + new->cap_effective = + cap_drop_fs_set(new->cap_effective); + + if (old->fsuid != 0 && new->fsuid == 0) + new->cap_effective = + cap_raise_fs_set(new->cap_effective, + new->cap_permitted); + } + break; + + default: + return -EINVAL; + } + + return 0; +} + +/* + * Rationale: code calling task_setscheduler, task_setioprio, and + * task_setnice, assumes that + * . if capable(cap_sys_nice), then those actions should be allowed + * . if not capable(cap_sys_nice), but acting on your own processes, + * then those actions should be allowed + * This is insufficient now since you can call code without suid, but + * yet with increased caps. + * So we check for increased caps on the target process. + */ +static int cap_safe_nice(struct task_struct *p) +{ + int is_subset; + + rcu_read_lock(); + is_subset = cap_issubset(__task_cred(p)->cap_permitted, + current_cred()->cap_permitted); + rcu_read_unlock(); + + if (!is_subset && !capable(CAP_SYS_NICE)) + return -EPERM; + return 0; +} + +/** + * cap_task_setscheduler - Detemine if scheduler policy change is permitted + * @p: The task to affect + * + * 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) +{ + return cap_safe_nice(p); +} + +/** + * 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); +} + +/** + * 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); +} + +/* + * 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) +{ + if (!capable(CAP_SETPCAP)) + return -EPERM; + if (!cap_valid(cap)) + return -EINVAL; + + cap_lower(new->cap_bset, cap); + return 0; +} + +/** + * 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) +{ + struct cred *new; + long error = 0; + + new = prepare_creds(); + if (!new) + return -ENOMEM; + + switch (option) { + case PR_CAPBSET_READ: + error = -EINVAL; + if (!cap_valid(arg2)) + goto error; + error = !!cap_raised(new->cap_bset, arg2); + goto no_change; + + case PR_CAPBSET_DROP: + error = cap_prctl_drop(new, arg2); + if (error < 0) + goto error; + goto changed; + + /* + * The next four prctl's remain to assist with transitioning a + * system from legacy UID=0 based privilege (when filesystem + * capabilities are not in use) to a system using filesystem + * capabilities only - as the POSIX.1e draft intended. + * + * Note: + * + * PR_SET_SECUREBITS = + * issecure_mask(SECURE_KEEP_CAPS_LOCKED) + * | issecure_mask(SECURE_NOROOT) + * | issecure_mask(SECURE_NOROOT_LOCKED) + * | issecure_mask(SECURE_NO_SETUID_FIXUP) + * | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED) + * + * will ensure that the current process and all of its + * children will be locked into a pure + * capability-based-privilege environment. + */ + case PR_SET_SECUREBITS: + error = -EPERM; + if ((((new->securebits & SECURE_ALL_LOCKS) >> 1) + & (new->securebits ^ arg2)) /*[1]*/ + || ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/ + || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/ + || (cap_capable(current, current_cred(), + current_cred()->user->user_ns, CAP_SETPCAP, + SECURITY_CAP_AUDIT) != 0) /*[4]*/ + /* + * [1] no changing of bits that are locked + * [2] no unlocking of locks + * [3] no setting of unsupported bits + * [4] doing anything requires privilege (go read about + * the "sendmail capabilities bug") + */ + ) + /* cannot change a locked bit */ + goto error; + new->securebits = arg2; + goto changed; + + case PR_GET_SECUREBITS: + error = new->securebits; + goto no_change; + + case PR_GET_KEEPCAPS: + if (issecure(SECURE_KEEP_CAPS)) + error = 1; + goto no_change; + + case PR_SET_KEEPCAPS: + error = -EINVAL; + if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */ + goto error; + error = -EPERM; + if (issecure(SECURE_KEEP_CAPS_LOCKED)) + goto error; + if (arg2) + new->securebits |= issecure_mask(SECURE_KEEP_CAPS); + else + new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); + goto changed; + + default: + /* No functionality available - continue with default */ + error = -ENOSYS; + goto error; + } + + /* Functionality provided */ +changed: + return commit_creds(new); + +no_change: +error: + abort_creds(new); + return error; +} + +/** + * 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; + + if (cap_capable(current, current_cred(), &init_user_ns, CAP_SYS_ADMIN, + SECURITY_CAP_NOAUDIT) == 0) + cap_sys_admin = 1; + return __vm_enough_memory(mm, pages, cap_sys_admin); +} + +/* + * cap_file_mmap - check if able to map given addr + * @file: unused + * @reqprot: unused + * @prot: unused + * @flags: unused + * @addr: address attempting to be mapped + * @addr_only: unused + * + * If the process is attempting to map memory below dac_mmap_min_addr they need + * CAP_SYS_RAWIO. The other parameters to this function are unused by the + * capability security module. Returns 0 if this mapping should be allowed + * -EPERM if not. + */ +int cap_file_mmap(struct file *file, unsigned long reqprot, + unsigned long prot, unsigned long flags, + unsigned long addr, unsigned long addr_only) +{ + int ret = 0; + + if (addr < dac_mmap_min_addr) { + ret = cap_capable(current, current_cred(), &init_user_ns, CAP_SYS_RAWIO, + SECURITY_CAP_AUDIT); + /* set PF_SUPERPRIV if it turns out we allow the low mmap */ + if (ret == 0) + current->flags |= PF_SUPERPRIV; + } + return ret; +} |