X-Git-Url: http://ftp.safe.ca/?p=safe%2Fjmp%2Flinux-2.6;a=blobdiff_plain;f=security%2Fcommoncap.c;h=beac0258c2a8f3a0cbad52ec9adf12e019264626;hp=302e8d0839a9c7afaacff955e4a67874192117be;hb=7eef4091a653c243a87e5375c54504cc03bec4d8;hpb=91ad997a34d7abca1f04e819e31eb9f3d4e20585 diff --git a/security/commoncap.c b/security/commoncap.c index 302e8d0..beac025 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -1,4 +1,4 @@ -/* Common capabilities, needed by capability.o and root_plug.o +/* Common capabilities, needed by capability.o and root_plug.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 @@ -8,6 +8,7 @@ */ #include +#include #include #include #include @@ -24,29 +25,12 @@ #include #include #include - -#ifdef CONFIG_SECURITY_FILE_CAPABILITIES -/* - * Because of the reduced scope of CAP_SETPCAP when filesystem - * capabilities are in effect, it is safe to allow this capability to - * be available in the default configuration. - */ -# define CAP_INIT_BSET CAP_FULL_SET -#else /* ie. ndef CONFIG_SECURITY_FILE_CAPABILITIES */ -# define CAP_INIT_BSET CAP_INIT_EFF_SET -#endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */ - -kernel_cap_t cap_bset = CAP_INIT_BSET; /* systemwide capability bound */ -EXPORT_SYMBOL(cap_bset); - -/* Global security state */ - -unsigned securebits = SECUREBITS_DEFAULT; /* systemwide security settings */ -EXPORT_SYMBOL(securebits); +#include +#include int cap_netlink_send(struct sock *sk, struct sk_buff *skb) { - NETLINK_CB(skb).eff_cap = current->cap_effective; + NETLINK_CB(skb).eff_cap = current_cap(); return 0; } @@ -56,17 +40,37 @@ int cap_netlink_recv(struct sk_buff *skb, int cap) return -EPERM; return 0; } - EXPORT_SYMBOL(cap_netlink_recv); -int cap_capable (struct task_struct *tsk, int cap) +/** + * cap_capable - Determine whether a task has a particular effective capability + * @tsk: The task to query + * @cred: The credentials to use + * @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, int cap, + int audit) { - /* Derived from include/linux/sched.h:capable. */ - if (cap_raised(tsk->cap_effective, cap)) - return 0; - return -EPERM; + return cap_raised(cred->cap_effective, cap) ? 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)) @@ -74,104 +78,164 @@ int cap_settime(struct timespec *ts, struct timezone *tz) return 0; } -int cap_ptrace (struct task_struct *parent, struct task_struct *child) +/** + * 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) { - /* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */ - if (!cap_issubset(child->cap_permitted, parent->cap_permitted) && - !__capable(parent, CAP_SYS_PTRACE)) - return -EPERM; - return 0; + int ret = 0; + + rcu_read_lock(); + if (!cap_issubset(__task_cred(child)->cap_permitted, + current_cred()->cap_permitted) && + !capable(CAP_SYS_PTRACE)) + ret = -EPERM; + rcu_read_unlock(); + return ret; } -int cap_capget (struct task_struct *target, kernel_cap_t *effective, - kernel_cap_t *inheritable, kernel_cap_t *permitted) +/** + * 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) { - /* Derived from kernel/capability.c:sys_capget. */ - *effective = cap_t (target->cap_effective); - *inheritable = cap_t (target->cap_inheritable); - *permitted = cap_t (target->cap_permitted); - return 0; -} + int ret = 0; -#ifdef CONFIG_SECURITY_FILE_CAPABILITIES + rcu_read_lock(); + if (!cap_issubset(current_cred()->cap_permitted, + __task_cred(parent)->cap_permitted) && + !has_capability(parent, CAP_SYS_PTRACE)) + ret = -EPERM; + rcu_read_unlock(); + return ret; +} -static inline int cap_block_setpcap(struct task_struct *target) +/** + * 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) { - /* - * No support for remote process capability manipulation with - * filesystem capability support. - */ - return (target != current); + 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) { - /* - * return 1 if changes to the inheritable set are limited - * to the old permitted set. +#ifdef CONFIG_SECURITY_FILE_CAPABILITIES + + /* they are so limited unless the current task has the CAP_SETPCAP + * capability */ - return !cap_capable(current, CAP_SETPCAP); + if (cap_capable(current, current_cred(), CAP_SETPCAP, + SECURITY_CAP_AUDIT) == 0) + return 0; +#endif + return 1; } -#else /* ie., ndef CONFIG_SECURITY_FILE_CAPABILITIES */ - -static inline int cap_block_setpcap(struct task_struct *t) { return 0; } -static inline int cap_inh_is_capped(void) { return 1; } - -#endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */ - -int cap_capset_check (struct task_struct *target, kernel_cap_t *effective, - kernel_cap_t *inheritable, kernel_cap_t *permitted) -{ - if (cap_block_setpcap(target)) { - return -EPERM; - } - if (cap_inh_is_capped() - && !cap_issubset(*inheritable, - cap_combine(target->cap_inheritable, - current->cap_permitted))) { +/** + * 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, - cap_combine (target->cap_permitted, - current->cap_permitted))) { + 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)) { + if (!cap_issubset(*effective, *permitted)) return -EPERM; - } + new->cap_effective = *effective; + new->cap_inheritable = *inheritable; + new->cap_permitted = *permitted; return 0; } -void cap_capset_set (struct task_struct *target, kernel_cap_t *effective, - kernel_cap_t *inheritable, kernel_cap_t *permitted) -{ - target->cap_effective = *effective; - target->cap_inheritable = *inheritable; - target->cap_permitted = *permitted; -} - +/* + * Clear proposed capability sets for execve(). + */ static inline void bprm_clear_caps(struct linux_binprm *bprm) { - cap_clear(bprm->cap_inheritable); - cap_clear(bprm->cap_permitted); + cap_clear(bprm->cred->cap_permitted); bprm->cap_effective = false; } #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; int error; - if (!inode->i_op || !inode->i_op->getxattr) + if (!inode->i_op->getxattr) return 0; error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0); @@ -180,79 +244,152 @@ 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; - if (!inode->i_op || !inode->i_op->removexattr) + if (!inode->i_op->removexattr) return 0; return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS); } -static inline int cap_from_disk(struct vfs_cap_data *caps, - struct linux_binprm *bprm, - int size) +/* + * 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 != XATTR_CAPS_SZ) + if (size < sizeof(magic_etc)) return -EINVAL; - magic_etc = le32_to_cpu(caps->magic_etc); + cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc); - switch ((magic_etc & VFS_CAP_REVISION_MASK)) { - case VFS_CAP_REVISION: - if (magic_etc & VFS_CAP_FLAGS_EFFECTIVE) - bprm->cap_effective = true; - else - bprm->cap_effective = false; - bprm->cap_permitted = to_cap_t(le32_to_cpu(caps->permitted)); - bprm->cap_inheritable = to_cap_t(le32_to_cpu(caps->inheritable)); - return 0; + 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; } -/* Locate any VFS capabilities: */ -static int get_file_caps(struct linux_binprm *bprm) +/* + * 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 vfs_cap_data incaps; - struct inode *inode; + struct cpu_vfs_cap_data vcaps; - if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID) { - bprm_clear_caps(bprm); + 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); - inode = dentry->d_inode; - if (!inode->i_op || !inode->i_op->getxattr) - goto out; - rc = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0); - if (rc > 0) { - if (rc == XATTR_CAPS_SZ) - rc = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, - &incaps, XATTR_CAPS_SZ); - else - rc = -EINVAL; - } - if (rc == -ENODATA || rc == -EOPNOTSUPP) { - /* no data, that's ok */ - rc = 0; + 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; } - if (rc < 0) - goto out; - rc = cap_from_disk(&incaps, bprm, rc); - if (rc) + rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective); + if (rc == -EINVAL) printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n", - __FUNCTION__, rc, bprm->filename); + __func__, rc, bprm->filename); out: dput(dentry); @@ -273,130 +410,214 @@ int cap_inode_killpriv(struct dentry *dentry) return 0; } -static inline int get_file_caps(struct linux_binprm *bprm) +int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps) +{ + memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data)); + return -ENODATA; +} + +static inline int get_file_caps(struct linux_binprm *bprm, bool *effective) { bprm_clear_caps(bprm); return 0; } #endif -int cap_bprm_set_security (struct linux_binprm *bprm) +/* + * 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) { + const struct cred *old = current_cred(); + struct cred *new = bprm->cred; + bool effective; int ret; - ret = get_file_caps(bprm); - if (ret) - printk(KERN_NOTICE "%s: get_file_caps returned %d for %s\n", - __FUNCTION__, ret, bprm->filename); + effective = false; + ret = get_file_caps(bprm, &effective); + if (ret < 0) + return ret; - /* To support inheritance of root-permissions and suid-root - * executables under compatibility mode, we raise all three - * capability sets for the file. - * - * If only the real uid is 0, we only raise the inheritable - * and permitted sets of the executable file. - */ - - if (!issecure (SECURE_NOROOT)) { - if (bprm->e_uid == 0 || current->uid == 0) { - cap_set_full (bprm->cap_inheritable); - cap_set_full (bprm->cap_permitted); + if (!issecure(SECURE_NOROOT)) { + /* + * 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 (bprm->e_uid == 0) - bprm->cap_effective = true; + if (new->euid == 0) + effective = true; } - return ret; -} - -void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe) -{ - /* Derived from fs/exec.c:compute_creds. */ - kernel_cap_t new_permitted, working; - - new_permitted = cap_intersect (bprm->cap_permitted, cap_bset); - working = cap_intersect (bprm->cap_inheritable, - current->cap_inheritable); - new_permitted = cap_combine (new_permitted, working); - - if (bprm->e_uid != current->uid || bprm->e_gid != current->gid || - !cap_issubset (new_permitted, current->cap_permitted)) { - set_dumpable(current->mm, suid_dumpable); - current->pdeath_signal = 0; - - if (unsafe & ~LSM_UNSAFE_PTRACE_CAP) { - if (!capable(CAP_SETUID)) { - bprm->e_uid = current->uid; - bprm->e_gid = current->gid; - } - if (!capable (CAP_SETPCAP)) { - new_permitted = cap_intersect (new_permitted, - current->cap_permitted); - } + /* 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; } + if (cap_limit_ptraced_target()) + new->cap_permitted = cap_intersect(new->cap_permitted, + old->cap_permitted); } - current->suid = current->euid = current->fsuid = bprm->e_uid; - current->sgid = current->egid = current->fsgid = bprm->e_gid; + new->suid = new->fsuid = new->euid; + new->sgid = new->fsgid = new->egid; - /* For init, we want to retain the capabilities set - * in the init_task struct. Thus we skip the usual - * capability rules */ + /* For init, we want to retain the capabilities set in the initial + * task. Thus we skip the usual capability rules + */ if (!is_global_init(current)) { - current->cap_permitted = new_permitted; - current->cap_effective = bprm->cap_effective ? - new_permitted : 0; + if (effective) + new->cap_effective = new->cap_permitted; + else + cap_clear(new->cap_effective); } + bprm->cap_effective = effective; - /* AUD: Audit candidate if current->cap_effective is set */ + /* + * 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; + } + } - current->keep_capabilities = 0; + new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS); + return 0; } -int cap_bprm_secureexec (struct linux_binprm *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) { - if (current->uid != 0) { + const struct cred *cred = current_cred(); + + if (cred->uid != 0) { if (bprm->cap_effective) return 1; - if (!cap_isclear(bprm->cap_permitted)) - return 1; - if (!cap_isclear(bprm->cap_inheritable)) + if (!cap_isclear(cred->cap_permitted)) return 1; } - return (current->euid != current->uid || - current->egid != current->gid); + return (cred->euid != cred->uid || + cred->egid != cred->gid); } -int cap_inode_setxattr(struct dentry *dentry, char *name, void *value, - size_t size, int flags) +/** + * 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; - } 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; } -int cap_inode_removexattr(struct dentry *dentry, char *name) +/** + * 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. * @@ -410,10 +631,10 @@ int cap_inode_removexattr(struct dentry *dentry, char *name) * 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 + * fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should * never happen. * - * -astor + * -astor * * cevans - New behaviour, Oct '99 * A process may, via prctl(), elect to keep its capabilities when it @@ -425,59 +646,60 @@ int cap_inode_removexattr(struct dentry *dentry, char *name) * files.. * Thanks to Olaf Kirch and Peter Benie for spotting this. */ -static inline void cap_emulate_setxuid (int old_ruid, int old_euid, - int old_suid) -{ - if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) && - (current->uid != 0 && current->euid != 0 && current->suid != 0) && - !current->keep_capabilities) { - cap_clear (current->cap_permitted); - cap_clear (current->cap_effective); - } - if (old_euid == 0 && current->euid != 0) { - cap_clear (current->cap_effective); - } - if (old_euid != 0 && current->euid == 0) { - current->cap_effective = current->cap_permitted; +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; } -int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid, - int flags) +/** + * 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. */ - if (!issecure (SECURE_NO_SETUID_FIXUP)) { - cap_emulate_setxuid (old_ruid, old_euid, old_suid); - } + /* 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: - { - uid_t old_fsuid = old_ruid; - - /* Copied from kernel/sys.c:setfsuid. */ - /* - * 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 && current->fsuid != 0) { - cap_t (current->cap_effective) &= - ~CAP_FS_MASK; - } - if (old_fsuid != 0 && current->fsuid == 0) { - cap_t (current->cap_effective) |= - (cap_t (current->cap_permitted) & - CAP_FS_MASK); - } - } - 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; } @@ -496,55 +718,76 @@ int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid, * yet with increased caps. * So we check for increased caps on the target process. */ -static inline int cap_safe_nice(struct task_struct *p) +static int cap_safe_nice(struct task_struct *p) { - if (!cap_issubset(p->cap_permitted, current->cap_permitted) && - !__capable(current, CAP_SYS_NICE)) + 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; } -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); } -int cap_task_kill(struct task_struct *p, struct siginfo *info, - int sig, u32 secid) +/* + * 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 (info != SEND_SIG_NOINFO && (is_si_special(info) || SI_FROMKERNEL(info))) - return 0; - - /* sigcont is permitted within same session */ - if (sig == SIGCONT && (task_session_nr(current) == task_session_nr(p))) - return 0; - - if (secid) - /* - * Signal sent as a particular user. - * Capabilities are ignored. May be wrong, but it's the - * only thing we can do at the moment. - * Used only by usb drivers? - */ - return 0; - if (cap_issubset(p->cap_permitted, current->cap_permitted)) - return 0; - if (capable(CAP_KILL)) - return 0; + if (!capable(CAP_SETPCAP)) + return -EPERM; + if (!cap_valid(cap)) + return -EINVAL; - return -EPERM; + cap_lower(new->cap_bset, cap); + return 0; } + #else int cap_task_setscheduler (struct task_struct *p, int policy, struct sched_param *lp) @@ -559,35 +802,153 @@ int cap_task_setnice (struct task_struct *p, int nice) { return 0; } -int cap_task_kill(struct task_struct *p, struct siginfo *info, - int sig, u32 secid) -{ - return 0; -} #endif -void cap_task_reparent_to_init (struct task_struct *p) +/** + * 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) { - p->cap_effective = CAP_INIT_EFF_SET; - p->cap_inheritable = CAP_INIT_INH_SET; - p->cap_permitted = CAP_FULL_SET; - p->keep_capabilities = 0; - return; + 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; + +#ifdef CONFIG_SECURITY_FILE_CAPABILITIES + 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(), 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; + +#endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */ + + 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; } -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; - if (cap_capable(current, CAP_SYS_ADMIN) == 0) + if (cap_capable(current, current_cred(), CAP_SYS_ADMIN, + SECURITY_CAP_NOAUDIT) == 0) cap_sys_admin = 1; return __vm_enough_memory(mm, pages, cap_sys_admin); } -