diff options
| -rw-r--r-- | Documentation/userspace-api/lsm.rst | 70 | ||||
| -rw-r--r-- | include/linux/lsm_hook_defs.h | 4 | ||||
| -rw-r--r-- | include/linux/lsm_hooks.h | 1 | ||||
| -rw-r--r-- | include/linux/security.h | 19 | ||||
| -rw-r--r-- | include/linux/syscalls.h | 5 | ||||
| -rw-r--r-- | include/uapi/linux/lsm.h | 36 | ||||
| -rw-r--r-- | kernel/sys_ni.c | 2 | ||||
| -rw-r--r-- | security/Makefile | 1 | ||||
| -rw-r--r-- | security/lsm_syscalls.c | 57 | ||||
| -rw-r--r-- | security/security.c | 152 |
10 files changed, 347 insertions, 0 deletions
diff --git a/Documentation/userspace-api/lsm.rst b/Documentation/userspace-api/lsm.rst new file mode 100644 index 000000000000..f8499f3e2826 --- /dev/null +++ b/Documentation/userspace-api/lsm.rst @@ -0,0 +1,70 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. Copyright (C) 2022 Casey Schaufler <casey@schaufler-ca.com> +.. Copyright (C) 2022 Intel Corporation + +===================================== +Linux Security Modules +===================================== + +:Author: Casey Schaufler +:Date: July 2023 + +Linux security modules (LSM) provide a mechanism to implement +additional access controls to the Linux security policies. + +The various security modules may support any of these attributes: + +``LSM_ATTR_CURRENT`` is the current, active security context of the +process. +The proc filesystem provides this value in ``/proc/self/attr/current``. +This is supported by the SELinux, Smack and AppArmor security modules. +Smack also provides this value in ``/proc/self/attr/smack/current``. +AppArmor also provides this value in ``/proc/self/attr/apparmor/current``. + +``LSM_ATTR_EXEC`` is the security context of the process at the time the +current image was executed. +The proc filesystem provides this value in ``/proc/self/attr/exec``. +This is supported by the SELinux and AppArmor security modules. +AppArmor also provides this value in ``/proc/self/attr/apparmor/exec``. + +``LSM_ATTR_FSCREATE`` is the security context of the process used when +creating file system objects. +The proc filesystem provides this value in ``/proc/self/attr/fscreate``. +This is supported by the SELinux security module. + +``LSM_ATTR_KEYCREATE`` is the security context of the process used when +creating key objects. +The proc filesystem provides this value in ``/proc/self/attr/keycreate``. +This is supported by the SELinux security module. + +``LSM_ATTR_PREV`` is the security context of the process at the time the +current security context was set. +The proc filesystem provides this value in ``/proc/self/attr/prev``. +This is supported by the SELinux and AppArmor security modules. +AppArmor also provides this value in ``/proc/self/attr/apparmor/prev``. + +``LSM_ATTR_SOCKCREATE`` is the security context of the process used when +creating socket objects. +The proc filesystem provides this value in ``/proc/self/attr/sockcreate``. +This is supported by the SELinux security module. + +Kernel interface +================ + +Set a security attribute of the current process +----------------------------------------------- + +.. kernel-doc:: security/lsm_syscalls.c + :identifiers: sys_lsm_set_self_attr + +Get the specified security attributes of the current process +------------------------------------------------------------ + +.. kernel-doc:: security/lsm_syscalls.c + :identifiers: sys_lsm_get_self_attr + +Additional documentation +======================== + +* Documentation/security/lsm.rst +* Documentation/security/lsm-development.rst diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index ff217a5ce552..c925a0d26edf 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -262,6 +262,10 @@ LSM_HOOK(int, 0, sem_semop, struct kern_ipc_perm *perm, struct sembuf *sops, LSM_HOOK(int, 0, netlink_send, struct sock *sk, struct sk_buff *skb) LSM_HOOK(void, LSM_RET_VOID, d_instantiate, struct dentry *dentry, struct inode *inode) +LSM_HOOK(int, -EOPNOTSUPP, getselfattr, unsigned int attr, + struct lsm_ctx __user *ctx, size_t *size, u32 flags) +LSM_HOOK(int, -EOPNOTSUPP, setselfattr, unsigned int attr, + struct lsm_ctx *ctx, size_t size, u32 flags) LSM_HOOK(int, -EINVAL, getprocattr, struct task_struct *p, const char *name, char **value) LSM_HOOK(int, -EINVAL, setprocattr, const char *name, void *value, size_t size) diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 7f0adb33caaa..a2ade0ffe9e7 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -25,6 +25,7 @@ #ifndef __LINUX_LSM_HOOKS_H #define __LINUX_LSM_HOOKS_H +#include <uapi/linux/lsm.h> #include <linux/security.h> #include <linux/init.h> #include <linux/rculist.h> diff --git a/include/linux/security.h b/include/linux/security.h index c81bca77f4f2..dd1fe487385d 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -60,6 +60,7 @@ struct fs_parameter; enum fs_value_type; struct watch; struct watch_notification; +struct lsm_ctx; /* Default (no) options for the capable function */ #define CAP_OPT_NONE 0x0 @@ -472,6 +473,10 @@ int security_sem_semctl(struct kern_ipc_perm *sma, int cmd); int security_sem_semop(struct kern_ipc_perm *sma, struct sembuf *sops, unsigned nsops, int alter); void security_d_instantiate(struct dentry *dentry, struct inode *inode); +int security_getselfattr(unsigned int attr, struct lsm_ctx __user *ctx, + size_t __user *size, u32 flags); +int security_setselfattr(unsigned int attr, struct lsm_ctx __user *ctx, + size_t size, u32 flags); int security_getprocattr(struct task_struct *p, int lsmid, const char *name, char **value); int security_setprocattr(int lsmid, const char *name, void *value, size_t size); @@ -1338,6 +1343,20 @@ static inline void security_d_instantiate(struct dentry *dentry, struct inode *inode) { } +static inline int security_getselfattr(unsigned int attr, + struct lsm_ctx __user *ctx, + size_t __user *size, u32 flags) +{ + return -EOPNOTSUPP; +} + +static inline int security_setselfattr(unsigned int attr, + struct lsm_ctx __user *ctx, + size_t size, u32 flags) +{ + return -EOPNOTSUPP; +} + static inline int security_getprocattr(struct task_struct *p, int lsmid, const char *name, char **value) { diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index fd9d12de7e92..4e1e56a24f1e 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -71,6 +71,7 @@ struct clone_args; struct open_how; struct mount_attr; struct landlock_ruleset_attr; +struct lsm_ctx; enum landlock_rule_type; struct cachestat_range; struct cachestat; @@ -949,6 +950,10 @@ asmlinkage long sys_cachestat(unsigned int fd, struct cachestat_range __user *cstat_range, struct cachestat __user *cstat, unsigned int flags); asmlinkage long sys_map_shadow_stack(unsigned long addr, unsigned long size, unsigned int flags); +asmlinkage long sys_lsm_get_self_attr(unsigned int attr, struct lsm_ctx *ctx, + size_t *size, __u32 flags); +asmlinkage long sys_lsm_set_self_attr(unsigned int attr, struct lsm_ctx *ctx, + size_t size, __u32 flags); /* * Architecture-specific system calls diff --git a/include/uapi/linux/lsm.h b/include/uapi/linux/lsm.h index f27c9a9cc376..eeda59a77c02 100644 --- a/include/uapi/linux/lsm.h +++ b/include/uapi/linux/lsm.h @@ -9,6 +9,36 @@ #ifndef _UAPI_LINUX_LSM_H #define _UAPI_LINUX_LSM_H +#include <linux/types.h> +#include <linux/unistd.h> + +/** + * struct lsm_ctx - LSM context information + * @id: the LSM id number, see LSM_ID_XXX + * @flags: LSM specific flags + * @len: length of the lsm_ctx struct, @ctx and any other data or padding + * @ctx_len: the size of @ctx + * @ctx: the LSM context value + * + * The @len field MUST be equal to the size of the lsm_ctx struct + * plus any additional padding and/or data placed after @ctx. + * + * In all cases @ctx_len MUST be equal to the length of @ctx. + * If @ctx is a string value it should be nul terminated with + * @ctx_len equal to `strlen(@ctx) + 1`. Binary values are + * supported. + * + * The @flags and @ctx fields SHOULD only be interpreted by the + * LSM specified by @id; they MUST be set to zero/0 when not used. + */ +struct lsm_ctx { + __u64 id; + __u64 flags; + __u64 len; + __u64 ctx_len; + __u8 ctx[]; +}; + /* * ID tokens to identify Linux Security Modules (LSMs) * @@ -51,4 +81,10 @@ #define LSM_ATTR_PREV 104 #define LSM_ATTR_SOCKCREATE 105 +/* + * LSM_FLAG_XXX definitions identify special handling instructions + * for the API. + */ +#define LSM_FLAG_SINGLE 0x0001 + #endif /* _UAPI_LINUX_LSM_H */ diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c index e1a6e3c675c0..1f61b8452a6e 100644 --- a/kernel/sys_ni.c +++ b/kernel/sys_ni.c @@ -171,6 +171,8 @@ COND_SYSCALL(landlock_add_rule); COND_SYSCALL(landlock_restrict_self); COND_SYSCALL(fadvise64_64); COND_SYSCALL_COMPAT(fadvise64_64); +COND_SYSCALL(lsm_get_self_attr); +COND_SYSCALL(lsm_set_self_attr); /* CONFIG_MMU only */ COND_SYSCALL(swapon); diff --git a/security/Makefile b/security/Makefile index 18121f8f85cd..59f238490665 100644 --- a/security/Makefile +++ b/security/Makefile @@ -7,6 +7,7 @@ obj-$(CONFIG_KEYS) += keys/ # always enable default capabilities obj-y += commoncap.o +obj-$(CONFIG_SECURITY) += lsm_syscalls.o obj-$(CONFIG_MMU) += min_addr.o # Object file lists diff --git a/security/lsm_syscalls.c b/security/lsm_syscalls.c new file mode 100644 index 000000000000..226ae80d9683 --- /dev/null +++ b/security/lsm_syscalls.c @@ -0,0 +1,57 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * System calls implementing the Linux Security Module API. + * + * Copyright (C) 2022 Casey Schaufler <casey@schaufler-ca.com> + * Copyright (C) 2022 Intel Corporation + */ + +#include <asm/current.h> +#include <linux/compiler_types.h> +#include <linux/err.h> +#include <linux/errno.h> +#include <linux/security.h> +#include <linux/stddef.h> +#include <linux/syscalls.h> +#include <linux/types.h> +#include <linux/lsm_hooks.h> +#include <uapi/linux/lsm.h> + +/** + * sys_lsm_set_self_attr - Set current task's security module attribute + * @attr: which attribute to set + * @ctx: the LSM contexts + * @size: size of @ctx + * @flags: reserved for future use + * + * Sets the calling task's LSM context. On success this function + * returns 0. If the attribute specified cannot be set a negative + * value indicating the reason for the error is returned. + */ +SYSCALL_DEFINE4(lsm_set_self_attr, unsigned int, attr, struct lsm_ctx __user *, + ctx, size_t, size, u32, flags) +{ + return security_setselfattr(attr, ctx, size, flags); +} + +/** + * sys_lsm_get_self_attr - Return current task's security module attributes + * @attr: which attribute to return + * @ctx: the user-space destination for the information, or NULL + * @size: pointer to the size of space available to receive the data + * @flags: special handling options. LSM_FLAG_SINGLE indicates that only + * attributes associated with the LSM identified in the passed @ctx be + * reported. + * + * Returns the calling task's LSM contexts. On success this + * function returns the number of @ctx array elements. This value + * may be zero if there are no LSM contexts assigned. If @size is + * insufficient to contain the return data -E2BIG is returned and + * @size is set to the minimum required size. In all other cases + * a negative value indicating the error is returned. + */ +SYSCALL_DEFINE4(lsm_get_self_attr, unsigned int, attr, struct lsm_ctx __user *, + ctx, size_t __user *, size, u32, flags) +{ + return security_getselfattr(attr, ctx, size, flags); +} diff --git a/security/security.c b/security/security.c index c66f9faefa40..9757d009113f 100644 --- a/security/security.c +++ b/security/security.c @@ -3837,6 +3837,158 @@ void security_d_instantiate(struct dentry *dentry, struct inode *inode) } EXPORT_SYMBOL(security_d_instantiate); +/* + * Please keep this in sync with it's counterpart in security/lsm_syscalls.c + */ + +/** + * security_getselfattr - Read an LSM attribute of the current process. + * @attr: which attribute to return + * @uctx: the user-space destination for the information, or NULL + * @size: pointer to the size of space available to receive the data + * @flags: special handling options. LSM_FLAG_SINGLE indicates that only + * attributes associated with the LSM identified in the passed @ctx be + * reported. + * + * A NULL value for @uctx can be used to get both the number of attributes + * and the size of the data. + * + * Returns the number of attributes found on success, negative value + * on error. @size is reset to the total size of the data. + * If @size is insufficient to contain the data -E2BIG is returned. + */ +int security_getselfattr(unsigned int attr, struct lsm_ctx __user *uctx, + size_t __user *size, u32 flags) +{ + struct security_hook_list *hp; + struct lsm_ctx lctx = { .id = LSM_ID_UNDEF, }; + u8 __user *base = (u8 __user *)uctx; + size_t total = 0; + size_t entrysize; + size_t left; + bool toobig = false; + bool single = false; + int count = 0; + int rc; + + if (attr == LSM_ATTR_UNDEF) + return -EINVAL; + if (size == NULL) + return -EINVAL; + if (get_user(left, size)) + return -EFAULT; + + if (flags) { + /* + * Only flag supported is LSM_FLAG_SINGLE + */ + if (flags != LSM_FLAG_SINGLE) + return -EINVAL; + if (uctx && copy_from_user(&lctx, uctx, sizeof(lctx))) + return -EFAULT; + /* + * If the LSM ID isn't specified it is an error. + */ + if (lctx.id == LSM_ID_UNDEF) + return -EINVAL; + single = true; + } + + /* + * In the usual case gather all the data from the LSMs. + * In the single case only get the data from the LSM specified. + */ + hlist_for_each_entry(hp, &security_hook_heads.getselfattr, list) { + if (single && lctx.id != hp->lsmid->id) + continue; + entrysize = left; + if (base) + uctx = (struct lsm_ctx __user *)(base + total); + rc = hp->hook.getselfattr(attr, uctx, &entrysize, flags); + if (rc == -EOPNOTSUPP) { + rc = 0; + continue; + } + if (rc == -E2BIG) { + toobig = true; + left = 0; + } else if (rc < 0) + return rc; + else + left -= entrysize; + + total += entrysize; + count += rc; + if (single) + break; + } + if (put_user(total, size)) + return -EFAULT; + if (toobig) + return -E2BIG; + if (count == 0) + return LSM_RET_DEFAULT(getselfattr); + return count; +} + +/* + * Please keep this in sync with it's counterpart in security/lsm_syscalls.c + */ + +/** + * security_setselfattr - Set an LSM attribute on the current process. + * @attr: which attribute to set + * @uctx: the user-space source for the information + * @size: the size of the data + * @flags: reserved for future use, must be 0 + * + * Set an LSM attribute for the current process. The LSM, attribute + * and new value are included in @uctx. + * + * Returns 0 on success, -EINVAL if the input is inconsistent, -EFAULT + * if the user buffer is inaccessible, E2BIG if size is too big, or an + * LSM specific failure. + */ +int security_setselfattr(unsigned int attr, struct lsm_ctx __user *uctx, + size_t size, u32 flags) +{ + struct security_hook_list *hp; + struct lsm_ctx *lctx; + int rc = LSM_RET_DEFAULT(setselfattr); + + if (flags) + return -EINVAL; + if (size < sizeof(*lctx)) + return -EINVAL; + if (size > PAGE_SIZE) + return -E2BIG; + + lctx = kmalloc(size, GFP_KERNEL); + if (lctx == NULL) + return -ENOMEM; + + if (copy_from_user(lctx, uctx, size)) { + rc = -EFAULT; + goto free_out; + } + + if (size < lctx->len || size < lctx->ctx_len + sizeof(*lctx) || + lctx->len < lctx->ctx_len + sizeof(*lctx)) { + rc = -EINVAL; + goto free_out; + } + + hlist_for_each_entry(hp, &security_hook_heads.setselfattr, list) + if ((hp->lsmid->id) == lctx->id) { + rc = hp->hook.setselfattr(attr, lctx, size, flags); + break; + } + +free_out: + kfree(lctx); + return rc; +} + /** * security_getprocattr() - Read an attribute for a task * @p: the task |