From 377179cd28cd417dcfb4396edb824533431e607e Mon Sep 17 00:00:00 2001 From: Mimi Zohar Date: Fri, 13 Jul 2018 14:05:56 -0400 Subject: security: define new LSM hook named security_kernel_load_data Differentiate between the kernel reading a file specified by userspace from the kernel loading a buffer containing data provided by userspace. This patch defines a new LSM hook named security_kernel_load_data(). Signed-off-by: Mimi Zohar Cc: Eric Biederman Cc: Luis R. Rodriguez Cc: Kees Cook Cc: Casey Schaufler Acked-by: Serge Hallyn Acked-by: Kees Cook Signed-off-by: James Morris --- include/linux/lsm_hooks.h | 6 ++++++ include/linux/security.h | 27 +++++++++++++++++++++++++++ 2 files changed, 33 insertions(+) (limited to 'include') diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 8f1131c8dd54..a08bc2587b96 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -576,6 +576,10 @@ * userspace to load a kernel module with the given name. * @kmod_name name of the module requested by the kernel * Return 0 if successful. + * @kernel_load_data: + * Load data provided by userspace. + * @id kernel load data identifier + * Return 0 if permission is granted. * @kernel_read_file: * Read a file specified by userspace. * @file contains the file structure pointing to the file being read @@ -1582,6 +1586,7 @@ union security_list_options { int (*kernel_act_as)(struct cred *new, u32 secid); int (*kernel_create_files_as)(struct cred *new, struct inode *inode); int (*kernel_module_request)(char *kmod_name); + int (*kernel_load_data)(enum kernel_load_data_id id); int (*kernel_read_file)(struct file *file, enum kernel_read_file_id id); int (*kernel_post_read_file)(struct file *file, char *buf, loff_t size, enum kernel_read_file_id id); @@ -1872,6 +1877,7 @@ struct security_hook_heads { struct hlist_head cred_getsecid; struct hlist_head kernel_act_as; struct hlist_head kernel_create_files_as; + struct hlist_head kernel_load_data; struct hlist_head kernel_read_file; struct hlist_head kernel_post_read_file; struct hlist_head kernel_module_request; diff --git a/include/linux/security.h b/include/linux/security.h index 63030c85ee19..3410acfe139c 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -159,6 +159,27 @@ extern int mmap_min_addr_handler(struct ctl_table *table, int write, typedef int (*initxattrs) (struct inode *inode, const struct xattr *xattr_array, void *fs_data); + +/* Keep the kernel_load_data_id enum in sync with kernel_read_file_id */ +#define __data_id_enumify(ENUM, dummy) LOADING_ ## ENUM, +#define __data_id_stringify(dummy, str) #str, + +enum kernel_load_data_id { + __kernel_read_file_id(__data_id_enumify) +}; + +static const char * const kernel_load_data_str[] = { + __kernel_read_file_id(__data_id_stringify) +}; + +static inline const char *kernel_load_data_id_str(enum kernel_load_data_id id) +{ + if ((unsigned)id >= LOADING_MAX_ID) + return kernel_load_data_str[LOADING_UNKNOWN]; + + return kernel_load_data_str[id]; +} + #ifdef CONFIG_SECURITY struct security_mnt_opts { @@ -320,6 +341,7 @@ void security_cred_getsecid(const struct cred *c, u32 *secid); int security_kernel_act_as(struct cred *new, u32 secid); int security_kernel_create_files_as(struct cred *new, struct inode *inode); int security_kernel_module_request(char *kmod_name); +int security_kernel_load_data(enum kernel_load_data_id id); int security_kernel_read_file(struct file *file, enum kernel_read_file_id id); int security_kernel_post_read_file(struct file *file, char *buf, loff_t size, enum kernel_read_file_id id); @@ -909,6 +931,11 @@ static inline int security_kernel_module_request(char *kmod_name) return 0; } +static inline int security_kernel_load_data(enum kernel_load_data_id id) +{ + return 0; +} + static inline int security_kernel_read_file(struct file *file, enum kernel_read_file_id id) { -- cgit v1.2.3 From 16c267aac86b463b1fcccd43c89f4c8e5c5c86fa Mon Sep 17 00:00:00 2001 From: Mimi Zohar Date: Fri, 13 Jul 2018 14:05:58 -0400 Subject: ima: based on policy require signed kexec kernel images The original kexec_load syscall can not verify file signatures, nor can the kexec image be measured. Based on policy, deny the kexec_load syscall. Signed-off-by: Mimi Zohar Cc: Eric Biederman Cc: Kees Cook Reviewed-by: Kees Cook Signed-off-by: James Morris --- include/linux/ima.h | 7 +++++++ security/integrity/ima/ima.h | 1 + security/integrity/ima/ima_main.c | 27 +++++++++++++++++++++++++++ security/integrity/ima/ima_policy.c | 2 ++ security/security.c | 7 ++++++- 5 files changed, 43 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/ima.h b/include/linux/ima.h index 0e4647e0eb60..84806b54b50a 100644 --- a/include/linux/ima.h +++ b/include/linux/ima.h @@ -11,6 +11,7 @@ #define _LINUX_IMA_H #include +#include #include struct linux_binprm; @@ -19,6 +20,7 @@ extern int ima_bprm_check(struct linux_binprm *bprm); extern int ima_file_check(struct file *file, int mask, int opened); extern void ima_file_free(struct file *file); extern int ima_file_mmap(struct file *file, unsigned long prot); +extern int ima_load_data(enum kernel_load_data_id id); extern int ima_read_file(struct file *file, enum kernel_read_file_id id); extern int ima_post_read_file(struct file *file, void *buf, loff_t size, enum kernel_read_file_id id); @@ -49,6 +51,11 @@ static inline int ima_file_mmap(struct file *file, unsigned long prot) return 0; } +static inline int ima_load_data(enum kernel_load_data_id id) +{ + return 0; +} + static inline int ima_read_file(struct file *file, enum kernel_read_file_id id) { return 0; diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h index 354bb5716ce3..78c15264b17b 100644 --- a/security/integrity/ima/ima.h +++ b/security/integrity/ima/ima.h @@ -232,6 +232,7 @@ int ima_policy_show(struct seq_file *m, void *v); #define IMA_APPRAISE_MODULES 0x08 #define IMA_APPRAISE_FIRMWARE 0x10 #define IMA_APPRAISE_POLICY 0x20 +#define IMA_APPRAISE_KEXEC 0x40 #ifdef CONFIG_IMA_APPRAISE int ima_appraise_measurement(enum ima_hooks func, diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index dca44cf7838e..71fecfef0939 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -496,6 +496,33 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size, MAY_READ, func, 0); } +/** + * ima_load_data - appraise decision based on policy + * @id: kernel load data caller identifier + * + * Callers of this LSM hook can not measure, appraise, or audit the + * data provided by userspace. Enforce policy rules requring a file + * signature (eg. kexec'ed kernel image). + * + * For permission return 0, otherwise return -EACCES. + */ +int ima_load_data(enum kernel_load_data_id id) +{ + if ((ima_appraise & IMA_APPRAISE_ENFORCE) != IMA_APPRAISE_ENFORCE) + return 0; + + switch (id) { + case LOADING_KEXEC_IMAGE: + if (ima_appraise & IMA_APPRAISE_KEXEC) { + pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n"); + return -EACCES; /* INTEGRITY_UNKNOWN */ + } + default: + break; + } + return 0; +} + static int __init init_ima(void) { int error; diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index cdcc9a7b4e24..d5b4958decc5 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -448,6 +448,8 @@ static int ima_appraise_flag(enum ima_hooks func) return IMA_APPRAISE_FIRMWARE; else if (func == POLICY_CHECK) return IMA_APPRAISE_POLICY; + else if (func == KEXEC_KERNEL_CHECK) + return IMA_APPRAISE_KEXEC; return 0; } diff --git a/security/security.c b/security/security.c index c2de2f134854..4927e7cc7d96 100644 --- a/security/security.c +++ b/security/security.c @@ -1058,7 +1058,12 @@ EXPORT_SYMBOL_GPL(security_kernel_post_read_file); int security_kernel_load_data(enum kernel_load_data_id id) { - return call_int_hook(kernel_load_data, 0, id); + int ret; + + ret = call_int_hook(kernel_load_data, 0, id); + if (ret) + return ret; + return ima_load_data(id); } int security_task_fix_setuid(struct cred *new, const struct cred *old, -- cgit v1.2.3