There are a few places in the kernel where LSMs would like to have visibility into the contents of a kernel buffer that has been loaded or read. While security_kernel_post_read_file() (which includes the buffer) exists as a pairing for security_kernel_read_file(), no such hook exists to pair with security_kernel_load_data().
Earlier proposals for just using security_kernel_post_read_file() with a NULL file argument were rejected (i.e. "file" should always be valid for the security_..._file hooks, but it appears at least one case was left in the kernel during earlier refactoring. (This will be fixed in a subsequent patch.)
Since not all cases of security_kernel_load_data() can have a single contiguous buffer made available to the LSM hook (e.g. kexec image segments are separately loaded), there needs to be a way for the LSM to reason about its expectations of the hook coverage. In order to handle this, add a "contents" argument to the "kernel_load_data" hook that indicates if the newly added "kernel_post_load_data" hook will be called with the full contents once loaded. That way, LSMs requiring full contents can choose to unilaterally reject "kernel_load_data" with contents=false (which is effectively the existing hook coverage), but when contents=true they can allow it and later evaluate the "kernel_post_load_data" hook once the buffer is loaded.
With this change, LSMs can gain coverage over non-file-backed data loads (e.g. init_module(2) and firmware userspace helper), which will happen in subsequent patches.
Additionally prepare IMA to start processing these cases.
Signed-off-by: Kees Cook keescook@chromium.org Reviewed-by: KP Singh kpsingh@google.com --- drivers/base/firmware_loader/fallback.c | 2 +- .../base/firmware_loader/fallback_platform.c | 2 +- include/linux/ima.h | 13 ++++++++-- include/linux/lsm_hook_defs.h | 4 +++- include/linux/lsm_hooks.h | 10 ++++++++ include/linux/security.h | 14 +++++++++-- kernel/kexec.c | 2 +- kernel/module.c | 2 +- security/integrity/ima/ima_main.c | 24 ++++++++++++++++++- security/loadpin/loadpin.c | 2 +- security/security.c | 20 +++++++++++++--- security/selinux/hooks.c | 2 +- 12 files changed, 82 insertions(+), 15 deletions(-)
diff --git a/drivers/base/firmware_loader/fallback.c b/drivers/base/firmware_loader/fallback.c index 283ca2de76d4..bff4717cc6b5 100644 --- a/drivers/base/firmware_loader/fallback.c +++ b/drivers/base/firmware_loader/fallback.c @@ -613,7 +613,7 @@ static bool fw_run_sysfs_fallback(u32 opt_flags) return false;
/* Also permit LSMs and IMA to fail firmware sysfs fallback */ - ret = security_kernel_load_data(LOADING_FIRMWARE); + ret = security_kernel_load_data(LOADING_FIRMWARE, false); if (ret < 0) return false;
diff --git a/drivers/base/firmware_loader/fallback_platform.c b/drivers/base/firmware_loader/fallback_platform.c index 6958ab1a8059..a12c79d47efc 100644 --- a/drivers/base/firmware_loader/fallback_platform.c +++ b/drivers/base/firmware_loader/fallback_platform.c @@ -17,7 +17,7 @@ int firmware_fallback_platform(struct fw_priv *fw_priv, u32 opt_flags) if (!(opt_flags & FW_OPT_FALLBACK_PLATFORM)) return -ENOENT;
- rc = security_kernel_load_data(LOADING_FIRMWARE); + rc = security_kernel_load_data(LOADING_FIRMWARE, false); if (rc) return rc;
diff --git a/include/linux/ima.h b/include/linux/ima.h index 64804f78408b..af9fb8c5f16a 100644 --- a/include/linux/ima.h +++ b/include/linux/ima.h @@ -20,7 +20,9 @@ extern void ima_post_create_tmpfile(struct inode *inode); extern void ima_file_free(struct file *file); extern int ima_file_mmap(struct file *file, unsigned long prot); extern int ima_file_mprotect(struct vm_area_struct *vma, unsigned long prot); -extern int ima_load_data(enum kernel_load_data_id id); +extern int ima_load_data(enum kernel_load_data_id id, bool contents); +extern int ima_post_load_data(char *buf, loff_t size, + enum kernel_load_data_id id, char *description); 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); @@ -78,7 +80,14 @@ static inline int ima_file_mprotect(struct vm_area_struct *vma, return 0; }
-static inline int ima_load_data(enum kernel_load_data_id id) +static inline int ima_load_data(enum kernel_load_data_id id, bool contents) +{ + return 0; +} + +static inline int ima_post_load_data(char *buf, loff_t size, + enum kernel_load_data_id id, + char *description) { return 0; } diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index 2a8c74d99015..83c6f1f5cc1e 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -184,7 +184,9 @@ LSM_HOOK(void, LSM_RET_VOID, cred_getsecid, const struct cred *c, u32 *secid) LSM_HOOK(int, 0, kernel_act_as, struct cred *new, u32 secid) LSM_HOOK(int, 0, kernel_create_files_as, struct cred *new, struct inode *inode) LSM_HOOK(int, 0, kernel_module_request, char *kmod_name) -LSM_HOOK(int, 0, kernel_load_data, enum kernel_load_data_id id) +LSM_HOOK(int, 0, kernel_load_data, enum kernel_load_data_id id, bool contents) +LSM_HOOK(int, 0, kernel_post_load_data, char *buf, loff_t size, + enum kernel_read_file_id id, char *description) LSM_HOOK(int, 0, kernel_read_file, struct file *file, enum kernel_read_file_id id) LSM_HOOK(int, 0, kernel_post_read_file, struct file *file, char *buf, diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 9e2e3e63719d..6bb4f1a0158c 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -635,7 +635,17 @@ * @kernel_load_data: * Load data provided by userspace. * @id kernel load data identifier + * @contents if a subsequent @kernel_post_load_data will be called. * Return 0 if permission is granted. + * @kernel_post_load_data: + * Load data provided by a non-file source (usually userspace buffer). + * @buf pointer to buffer containing the data contents. + * @size length of the data contents. + * @id kernel load data identifier + * @description a text description of what was loaded, @id-specific + * Return 0 if permission is granted. + * This must be paired with a prior @kernel_load_data call that had + * @contents set to true. * @kernel_read_file: * Read a file specified by userspace. * @file contains the file structure pointing to the file being read diff --git a/include/linux/security.h b/include/linux/security.h index 42df0d9b4c37..51c8e4e6b7cc 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -387,7 +387,10 @@ 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_load_data(enum kernel_load_data_id id, bool contents); +int security_kernel_post_load_data(char *buf, loff_t size, + enum kernel_load_data_id id, + char *description); 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); @@ -1014,7 +1017,14 @@ 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) +static inline int security_kernel_load_data(enum kernel_load_data_id id, bool contents) +{ + return 0; +} + +static inline int security_kernel_post_load_data(char *buf, loff_t size, + enum kernel_load_data_id id, + char *description) { return 0; } diff --git a/kernel/kexec.c b/kernel/kexec.c index f977786fe498..c82c6c06f051 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -205,7 +205,7 @@ static inline int kexec_load_check(unsigned long nr_segments, return -EPERM;
/* Permit LSMs and IMA to fail the kexec */ - result = security_kernel_load_data(LOADING_KEXEC_IMAGE); + result = security_kernel_load_data(LOADING_KEXEC_IMAGE, false); if (result < 0) return result;
diff --git a/kernel/module.c b/kernel/module.c index 0f11eaed047e..f47209e0fde6 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -3014,7 +3014,7 @@ static int copy_module_from_user(const void __user *umod, unsigned long len, if (info->len < sizeof(*(info->hdr))) return -ENOEXEC;
- err = security_kernel_load_data(LOADING_MODULE); + err = security_kernel_load_data(LOADING_MODULE, false); if (err) return err;
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 5f89970c5ab7..9dd9c5f4d736 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -676,6 +676,8 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size, /** * ima_load_data - appraise decision based on policy * @id: kernel load data caller identifier + * @contents: whether the full contents will be available in a later + * call to ima_post_load_data(). * * Callers of this LSM hook can not measure, appraise, or audit the * data provided by userspace. Enforce policy rules requring a file @@ -683,7 +685,7 @@ int ima_post_read_file(struct file *file, void *buf, loff_t size, * * For permission return 0, otherwise return -EACCES. */ -int ima_load_data(enum kernel_load_data_id id) +int ima_load_data(enum kernel_load_data_id id, bool contents) { bool ima_enforce, sig_enforce;
@@ -723,6 +725,26 @@ int ima_load_data(enum kernel_load_data_id id) return 0; }
+/** + * ima_post_load_data - appraise decision based on policy + * @buf: pointer to in memory file contents + * @size: size of in memory file contents + * @id: kernel load data caller identifier + * @description: @id-specific description of contents + * + * Measure/appraise/audit in memory buffer based on policy. Policy rules + * are written in terms of a policy identifier. + * + * On success return 0. On integrity appraisal error, assuming the file + * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. + */ +int ima_post_load_data(char *buf, loff_t size, + enum kernel_load_data_id load_id, + char *description) +{ + return 0; +} + /* * process_buffer_measurement - Measure the buffer to ima log. * @inode: inode associated with the object being measured (NULL for KEY_CHECK) diff --git a/security/loadpin/loadpin.c b/security/loadpin/loadpin.c index 163c48216d13..28782412febb 100644 --- a/security/loadpin/loadpin.c +++ b/security/loadpin/loadpin.c @@ -177,7 +177,7 @@ static int loadpin_read_file(struct file *file, enum kernel_read_file_id id) return 0; }
-static int loadpin_load_data(enum kernel_load_data_id id) +static int loadpin_load_data(enum kernel_load_data_id id, bool contents) { return loadpin_read_file(NULL, (enum kernel_read_file_id) id); } diff --git a/security/security.c b/security/security.c index 19d3150f68f4..531b855826fc 100644 --- a/security/security.c +++ b/security/security.c @@ -1695,17 +1695,31 @@ int security_kernel_post_read_file(struct file *file, char *buf, loff_t size, } EXPORT_SYMBOL_GPL(security_kernel_post_read_file);
-int security_kernel_load_data(enum kernel_load_data_id id) +int security_kernel_load_data(enum kernel_load_data_id id, bool contents) { int ret;
- ret = call_int_hook(kernel_load_data, 0, id); + ret = call_int_hook(kernel_load_data, 0, id, contents); if (ret) return ret; - return ima_load_data(id); + return ima_load_data(id, contents); } EXPORT_SYMBOL_GPL(security_kernel_load_data);
+int security_kernel_post_load_data(char *buf, loff_t size, + enum kernel_load_data_id id, + char *description) +{ + int ret; + + ret = call_int_hook(kernel_post_load_data, 0, buf, size, id, + description); + if (ret) + return ret; + return ima_post_load_data(buf, size, id, description); +} +EXPORT_SYMBOL_GPL(security_kernel_post_load_data); + int security_task_fix_setuid(struct cred *new, const struct cred *old, int flags) { diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index 96f5f8b3b9f0..558beee97d8d 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -4018,7 +4018,7 @@ static int selinux_kernel_read_file(struct file *file, return rc; }
-static int selinux_kernel_load_data(enum kernel_load_data_id id) +static int selinux_kernel_load_data(enum kernel_load_data_id id, bool contents) { int rc = 0;