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authorKees Cook <keescook@chromium.org>2020-10-02 10:38:20 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2020-10-05 13:37:03 +0200
commitb64fcae74b6d6940d14243c963ab0089e8f0d82d (patch)
tree301791490a1bce0d017a380cc37475510ecee286 /security
parent885352881f11f1f3113d8eb877786bcb6d720544 (diff)
LSM: Introduce kernel_post_load_data() hook
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> Link: https://lore.kernel.org/r/20201002173828.2099543-9-keescook@chromium.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'security')
-rw-r--r--security/integrity/ima/ima_main.c24
-rw-r--r--security/loadpin/loadpin.c2
-rw-r--r--security/security.c20
-rw-r--r--security/selinux/hooks.c2
4 files changed, 42 insertions, 6 deletions
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;