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 <zohar@linux.vnet.ibm.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Kees Cook <keescook@chromium.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: James Morris <james.morris@microsoft.com>

diff --git a/include/linux/ima.h b/include/linux/ima.h
index 0e4647e0eb60caf9fc5f22ef5ecf1888771a4d9e..84806b54b50a1c2633aa7351f216f36ae7052718 100644 (file)
--- a/include/linux/ima.h
+++ b/include/linux/ima.h
@@ -11,6 +11,7 @@
 #define _LINUX_IMA_H
 
 #include <linux/fs.h>
+#include <linux/security.h>
 #include <linux/kexec.h>
 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 354bb5716ce329a39e43413a9ed373008c901b1e..78c15264b17b30ba6f7e5704412e7f5080243bd5 100644 (file)
--- 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 dca44cf7838eaddf882212faedc9759a391f7723..71fecfef0939e8952a8f2ef07e6f7ed62fda1b51 100644 (file)
--- 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 cdcc9a7b4e24825bcc9c41d0e81c14b03993acb0..d5b4958decc501c4a09d8e35f71365039855db36 100644 (file)
--- 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 c2de2f13485498e81e1109579d35018f7d2887ce..4927e7cc7d960a2222bd98516337e6edb98efacb 100644 (file)
--- 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,