[PATCH 3/3] ima: based on policy require signed kexec kernel images

Mimi Zohar
2018-04-12T22:42:32Z

The original kexec_load syscall can not verify file signatures. This
patch differentiates between the kexec_load and kexec_file_load
syscalls.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
---
security/integrity/ima/ima.h | 1 +
security/integrity/ima/ima_main.c | 9 +++++++++
security/integrity/ima/ima_policy.c | 2 ++
3 files changed, 12 insertions(+)

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 35fe91aa1fc9..03c9c37ee345 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -233,6 +233,7 @@ 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 74d0bd7e76d7..754ece08e1c6 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -444,6 +444,15 @@ int ima_read_file(struct file *file, enum kernel_read_file_id read_id)
}
return 0; /* We rely on module signature checking */
}
+
+ if (!file && read_id == READING_KEXEC_IMAGE) {
+ if ((ima_appraise & IMA_APPRAISE_KEXEC) &&
+ (ima_appraise & IMA_APPRAISE_ENFORCE)) {
+ pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file syscall.\n");
+ return -EACCES; /* INTEGRITY_UNKNOWN */
+ }
+ return 0;
+ }
return 0;
}

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 1bdb5bc57568..3444352caf80 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -443,6 +443,8 @@ 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;
}

--
2.7.5