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authorJiri Bohac <jbohac@suse.cz>2019-08-19 17:17:44 -0700
committerJames Morris <jmorris@namei.org>2019-08-19 21:54:15 -0700
commit99d5cadfde2b1acb7650021df5abaa5ec447dd10 (patch)
tree49af3ab9d60ad3191426f616750002f1720562cc /kernel
parentfef5dad9876034253d59acbf8c0c314f4d94cf87 (diff)
kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE
This is a preparatory patch for kexec_file_load() lockdown. A locked down kernel needs to prevent unsigned kernel images from being loaded with kexec_file_load(). Currently, the only way to force the signature verification is compiling with KEXEC_VERIFY_SIG. This prevents loading usigned images even when the kernel is not locked down at runtime. This patch splits KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE. Analogous to the MODULE_SIG and MODULE_SIG_FORCE for modules, KEXEC_SIG turns on the signature verification but allows unsigned images to be loaded. KEXEC_SIG_FORCE disallows images without a valid signature. Signed-off-by: Jiri Bohac <jbohac@suse.cz> Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Matthew Garrett <mjg59@google.com> cc: kexec@lists.infradead.org Signed-off-by: James Morris <jmorris@namei.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/kexec_file.c60
1 files changed, 51 insertions, 9 deletions
diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index ef7b951a8087..972931201995 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -88,7 +88,7 @@ int __weak arch_kimage_file_post_load_cleanup(struct kimage *image)
return kexec_image_post_load_cleanup_default(image);
}
-#ifdef CONFIG_KEXEC_VERIFY_SIG
+#ifdef CONFIG_KEXEC_SIG
static int kexec_image_verify_sig_default(struct kimage *image, void *buf,
unsigned long buf_len)
{
@@ -177,6 +177,51 @@ void kimage_file_post_load_cleanup(struct kimage *image)
image->image_loader_data = NULL;
}
+#ifdef CONFIG_KEXEC_SIG
+static int
+kimage_validate_signature(struct kimage *image)
+{
+ const char *reason;
+ int ret;
+
+ ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf,
+ image->kernel_buf_len);
+ switch (ret) {
+ case 0:
+ break;
+
+ /* Certain verification errors are non-fatal if we're not
+ * checking errors, provided we aren't mandating that there
+ * must be a valid signature.
+ */
+ case -ENODATA:
+ reason = "kexec of unsigned image";
+ goto decide;
+ case -ENOPKG:
+ reason = "kexec of image with unsupported crypto";
+ goto decide;
+ case -ENOKEY:
+ reason = "kexec of image with unavailable key";
+ decide:
+ if (IS_ENABLED(CONFIG_KEXEC_SIG_FORCE)) {
+ pr_notice("%s rejected\n", reason);
+ return ret;
+ }
+
+ return 0;
+
+ /* All other errors are fatal, including nomem, unparseable
+ * signatures and signature check failures - even if signatures
+ * aren't required.
+ */
+ default:
+ pr_notice("kernel signature verification failed (%d).\n", ret);
+ }
+
+ return ret;
+}
+#endif
+
/*
* In file mode list of segments is prepared by kernel. Copy relevant
* data from user space, do error checking, prepare segment list
@@ -186,7 +231,7 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
const char __user *cmdline_ptr,
unsigned long cmdline_len, unsigned flags)
{
- int ret = 0;
+ int ret;
void *ldata;
loff_t size;
@@ -205,14 +250,11 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd,
if (ret)
goto out;
-#ifdef CONFIG_KEXEC_VERIFY_SIG
- ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf,
- image->kernel_buf_len);
- if (ret) {
- pr_debug("kernel signature verification failed.\n");
+#ifdef CONFIG_KEXEC_SIG
+ ret = kimage_validate_signature(image);
+
+ if (ret)
goto out;
- }
- pr_debug("kernel signature verification successful.\n");
#endif
/* It is possible that there no initramfs is being loaded */
if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {