vboot: Add flag to vbutil_kernel for reconstruction of vmlinuz image

Adding functionality to allow for rebuilding of vmlinuz after it
has been processed into vblock and header stripped.  Basically appends
the 16-bit header of a vmlinuz image onto the end of the vblock.
BUG=chromium:438302
BRANCH=none
TEST=Successfully ran "make runalltests".
     Also, ran:
     1. Repack kernel block (so that 16-bit header is included):
        "vbutil_kernel --pack kern_0 ..."
     2. Verify kernel: "vbutil_kernel --verify kern_0 ... ".  This should
        be done before booting into kernel, but not necessary for it to work.
     3. Rebuild vmlinuz image:
        "vbutil_kernel --get-vmlinuz kern_0 --vmlinuz-out vm.out"
     4. Set up kexec with vmlinuz (this should complete with no errors):
        "kexec -l vm.out (other kernel cmd line args)"
     5. Boot into kernel:
        "kexec -e"

Change-Id: Iaa1582a1aedf70b43cdb3a56cde1fb248f1793d4
Signed-off-by: Shelley Chen <shchen@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/232750
Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>

3 files changed, 114 insertions, 4 deletions

diff --git a/firmware/include/vboot_struct.h b/firmware/include/vboot_struct.h
index 923e63cd..9e845ef8 100644
--- a/firmware/include/vboot_struct.h
+++ b/firmware/include/vboot_struct.h
@@ -180,9 +180,9 @@ typedef struct VbFirmwarePreambleHeader {
 /****************************************************************************/
 
 #define KERNEL_PREAMBLE_HEADER_VERSION_MAJOR 2
-#define KERNEL_PREAMBLE_HEADER_VERSION_MINOR 0
+#define KERNEL_PREAMBLE_HEADER_VERSION_MINOR 1
 
-/* Preamble block for kernel
+/* Preamble block for kernel, version 2.0
  *
  * This should be followed by:
  *   1) The signature data for the kernel body, pointed to by
@@ -190,7 +190,7 @@ typedef struct VbFirmwarePreambleHeader {
  *   2) The signature data for (VBFirmwarePreambleHeader + body signature
  *      data), pointed to by preamble_signature.sig_offset.
  */
-typedef struct VbKernelPreambleHeader {
+typedef struct VbKernelPreambleHeader2_0 {
 	/*
 	 * Size of this preamble, including keys, signatures, and padding, in
 	 * bytes
@@ -213,9 +213,56 @@ typedef struct VbKernelPreambleHeader {
 	uint64_t bootloader_size;
 	/* Signature for the kernel body */
 	VbSignature body_signature;
+} __attribute__((packed)) VbKernelPreambleHeader2_0;
+
+#define EXPECTED_VBKERNELPREAMBLEHEADER2_0_SIZE 96
+
+/* Preamble block for kernel, version 2.1
+ *
+ * This should be followed by:
+ *   1) The signature data for the kernel body, pointed to by
+ *      body_signature.sig_offset.
+ *   2) The signature data for (VBFirmwarePreambleHeader + body signature
+ *      data), pointed to by preamble_signature.sig_offset.
+ *   3) The 16-bit vmlinuz header, which is used for reconstruction of
+ *      vmlinuz image.
+ */
+typedef struct VbKernelPreambleHeader {
+	/*
+	 * Size of this preamble, including keys, signatures, vmlinuz header,
+	 * and padding, in bytes
+	 */
+	uint64_t preamble_size;
+	/* Signature for this preamble (header + body signature) */
+	VbSignature preamble_signature;
+	/* Version of this header format */
+	uint32_t header_version_major;
+	/* Version of this header format */
+	uint32_t header_version_minor;
+
+	/* Kernel version */
+	uint64_t kernel_version;
+	/* Load address for kernel body */
+	uint64_t body_load_address;
+	/* Address of bootloader, after body is loaded at body_load_address */
+	uint64_t bootloader_address;
+	/* Size of bootloader in bytes */
+	uint64_t bootloader_size;
+	/* Signature for the kernel body */
+	VbSignature body_signature;
+	/*
+	 * Fields added in header version 2.1.  You must verify the header
+	 * version before reading these fields!
+	 */
+	/* Address of 16-bit header for vmlinuz reassembly.  Readers should
+	   return 0 for header version < 2.1 */
+	uint64_t vmlinuz_header_address;
+	/* Size of 16-bit header for vmlinuz in bytes.  Readers should return 0
+	   for header version < 2.1 */
+	uint64_t vmlinuz_header_size;
 } __attribute__((packed)) VbKernelPreambleHeader;
 
-#define EXPECTED_VBKERNELPREAMBLEHEADER_SIZE 96
+#define EXPECTED_VBKERNELPREAMBLEHEADER2_1_SIZE 112
 
 /****************************************************************************/
 
diff --git a/firmware/lib/include/vboot_common.h b/firmware/lib/include/vboot_common.h
index 83064d2b..f792d1a2 100644
--- a/firmware/lib/include/vboot_common.h
+++ b/firmware/lib/include/vboot_common.h
@@ -149,6 +149,25 @@ int VerifyKernelPreamble(const VbKernelPreambleHeader *preamble,
 
 
 /**
+ * Retrieve the 16-bit vmlinuz header address and size from the kernel preamble
+ * if there is one.  These are only available in Kernel Preamble Header version
+ * >= 2.1.  If given a header 2.0 or lower, will set address and size to 0 (this
+ * is not considered an error).
+ *
+ * Returns VBOOT_SUCCESS if successful.
+ */
+int VbGetKernelVmlinuzHeader(const VbKernelPreambleHeader *preamble,
+			     uint64_t *vmlinuz_header_address,
+			     uint64_t *vmlinuz_header_size);
+
+/**
+ * Verify that the Vmlinuz Header is contained inside of the kernel blob.
+ *
+ * Returns VBOOT_SUCCESS or VBOOT_PREAMBLE_INVALID on error
+ */
+int VerifyVmlinuzInsideKBlob(uint64_t kblob, uint64_t kblob_size,
+			     uint64_t header, uint64_t header_size);
+/**
  * Initialize a verified boot shared data structure.
  *
  * Returns 0 if success, non-zero if error.
diff --git a/firmware/lib/vboot_common.c b/firmware/lib/vboot_common.c
index 3811e1ef..2cb01f37 100644
--- a/firmware/lib/vboot_common.c
+++ b/firmware/lib/vboot_common.c
@@ -435,10 +435,54 @@ int VerifyKernelPreamble(const VbKernelPreambleHeader *preamble,
 		return VBOOT_PREAMBLE_INVALID;
 	}
 
+	/*
+	 * If the preamble header version is at least 2.1, verify we have space
+	 * for the added fields from 2.1.
+	 */
+	if (preamble->header_version_minor >= 1) {
+		if(size < EXPECTED_VBKERNELPREAMBLEHEADER2_1_SIZE) {
+			VBDEBUG(("Not enough data for preamble header 2.1.\n"));
+			return VBOOT_PREAMBLE_INVALID;
+		}
+	}
+
 	/* Success */
 	return VBOOT_SUCCESS;
 }
 
+int VbGetKernelVmlinuzHeader(const VbKernelPreambleHeader *preamble,
+			     uint64_t *vmlinuz_header_address,
+			     uint64_t *vmlinuz_header_size)
+{
+	*vmlinuz_header_address = 0;
+	*vmlinuz_header_size = 0;
+	if (preamble->header_version_minor > 0) {
+		/*
+		 * Set header and size only if the preamble header version is >
+		 * 2.1 as they don't exist in version 2.0 (Note that we don't
+		 * need to check header_version_major; if that's not 2 then
+		 * VerifyKernelPreamble() would have already failed.
+		 */
+		*vmlinuz_header_address = preamble->vmlinuz_header_address;
+		*vmlinuz_header_size = preamble->vmlinuz_header_size;
+	}
+	return VBOOT_SUCCESS;
+}
+
+int VerifyVmlinuzInsideKBlob(uint64_t kblob, uint64_t kblob_size,
+			     uint64_t header, uint64_t header_size)
+{
+	uint64_t end = header-kblob;
+	if (end > kblob_size)
+		return VBOOT_PREAMBLE_INVALID;
+	if (UINT64_MAX - end < header_size)
+		return VBOOT_PREAMBLE_INVALID;
+	if (end + header_size > kblob_size)
+		return VBOOT_PREAMBLE_INVALID;
+
+	return VBOOT_SUCCESS;
+}
+
 uint64_t VbSharedDataReserve(VbSharedDataHeader *header, uint64_t size)
 {
 	uint64_t offs = header->data_used;