Vboot Reference: Add functions to verify signed kernel images.

src/platform/vboot_reference/include/kernel_image.h

+/* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ *
+ * Data structure and API definitions for a verified boot kernel image.
+ */
+
+#ifndef VBOOT_REFERENCE_KERNEL_IMAGE_H_
+#define VBOOT_REFERENCE_KERNEL_IMAGE_H_
+
+#include <inttypes.h>
+
+#include "rsa.h"
+#include "sha.h"
+
+#define KERNEL_MAGIC "CHROMEOS"
+#define KERNEL_MAGIC_SIZE 8
+
+/* Kernel config file options according to the Chrome OS drive map design. */
+typedef struct kconfig_options {
+  uint32_t version[2];  /* Configuration file version. */
+  uint32_t kernel_len;  /* Size of the kernel. */
+  uint64_t kernel_load_addr;  /* Load address in memory for the kernel image */
+  uint64_t kernel_entry_addr;  /* Address to jump to after kernel is loaded. */
+} kconfig_options;
+
+
+typedef struct KernelImage {
+  uint8_t magic[KERNEL_MAGIC_SIZE];
+  /* Key header */
+  uint16_t header_version;  /* Header version. */
+  uint16_t header_len;  /* Length of the header. */
+  uint16_t firmware_sign_algorithm;  /* Signature algorithm used by the firmware
+                                      * signing key (used to sign this kernel
+                                      * header. */
+  uint16_t kernel_sign_algorithm;  /* Signature algorithm used by the kernel
+                                    * signing key. */
+  uint16_t kernel_key_version;  /* Key Version# for preventing rollbacks. */
+  uint8_t* kernel_sign_key;  /* Pre-processed public half of signing key. */
+  /* TODO(gauravsh): Do we need a choice of digest algorithms for the header
+   * checksum? */
+  uint8_t header_checksum[SHA512_DIGEST_SIZE];  /* SHA-512 Crytographic hash of
+                                                 * the concatenation of the
+                                                 * header fields, i.e.
+                                                 * [header_len,
+                                                 * firmware_sign_algorithm,
+                                                 * sign_algorithm, sign_key,
+                                                 * key_version] */
+
+  uint8_t* kernel_key_signature;   /* Signature of the header above. */
+
+  uint16_t kernel_version;  /* Kernel Version# for preventing rollbacks. */
+  kconfig_options options;  /* Other kernel/bootloader options. */
+
+  uint8_t* config_signature;  /* Signature of the kernel config file. */
+
+  /* The kernel signature comes first as it may allow us to parallelize
+   * the kernel data fetch and RSA public key operation.
+   */
+  uint8_t* kernel_signature;  /* Signature on [kernel_data]. */
+  uint8_t* kernel_data;  /* Actual kernel data. */
+
+} KernelImage;
+
+/* Allocate and return a new KernelImage structure. */
+KernelImage* KernelImageNew(void);
+
+/* Deep free the contents of [image]. */
+void KernelImageFree(KernelImage* image);
+
+/* Read kernel data from file named [input_file].
+ *
+ * Returns a filled up KernelImage on success, NULL on error.
+ */
+KernelImage* ReadKernelImage(const char* input_file);
+
+/* Write kernel key header from [image] to an open file pointed by the
+ * file descriptor [fd].
+ */
+void WriteKernelHeader(int fd, KernelImage* image);
+
+/* Write kernel config from [image] to an open file pointed by the
+ * file descriptor [fd].
+ */
+void WriteKernelConfig(int fd, KernelImage* image);
+
+/* Write kernel data from [image] to a file named [input_file].
+ *
+ * Return [image] on success, NULL on error.
+ */
+KernelImage* WriteKernelImage(const char* input_file,
+                              KernelImage* image);
+
+/* Pretty print the contents of [image]. Only headers and metadata information
+ * is printed.
+ */
+void PrintKernelImage(const KernelImage* image);
+
+/* Error Codes for VerifyFirmware. */
+#define VERIFY_KERNEL_SUCCESS 0
+#define VERIFY_KERNEL_INVALID_IMAGE 1
+#define VERIFY_KERNEL_KEY_SIGNATURE_FAILED 2
+#define VERIFY_KERNEL_INVALID_ALGORITHM 3
+#define VERIFY_KERNEL_CONFIG_SIGNATURE_FAILED 4
+#define VERIFY_KERNEL_SIGNATURE_FAILED 5
+#define VERIFY_KERNEL_WRONG_MAGIC 6
+#define VERIFY_KERNEL_MAX 7  /* Generic catch-all. */
+
+char* kVerifyKernelErrors[VERIFY_KERNEL_MAX];
+
+/* Checks for the sanity of the kernel header pointed by [kernel_header_blob].
+ * If [dev_mode] is enabled, also checks the firmware key signature using the
+ * pre-processed public firmware signing  key [firmware_sign_key_blob].
+ *
+ * On success, put firmware signature algorithm in [firmware_algorithm],
+ * kernel signature algorithm in [kernel_algorithm], kernel header
+ * length in [header_len], and return 0.
+ * Else, return error code on failure.
+ */
+int VerifyFirmwareHeader(const uint8_t* firmware_sign_key_blob,
+                         const uint8_t* kernel_header_blob,
+                         const int dev_mode,
+                         int* firmware_algorithm,
+                         int* kernel_algorithm,
+                         int* header_len);
+
+/* Checks the kernel config (analogous to preamble for firmware) signature on
+ * kernel config pointed by [kernel_config_blob] using the signing key
+ * [kernel_sign_key].
+ *
+ * On success, put kernel length into [kernel_len], and return 0.
+ * Else, return error code on failure.
+ */
+int VerifyKernelConfig(RSAPublicKey* kernel_sign_key,
+                       const uint8_t* kernel_config_blob,
+                       int algorithm,
+                       int* kernel_len);
+
+/* Checks the signature on the kernel data at location [kernel_data_start].
+ * The length of the actual kernel data is kernel _len and it is assumed to
+ * be prepended with the signature whose size depends on the signature_algorithm
+ * [algorithm].
+ *
+ * Return 0 on success, error code on failure.
+ */
+int VerifyKernelData(RSAPublicKey* kernel_sign_key,
+                     const uint8_t* kernel_data_start,
+                     int kernel_len,
+                     int algorithm);
+
+/* Performs a chained verify of the kernel blob [kernel_blob]. If
+ * [dev_mode] is 0 [inactive], then the pre-processed public signing key
+ * [root_key_blob] is used to verify the signature of the signing key,
+ * else the check is skipped.
+ *
+ * TODO(gauravsh): Does the dev mode only effect the R/W firmware verification,
+ * or kernel verification, or both?
+ *
+ * Returns 0 on success, error code on failure.
+ *
+ * NOTE: The length of the kernel blob is derived from reading the fields
+ * in the first few bytes of the buffer. This might look risky but in firmware
+ * land, the start address of the kernel_blob will always be fixed depending
+ * on the memory map on the particular platform. In addition, the signature on
+ * length itself is checked early in the verification process for extra safety.
+ */
+int VerifyKernel(const uint8_t* signing_key_blob,
+                 const uint8_t* kernel_blob,
+                 const int dev_mode);
+
+/* Performs a chained verify of the kernel [image]. If [dev_mode] is
+ * 0 (inactive), then the [firmware_signing_key] is used to verify the signature
+ * of the signing key, else the check is skipped.
+ *
+ * Returns 0 on success, error code on failure.
+ */
+int VerifyKernelImage(const RSAPublicKey* firmware_signing_key,
+                      const KernelImage* image,
+                      int dev_mode);
+
+
+/* Maps error codes from VerifyKernel*() to error description. */
+const char* VerifyKernelErrorString(int error);
+
+/* Add a kernel signing key signature to the key header to a kernel image
+ * [image] using the private key in file [firmware_key_file].
+ *
+ * Return 1 on success, 0 on failure.
+ */
+int AddKernelKeySignature(KernelImage* image, const char* firmware_key_file);
+
+/* Add a kernel and kernel config signature to a kernel image [image]
+ * using the private signing key in file [kernel_sigining_key_file].
+ *
+ * Return 1 on success, 0 on failure.
+ */
+int AddKernelSignature(KernelImage* image, const char* kernel_sigining_key_file,
+                       int algorithm);
+
+#endif  /* VBOOT_REFERENCE_KERNEL_IMAGE_H_ */