u-boot: fit: add support to decrypt fit with aes

This commit add to u-boot the support to decrypt
fit image encrypted with aes. The FIT image contains
the key name and the IV name. Then u-boot look for
the key and IV in his device tree and decrypt images
before moving to the next stage.

Signed-off-by: Philippe Reynes <philippe.reynes@softathome.com>

common/image-cipher.c

@@ -24,6 +24,7 @@ struct cipher_algo cipher_algos[] = {
 		.calculate_type = EVP_aes_128_cbc,
 #endif
 		.encrypt = image_aes_encrypt,
+		.decrypt = image_aes_decrypt,
 		.add_cipher_data = image_aes_add_cipher_data
 	},
 	{
@@ -34,6 +35,7 @@ struct cipher_algo cipher_algos[] = {
 		.calculate_type = EVP_aes_192_cbc,
 #endif
 		.encrypt = image_aes_encrypt,
+		.decrypt = image_aes_decrypt,
 		.add_cipher_data = image_aes_add_cipher_data
 	},
 	{
@@ -44,6 +46,7 @@ struct cipher_algo cipher_algos[] = {
 		.calculate_type = EVP_aes_256_cbc,
 #endif
 		.encrypt = image_aes_encrypt,
+		.decrypt = image_aes_decrypt,
 		.add_cipher_data = image_aes_add_cipher_data
 	}
 };
@@ -61,3 +64,104 @@ struct cipher_algo *image_get_cipher_algo(const char *full_name)
 
 	return NULL;
 }
+
+static int fit_image_setup_decrypt(struct image_cipher_info *info,
+				   const void *fit, int image_noffset,
+				   int cipher_noffset)
+{
+	const void *fdt = gd_fdt_blob();
+	const char *node_name;
+	char node_path[128];
+	int noffset;
+	char *algo_name;
+	int ret;
+
+	node_name = fit_get_name(fit, image_noffset, NULL);
+	if (!node_name) {
+		printf("Can't get node name\n");
+		return -1;
+	}
+
+	if (fit_image_cipher_get_algo(fit, cipher_noffset, &algo_name)) {
+		printf("Can't get algo name for cipher '%s' in image '%s'\n",
+		       node_name, node_name);
+		return -1;
+	}
+
+	info->keyname = fdt_getprop(fit, cipher_noffset, "key-name-hint", NULL);
+	if (!info->keyname) {
+		printf("Can't get key name\n");
+		return -1;
+	}
+
+	info->ivname = fdt_getprop(fit, cipher_noffset, "iv-name-hint", NULL);
+	if (!info->ivname) {
+		printf("Can't get IV name\n");
+		return -1;
+	}
+
+	info->fit = fit;
+	info->node_noffset = image_noffset;
+	info->name = algo_name;
+	info->cipher = image_get_cipher_algo(algo_name);
+	if (!info->cipher) {
+		printf("Can't get cipher\n");
+		return -1;
+	}
+
+	ret = fit_image_get_data_size_unciphered(fit, image_noffset,
+						 &info->size_unciphered);
+	if (ret) {
+		printf("Can't get size of unciphered data\n");
+		return -1;
+	}
+
+	/*
+	 * Search the cipher node in the u-boot fdt
+	 * the path should be: /cipher/key-<algo>-<key>-<iv>
+	 */
+	snprintf(node_path, sizeof(node_path), "/%s/key-%s-%s-%s",
+		 FIT_CIPHER_NODENAME, algo_name, info->keyname, info->ivname);
+
+	noffset = fdt_path_offset(fdt, node_path);
+	if (noffset < 0) {
+		printf("Can't found cipher node offset\n");
+		return -1;
+	}
+
+	/* read key */
+	info->key = fdt_getprop(fdt, noffset, "key", NULL);
+	if (!info->key) {
+		printf("Can't get key in cipher node '%s'\n", node_path);
+		return -1;
+	}
+
+	/* read iv */
+	info->iv = fdt_getprop(fdt, noffset, "iv", NULL);
+	if (!info->iv) {
+		printf("Can't get IV in cipher node '%s'\n", node_path);
+		return -1;
+	}
+
+	return 0;
+}
+
+int fit_image_decrypt_data(const void *fit,
+			   int image_noffset, int cipher_noffset,
+			   const void *data_ciphered, size_t size_ciphered,
+			   void **data_unciphered, size_t *size_unciphered)
+{
+	struct image_cipher_info info;
+	int ret;
+
+	ret = fit_image_setup_decrypt(&info, fit, image_noffset,
+				      cipher_noffset);
+	if (ret < 0)
+		goto out;
+
+	ret = info.cipher->decrypt(&info, data_ciphered, size_ciphered,
+				   data_unciphered, size_unciphered);
+
+ out:
+	return ret;
+}

common/image-fit.c

@@ -947,6 +947,31 @@ int fit_image_get_data_size(const void *fit, int noffset, int *data_size)
 	return 0;
 }
 
+/**
+ * Get 'data-size-unciphered' property from a given image node.
+ *
+ * @fit: pointer to the FIT image header
+ * @noffset: component image node offset
+ * @data_size: holds the data-size property
+ *
+ * returns:
+ *     0, on success
+ *     -ENOENT if the property could not be found
+ */
+int fit_image_get_data_size_unciphered(const void *fit, int noffset,
+				       size_t *data_size)
+{
+	const fdt32_t *val;
+
+	val = fdt_getprop(fit, noffset, "data-size-unciphered", NULL);
+	if (!val)
+		return -ENOENT;
+
+	*data_size = (size_t)fdt32_to_cpu(*val);
+
+	return 0;
+}
+
 /**
  * fit_image_get_data_and_size - get data and its size including
  *				 both embedded and external data
@@ -1381,6 +1406,32 @@ int fit_all_image_verify(const void *fit)
 	return 1;
 }
 
+#ifdef CONFIG_FIT_CIPHER
+static int fit_image_uncipher(const void *fit, int image_noffset,
+			      void **data, size_t *size)
+{
+	int cipher_noffset, ret;
+	void *dst;
+	size_t size_dst;
+
+	cipher_noffset = fdt_subnode_offset(fit, image_noffset,
+					    FIT_CIPHER_NODENAME);
+	if (cipher_noffset < 0)
+		return 0;
+
+	ret = fit_image_decrypt_data(fit, image_noffset, cipher_noffset,
+				     *data, *size, &dst, &size_dst);
+	if (ret)
+		goto out;
+
+	*data = dst;
+	*size = size_dst;
+
+ out:
+	return ret;
+}
+#endif /* CONFIG_FIT_CIPHER */
+
 /**
  * fit_image_check_os - check whether image node is of a given os type
  * @fit: pointer to the FIT format image header
@@ -1981,6 +2032,18 @@ int fit_image_load(bootm_headers_t *images, ulong addr,
 		return -ENOENT;
 	}
 
+#ifdef CONFIG_FIT_CIPHER
+	/* Decrypt data before uncompress/move */
+	if (IMAGE_ENABLE_DECRYPT) {
+		puts("   Decrypting Data ... ");
+		if (fit_image_uncipher(fit, noffset, &buf, &size)) {
+			puts("Error\n");
+			return -EACCES;
+		}
+		puts("OK\n");
+	}
+#endif
+
 #if !defined(USE_HOSTCC) && defined(CONFIG_FIT_IMAGE_POST_PROCESS)
 	/* perform any post-processing on the image data */
 	board_fit_image_post_process(&buf, &size);

include/image.h

@@ -1023,6 +1023,8 @@ int fit_image_get_data_offset(const void *fit, int noffset, int *data_offset);
 int fit_image_get_data_position(const void *fit, int noffset,
 				int *data_position);
 int fit_image_get_data_size(const void *fit, int noffset, int *data_size);
+int fit_image_get_data_size_unciphered(const void *fit, int noffset,
+				       size_t *data_size);
 int fit_image_get_data_and_size(const void *fit, int noffset,
 				const void **data, size_t *size);
 
@@ -1066,6 +1068,7 @@ int fit_image_verify_with_data(const void *fit, int image_noffset,
 int fit_image_verify(const void *fit, int noffset);
 int fit_config_verify(const void *fit, int conf_noffset);
 int fit_all_image_verify(const void *fit);
+int fit_config_decrypt(const void *fit, int conf_noffset);
 int fit_image_check_os(const void *fit, int noffset, uint8_t os);
 int fit_image_check_arch(const void *fit, int noffset, uint8_t arch);
 int fit_image_check_type(const void *fit, int noffset, uint8_t type);
@@ -1293,6 +1296,11 @@ int fit_image_verify_required_sigs(const void *fit, int image_noffset,
 int fit_image_check_sig(const void *fit, int noffset, const void *data,
 		size_t size, int required_keynode, char **err_msgp);
 
+int fit_image_decrypt_data(const void *fit,
+			   int image_noffset, int cipher_noffset,
+			   const void *data, size_t size,
+			   void **data_unciphered, size_t *size_unciphered);
+
 /**
  * fit_region_make_list() - Make a list of regions to hash
  *
@@ -1367,6 +1375,10 @@ struct cipher_algo {
 
 	int (*add_cipher_data)(struct image_cipher_info *info,
 			       void *keydest);
+
+	int (*decrypt)(struct image_cipher_info *info,
+		       const void *cipher, size_t cipher_len,
+		       void **data, size_t *data_len);
 };
 
 int fit_image_cipher_get_algo(const void *fit, int noffset, char **algo);

include/u-boot/aes.h

@@ -28,4 +28,17 @@ int image_aes_add_cipher_data(struct image_cipher_info *info, void *keydest)
 }
 #endif /* IMAGE_ENABLE_ENCRYPT */
 
+#if IMAGE_ENABLE_DECRYPT
+int image_aes_decrypt(struct image_cipher_info *info,
+		      const void *cipher, size_t cipher_len,
+		      void **data, size_t *size);
+#else
+int image_aes_decrypt(struct image_cipher_info *info,
+		      const void *cipher, size_t cipher_len,
+		      void **data, size_t *size)
+{
+	return -ENXIO;
+}
+#endif /* IMAGE_ENABLE_DECRYPT */
+
 #endif

lib/Makefile

@@ -21,6 +21,7 @@ obj-$(CONFIG_ASN1_DECODER) += asn1_decoder.o
 obj-y += crypto/
 
 obj-$(CONFIG_AES) += aes.o
+obj-$(CONFIG_AES) += aes/
 obj-$(CONFIG_$(SPL_TPL_)BINMAN_FDT) += binman.o
 
 ifndef API_BUILD

lib/aes/Makefile

@@ -0,0 +1,5 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Copyright (c) 2019, Softathome
+
+obj-$(CONFIG_$(SPL_)FIT_CIPHER) += aes-decrypt.o

lib/aes/aes-decrypt.c

@@ -0,0 +1,41 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (c) 2019, softathome
+ */
+
+#ifndef USE_HOSTCC
+#include <common.h>
+#include <malloc.h>
+#endif
+#include <image.h>
+#include <uboot_aes.h>
+
+int image_aes_decrypt(struct image_cipher_info *info,
+		      const void *cipher, size_t cipher_len,
+		      void **data, size_t *size)
+{
+#ifndef USE_HOSTCC
+	unsigned char key_exp[AES256_EXPAND_KEY_LENGTH];
+	unsigned int aes_blocks, key_len = info->cipher->key_len;
+
+	*data = malloc(cipher_len);
+	if (!*data) {
+		printf("Can't allocate memory to decrypt\n");
+		return -ENOMEM;
+	}
+	*size = info->size_unciphered;
+
+	memcpy(&key_exp[0], info->key, key_len);
+
+	/* First we expand the key. */
+	aes_expand_key((u8 *)info->key, key_len, key_exp);
+
+	/* Calculate the number of AES blocks to encrypt. */
+	aes_blocks = DIV_ROUND_UP(cipher_len, AES_BLOCK_LENGTH);
+
+	aes_cbc_decrypt_blocks(key_len, key_exp, (u8 *)info->iv,
+			       (u8 *)cipher, *data, aes_blocks);
+#endif
+
+	return 0;
+}

tools/Makefile

@@ -77,7 +77,7 @@ RSA_OBJS-$(CONFIG_FIT_SIGNATURE) := $(addprefix lib/rsa/, \
 					rsa-mod-exp.o)
 
 AES_OBJS-$(CONFIG_FIT_CIPHER) := $(addprefix lib/aes/, \
-					aes-encrypt.o)
+					aes-encrypt.o aes-decrypt.o)
 
 ROCKCHIP_OBS = lib/rc4.o rkcommon.o rkimage.o rksd.o rkspi.o