boot: image: add a stage pre-load

Add a stage pre-load that could
check or modify an image.

For the moment, only a header with a signature is
supported. This header has the following format:
- magic : 4 bytes
- version : 4 bytes
- header size : 4 bytes
- image size : 4 bytes
- offset image signature : 4 bytes
- flags : 4 bytes
- reserved0 : 4 bytes
- reserved1 : 4 bytes
- sha256 of the image signature : 32 bytes
- signature of the first 64 bytes : n bytes
- image signature : n bytes
- padding : up to header size

The stage uses a node /image/pre-load/sig to
get some informations:
- algo-name (mandatory) : name of the algo used to sign
- padding-name : name of padding used to sign
- signature-size : size of the signature (in the header)
- mandatory : set to yes if this sig is mandatory
- public-key (madatory) : value of the public key

Before running the image, the stage pre-load checks
the signature provided in the header.

This is an initial support, later we could add the
support of:
- ciphering
- uncompressing
- ...

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

4 files changed, 486 insertions, 0 deletions

diff --git a/boot/Kconfig b/boot/Kconfig
index a395529..b3580bd 100644
--- a/boot/Kconfig
+++ b/boot/Kconfig
@@ -1023,6 +1023,61 @@ config RESET_TO_RETRY
 
 endmenu
 
+menu "Image support"
+
+config IMAGE_PRE_LOAD
+	bool "Image pre-load support"
+	help
+	  Enable an image pre-load stage in the SPL.
+	  This pre-load stage allows to do some manipulation
+	  or check (for example signature check) on an image
+	  before launching it.
+
+config SPL_IMAGE_PRE_LOAD
+	bool "Image pre-load support within SPL"
+	depends on SPL && IMAGE_PRE_LOAD
+	help
+	  Enable an image pre-load stage in the SPL.
+	  This pre-load stage allows to do some manipulation
+	  or check (for example signature check) on an image
+	  before launching it.
+
+config IMAGE_PRE_LOAD_SIG
+	bool "Image pre-load signature support"
+	depends on IMAGE_PRE_LOAD
+	select FIT_SIGNATURE
+	select RSA
+	select RSA_VERIFY_WITH_PKEY
+	help
+	  Enable signature check support in the pre-load stage.
+	  For this feature a very simple header is added before
+	  the image with few fields:
+	  - a magic
+	  - the image size
+	  - the signature
+	  All other information (header size, type of signature,
+	  ...) are provided in the node /image/pre-load/sig of
+	  u-boot.
+
+config SPL_IMAGE_PRE_LOAD_SIG
+	bool "Image pre-load signature support witin SPL"
+	depends on SPL_IMAGE_PRE_LOAD && IMAGE_PRE_LOAD_SIG
+	select SPL_FIT_SIGNATURE
+	select SPL_RSA
+	select SPL_RSA_VERIFY_WITH_PKEY
+	help
+	  Enable signature check support in the pre-load stage in the SPL.
+	  For this feature a very simple header is added before
+	  the image with few fields:
+	  - a magic
+	  - the image size
+	  - the signature
+	  All other information (header size, type of signature,
+	  ...) are provided in the node /image/pre-load/sig of
+	  u-boot.
+
+endmenu
+
 config USE_BOOTARGS
 	bool "Enable boot arguments"
 	help
diff --git a/boot/Makefile b/boot/Makefile
index 75366c8..1b99e6e 100644
--- a/boot/Makefile
+++ b/boot/Makefile
@@ -22,6 +22,7 @@ obj-$(CONFIG_$(SPL_TPL_)OF_LIBFDT) += image-fdt.o
 obj-$(CONFIG_$(SPL_TPL_)FIT_SIGNATURE) += fdt_region.o
 obj-$(CONFIG_$(SPL_TPL_)FIT) += image-fit.o
 obj-$(CONFIG_$(SPL_)MULTI_DTB_FIT) += boot_fit.o common_fit.o
+obj-$(CONFIG_$(SPL_TPL_)IMAGE_PRE_LOAD) += image-pre-load.o
 obj-$(CONFIG_$(SPL_TPL_)IMAGE_SIGN_INFO) += image-sig.o
 obj-$(CONFIG_$(SPL_TPL_)FIT_SIGNATURE) += image-fit-sig.o
 obj-$(CONFIG_$(SPL_TPL_)FIT_CIPHER) += image-cipher.o
diff --git a/boot/image-pre-load.c b/boot/image-pre-load.c
new file mode 100644
index 0000000..78d8906
--- /dev/null
+++ b/boot/image-pre-load.c
@@ -0,0 +1,416 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2021 Philippe Reynes <philippe.reynes@softathome.com>
+ */
+
+#include <common.h>
+#include <asm/global_data.h>
+DECLARE_GLOBAL_DATA_PTR;
+#include <image.h>
+#include <mapmem.h>
+
+#include <u-boot/sha256.h>
+
+#define IMAGE_PRE_LOAD_SIG_MAGIC		0x55425348
+#define IMAGE_PRE_LOAD_SIG_OFFSET_MAGIC		0
+#define IMAGE_PRE_LOAD_SIG_OFFSET_IMG_LEN	4
+#define IMAGE_PRE_LOAD_SIG_OFFSET_SIG		8
+
+#define IMAGE_PRE_LOAD_PATH			"/image/pre-load/sig"
+#define IMAGE_PRE_LOAD_PROP_ALGO_NAME		"algo-name"
+#define IMAGE_PRE_LOAD_PROP_PADDING_NAME	"padding-name"
+#define IMAGE_PRE_LOAD_PROP_SIG_SIZE		"signature-size"
+#define IMAGE_PRE_LOAD_PROP_PUBLIC_KEY		"public-key"
+#define IMAGE_PRE_LOAD_PROP_MANDATORY		"mandatory"
+
+#ifndef CONFIG_SYS_BOOTM_LEN
+/* use 8MByte as default max gunzip size */
+#define CONFIG_SYS_BOOTM_LEN	0x800000
+#endif
+
+/*
+ * Information in the device-tree about the signature in the header
+ */
+struct image_sig_info {
+	char *algo_name;	/* Name of the algo (eg: sha256,rsa2048) */
+	char *padding_name;	/* Name of the padding */
+	u8 *key;		/* Public signature key */
+	int key_len;		/* Length of the public key */
+	u32 sig_size;		/* size of the signature (in the header) */
+	int mandatory;		/* Set if the signature is mandatory */
+
+	struct image_sign_info sig_info; /* Signature info */
+};
+
+/*
+ * Header of the signature header
+ */
+struct sig_header_s {
+	u32 magic;
+	u32 version;
+	u32 header_size;
+	u32 image_size;
+	u32 offset_img_sig;
+	u32 flags;
+	u32 reserved0;
+	u32 reserved1;
+	u8 sha256_img_sig[SHA256_SUM_LEN];
+};
+
+#define SIG_HEADER_LEN			(sizeof(struct sig_header_s))
+
+/*
+ * Offset of the image
+ *
+ * This value is used to skip the header before really launching the image
+ */
+ulong image_load_offset;
+
+/*
+ * This function gathers information about the signature check
+ * that could be done before launching the image.
+ *
+ * return:
+ * < 0 => an error has occurred
+ *   0 => OK
+ *   1 => no setup
+ */
+static int image_pre_load_sig_setup(struct image_sig_info *info)
+{
+	const void *algo_name, *padding_name, *key, *mandatory;
+	const u32 *sig_size;
+	int key_len;
+	int node, ret = 0;
+
+	if (!info) {
+		log_err("ERROR: info is NULL for image pre-load sig check\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	memset(info, 0, sizeof(*info));
+
+	node = fdt_path_offset(gd_fdt_blob(), IMAGE_PRE_LOAD_PATH);
+	if (node < 0) {
+		log_info("INFO: no info for image pre-load sig check\n");
+		ret = 1;
+		goto out;
+	}
+
+	algo_name = fdt_getprop(gd_fdt_blob(), node,
+				IMAGE_PRE_LOAD_PROP_ALGO_NAME, NULL);
+	if (!algo_name) {
+		printf("ERROR: no algo_name for image pre-load sig check\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	padding_name = fdt_getprop(gd_fdt_blob(), node,
+				   IMAGE_PRE_LOAD_PROP_PADDING_NAME, NULL);
+	if (!padding_name) {
+		log_info("INFO: no padding_name provided, so using pkcs-1.5\n");
+		padding_name = "pkcs-1.5";
+	}
+
+	sig_size = fdt_getprop(gd_fdt_blob(), node,
+			       IMAGE_PRE_LOAD_PROP_SIG_SIZE, NULL);
+	if (!sig_size) {
+		log_err("ERROR: no signature-size for image pre-load sig check\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	key = fdt_getprop(gd_fdt_blob(), node,
+			  IMAGE_PRE_LOAD_PROP_PUBLIC_KEY, &key_len);
+	if (!key) {
+		log_err("ERROR: no key for image pre-load sig check\n");
+		ret = -EINVAL;
+		goto out;
+	}
+
+	info->algo_name		= (char *)algo_name;
+	info->padding_name	= (char *)padding_name;
+	info->key		= (uint8_t *)key;
+	info->key_len		= key_len;
+	info->sig_size		= fdt32_to_cpu(*sig_size);
+
+	mandatory = fdt_getprop(gd_fdt_blob(), node,
+				IMAGE_PRE_LOAD_PROP_MANDATORY, NULL);
+	if (mandatory && !strcmp((char *)mandatory, "yes"))
+		info->mandatory = 1;
+
+	/* Compute signature information */
+	info->sig_info.name     = info->algo_name;
+	info->sig_info.padding  = image_get_padding_algo(info->padding_name);
+	info->sig_info.checksum = image_get_checksum_algo(info->sig_info.name);
+	info->sig_info.crypto   = image_get_crypto_algo(info->sig_info.name);
+	info->sig_info.key      = info->key;
+	info->sig_info.keylen   = info->key_len;
+
+ out:
+	return ret;
+}
+
+static int image_pre_load_sig_get_magic(ulong addr, u32 *magic)
+{
+	struct sig_header_s *sig_header;
+	int ret = 0;
+
+	sig_header = (struct sig_header_s *)map_sysmem(addr, SIG_HEADER_LEN);
+	if (!sig_header) {
+		log_err("ERROR: can't map first header\n");
+		ret = -EFAULT;
+		goto out;
+	}
+
+	*magic = fdt32_to_cpu(sig_header->magic);
+
+	unmap_sysmem(sig_header);
+
+ out:
+	return ret;
+}
+
+static int image_pre_load_sig_get_header_size(ulong addr, u32 *header_size)
+{
+	struct sig_header_s *sig_header;
+	int ret = 0;
+
+	sig_header = (struct sig_header_s *)map_sysmem(addr, SIG_HEADER_LEN);
+	if (!sig_header) {
+		log_err("ERROR: can't map first header\n");
+		ret = -EFAULT;
+		goto out;
+	}
+
+	*header_size = fdt32_to_cpu(sig_header->header_size);
+
+	unmap_sysmem(sig_header);
+
+ out:
+	return ret;
+}
+
+/*
+ * return:
+ * < 0 => no magic and magic mandatory (or error when reading magic)
+ *   0 => magic found
+ *   1 => magic NOT found
+ */
+static int image_pre_load_sig_check_magic(struct image_sig_info *info, ulong addr)
+{
+	u32 magic;
+	int ret = 1;
+
+	ret = image_pre_load_sig_get_magic(addr, &magic);
+	if (ret < 0)
+		goto out;
+
+	if (magic != IMAGE_PRE_LOAD_SIG_MAGIC) {
+		if (info->mandatory) {
+			log_err("ERROR: signature is mandatory\n");
+			ret = -EINVAL;
+			goto out;
+		}
+		ret = 1;
+		goto out;
+	}
+
+	ret = 0; /* magic found */
+
+ out:
+	return ret;
+}
+
+static int image_pre_load_sig_check_header_sig(struct image_sig_info *info, ulong addr)
+{
+	void *header;
+	struct image_region reg;
+	u32 sig_len;
+	u8 *sig;
+	int ret = 0;
+
+	/* Only map header of the header and its signature */
+	header = (void *)map_sysmem(addr, SIG_HEADER_LEN + info->sig_size);
+	if (!header) {
+		log_err("ERROR: can't map header\n");
+		ret = -EFAULT;
+		goto out;
+	}
+
+	reg.data = header;
+	reg.size = SIG_HEADER_LEN;
+
+	sig = (uint8_t *)header + SIG_HEADER_LEN;
+	sig_len = info->sig_size;
+
+	ret = info->sig_info.crypto->verify(&info->sig_info, &reg, 1, sig, sig_len);
+	if (ret) {
+		log_err("ERROR: header signature check has failed (err=%d)\n", ret);
+		ret = -EINVAL;
+		goto out_unmap;
+	}
+
+ out_unmap:
+	unmap_sysmem(header);
+
+ out:
+	return ret;
+}
+
+static int image_pre_load_sig_check_img_sig_sha256(struct image_sig_info *info, ulong addr)
+{
+	struct sig_header_s *sig_header;
+	u32 header_size, offset_img_sig;
+	void *header;
+	u8 sha256_img_sig[SHA256_SUM_LEN];
+	int ret = 0;
+
+	sig_header = (struct sig_header_s *)map_sysmem(addr, SIG_HEADER_LEN);
+	if (!sig_header) {
+		log_err("ERROR: can't map first header\n");
+		ret = -EFAULT;
+		goto out;
+	}
+
+	header_size = fdt32_to_cpu(sig_header->header_size);
+	offset_img_sig = fdt32_to_cpu(sig_header->offset_img_sig);
+
+	header = (void *)map_sysmem(addr, header_size);
+	if (!header) {
+		log_err("ERROR: can't map header\n");
+		ret = -EFAULT;
+		goto out_sig_header;
+	}
+
+	sha256_csum_wd(header + offset_img_sig, info->sig_size,
+		       sha256_img_sig, CHUNKSZ_SHA256);
+
+	ret = memcmp(sig_header->sha256_img_sig, sha256_img_sig, SHA256_SUM_LEN);
+	if (ret) {
+		log_err("ERROR: sha256 of image signature is invalid\n");
+		ret = -EFAULT;
+		goto out_header;
+	}
+
+ out_header:
+	unmap_sysmem(header);
+ out_sig_header:
+	unmap_sysmem(sig_header);
+ out:
+	return ret;
+}
+
+static int image_pre_load_sig_check_img_sig(struct image_sig_info *info, ulong addr)
+{
+	struct sig_header_s *sig_header;
+	u32 header_size, image_size, offset_img_sig;
+	void *image;
+	struct image_region reg;
+	u32 sig_len;
+	u8 *sig;
+	int ret = 0;
+
+	sig_header = (struct sig_header_s *)map_sysmem(addr, SIG_HEADER_LEN);
+	if (!sig_header) {
+		log_err("ERROR: can't map first header\n");
+		ret = -EFAULT;
+		goto out;
+	}
+
+	header_size = fdt32_to_cpu(sig_header->header_size);
+	image_size = fdt32_to_cpu(sig_header->image_size);
+	offset_img_sig = fdt32_to_cpu(sig_header->offset_img_sig);
+
+	unmap_sysmem(sig_header);
+
+	image = (void *)map_sysmem(addr, header_size + image_size);
+	if (!image) {
+		log_err("ERROR: can't map full image\n");
+		ret = -EFAULT;
+		goto out;
+	}
+
+	reg.data = image + header_size;
+	reg.size = image_size;
+
+	sig = (uint8_t *)image + offset_img_sig;
+	sig_len = info->sig_size;
+
+	ret = info->sig_info.crypto->verify(&info->sig_info, &reg, 1, sig, sig_len);
+	if (ret) {
+		log_err("ERROR: signature check has failed (err=%d)\n", ret);
+		ret = -EINVAL;
+		goto out_unmap_image;
+	}
+
+	log_info("INFO: signature check has succeed\n");
+
+ out_unmap_image:
+	unmap_sysmem(image);
+
+ out:
+	return ret;
+}
+
+int image_pre_load_sig(ulong addr)
+{
+	struct image_sig_info info;
+	int ret;
+
+	ret = image_pre_load_sig_setup(&info);
+	if (ret < 0)
+		goto out;
+	if (ret > 0) {
+		ret = 0;
+		goto out;
+	}
+
+	ret = image_pre_load_sig_check_magic(&info, addr);
+	if (ret < 0)
+		goto out;
+	if (ret > 0) {
+		ret = 0;
+		goto out;
+	}
+
+	/* Check the signature of the signature header */
+	ret = image_pre_load_sig_check_header_sig(&info, addr);
+	if (ret < 0)
+		goto out;
+
+	/* Check sha256 of the image signature */
+	ret = image_pre_load_sig_check_img_sig_sha256(&info, addr);
+	if (ret < 0)
+		goto out;
+
+	/* Check the image signature */
+	ret = image_pre_load_sig_check_img_sig(&info, addr);
+	if (!ret) {
+		u32 header_size;
+
+		ret = image_pre_load_sig_get_header_size(addr, &header_size);
+		if (ret) {
+			log_err("%s: can't get header size\n", __func__);
+			ret = -EINVAL;
+			goto out;
+		}
+
+		image_load_offset += header_size;
+	}
+
+ out:
+	return ret;
+}
+
+int image_pre_load(ulong addr)
+{
+	int ret = 0;
+
+	image_load_offset = 0;
+
+	if (CONFIG_IS_ENABLED(IMAGE_PRE_LOAD_SIG))
+		ret = image_pre_load_sig(addr);
+
+	return ret;
+}
diff --git a/include/image.h b/include/image.h
index 97e5f2e..fbcf70f 100644
--- a/include/image.h
+++ b/include/image.h
@@ -48,6 +48,7 @@ struct fdt_region;
 extern ulong image_load_addr;		/* Default Load Address */
 extern ulong image_save_addr;		/* Default Save Address */
 extern ulong image_save_size;		/* Default Save Size */
+extern ulong image_load_offset;	/* Default Load Address Offset */
 
 /* An invalid size, meaning that the image size is not known */
 #define IMAGE_SIZE_INVAL	(-1UL)
@@ -1324,6 +1325,19 @@ struct crypto_algo *image_get_crypto_algo(const char *full_name);
 struct padding_algo *image_get_padding_algo(const char *name);
 
 /**
+ * image_pre_load() - Manage pre load header
+ *
+ * Manage the pre-load header before launching the image.
+ * It checks the signature of the image. It also set the
+ * variable image_load_offset to skip this header before
+ * launching the image.
+ *
+ * @param addr		Address of the image
+ * @return: 0 on success, -ve on error
+ */
+int image_pre_load(ulong addr);
+
+/**
  * fit_image_verify_required_sigs() - Verify signatures marked as 'required'
  *
  * @fit:		FIT to check