/*
   * Copyright (c) 2013, Google Inc.
   *
   * SPDX-License-Identifier:	GPL-2.0+
   */
  
  #ifndef USE_HOSTCC
  #include <common.h>
  #include <fdtdec.h>
  #include <asm/types.h>
  #include <asm/byteorder.h>
  #include <asm/errno.h>
  #include <asm/types.h>
  #include <asm/unaligned.h>
  #include <dm.h>
  #else
  #include "fdt_host.h"
  #include "mkimage.h"
  #include <fdt_support.h>
  #endif
  #include <u-boot/rsa-mod-exp.h>
  #include <u-boot/rsa.h>
  
  /* Default public exponent for backward compatibility */
  #define RSA_DEFAULT_PUBEXP	65537
  
  /**
   * rsa_verify_key() - Verify a signature against some data using RSA Key
   *
   * Verify a RSA PKCS1.5 signature against an expected hash using
   * the RSA Key properties in prop structure.
   *
   * @prop:	Specifies key
   * @sig:	Signature
   * @sig_len:	Number of bytes in signature
   * @hash:	Pointer to the expected hash
   * @algo:	Checksum algo structure having information on RSA padding etc.
   * @return 0 if verified, -ve on error
   */
  static int rsa_verify_key(struct key_prop *prop, const uint8_t *sig,
  			  const uint32_t sig_len, const uint8_t *hash,
  			  struct checksum_algo *algo)
  {
  	const uint8_t *padding;
  	int pad_len;
  	int ret;
  #if !defined(USE_HOSTCC)
  	struct udevice *mod_exp_dev;
  #endif
  
  	if (!prop || !sig || !hash || !algo)
  		return -EIO;
  
  	if (sig_len != (prop->num_bits / 8)) {
  		debug("Signature is of incorrect length %d
  ", sig_len);
  		return -EINVAL;
  	}
  
  	debug("Checksum algorithm: %s", algo->name);
  
  	/* Sanity check for stack size */
  	if (sig_len > RSA_MAX_SIG_BITS / 8) {
  		debug("Signature length %u exceeds maximum %d
  ", sig_len,
  		      RSA_MAX_SIG_BITS / 8);
  		return -EINVAL;
  	}
  
  	uint8_t buf[sig_len];
  
  #if !defined(USE_HOSTCC)
  	ret = uclass_get_device(UCLASS_MOD_EXP, 0, &mod_exp_dev);
  	if (ret) {
  		printf("RSA: Can't find Modular Exp implementation
  ");
  		return -EINVAL;
  	}
  
  	ret = rsa_mod_exp(mod_exp_dev, sig, sig_len, prop, buf);
  #else
  	ret = rsa_mod_exp_sw(sig, sig_len, prop, buf);
  #endif
  	if (ret) {
  		debug("Error in Modular exponentation
  ");
  		return ret;
  	}
  
  	padding = algo->rsa_padding;
  	pad_len = algo->pad_len - algo->checksum_len;
  
  	/* Check pkcs1.5 padding bytes. */
  	if (memcmp(buf, padding, pad_len)) {
  		debug("In RSAVerify(): Padding check failed!
  ");
  		return -EINVAL;
  	}
  
  	/* Check hash. */
  	if (memcmp((uint8_t *)buf + pad_len, hash, sig_len - pad_len)) {
  		debug("In RSAVerify(): Hash check failed!
  ");
  		return -EACCES;
  	}
  
  	return 0;
  }
  
  /**
   * rsa_verify_with_keynode() - Verify a signature against some data using
   * information in node with prperties of RSA Key like modulus, exponent etc.
   *
   * Parse sign-node and fill a key_prop structure with properties of the
   * key.  Verify a RSA PKCS1.5 signature against an expected hash using
   * the properties parsed
   *
   * @info:	Specifies key and FIT information
   * @hash:	Pointer to the expected hash
   * @sig:	Signature
   * @sig_len:	Number of bytes in signature
   * @node:	Node having the RSA Key properties
   * @return 0 if verified, -ve on error
   */
  static int rsa_verify_with_keynode(struct image_sign_info *info,
  				   const void *hash, uint8_t *sig,
  				   uint sig_len, int node)
  {
  	const void *blob = info->fdt_blob;
  	struct key_prop prop;
  	int length;
  	int ret = 0;
  
  	if (node < 0) {
  		debug("%s: Skipping invalid node", __func__);
  		return -EBADF;
  	}
  
  	prop.num_bits = fdtdec_get_int(blob, node, "rsa,num-bits", 0);
  
  	prop.n0inv = fdtdec_get_int(blob, node, "rsa,n0-inverse", 0);
  
  	prop.public_exponent = fdt_getprop(blob, node, "rsa,exponent", &length);
  	if (!prop.public_exponent || length < sizeof(uint64_t))
  		prop.public_exponent = NULL;
  
  	prop.exp_len = sizeof(uint64_t);
  
  	prop.modulus = fdt_getprop(blob, node, "rsa,modulus", NULL);
  
  	prop.rr = fdt_getprop(blob, node, "rsa,r-squared", NULL);
  
  	if (!prop.num_bits || !prop.modulus) {
  		debug("%s: Missing RSA key info", __func__);
  		return -EFAULT;
  	}
  
  	ret = rsa_verify_key(&prop, sig, sig_len, hash, info->algo->checksum);
  
  	return ret;
  }
  
  int rsa_verify(struct image_sign_info *info,
  	       const struct image_region region[], int region_count,
  	       uint8_t *sig, uint sig_len)
  {
  	const void *blob = info->fdt_blob;
  	/* Reserve memory for maximum checksum-length */
  	uint8_t hash[info->algo->checksum->pad_len];
  	int ndepth, noffset;
  	int sig_node, node;
  	char name[100];
  	int ret;
  
  	/*
  	 * Verify that the checksum-length does not exceed the
  	 * rsa-signature-length
  	 */
  	if (info->algo->checksum->checksum_len >
  	    info->algo->checksum->pad_len) {
  		debug("%s: invlaid checksum-algorithm %s for %s
  ",
  		      __func__, info->algo->checksum->name, info->algo->name);
  		return -EINVAL;
  	}
  
  	sig_node = fdt_subnode_offset(blob, 0, FIT_SIG_NODENAME);
  	if (sig_node < 0) {
  		debug("%s: No signature node found
  ", __func__);
  		return -ENOENT;
  	}
  
  	/* Calculate checksum with checksum-algorithm */
  	ret = info->algo->checksum->calculate(info->algo->checksum->name,
  					region, region_count, hash);
  	if (ret < 0) {
  		debug("%s: Error in checksum calculation
  ", __func__);
  		return -EINVAL;
  	}
  
  	/* See if we must use a particular key */
  	if (info->required_keynode != -1) {
  		ret = rsa_verify_with_keynode(info, hash, sig, sig_len,
  			info->required_keynode);
  		if (!ret)
  			return ret;
  	}
  
  	/* Look for a key that matches our hint */
  	snprintf(name, sizeof(name), "key-%s", info->keyname);
  	node = fdt_subnode_offset(blob, sig_node, name);
  	ret = rsa_verify_with_keynode(info, hash, sig, sig_len, node);
  	if (!ret)
  		return ret;
  
  	/* No luck, so try each of the keys in turn */
  	for (ndepth = 0, noffset = fdt_next_node(info->fit, sig_node, &ndepth);
  			(noffset >= 0) && (ndepth > 0);
  			noffset = fdt_next_node(info->fit, noffset, &ndepth)) {
  		if (ndepth == 1 && noffset != node) {
  			ret = rsa_verify_with_keynode(info, hash, sig, sig_len,
  						      noffset);
  			if (!ret)
  				break;
  		}
  	}
  
  	return ret;
  }