/*
   * Copyright (c) 2013, Google Inc.
   *
   * SPDX-License-Identifier:	GPL-2.0+
   */
  
  #include "mkimage.h"
  #include <stdio.h>
  #include <string.h>
  #include <image.h>
  #include <time.h>
  #include <openssl/rsa.h>
  #include <openssl/pem.h>
  #include <openssl/err.h>
  #include <openssl/ssl.h>
  #include <openssl/evp.h>
  
  #if OPENSSL_VERSION_NUMBER >= 0x10000000L
  #define HAVE_ERR_REMOVE_THREAD_STATE
  #endif
  
  static int rsa_err(const char *msg)
  {
  	unsigned long sslErr = ERR_get_error();
  
  	fprintf(stderr, "%s", msg);
  	fprintf(stderr, ": %s
  ",
  		ERR_error_string(sslErr, 0));
  
  	return -1;
  }
  
  /**
   * rsa_get_pub_key() - read a public key from a .crt file
   *
   * @keydir:	Directory containins the key
   * @name	Name of key file (will have a .crt extension)
   * @rsap	Returns RSA object, or NULL on failure
   * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
   */
  static int rsa_get_pub_key(const char *keydir, const char *name, RSA **rsap)
  {
  	char path[1024];
  	EVP_PKEY *key;
  	X509 *cert;
  	RSA *rsa;
  	FILE *f;
  	int ret;
  
  	*rsap = NULL;
  	snprintf(path, sizeof(path), "%s/%s.crt", keydir, name);
  	f = fopen(path, "r");
  	if (!f) {
  		fprintf(stderr, "Couldn't open RSA certificate: '%s': %s
  ",
  			path, strerror(errno));
  		return -EACCES;
  	}
  
  	/* Read the certificate */
  	cert = NULL;
  	if (!PEM_read_X509(f, &cert, NULL, NULL)) {
  		rsa_err("Couldn't read certificate");
  		ret = -EINVAL;
  		goto err_cert;
  	}
  
  	/* Get the public key from the certificate. */
  	key = X509_get_pubkey(cert);
  	if (!key) {
  		rsa_err("Couldn't read public key
  ");
  		ret = -EINVAL;
  		goto err_pubkey;
  	}
  
  	/* Convert to a RSA_style key. */
  	rsa = EVP_PKEY_get1_RSA(key);
  	if (!rsa) {
  		rsa_err("Couldn't convert to a RSA style key");
  		ret = -EINVAL;
  		goto err_rsa;
  	}
  	fclose(f);
  	EVP_PKEY_free(key);
  	X509_free(cert);
  	*rsap = rsa;
  
  	return 0;
  
  err_rsa:
  	EVP_PKEY_free(key);
  err_pubkey:
  	X509_free(cert);
  err_cert:
  	fclose(f);
  	return ret;
  }
  
  /**
   * rsa_get_priv_key() - read a private key from a .key file
   *
   * @keydir:	Directory containins the key
   * @name	Name of key file (will have a .key extension)
   * @rsap	Returns RSA object, or NULL on failure
   * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
   */
  static int rsa_get_priv_key(const char *keydir, const char *name, RSA **rsap)
  {
  	char path[1024];
  	RSA *rsa;
  	FILE *f;
  
  	*rsap = NULL;
  	snprintf(path, sizeof(path), "%s/%s.key", keydir, name);
  	f = fopen(path, "r");
  	if (!f) {
  		fprintf(stderr, "Couldn't open RSA private key: '%s': %s
  ",
  			path, strerror(errno));
  		return -ENOENT;
  	}
  
  	rsa = PEM_read_RSAPrivateKey(f, 0, NULL, path);
  	if (!rsa) {
  		rsa_err("Failure reading private key");
  		fclose(f);
  		return -EPROTO;
  	}
  	fclose(f);
  	*rsap = rsa;
  
  	return 0;
  }
  
  static int rsa_init(void)
  {
  	int ret;
  
  	ret = SSL_library_init();
  	if (!ret) {
  		fprintf(stderr, "Failure to init SSL library
  ");
  		return -1;
  	}
  	SSL_load_error_strings();
  
  	OpenSSL_add_all_algorithms();
  	OpenSSL_add_all_digests();
  	OpenSSL_add_all_ciphers();
  
  	return 0;
  }
  
  static void rsa_remove(void)
  {
  	CRYPTO_cleanup_all_ex_data();
  	ERR_free_strings();
  #ifdef HAVE_ERR_REMOVE_THREAD_STATE
  	ERR_remove_thread_state(NULL);
  #else
  	ERR_remove_state(0);
  #endif
  	EVP_cleanup();
  }
  
  static int rsa_sign_with_key(RSA *rsa, struct checksum_algo *checksum_algo,
  		const struct image_region region[], int region_count,
  		uint8_t **sigp, uint *sig_size)
  {
  	EVP_PKEY *key;
  	EVP_MD_CTX *context;
  	int size, ret = 0;
  	uint8_t *sig;
  	int i;
  
  	key = EVP_PKEY_new();
  	if (!key)
  		return rsa_err("EVP_PKEY object creation failed");
  
  	if (!EVP_PKEY_set1_RSA(key, rsa)) {
  		ret = rsa_err("EVP key setup failed");
  		goto err_set;
  	}
  
  	size = EVP_PKEY_size(key);
  	sig = malloc(size);
  	if (!sig) {
  		fprintf(stderr, "Out of memory for signature (%d bytes)
  ",
  			size);
  		ret = -ENOMEM;
  		goto err_alloc;
  	}
  
  	context = EVP_MD_CTX_create();
  	if (!context) {
  		ret = rsa_err("EVP context creation failed");
  		goto err_create;
  	}
  	EVP_MD_CTX_init(context);
  	if (!EVP_SignInit(context, checksum_algo->calculate_sign())) {
  		ret = rsa_err("Signer setup failed");
  		goto err_sign;
  	}
  
  	for (i = 0; i < region_count; i++) {
  		if (!EVP_SignUpdate(context, region[i].data, region[i].size)) {
  			ret = rsa_err("Signing data failed");
  			goto err_sign;
  		}
  	}
  
  	if (!EVP_SignFinal(context, sig, sig_size, key)) {
  		ret = rsa_err("Could not obtain signature");
  		goto err_sign;
  	}
  	EVP_MD_CTX_cleanup(context);
  	EVP_MD_CTX_destroy(context);
  	EVP_PKEY_free(key);
  
  	debug("Got signature: %d bytes, expected %d
  ", *sig_size, size);
  	*sigp = sig;
  	*sig_size = size;
  
  	return 0;
  
  err_sign:
  	EVP_MD_CTX_destroy(context);
  err_create:
  	free(sig);
  err_alloc:
  err_set:
  	EVP_PKEY_free(key);
  	return ret;
  }
  
  int rsa_sign(struct image_sign_info *info,
  	     const struct image_region region[], int region_count,
  	     uint8_t **sigp, uint *sig_len)
  {
  	RSA *rsa;
  	int ret;
  
  	ret = rsa_init();
  	if (ret)
  		return ret;
  
  	ret = rsa_get_priv_key(info->keydir, info->keyname, &rsa);
  	if (ret)
  		goto err_priv;
  	ret = rsa_sign_with_key(rsa, info->algo->checksum, region,
  				region_count, sigp, sig_len);
  	if (ret)
  		goto err_sign;
  
  	RSA_free(rsa);
  	rsa_remove();
  
  	return ret;
  
  err_sign:
  	RSA_free(rsa);
  err_priv:
  	rsa_remove();
  	return ret;
  }
  
  /*
   * rsa_get_exponent(): - Get the public exponent from an RSA key
   */
  static int rsa_get_exponent(RSA *key, uint64_t *e)
  {
  	int ret;
  	BIGNUM *bn_te;
  	uint64_t te;
  
  	ret = -EINVAL;
  	bn_te = NULL;
  
  	if (!e)
  		goto cleanup;
  
  	if (BN_num_bits(key->e) > 64)
  		goto cleanup;
  
  	*e = BN_get_word(key->e);
  
  	if (BN_num_bits(key->e) < 33) {
  		ret = 0;
  		goto cleanup;
  	}
  
  	bn_te = BN_dup(key->e);
  	if (!bn_te)
  		goto cleanup;
  
  	if (!BN_rshift(bn_te, bn_te, 32))
  		goto cleanup;
  
  	if (!BN_mask_bits(bn_te, 32))
  		goto cleanup;
  
  	te = BN_get_word(bn_te);
  	te <<= 32;
  	*e |= te;
  	ret = 0;
  
  cleanup:
  	if (bn_te)
  		BN_free(bn_te);
  
  	return ret;
  }
  
  /*
   * rsa_get_params(): - Get the important parameters of an RSA public key
   */
  int rsa_get_params(RSA *key, uint64_t *exponent, uint32_t *n0_invp,
  		   BIGNUM **modulusp, BIGNUM **r_squaredp)
  {
  	BIGNUM *big1, *big2, *big32, *big2_32;
  	BIGNUM *n, *r, *r_squared, *tmp;
  	BN_CTX *bn_ctx = BN_CTX_new();
  	int ret = 0;
  
  	/* Initialize BIGNUMs */
  	big1 = BN_new();
  	big2 = BN_new();
  	big32 = BN_new();
  	r = BN_new();
  	r_squared = BN_new();
  	tmp = BN_new();
  	big2_32 = BN_new();
  	n = BN_new();
  	if (!big1 || !big2 || !big32 || !r || !r_squared || !tmp || !big2_32 ||
  	    !n) {
  		fprintf(stderr, "Out of memory (bignum)
  ");
  		return -ENOMEM;
  	}
  
  	if (0 != rsa_get_exponent(key, exponent))
  		ret = -1;
  
  	if (!BN_copy(n, key->n) || !BN_set_word(big1, 1L) ||
  	    !BN_set_word(big2, 2L) || !BN_set_word(big32, 32L))
  		ret = -1;
  
  	/* big2_32 = 2^32 */
  	if (!BN_exp(big2_32, big2, big32, bn_ctx))
  		ret = -1;
  
  	/* Calculate n0_inv = -1 / n[0] mod 2^32 */
  	if (!BN_mod_inverse(tmp, n, big2_32, bn_ctx) ||
  	    !BN_sub(tmp, big2_32, tmp))
  		ret = -1;
  	*n0_invp = BN_get_word(tmp);
  
  	/* Calculate R = 2^(# of key bits) */
  	if (!BN_set_word(tmp, BN_num_bits(n)) ||
  	    !BN_exp(r, big2, tmp, bn_ctx))
  		ret = -1;
  
  	/* Calculate r_squared = R^2 mod n */
  	if (!BN_copy(r_squared, r) ||
  	    !BN_mul(tmp, r_squared, r, bn_ctx) ||
  	    !BN_mod(r_squared, tmp, n, bn_ctx))
  		ret = -1;
  
  	*modulusp = n;
  	*r_squaredp = r_squared;
  
  	BN_free(big1);
  	BN_free(big2);
  	BN_free(big32);
  	BN_free(r);
  	BN_free(tmp);
  	BN_free(big2_32);
  	if (ret) {
  		fprintf(stderr, "Bignum operations failed
  ");
  		return -ENOMEM;
  	}
  
  	return ret;
  }
  
  static int fdt_add_bignum(void *blob, int noffset, const char *prop_name,
  			  BIGNUM *num, int num_bits)
  {
  	int nwords = num_bits / 32;
  	int size;
  	uint32_t *buf, *ptr;
  	BIGNUM *tmp, *big2, *big32, *big2_32;
  	BN_CTX *ctx;
  	int ret;
  
  	tmp = BN_new();
  	big2 = BN_new();
  	big32 = BN_new();
  	big2_32 = BN_new();
  	if (!tmp || !big2 || !big32 || !big2_32) {
  		fprintf(stderr, "Out of memory (bignum)
  ");
  		return -ENOMEM;
  	}
  	ctx = BN_CTX_new();
  	if (!tmp) {
  		fprintf(stderr, "Out of memory (bignum context)
  ");
  		return -ENOMEM;
  	}
  	BN_set_word(big2, 2L);
  	BN_set_word(big32, 32L);
  	BN_exp(big2_32, big2, big32, ctx); /* B = 2^32 */
  
  	size = nwords * sizeof(uint32_t);
  	buf = malloc(size);
  	if (!buf) {
  		fprintf(stderr, "Out of memory (%d bytes)
  ", size);
  		return -ENOMEM;
  	}
  
  	/* Write out modulus as big endian array of integers */
  	for (ptr = buf + nwords - 1; ptr >= buf; ptr--) {
  		BN_mod(tmp, num, big2_32, ctx); /* n = N mod B */
  		*ptr = cpu_to_fdt32(BN_get_word(tmp));
  		BN_rshift(num, num, 32); /*  N = N/B */
  	}
  
  	ret = fdt_setprop(blob, noffset, prop_name, buf, size);
  	if (ret) {
  		fprintf(stderr, "Failed to write public key to FIT
  ");
  		return -ENOSPC;
  	}
  	free(buf);
  	BN_free(tmp);
  	BN_free(big2);
  	BN_free(big32);
  	BN_free(big2_32);
  
  	return ret;
  }
  
  int rsa_add_verify_data(struct image_sign_info *info, void *keydest)
  {
  	BIGNUM *modulus, *r_squared;
  	uint64_t exponent;
  	uint32_t n0_inv;
  	int parent, node;
  	char name[100];
  	int ret;
  	int bits;
  	RSA *rsa;
  
  	debug("%s: Getting verification data
  ", __func__);
  	ret = rsa_get_pub_key(info->keydir, info->keyname, &rsa);
  	if (ret)
  		return ret;
  	ret = rsa_get_params(rsa, &exponent, &n0_inv, &modulus, &r_squared);
  	if (ret)
  		return ret;
  	bits = BN_num_bits(modulus);
  	parent = fdt_subnode_offset(keydest, 0, FIT_SIG_NODENAME);
  	if (parent == -FDT_ERR_NOTFOUND) {
  		parent = fdt_add_subnode(keydest, 0, FIT_SIG_NODENAME);
  		if (parent < 0) {
  			ret = parent;
  			if (ret != -FDT_ERR_NOSPACE) {
  				fprintf(stderr, "Couldn't create signature node: %s
  ",
  					fdt_strerror(parent));
  			}
  		}
  	}
  	if (ret)
  		goto done;
  
  	/* Either create or overwrite the named key node */
  	snprintf(name, sizeof(name), "key-%s", info->keyname);
  	node = fdt_subnode_offset(keydest, parent, name);
  	if (node == -FDT_ERR_NOTFOUND) {
  		node = fdt_add_subnode(keydest, parent, name);
  		if (node < 0) {
  			ret = node;
  			if (ret != -FDT_ERR_NOSPACE) {
  				fprintf(stderr, "Could not create key subnode: %s
  ",
  					fdt_strerror(node));
  			}
  		}
  	} else if (node < 0) {
  		fprintf(stderr, "Cannot select keys parent: %s
  ",
  			fdt_strerror(node));
  		ret = node;
  	}
  
  	if (!ret) {
  		ret = fdt_setprop_string(keydest, node, "key-name-hint",
  				 info->keyname);
  	}
  	if (!ret)
  		ret = fdt_setprop_u32(keydest, node, "rsa,num-bits", bits);
  	if (!ret)
  		ret = fdt_setprop_u32(keydest, node, "rsa,n0-inverse", n0_inv);
  	if (!ret) {
  		ret = fdt_setprop_u64(keydest, node, "rsa,exponent", exponent);
  	}
  	if (!ret) {
  		ret = fdt_add_bignum(keydest, node, "rsa,modulus", modulus,
  				     bits);
  	}
  	if (!ret) {
  		ret = fdt_add_bignum(keydest, node, "rsa,r-squared", r_squared,
  				     bits);
  	}
  	if (!ret) {
  		ret = fdt_setprop_string(keydest, node, FIT_ALGO_PROP,
  					 info->algo->name);
  	}
  	if (info->require_keys) {
  		ret = fdt_setprop_string(keydest, node, "required",
  					 info->require_keys);
  	}
  done:
  	BN_free(modulus);
  	BN_free(r_squared);
  	if (ret)
  		return ret == -FDT_ERR_NOSPACE ? -ENOSPC : -EIO;
  
  	return 0;
  }