// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright (c) 2013, Google Inc.
 */

#ifndef USE_HOSTCC
#include <common.h>
#include <fdtdec.h>
#include <asm/types.h>
#include <asm/byteorder.h>
#include <linux/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_padding() - Verify RSA message padding is valid
 *
 * Verify a RSA message's padding is consistent with PKCS1.5
 * padding as described in the RSA PKCS#1 v2.1 standard.
 *
 * @msg:        Padded message
 * @pad_len:    Number of expected padding bytes
 * @algo:       Checksum algo structure having information on DER encoding etc.
 * @return 0 on success, != 0 on failure
 */
static int rsa_verify_padding(const uint8_t *msg, const int pad_len,
                              struct checksum_algo *algo)
{
        int ff_len;
        int ret;

        /* first byte must be 0x00 */
        ret = *msg++;
        /* second byte must be 0x01 */
        ret |= *msg++ ^ 0x01;
        /* next ff_len bytes must be 0xff */
        ff_len = pad_len - algo->der_len - 3;
        ret |= *msg ^ 0xff;
        ret |= memcmp(msg, msg+1, ff_len-1);
        msg += ff_len;
        /* next byte must be 0x00 */
        ret |= *msg++;
        /* next der_len bytes must match der_prefix */
        ret |= memcmp(msg, algo->der_prefix, algo->der_len);

        return ret;
}

int padding_pkcs_15_verify(struct image_sign_info *info,
                           uint8_t *msg, int msg_len,
                           const uint8_t *hash, int hash_len)
{
        struct checksum_algo *checksum = info->checksum;
        int ret, pad_len = msg_len - checksum->checksum_len;

        /* Check pkcs1.5 padding bytes. */
        ret = rsa_verify_padding(msg, pad_len, checksum);
        if (ret) {
                debug("In RSAVerify(): Padding check failed!\n");
                return -EINVAL;
        }

        /* Check hash. */
        if (memcmp((uint8_t *)msg + pad_len, hash, msg_len - pad_len)) {
                debug("In RSAVerify(): Hash check failed!\n");
                return -EACCES;
        }

        return 0;
}

#ifdef CONFIG_FIT_ENABLE_RSASSA_PSS_SUPPORT
static void u32_i2osp(uint32_t val, uint8_t *buf)
{
        buf[0] = (uint8_t)((val >> 24) & 0xff);
        buf[1] = (uint8_t)((val >> 16) & 0xff);
        buf[2] = (uint8_t)((val >>  8) & 0xff);
        buf[3] = (uint8_t)((val >>  0) & 0xff);
}

/**
 * mask_generation_function1() - generate an octet string
 *
 * Generate an octet string used to check rsa signature.
 * It use an input octet string and a hash function.
 *
 * @checksum:   A Hash function
 * @seed:       Specifies an input variable octet string
 * @seed_len:   Size of the input octet string
 * @output:     Specifies the output octet string
 * @output_len: Size of the output octet string
 * @return 0 if the octet string was correctly generated, others on error
 */
static int mask_generation_function1(struct checksum_algo *checksum,
                                     uint8_t *seed, int seed_len,
                                     uint8_t *output, int output_len)
{
        struct image_region region[2];
        int ret = 0, i, i_output = 0, region_count = 2;
        uint32_t counter = 0;
        uint8_t buf_counter[4], *tmp;
        int hash_len = checksum->checksum_len;

        memset(output, 0, output_len);

        region[0].data = seed;
        region[0].size = seed_len;
        region[1].data = &buf_counter[0];
        region[1].size = 4;

        tmp = malloc(hash_len);
        if (!tmp) {
                debug("%s: can't allocate array tmp\n", __func__);
                ret = -ENOMEM;
                goto out;
        }

        while (i_output < output_len) {
                u32_i2osp(counter, &buf_counter[0]);

                ret = checksum->calculate(checksum->name,
                                          region, region_count,
                                          tmp);
                if (ret < 0) {
                        debug("%s: Error in checksum calculation\n", __func__);
                        goto out;
                }

                i = 0;
                while ((i_output < output_len) && (i < hash_len)) {
                        output[i_output] = tmp[i];
                        i_output++;
                        i++;
                }

                counter++;
        }

out:
        free(tmp);

        return ret;
}

static int compute_hash_prime(struct checksum_algo *checksum,
                              uint8_t *pad, int pad_len,
                              uint8_t *hash, int hash_len,
                              uint8_t *salt, int salt_len,
                              uint8_t *hprime)
{
        struct image_region region[3];
        int ret, region_count = 3;

        region[0].data = pad;
        region[0].size = pad_len;
        region[1].data = hash;
        region[1].size = hash_len;
        region[2].data = salt;
        region[2].size = salt_len;

        ret = checksum->calculate(checksum->name, region, region_count, hprime);
        if (ret < 0) {
                debug("%s: Error in checksum calculation\n", __func__);
                goto out;
        }

out:
        return ret;
}

int padding_pss_verify(struct image_sign_info *info,
                       uint8_t *msg, int msg_len,
                       const uint8_t *hash, int hash_len)
{
        uint8_t *masked_db = NULL;
        int masked_db_len = msg_len - hash_len - 1;
        uint8_t *h = NULL, *hprime = NULL;
        int h_len = hash_len;
        uint8_t *db_mask = NULL;
        int db_mask_len = masked_db_len;
        uint8_t *db = NULL, *salt = NULL;
        int db_len = masked_db_len, salt_len = msg_len - hash_len - 2;
        uint8_t pad_zero[8] = { 0 };
        int ret, i, leftmost_bits = 1;
        uint8_t leftmost_mask;
        struct checksum_algo *checksum = info->checksum;

        /* first, allocate everything */
        masked_db = malloc(masked_db_len);
        h = malloc(h_len);
        db_mask = malloc(db_mask_len);
        db = malloc(db_len);
        salt = malloc(salt_len);
        hprime = malloc(hash_len);
        if (!masked_db || !h || !db_mask || !db || !salt || !hprime) {
                printf("%s: can't allocate some buffer\n", __func__);
                ret = -ENOMEM;
                goto out;
        }

        /* step 4: check if the last byte is 0xbc */
        if (msg[msg_len - 1] != 0xbc) {
                printf("%s: invalid pss padding (0xbc is missing)\n", __func__);
                ret = -EINVAL;
                goto out;
        }

        /* step 5 */
        memcpy(masked_db, msg, masked_db_len);
        memcpy(h, msg + masked_db_len, h_len);

        /* step 6 */
        leftmost_mask = (0xff >> (8 - leftmost_bits)) << (8 - leftmost_bits);
        if (masked_db[0] & leftmost_mask) {
                printf("%s: invalid pss padding ", __func__);
                printf("(leftmost bit of maskedDB not zero)\n");
                ret = -EINVAL;
                goto out;
        }

        /* step 7 */
        mask_generation_function1(checksum, h, h_len, db_mask, db_mask_len);

        /* step 8 */
        for (i = 0; i < db_len; i++)
                db[i] = masked_db[i] ^ db_mask[i];

        /* step 9 */
        db[0] &= 0xff >> leftmost_bits;

        /* step 10 */
        if (db[0] != 0x01) {
                printf("%s: invalid pss padding ", __func__);
                printf("(leftmost byte of db isn't 0x01)\n");
                ret = EINVAL;
                goto out;
        }

        /* step 11 */
        memcpy(salt, &db[1], salt_len);

        /* step 12 & 13 */
        compute_hash_prime(checksum, pad_zero, 8,
                           (uint8_t *)hash, hash_len,
                           salt, salt_len, hprime);

        /* step 14 */
        ret = memcmp(h, hprime, hash_len);

out:
        free(hprime);
        free(salt);
        free(db);
        free(db_mask);
        free(h);
        free(masked_db);

        return ret;
}
#endif

/**
 * 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.
 *
 * @info:       Specifies key and FIT information
 * @prop:       Specifies key
 * @sig:        Signature
 * @sig_len:    Number of bytes in signature
 * @hash:       Pointer to the expected hash
 * @key_len:    Number of bytes in rsa key
 * @return 0 if verified, -ve on error
 */
static int rsa_verify_key(struct image_sign_info *info,
                          struct key_prop *prop, const uint8_t *sig,
                          const uint32_t sig_len, const uint8_t *hash,
                          const uint32_t key_len)
{
        int ret;
#if !defined(USE_HOSTCC)
        struct udevice *mod_exp_dev;
#endif
        struct checksum_algo *checksum = info->checksum;
        struct padding_algo *padding = info->padding;
        int hash_len;

        if (!prop || !sig || !hash || !checksum)
                return -EIO;

        if (sig_len != (prop->num_bits / 8)) {
                debug("Signature is of incorrect length %d\n", sig_len);
                return -EINVAL;
        }

        debug("Checksum algorithm: %s", checksum->name);

        /* Sanity check for stack size */
        if (sig_len > RSA_MAX_SIG_BITS / 8) {
                debug("Signature length %u exceeds maximum %d\n", sig_len,
                      RSA_MAX_SIG_BITS / 8);
                return -EINVAL;
        }

        uint8_t buf[sig_len];
        hash_len = checksum->checksum_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\n");
                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\n");
                return ret;
        }

        ret = padding->verify(info, buf, key_len, hash, hash_len);
        if (ret) {
                debug("In RSAVerify(): padding check failed!\n");
                return ret;
        }

        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(info, &prop, sig, sig_len, hash,
                             info->crypto->key_len);

        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->crypto->key_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->checksum->checksum_len >
            info->crypto->key_len) {
                debug("%s: invlaid checksum-algorithm %s for %s\n",
                      __func__, info->checksum->name, info->crypto->name);
                return -EINVAL;
        }

        sig_node = fdt_subnode_offset(blob, 0, FIT_SIG_NODENAME);
        if (sig_node < 0) {
                debug("%s: No signature node found\n", __func__);
                return -ENOENT;
        }

        /* Calculate checksum with checksum-algorithm */
        ret = info->checksum->calculate(info->checksum->name,
                                        region, region_count, hash);
        if (ret < 0) {
                debug("%s: Error in checksum calculation\n", __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;
}