/*
    CertStoreBearSSL.cpp - Library for Arduino ESP8266
    Copyright (c) 2018 Earle F. Philhower, III

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include "CertStoreBearSSL.h"
#include <memory>


#if defined(DEBUG_ESP_SSL) && defined(DEBUG_ESP_PORT)
#define DEBUG_BSSL(fmt, ...)  DEBUG_ESP_PORT.printf_P((PGM_P)PSTR( "BSSL:" fmt), ## __VA_ARGS__)
#else
#define DEBUG_BSSL(...)
#endif

namespace BearSSL {

extern "C" {
    // Callback for the x509 decoder
    static void dn_append(void *ctx, const void *buf, size_t len) {
        br_sha256_context *sha1 = (br_sha256_context*)ctx;
        br_sha256_update(sha1, buf, len);
    }
}


CertStore::~CertStore() {
    free(_indexName);
    free(_dataName);
}

CertStore::CertInfo CertStore::_preprocessCert(uint32_t length, uint32_t offset, const void *raw) {
    CertStore::CertInfo ci;

    // Clear the CertInfo
    memset(&ci, 0, sizeof(ci));

    // Process it using SHA256, same as the hashed_dn
    br_x509_decoder_context *ctx = new (std::nothrow) br_x509_decoder_context;
    br_sha256_context *sha256 = new (std::nothrow) br_sha256_context;
    if (!ctx || !sha256) {
        if (ctx) {
            delete ctx;
        }
        if (sha256) {
            delete sha256;
        }
        DEBUG_BSSL("CertStore::_preprocessCert: OOM\n");
        return ci;
    }

    br_sha256_init(sha256);
    br_x509_decoder_init(ctx, dn_append, sha256, nullptr, nullptr);
    br_x509_decoder_push(ctx, (const void*)raw, length);

    // Copy result to structure
    br_sha256_out(sha256, &ci.sha256);
    ci.length = length;
    ci.offset = offset;

    // Clean up allocated memory
    delete sha256;
    delete ctx;

    // Return result
    return ci;
}

// The certs.ar file is a UNIX ar format file, concatenating all the
// individual certificates into a single blob in a space-efficient way.
int CertStore::initCertStore(fs::FS &fs, const char *indexFileName, const char *dataFileName) {
    int count = 0;
    uint32_t offset = 0;

    _fs = &fs;

    // In case initCertStore called multiple times, don't leak old filenames
    free(_indexName);
    free(_dataName);

    // No strdup_P, so manually do it
    _indexName = (char *)malloc(strlen_P(indexFileName) + 1);
    _dataName = (char *)malloc(strlen_P(dataFileName) + 1);
    if (!_indexName || !_dataName) {
        free(_indexName);
        free(_dataName);
        return 0;
    }
    memcpy_P(_indexName, indexFileName, strlen_P(indexFileName) + 1);
    memcpy_P(_dataName, dataFileName, strlen_P(dataFileName) + 1);

    fs::File index = _fs->open(_indexName, "w");
    if (!index) {
        return 0;
    }

    fs::File data = _fs->open(_dataName, "r");
    if (!data) {
        index.close();
        return 0;
    }

    uint8_t magic[8];
    if (data.read(magic, sizeof(magic)) != sizeof(magic) ||
            memcmp(magic, "!<arch>\n", sizeof(magic))) {
        data.close();
        index.close();
        return 0;
    }
    offset += sizeof(magic);

    while (true) {
        uint8_t fileHeader[60];
        // 0..15 = filename in ASCII
        // 48...57 = length in decimal ASCII
        int32_t length;
        if (data.read(fileHeader, sizeof(fileHeader)) != sizeof(fileHeader)) {
            break;
        }
        offset += sizeof(fileHeader);
        fileHeader[58] = 0;
        if (1 != sscanf((char *)(fileHeader + 48), "%ld", &length) || !length) {
            break;
        }

        void *raw = malloc(length);
        if (!raw) {
            break;
        }
        if (data.read((uint8_t *)raw, length) != length) {
            free(raw);
            break;
        }

        // If the filename starts with "//" then this is a rename file, skip it
        if (fileHeader[0] != '/' || fileHeader[1] != '/') {
            CertStore::CertInfo ci = _preprocessCert(length, offset, raw);
            if (index.write((uint8_t *)&ci, sizeof(ci)) != (ssize_t)sizeof(ci)) {
                free(raw);
                break;
            }
            count++;
        }

        offset += length;
        free(raw);
        if (offset & 1) {
            uint8_t x;
            data.read(&x, 1);
            offset++;
        }
    }
    data.close();
    index.close();
    return count;
}

void CertStore::installCertStore(br_x509_minimal_context *ctx) {
    br_x509_minimal_set_dynamic(ctx, (void*)this, findHashedTA, freeHashedTA);
}

const br_x509_trust_anchor *CertStore::findHashedTA(void *ctx, void *hashed_dn, size_t len) {
    CertStore *cs = static_cast<CertStore*>(ctx);
    CertStore::CertInfo ci;

    if (!cs || len != sizeof(ci.sha256) || !cs->_indexName || !cs->_dataName || !cs->_fs) {
        return nullptr;
    }

    fs::File index = cs->_fs->open(cs->_indexName, "r");
    if (!index) {
        return nullptr;
    }

    while (index.read((uint8_t *)&ci, sizeof(ci)) == sizeof(ci)) {
        if (!memcmp(ci.sha256, hashed_dn, sizeof(ci.sha256))) {
            index.close();
            uint8_t *der = (uint8_t*)malloc(ci.length);
            if (!der) {
                return nullptr;
            }
            fs::File data = cs->_fs->open(cs->_dataName, "r");
            if (!data) {
                free(der);
                return nullptr;
            }
            if (!data.seek(ci.offset, fs::SeekSet)) {
                data.close();
                free(der);
                return nullptr;
            }
            if (data.read(der, ci.length) != (int)ci.length) {
                free(der);
                return nullptr;
            }
            data.close();
            cs->_x509 = new (std::nothrow) X509List(der, ci.length);
            free(der);
            if (!cs->_x509) {
                DEBUG_BSSL("CertStore::findHashedTA: OOM\n");
                return nullptr;
            }

            br_x509_trust_anchor *ta = (br_x509_trust_anchor*)cs->_x509->getTrustAnchors();
            memcpy(ta->dn.data, ci.sha256, sizeof(ci.sha256));
            ta->dn.len = sizeof(ci.sha256);

            return ta;
        }
    }
    index.close();
    return nullptr;
}

void CertStore::freeHashedTA(void *ctx, const br_x509_trust_anchor *ta) {
    CertStore *cs = static_cast<CertStore*>(ctx);
    (void) ta; // Unused
    delete cs->_x509;
    cs->_x509 = nullptr;
}

}
