/*
** Copyright (C) 2020  Johannes Kepler University Linz, Institute of Networks and Security
** Copyright (C) 2020  CDL Digidow <https://www.digidow.eu/>
**
** Licensed under the EUPL, Version 1.2 or – as soon they will be approved by
** the European Commission - subsequent versions of the EUPL (the "Licence").
** You may not use this work except in compliance with the Licence.
** 
** You should have received a copy of the European Union Public License along
** with this program.  If not, you may obtain a copy of the Licence at:
** <https://joinup.ec.europa.eu/software/page/eupl>
** 
** Unless required by applicable law or agreed to in writing, software
** distributed under the Licence is distributed on an "AS IS" basis,
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
** See the Licence for the specific language governing permissions and
** limitations under the Licence.
**
*/

#include <ecdaa-tpm.h>
#include <tss2/tss2_sys.h>
#include <tss2/tss2_tcti_mssim.h>
#include <tss2/tss2_tcti_device.h>
#include <string.h>

#define ECP_FP256BN_LENGTH 65

const char *pub_key_filename = "pub_key.txt";
const char *handle_filename = "handle.txt";

struct tpm_context {
    struct ecdaa_tpm_context tpm_ctx;
    uint8_t serialized_public_key[ECP_FP256BN_LENGTH];
    ECP_FP256BN public_key;
    unsigned char tcti_buffer[256];
    TSS2_TCTI_CONTEXT *tcti_context;
};

static void tpm_cleanup(struct tpm_context *ctx);
static int tpm_initialize(struct tpm_context *ctx, const char *pub_key_filename, const char *handle_filename);

int read_public_key_from_files(uint8_t *public_key,
        TPM2_HANDLE *key_handle,
        const char *pub_key_filename,
        const char *handle_filename)
{
    int ret = 0;

    FILE *pub_key_file_ptr = fopen(pub_key_filename, "r");
    printf("Reading: %s\n",pub_key_filename);
    if (NULL == pub_key_file_ptr)
        return -1;
    do {
        for (unsigned i=0; i < ECP_FP256BN_LENGTH; i++) {
            unsigned byt;
            if (fscanf(pub_key_file_ptr, "%02X", &byt) != 1) {
                ret = -1;
	    	printf("i=%d, fscanf did not read a byte\n",i);
                break;
            }
            public_key[i] = (uint8_t)byt;
        }
    } while(0);
    (void)fclose(pub_key_file_ptr);
    if (0 != ret)
        return -1;

    FILE *handle_file_ptr = fopen(handle_filename, "r");
    printf("Reading: %s\n",handle_filename);
    if (NULL == handle_file_ptr)
        return -1;
    do {
        for (int i=(sizeof(TPM2_HANDLE)-1); i >= 0; i--) {
            unsigned byt;
            if (fscanf(handle_file_ptr, "%02X", &byt) != 1) {
                ret = -1;
                break;
            }
            *key_handle += byt<<(i*8);
        }
        if (0 != ret)
            break;
    } while(0);
    (void)fclose(handle_file_ptr);

    return ret;
}

static int tpm_initialize(struct tpm_context *ctx, const char *pub_key_filename, const char *handle_filename)
{
    const char *device_conf = "/dev/tpm0";

    memset(ctx->tcti_buffer, 0, sizeof(ctx->tcti_buffer));

    int ret = 0;

    TPM2_HANDLE key_handle = 0;

    if (0 != read_public_key_from_files(ctx->serialized_public_key, &key_handle, pub_key_filename, handle_filename)) {
        printf("Error: error reading in public key files '%s' and '%s'\n", pub_key_filename, handle_filename);
        return -1;
    }

    ctx->tcti_context = (TSS2_TCTI_CONTEXT*)ctx->tcti_buffer;
    size_t size;
    ret = Tss2_Tcti_Device_Init(NULL, &size, device_conf);
    if (TSS2_RC_SUCCESS != ret) {
        printf("Failed to get allocation size for tcti context\n");
        return -1;
    }
    if (size > sizeof(ctx->tcti_buffer)) {
        printf("Error: device TCTI context size larger than pre-allocated buffer\n");
        return -1;
    }
    ret = Tss2_Tcti_Device_Init(ctx->tcti_context, &size, device_conf);
    if (TSS2_RC_SUCCESS != ret) {
        printf("Error: Unable to initialize device TCTI context\n");
        return -1;
    }

    ret = ecdaa_tpm_context_init(&ctx->tpm_ctx, key_handle, NULL, 0, ctx->tcti_context);
    if (0 != ret) {
        printf("Error: ecdaa_tpm_context_init failed: 0x%x\n", ret);
        return -1;
    }

    return 0;
}

static void tpm_cleanup(struct tpm_context *ctx)
{
    ecdaa_tpm_context_free(&ctx->tpm_ctx);

    if (NULL != ctx->tcti_context) {
        Tss2_Tcti_Finalize(ctx->tcti_context);
    }
}