/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2014 The FreeBSD Foundation
 *
 * This software was developed by Edward Tomasz Napierala under sponsorship
 * from the FreeBSD Foundation.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */

#include <sys/param.h>
#include <sys/capsicum.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <assert.h>
#include <capsicum_helpers.h>
#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <openssl/evp.h>
#include <openssl/err.h>
#include <openssl/pem.h>

#include "uefisign.h"

static void
load(struct executable *x)
{
        int error, fd;
        struct stat sb;
        char *buf;
        size_t nread, len;

        fd = fileno(x->x_fp);

        error = fstat(fd, &sb);
        if (error != 0)
                err(1, "%s: fstat", x->x_path);

        len = sb.st_size;
        if (len <= 0)
                errx(1, "%s: file is empty", x->x_path);

        buf = malloc(len);
        if (buf == NULL)
                err(1, "%s: cannot malloc %zd bytes", x->x_path, len);

        nread = fread(buf, len, 1, x->x_fp);
        if (nread != 1)
                err(1, "%s: fread", x->x_path);

        x->x_buf = buf;
        x->x_len = len;
}

static void
digest_range(struct executable *x, EVP_MD_CTX *mdctx, off_t off, size_t len)
{
        int ok;

        range_check(x, off, len, "chunk");

        ok = EVP_DigestUpdate(mdctx, x->x_buf + off, len);
        if (ok == 0) {
                ERR_print_errors_fp(stderr);
                errx(1, "EVP_DigestUpdate(3) failed");
        }
}

static void
digest(struct executable *x)
{
        EVP_MD_CTX *mdctx;
        const EVP_MD *md;
        size_t sum_of_bytes_hashed;
        int i, ok;

        /*
         * Windows Authenticode Portable Executable Signature Format
         * spec version 1.0 specifies MD5 and SHA1.  However, pesign
         * and sbsign both use SHA256, so do the same.
         */
        md = EVP_get_digestbyname(DIGEST);
        if (md == NULL) {
                ERR_print_errors_fp(stderr);
                errx(1, "EVP_get_digestbyname(\"%s\") failed", DIGEST);
        }

        mdctx = EVP_MD_CTX_create();
        if (mdctx == NULL) {
                ERR_print_errors_fp(stderr);
                errx(1, "EVP_MD_CTX_create(3) failed");
        }

        ok = EVP_DigestInit_ex(mdctx, md, NULL);
        if (ok == 0) {
                ERR_print_errors_fp(stderr);
                errx(1, "EVP_DigestInit_ex(3) failed");
        }

        /*
         * According to the Authenticode spec, we need to compute
         * the digest in a rather... specific manner; see "Calculating
         * the PE Image Hash" part of the spec for details.
         *
         * First, everything from 0 to before the PE checksum.
         */
        digest_range(x, mdctx, 0, x->x_checksum_off);

        /*
         * Second, from after the PE checksum to before the Certificate
         * entry in Data Directory.
         */
        digest_range(x, mdctx, x->x_checksum_off + x->x_checksum_len,
            x->x_certificate_entry_off -
            (x->x_checksum_off + x->x_checksum_len));

        /*
         * Then, from after the Certificate entry to the end of headers.
         */
        digest_range(x, mdctx,
            x->x_certificate_entry_off + x->x_certificate_entry_len,
            x->x_headers_len -
            (x->x_certificate_entry_off + x->x_certificate_entry_len));

        /*
         * Then, each section in turn, as specified in the PE Section Table.
         *
         * XXX: Sorting.
         */
        sum_of_bytes_hashed = x->x_headers_len;
        for (i = 0; i < x->x_nsections; i++) {
                digest_range(x, mdctx,
                    x->x_section_off[i], x->x_section_len[i]);
                sum_of_bytes_hashed += x->x_section_len[i];
        }

        /*
         * I believe this can happen with overlapping sections.
         */
        if (sum_of_bytes_hashed > x->x_len)
                errx(1, "number of bytes hashed is larger than file size");

        /*
         * I can't really explain this one; just do what the spec says.
         */
        if (sum_of_bytes_hashed < x->x_len) {
                digest_range(x, mdctx, sum_of_bytes_hashed,
                    x->x_len - (signature_size(x) + sum_of_bytes_hashed));
        }

        ok = EVP_DigestFinal_ex(mdctx, x->x_digest, &x->x_digest_len);
        if (ok == 0) {
                ERR_print_errors_fp(stderr);
                errx(1, "EVP_DigestFinal_ex(3) failed");
        }

        EVP_MD_CTX_destroy(mdctx);
}

static void
show_digest(const struct executable *x)
{
        int i;

        printf("computed %s digest ", DIGEST);
        for (i = 0; i < (int)x->x_digest_len; i++)
                printf("%02x", (unsigned char)x->x_digest[i]);
        printf("; digest len %u\n", x->x_digest_len);
}

static void
send_digest(const struct executable *x, int pipefd)
{

        send_chunk(x->x_digest, x->x_digest_len, pipefd);
}

static void
receive_signature(struct executable *x, int pipefd)
{

        receive_chunk(&x->x_signature, &x->x_signature_len, pipefd);
}

static void
save(struct executable *x, FILE *fp, const char *path)
{
        size_t nwritten;

        assert(fp != NULL);
        assert(path != NULL);

        nwritten = fwrite(x->x_buf, x->x_len, 1, fp);
        if (nwritten != 1)
                err(1, "%s: fwrite", path);
}

int
child(const char *inpath, const char *outpath, int pipefd,
    bool Vflag, bool vflag)
{
        FILE *outfp = NULL, *infp = NULL;
        struct executable *x;

        infp = checked_fopen(inpath, "r");
        if (outpath != NULL)
                outfp = checked_fopen(outpath, "w");

        if (caph_enter() < 0)
                err(1, "cap_enter");

        x = calloc(1, sizeof(*x));
        if (x == NULL)
                err(1, "calloc");
        x->x_path = inpath;
        x->x_fp = infp;

        load(x);
        parse(x);
        if (Vflag) {
                if (signature_size(x) == 0)
                        errx(1, "file not signed");

                printf("file contains signature\n");
                if (vflag) {
                        digest(x);
                        show_digest(x);
                        show_certificate(x);
                }
        } else {
                if (signature_size(x) != 0)
                        errx(1, "file already signed");

                digest(x);
                if (vflag)
                        show_digest(x);
                send_digest(x, pipefd);
                receive_signature(x, pipefd);
                update(x);
                save(x, outfp, outpath);
        }

        return (0);
}