// crossfire: distributed brute force infrastructure
//
// Copyright (C) 2020 haskal
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program 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 Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

#pragma once

#include <sys/types.h>
#include <elf.h>
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <stdint.h>
#include <stdbool.h>
#include <sys/mman.h>
#include <errno.h>

#define _SELF_NAME "/proc/self/exe"

#if ELF_BITS == 32
#define Elf_Ehdr Elf32_Ehdr
#define Elf_Shdr Elf32_Shdr
#elif ELF_BITS == 64
#define Elf_Ehdr Elf64_Ehdr
#define Elf_Shdr Elf64_Shdr
#endif

#define CHK_GENERIC(what, ret) if (what) { return ret; }
#define CHK_NULL_NULL(what) CHK_GENERIC(what == NULL, NULL)
#define CHK_NEG_NEG(what) CHK_GENERIC(what < 0, -1)

static inline char* readlink_exactly(const char* name) {
    ssize_t len;
    ssize_t blen = 256;
    char* s = malloc(blen);
    CHK_NULL_NULL(s);
    while (true) {
        len = readlink(name, s, blen - 1);
        if (len == (blen - 1)) {
            free(s);
            blen *= 2;
            s = malloc(blen);
            CHK_NULL_NULL(s);
        } else if (len < 0) {
            return NULL;
        } else {
            return s;
        }
    }
}

static inline int readexactly(int fd, uint8_t* buf, size_t size) {
    for (size_t i = 0; i < size;) {
        ssize_t res = read(fd, &buf[i], size - i);
        if (res < 0) {
            if (errno == EINTR) { continue; }
            return -1;
        }
        i += res;
    }
    return size;
}

typedef struct {
    char* self_name;
    size_t self_size;
    void* self_mm;
    Elf_Ehdr* ehdr;
    char* strs;
} boot_ctx;

typedef struct {
    off_t offset;
    size_t size;
} boot_lookup;

static int init_boot_ctx(boot_ctx* ctx) {
    // i fucking hate C
    char* self_name = readlink_exactly(_SELF_NAME);
    CHK_GENERIC(self_name == NULL, -1);
    ctx->self_name = self_name;
    int fd = open(self_name, O_RDONLY);
    CHK_NEG_NEG(fd);
    ssize_t len = lseek(fd, 0, SEEK_END);
    CHK_NEG_NEG(len);
    ctx->self_size = len;
    void* map = mmap(NULL, len, PROT_READ, MAP_SHARED, fd, 0);
    CHK_GENERIC(map == MAP_FAILED, -1);
    CHK_NEG_NEG(close(fd));
    ctx->self_mm = map;
    ctx->ehdr = map;
    off_t shdr_off = ctx->ehdr->e_shoff + (ctx->ehdr->e_shstrndx * ctx->ehdr->e_shentsize);
    Elf_Shdr* shdr = (void*) (((uint8_t*) map) + shdr_off);
    ctx->strs = ((uint8_t*) map) + shdr->sh_offset;
    return 0;
}

static boot_lookup boot_ctx_lookup(boot_ctx* ctx, const char* sectname) {
    boot_lookup bl = { (off_t) -1, (size_t) -1 };
    for (size_t i = 0; i < ctx->ehdr->e_shnum; i++) {
        Elf_Shdr* shdr = (void*) (((uint8_t*) ctx->self_mm)
                + ctx->ehdr->e_shoff + (i * ctx->ehdr->e_shentsize));
        if (!strcmp(ctx->strs + shdr->sh_name, sectname)) {
            bl.offset = shdr->sh_offset;
            bl.size = shdr->sh_size;
            return bl;
        }
    }
    return bl;
}

static void unload_boot_ctx(boot_ctx* ctx) {
    free(ctx->self_name);
    if (munmap(ctx->self_mm, ctx->self_size) < 0) {
        printf("NO SHONKS\n");
        exit(-1);
    }
}