Implement first working draft of CRC patching
This commit is contained in:
parent
c8da6e4f4c
commit
341e0cecf8
2
crc.c
2
crc.c
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@ -1,5 +1,5 @@
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/*
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* This file is part of patchelfcrc .
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* This file is part of patchelfcrc.
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* Copyright (c) 2022 Mario Hüttel.
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*
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* This program is free software: you can redistribute it and/or modify
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164
elfpatch.c
164
elfpatch.c
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@ -43,7 +43,46 @@ struct elfpatch {
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} \
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} while(0)
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#define print_err(fmt, ...) fprintf(stderr, (fmt), ## __VA_ARGS__);
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/**
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* @brief Convert a series of 4 bytes into a uint32_t dpending on endianess
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* @param data 4 bytes
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* @param little_endian data is little endian
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* @return uint32
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*/
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static uint32_t get_uint32_from_byte_string(const uint8_t *data, bool little_endian)
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{
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uint32_t out = 0ul;
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int i;
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for (i = 0; i < 4; i++) {
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if (little_endian)
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out >>= 8u;
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else
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out <<= 8u;
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out |= (((uint32_t)data[i]) << (little_endian ? 24u : 0u));
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}
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return out;
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}
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static void write_crc_to_byte_array(uint8_t *byte_array, uint32_t crc, uint8_t crc_size_bytes, bool little_endian)
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{
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int i;
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if (!byte_array)
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return;
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for (i = 0; i < crc_size_bytes; i++) {
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if (little_endian) {
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byte_array[i] = (uint8_t)(crc & 0xFFul);
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crc >>= 8u;
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} else {
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byte_array[i] = (uint8_t)((crc & 0xFF000000ul) >> 24u);
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crc <<= 8u;
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}
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}
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}
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static void free_elf_section_element(struct elf_section *sec)
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{
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@ -278,7 +317,6 @@ static struct elf_section *find_section_in_list(SlList *list, const char *name)
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}
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}
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return ret;
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}
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@ -368,6 +406,128 @@ int elf_patch_compute_crc_over_section(elfpatch_handle_t *ep, const char *sectio
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return 0;
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}
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int elf_patch_write_crcs_to_section(elfpatch_handle_t *ep, const char *section, const SlList *section_name_list,
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const uint32_t *crcs, uint8_t crc_size_bits, uint32_t start_magic, uint32_t end_magic,
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bool check_start_magic, bool check_end_magic, enum crc_format format, bool little_endian)
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{
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int ret = -1;
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struct elf_section *output_section;
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Elf_Data *output_sec_data;
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const SlList *iter;
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size_t needed_space;
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size_t crc_count;
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uint8_t crc_size_bytes;
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uint8_t *sec_bytes;
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size_t idx;
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ret_val_if_ep_err(ep, -1000);
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print_debug("== Patch output file ==\n");
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if (crc_size_bits < 1u || crc_size_bits > 32u) {
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print_err("Unsupported CRC size: %u", (unsigned int)crc_size_bits);
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return -1;
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}
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if (format != FORMAT_BARE) {
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print_err("Currently only bare format is supported!\n");
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return -1;
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}
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/* All pointer parameters are required */
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if (!section || !section_name_list || !crcs)
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return -1000;
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output_section = find_section_in_list(ep->sections, section);
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if (!output_section) {
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print_err("Cannot find output section '%s' to place CRCs. Exiting.\n", section);
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goto ret_err;
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}
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/* Get data object of section */
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output_sec_data = elf_getdata(output_section->scn, NULL);
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sec_bytes = (uint8_t *)output_sec_data->d_buf;
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/* Check the start and end magics */
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if (check_start_magic) {
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if (get_uint32_from_byte_string(sec_bytes, little_endian) != start_magic) {
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print_err("Start magic does not match: expected: 0x%08x, got: 0x%08x\n",
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start_magic, get_uint32_from_byte_string(sec_bytes, little_endian));
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goto ret_err;
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}
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print_debug("Start magic matching: 0x%08x\n", start_magic);
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}
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if (check_end_magic) {
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if (get_uint32_from_byte_string(&sec_bytes[output_sec_data->d_size - 4], little_endian) != end_magic) {
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print_err("End magic does not match: expected: 0x%08x, got: 0x%08x\n",
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end_magic,
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get_uint32_from_byte_string(&sec_bytes[output_sec_data->d_size - 4], little_endian));
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goto ret_err;
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}
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print_debug("End magic matching: 0x%08x\n", end_magic);
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}
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/* Calculate Bytes needed for CRC */
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crc_size_bytes = (crc_size_bits + 7u) / 8u;
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crc_count = sl_list_length(section_name_list);
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print_debug("CRC requires %u bytes.\n", (unsigned int)crc_size_bytes);
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switch (format) {
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case FORMAT_BARE:
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needed_space = crc_size_bytes * crc_count;
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break;
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default:
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needed_space = 0;
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print_err("Unsupported CRC output format\n");
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goto ret_err;
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}
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/* Add existing magic numbers to required space */
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if (check_start_magic)
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needed_space += 4u;
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if (check_end_magic)
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needed_space += 4u;
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print_debug("Required space for %zu CRCs %s: %zu (available: %zu)\n",
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crc_count,
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(check_start_magic || check_end_magic ? "including magic values" : ""),
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needed_space,
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output_sec_data->d_size
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);
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if (needed_space > output_sec_data->d_size) {
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print_err("Not enough space in section. %zu bytes available but %zu needed\n",
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output_sec_data->d_size, needed_space);
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}
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/* Checks finished. Write data to output section */
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if (format == FORMAT_BARE) {
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if (check_start_magic)
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sec_bytes += 4;
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for (iter = section_name_list, idx = 0; iter; iter = sl_list_next(iter), idx++) {
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print_debug("Write CRC 0x%08x (%u bytes) for section %s\n", crcs[idx],
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(unsigned int)crc_size_bytes,
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iter->data);
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write_crc_to_byte_array(sec_bytes, crcs[idx], crc_size_bytes, little_endian);
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sec_bytes += crc_size_bytes;
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}
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}
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/* Update ELF file */
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if (ep->readonly) {
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print_debug("DRY RUN: File will not be updated\n");
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ret = 0;
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} else {
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if (elf_update(ep->elf, ELF_C_WRITE) < 0) {
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print_err("Error writing ELF file: %s\n", elf_errmsg(-1));
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} else {
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ret = 0;
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}
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}
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ret_err:
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return ret;
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}
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void elf_patch_close_and_free(elfpatch_handle_t *ep)
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{
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ret_if_ep_err(ep);
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@ -4,6 +4,7 @@
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#include <stdint.h>
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#include <patchelfcrc/crc.h>
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#include <stdbool.h>
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#include <linklist-lib/singly-linked-list.h>
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typedef struct elfpatch elfpatch_handle_t;
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@ -13,6 +14,10 @@ enum granularity {
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GRANULARITY_32BIT = 32,
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};
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enum crc_format {
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FORMAT_BARE = 0,
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FORMAT_STRUCT,
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};
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elfpatch_handle_t *elf_patch_open(const char *path, bool readonly);
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@ -28,4 +33,17 @@ int elf_patch_compute_crc_over_section(elfpatch_handle_t *ep, const char *sectio
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void elf_patch_close_and_free(elfpatch_handle_t *ep);
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/**
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* @brief Write CRCs to output section. This will have no effect, if file is opened read onyl
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* @param ep Elf patch object
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* @param[in] section Section name to place CRCs in
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* @param[in] section_name_list The list of sections the data belongs to
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* @param[in] crcs CRCs. Must be of the same lenght as the \p section_name_list
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* @return 0 Success
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* @return -1000 Parameter error
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* @return -1 internal error
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*/
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int elf_patch_write_crcs_to_section(elfpatch_handle_t *ep, const char *section, const SlList *section_name_list,
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const uint32_t *crcs, uint8_t crc_size_bits, uint32_t start_magic, uint32_t end_magic,
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bool check_start_magic, bool check_end_magic, enum crc_format format, bool little_endian);
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#endif /* _ELFPATCH_H_ */
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@ -3,7 +3,7 @@
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#include <stdbool.h>
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#define print_err(fmt, ...) fprintf(stderr, (fmt), ## __VA_ARGS__);
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#define print_err(fmt, ...) fprintf(stderr, "[ERR] " fmt, ## __VA_ARGS__);
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void print_debug(const char *fmt, ...);
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@ -1 +1 @@
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Subproject commit 18b3ab377ac30516f977e9831813ea37189d4028
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Subproject commit c20b5c2528a46fe6a4aa74631ae3b628f73ac24f
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27
main.c
27
main.c
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@ -31,11 +31,6 @@
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const char *argp_program_bug_address = "<mario [dot] huettel [at] linux [dot] com>";
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enum crc_format {
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FORMAT_BARE = 0,
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FORMAT_STRUCT,
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};
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#define ARG_KEY_DRY_RUN (1)
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#define ARG_KEY_START_MAGIC (2)
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#define ARG_KEY_END_MAGIC (3)
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@ -55,6 +50,7 @@ struct command_line_options {
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bool list;
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SlList *section_list;
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const char *elf_path;
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const char *output_section;
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};
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static error_t parse_opt(int key, char *arg, struct argp_state *state)
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@ -108,6 +104,9 @@ static error_t parse_opt(int key, char *arg, struct argp_state *state)
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else if (!strcmp(arg, "word"))
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args->granularity = GRANULARITY_32BIT;
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break;
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case 'O':
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args->output_section = arg;
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break;
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case ARGP_KEY_ARG:
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if (state->arg_num >= 1)
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argp_usage(state);
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@ -178,6 +177,7 @@ static void prepare_default_opts(struct command_line_options *opts)
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opts->list = false;
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opts->section_list = NULL;
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opts->elf_path = NULL;
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opts->output_section = NULL;
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}
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static void print_verbose_start_info(const struct command_line_options *cmd_opts)
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@ -210,6 +210,10 @@ static void print_verbose_start_info(const struct command_line_options *cmd_opts
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print_debug("ELF file: %s\n", cmd_opts->elf_path);
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}
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if (cmd_opts->output_section) {
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print_debug("Output section: %s\n", cmd_opts->output_section);
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}
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if (cmd_opts->section_list) {
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for (list_iter = cmd_opts->section_list, i = 1; list_iter; list_iter = sl_list_next(list_iter), i++) {
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print_debug("Input section [%d]: \"%s\"\n", i, (const char *)list_iter->data);
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@ -342,6 +346,10 @@ int main(int argc, char **argv)
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return -1;
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}
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if (!cmd_opts.output_section) {
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print_err("No output section specified. Will continue but not patch file.\n");
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}
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if (cmd_opts.list) {
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list_predefined_crcs();
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goto free_cmds;
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@ -377,6 +385,15 @@ int main(int argc, char **argv)
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print_crcs(cmd_opts.section_list, crcs);
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}
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if (cmd_opts.output_section) {
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if (elf_patch_write_crcs_to_section(ep, cmd_opts.output_section, cmd_opts.section_list,
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crcs, 32, cmd_opts.start_magic, cmd_opts.end_magic,
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cmd_opts.has_start_magic, cmd_opts.has_end_magic,
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FORMAT_BARE, cmd_opts.little_endian)) {
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ret = -1;
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}
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}
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elf_patch_close_and_free(ep);
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free_cmds:
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