Fix #4: Add support for endianess in struct output format

* Add more section types to prevent "unknown" from printing
* Add alloc, exec, and write flags of sections to output table

AUR/PKGBUILD

@@ -1,14 +1,14 @@
 # Maintainer: Mario Hüttel <mario (dot) huettel (!) gmx (dot) net>
 
 pkgname=patchelfcrc
-pkgver=5e7f697
+pkgver=v1.0.0_rc1
 pkgrel=1
 pkgdesc="Tool for patching CRC checksums of sections into ELF binaries"
 arch=('i686' 'x86_64')
 url="https://git.shimatta.de/mhu/patchelfcrc"
 licence=('GPLv2')
 depends=('libelf' 'libxml2')
-makedepends=('cmake' 'pandoc' 'git' 'gvim')
+makedepends=('cmake' 'pandoc' 'git' 'gvim' 'bash')
 provides=('patchelfcrc')
 source=("${pkgname}-git"::"git+https://git.shimatta.de/mhu/patchelfcrc" "git+https://git.shimatta.de/3rd-party/libfort.git" "git+https://git.shimatta.de/mhu/linklist-lib")
 sha1sums=('SKIP' 'SKIP' 'SKIP')

man/CMakeLists.txt

@@ -10,10 +10,10 @@ add_custom_command(
 	OUTPUT
 		${CMAKE_CURRENT_BINARY_DIR}/${MAN_PAGE_NAME}
 	COMMAND
-		bash -c "pandoc \"${CMAKE_CURRENT_SOURCE_DIR}/patchelfcrc.1.md\" -s -t man | gzip > \"${CMAKE_CURRENT_BINARY_DIR}/${MAN_PAGE_NAME}\""
+		bash -c "cat \"${CMAKE_CURRENT_SOURCE_DIR}/patchelfcrc.1.md\" | sed \"s/!version!/`git describe --tags --always --dirty`/\" | pandoc  -s -t man | gzip > \"${CMAKE_CURRENT_BINARY_DIR}/${MAN_PAGE_NAME}\""
 	VERBATIM
 	WORKING_DIRECTORY
-		${CMAKE_CURRENT_BINARY_DIR}
+		${CMAKE_CURRENT_SOURCE_DIR}
 	MAIN_DEPENDENCY
 		${CMAKE_CURRENT_SOURCE_DIR}/patchelfcrc.1.md
 )

man/patchelfcrc.1.md

@@ -1,4 +1,4 @@
-% patchelfcrc(1) 0.0.2
+% patchelfcrc(1) !version!
 % Mario Huettel
 % October 2022
 
@@ -136,4 +136,4 @@ The output sections start and end are checked for the given magic numbers in ord
 The memory is interpreted as *little endian* and the CRC calculation granularity is a 32 bit *word*.
 
 # BUGS
-Currently, reversed CRC algorithms are not implemented.
+None

src/crc.c

@@ -34,13 +34,26 @@ int crc_len_from_poly(uint64_t polynomial)
 	return pos;
 }
 
+static uint32_t reverse_short_poly(uint32_t poly, uint8_t len)
+{
+	uint8_t i;
+	uint32_t ret = 0ul;
+
+	for (i = 0; i < len; i++) {
+		ret <<= 1;
+		ret |= (poly & 1u);
+		poly >>= 1;
+	}
+
+	return ret;
+}
+
 static uint64_t shorten_polynomial(uint64_t poly)
 {
 	int i;
-
+	for (i = 32; i >= 0; i--) {
-	for (i = 31; i <= 0; i--) {
+		if (poly & ((uint64_t)1ull << i)) {
-		if (poly & (1 << i)) {
+			poly &= ~((uint64_t)1ull<<i);
-			poly &= ~(1<<i);
 			break;
 		}
 	}
@@ -55,14 +68,22 @@ static void internal_push_byte(struct crc_calc *crc, const uint8_t *data, size_t
 
 	crc_val = crc->crc_val;
 
-	for (i = 0; i < len; i++, data++) {
+	if (crc->settings.rev) {
-		crc_val = ((crc_val << 8) & crc->crc_mask) ^ crc->table[((crc_val >> (crc->crc_length-8u)) & 0xff) ^ *data];
+		for (i = 0; i < len; i++, data++) {
+			crc_val = (crc_val >> 8) ^ crc->table[((crc_val & 0xFF) ^ *data)];
+		}
+	} else {
+		/* Non reversed algo */
+		for (i = 0; i < len; i++, data++) {
+			crc_val = ((crc_val << 8) & crc->crc_mask) ^
+				crc->table[((crc_val >> (crc->crc_length-8u)) & 0xff) ^ *data];
+		}
 	}
 
 	crc->crc_val = crc_val;
 }
 
-static void fill_crc_table(struct crc_calc *crc)
+static void fill_crc_table_non_reversed(struct crc_calc *crc)
 {
 	uint32_t input;
 	uint32_t crc_reg;
@@ -86,10 +107,44 @@ static void fill_crc_table(struct crc_calc *crc)
 				crc_reg <<= 1;
 			}
 		}
-		crc->table[input] = crc_reg;
+		crc->table[input] = crc_reg & crc->crc_mask;
 	}
 }
 
+static void fill_crc_table_reversed(struct crc_calc *crc)
+{
+	uint32_t input;
+	uint32_t crc_reg;
+	uint32_t short_poly;
+	int i;
+
+	short_poly = (uint32_t)shorten_polynomial(crc->settings.polynomial);
+	short_poly = reverse_short_poly(short_poly, crc->crc_length);
+
+	for (input = 0; input <= 255u; input++) {
+		crc_reg = (uint32_t)input;
+		for (i = 0; i < 8; i++) {
+			/* Check LSB for reversed CRC shifting */
+			if (crc_reg & 1u) {
+				crc_reg >>= 1;
+				crc_reg ^= short_poly;
+			} else {
+				crc_reg >>= 1;
+			}
+		}
+		crc->table[input] = crc_reg & crc->crc_mask;
+	}
+
+}
+
+static void fill_crc_table(struct crc_calc *crc)
+{
+	if (crc->settings.rev)
+		fill_crc_table_reversed(crc);
+	else
+		fill_crc_table_non_reversed(crc);
+}
+
 void crc_init(struct crc_calc *crc, const struct crc_settings *settings)
 {
 	uint32_t i;

src/elfpatch.c

@@ -30,6 +30,19 @@
 #include <fort.h>
 #include <inttypes.h>
 #include <patchelfcrc/crc-output-struct.h>
+#include <byteswap.h>
+
+static const union  {
+	uint8_t data[4];
+	uint32_t val;
+} _endianess_check_union = {{1u, 2u, 3u, 4u}};
+
+enum endianess {
+	END_LITTLE = 0x04030201ul,
+	END_BIG = 0x01020304ul,
+};
+
+#define HOST_ENDIANESS (_endianess_check_union.val)
 
 struct elf_section {
 	GElf_Shdr section_header;
@@ -55,16 +68,16 @@ struct elfpatch {
 #define is_elfpatch_struct(x) ((x) && (x)->magic == (ELFPATCH_MAGIC))
 
 #define ret_if_ep_err(ep) do { \
-	if (!is_elfpatch_struct((ep))) { \
+		if (!is_elfpatch_struct((ep))) { \
-	return; \
+			return; \
-	} \
+		} \
-	} while(0)
+	} while (0)
 
 #define ret_val_if_ep_err(ep, val) do { \
-	if (!is_elfpatch_struct((ep))) { \
+		if (!is_elfpatch_struct((ep))) { \
-	return (val); \
+			return val; \
-	} \
+		} \
-	} while(0)
+	} while (0)
 
 /**
  * @brief Convert a series of 4 bytes into a uint32_t dpending on endianess
@@ -77,15 +90,16 @@ static uint32_t get_uint32_from_byte_string(const uint8_t *data, bool little_end
 	uint32_t out = 0ul;
 	int i;
 
+	/* Always shift in in big endian format */
 	for (i = 0; i < 4; i++) {
-		if (little_endian)
-			out >>= 8u;
-		else
 			out <<= 8u;
-
+		out |= (uint32_t)data[i];
-		out |= (((uint32_t)data[i]) << (little_endian ? 24u : 0u));
 	}
 
+	/* Swap bytes if little endian */
+	if (little_endian)
+		out = bswap_32(out);
+
 	return out;
 }
 
@@ -96,14 +110,12 @@ static void write_crc_to_byte_array(uint8_t *byte_array, uint32_t crc, uint8_t c
 	if (!byte_array)
 		return;
 
+	if (!little_endian)
+		crc = bswap_32(crc);
+
 	for (i = 0; i < crc_size_bytes; i++) {
-		if (little_endian) {
+		byte_array[i] = (uint8_t)(crc & 0xFFul);
-			byte_array[i] = (uint8_t)(crc & 0xFFul);
+		crc >>= 8u;
-			crc >>= 8u;
-		} else {
-			byte_array[i] = (uint8_t)((crc & 0xFF000000ul) >> 24u);
-			crc <<= 8u;
-		}
 	}
 }
 
@@ -136,6 +148,14 @@ static const char *section_type_to_str(Elf64_Word type)
 		return "INIT_ARRAY";
 	case SHT_FINI_ARRAY:
 		return "FINI_ARRAY";
+	case SHT_PREINIT_ARRAY:
+		return "PREINIT_ARRAY";
+	case SHT_DYNAMIC:
+		return "DYNAMIC";
+	case SHT_ARM_ATTRIBUTES:
+		return "ARM_ATTRIBUTES";
+	case SHT_ARM_PREEMPTMAP:
+		return "ARM_PREEMPTMAP";
 	default:
 		break;
 	}
@@ -147,6 +167,7 @@ static void print_sections(elfpatch_handle_t *ep)
 	SlList *iter;
 	ft_table_t *table;
 	const struct elf_section *section;
+	bool alloc, write, exec;
 
 	ret_if_ep_err(ep);
 
@@ -162,15 +183,23 @@ static void print_sections(elfpatch_handle_t *ep)
 
 	/* Write header */
 	ft_set_cell_prop(table, 0, FT_ANY_COLUMN, FT_CPROP_ROW_TYPE, FT_ROW_HEADER);
-	ft_write_ln(table, "Section", "Type", "Size", "VMA", "LMA", "File Offset");
+	ft_write_ln(table, "Section", "Type", "ALLOC", "WRITE", "EXEC", "Size", "VMA", "LMA", "File Offset");
 
 	for (iter = ep->sections; iter; iter = sl_list_next(iter)) {
 		section = (const struct elf_section *)iter->data;
 		if (!section)
 			continue;
-		ft_printf_ln(table, "%s|%s|%lu|%p|%p|%p",
+
+		alloc = !!(section->section_header.sh_flags & SHF_ALLOC);
+		write = !!(section->section_header.sh_flags & SHF_WRITE);
+		exec = !!(section->section_header.sh_flags & SHF_EXECINSTR);
+
+		ft_printf_ln(table, "%s|%s|%s|%s|%s|%lu|%p|%p|%p",
 			     section->name,
 			     section_type_to_str(section->section_header.sh_type),
+			     alloc ? "x" : "",
+			     write ? "x" : "",
+			     exec ? "x" : "",
 			     section->section_header.sh_size,
 			     (void *)section->section_header.sh_addr,
 			     (void *)section->lma,
@@ -197,7 +226,7 @@ static SlList *elf_patch_get_sections(elfpatch_handle_t *ep)
 		sl_list_free_full(ret, (void (*)(void *))free_elf_section_element);
 	ep->sections = NULL;
 
-	if (elf_getshdrstrndx (ep->elf , &shstrndx) != 0) {
+	if (elf_getshdrstrndx(ep->elf, &shstrndx) != 0) {
 		print_err("ELF error: %s\n", elf_errmsg(-1));
 		goto ret_free_section_list;
 	}
@@ -218,9 +247,10 @@ static SlList *elf_patch_get_sections(elfpatch_handle_t *ep)
 		sec->lma = (uint64_t)sec->section_header.sh_addr;
 
 		name = elf_strptr(ep->elf, shstrndx, sec->section_header.sh_name);
-		if (name) {
+
+		if (name)
 			sec->name = strdup(name);
-		}
+
 		ret = sl_list_append(ret, sec);
 	}
 
@@ -260,6 +290,12 @@ static int elf_patch_read_program_headers(elfpatch_handle_t *ep)
 		return -1;
 	}
 
+	if (header_count == 0) {
+		/* No program headers found. This ELF file is probably not linked */
+		ep->program_headers_count = 0;
+		return 0;
+	}
+
 	ep->program_headers = (GElf_Phdr *)malloc(header_count * sizeof(GElf_Phdr));
 	if (!ep->program_headers) {
 		/* Mem error. Abort. Program will crash eventually */
@@ -305,9 +341,11 @@ static void resolve_section_lmas(elfpatch_handle_t *ep)
 		if (!sec)
 			continue;
 
+		/* By default each sections LMA is assumed to be its LMA as well */
+		sec->lma = (uint64_t)sec->section_header.sh_addr;
+
 		if (sec->section_header.sh_type == SHT_NOBITS) {
 			/* Section does not contain data. It may be allocated but is not loaded. Therefore, LMA=VMA. */
-			sec->lma = (uint64_t)sec->section_header.sh_addr;
 			continue;
 		}
 
@@ -431,15 +469,13 @@ elfpatch_handle_t *elf_patch_open(const char *path, bool readonly, bool expect_l
 		switch (ident[5]) {
 		case 1:
 			print_debug("ELF Endianess: little\n");
-			if (!expect_little_endian) {
+			if (!expect_little_endian)
 				print_err("Big endian format expected. File is little endian. Double check settings!\n");
-			}
 			break;
 		case 2:
 			print_debug("ELF Endianess: big\n");
-			if (expect_little_endian) {
+			if (expect_little_endian)
 				print_err("Little endian format expected. File is big endian. Double check settings!\n");
-			}
 			break;
 		default:
 			print_err("Cannot determine endianess of ELF file. EI_DATA is: %d\n", ident[5]);
@@ -454,9 +490,8 @@ close_elf:
 		ep->elf = NULL;
 	}
 close_fd:
-	if (ep->fd > 0) {
+	if (ep->fd > 0)
 		close(ep->fd);
-	}
 free_struct:
 	free(ep);
 	ep = NULL;
@@ -491,14 +526,14 @@ int elf_patch_check_for_section(elfpatch_handle_t *ep, const char *section)
 	return ret;
 }
 
-static size_t translate_index(size_t index, enum granularity granularity, bool little_endian)
+static size_t translate_index(size_t index, enum granularity granularity, bool little_endian, bool reversed)
 {
 	size_t word_idx;
 	size_t part_idx;
 	size_t d_index;
 	size_t gran_in_bytes;
 
-	if (!little_endian || granularity == GRANULARITY_BYTE)
+	if ((!little_endian && !reversed) || (little_endian && reversed) || granularity == GRANULARITY_BYTE)
 		return index;
 
 	gran_in_bytes = (size_t)granularity / 8u;
@@ -548,8 +583,9 @@ int elf_patch_compute_crc_over_section(elfpatch_handle_t *ep, const char *sectio
 		return -2;
 	}
 
-	/* If big endian or granularity is byte, simply compute CRC. No reordering is necessary */
+	/* If big endian for non reversed / little endian for reversed or granularity is byte, simply compute CRC. No reordering is necessary */
-	if (!little_endian || granularity == GRANULARITY_BYTE) {
+	if ((!little_endian && !crc->settings.rev) || (little_endian && crc->settings.rev) ||
+			granularity == GRANULARITY_BYTE) {
 		crc_push_bytes(crc, data->d_buf, data->d_size);
 	} else {
 		/* Little endian case with > byte sized chunks */
@@ -561,14 +597,17 @@ int elf_patch_compute_crc_over_section(elfpatch_handle_t *ep, const char *sectio
 				  section, padding_count);
 		}
 
-		for (idx = 0; idx < data->d_size; idx++) {
+		for (idx = 0; idx < data->d_size; idx++)
-			crc_push_byte(crc, ((char *)data->d_buf)[translate_index(idx, granularity, little_endian)]);
+			crc_push_byte(crc,
-		}
+				      ((char *)data->d_buf)[
+					translate_index(idx, granularity,
+						little_endian,
+						crc->settings.rev)
+					]);
 
 		/* Pad with zeroes */
-		for (idx = 0; idx < padding_count; idx++) {
+		for (idx = 0; idx < padding_count; idx++)
 			crc_push_byte(crc, 0x00);
-		}
 	}
 
 	return 0;
@@ -649,6 +688,7 @@ int elf_patch_write_crcs_to_section(elfpatch_handle_t *ep, const char *output_se
 	struct crc_out_struct_32bit crc_32bit;
 	struct crc_out_struct_64bit crc_64bit;
 	uint64_t in_sec_addr, in_sec_len;
+	bool needs_byteswap;
 
 	ret_val_if_ep_err(ep, -1000);
 
@@ -711,8 +751,8 @@ int elf_patch_write_crcs_to_section(elfpatch_handle_t *ep, const char *output_se
 
 	print_debug("Single CRC requires %u bytes.\n", (unsigned int)crc_size_bytes);
 
-	needed_space = calculate_needed_space_for_crcs(format, crc_data->elf_bits, check_start_magic, check_end_magic, crc_size_bytes,
+	needed_space = calculate_needed_space_for_crcs(format, crc_data->elf_bits, check_start_magic,
-						       crc_count);
+		check_end_magic, crc_size_bytes, crc_count);
 
 	print_debug("Required space for %zu CRCs%s: %zu (available: %zu)\n",
 		    crc_count,
@@ -746,6 +786,12 @@ int elf_patch_write_crcs_to_section(elfpatch_handle_t *ep, const char *output_se
 		if (check_start_magic && crc_data->elf_bits == 64)
 			sec_bytes += 4u;
 
+		needs_byteswap = false;
+		if ((HOST_ENDIANESS != END_LITTLE && little_endian) ||
+				(HOST_ENDIANESS == END_LITTLE && !little_endian)) {
+			needs_byteswap = true;
+		}
+
 		for (iter = crc_data->crc_entries, idx = 0; iter; iter = sl_list_next(iter), idx++) {
 			crc_entry = (struct crc_entry *)iter->data;
 			in_sec_addr = use_vma ? crc_entry->vma : crc_entry->lma;
@@ -756,18 +802,19 @@ int elf_patch_write_crcs_to_section(elfpatch_handle_t *ep, const char *output_se
 			print_debug("Corresponding input section at 0x%"PRIx64", length: %"PRIu64"\n",
 				    in_sec_addr,
 				    in_sec_len);
+
 			if (crc_data->elf_bits == 32) {
-				crc_32bit.crc = crc_entry->crc;
+				crc_32bit.crc = needs_byteswap ? bswap_32(crc_entry->crc) : crc_entry->crc;
-				crc_32bit.length = (uint32_t)in_sec_len;
+				crc_32bit.length = needs_byteswap ? bswap_32((uint32_t)in_sec_len) : (uint32_t)in_sec_len;
-				crc_32bit.start_address = (uint32_t)in_sec_addr;
+				crc_32bit.start_address = needs_byteswap ? bswap_32((uint32_t)in_sec_addr) : (uint32_t)in_sec_addr;
 				memcpy(sec_bytes, &crc_32bit, sizeof(crc_32bit));
 				sec_bytes += sizeof(crc_32bit);
 			} else {
 				/* 64 bit case */
-				crc_64bit.crc = crc_entry->crc;
+				crc_64bit.crc = needs_byteswap ? bswap_32(crc_entry->crc) : crc_entry->crc;
 				crc_64bit._unused_dummy = 0ul;
-				crc_64bit.length = in_sec_len;
+				crc_64bit.length = needs_byteswap ? bswap_64(in_sec_len) : in_sec_len;
-				crc_64bit.start_address = in_sec_addr;
+				crc_64bit.start_address = needs_byteswap ? bswap_64(in_sec_addr) : in_sec_addr;
 				memcpy(sec_bytes, &crc_64bit, sizeof(crc_64bit));
 				sec_bytes += sizeof(crc_64bit);
 			}
@@ -782,11 +829,10 @@ int elf_patch_write_crcs_to_section(elfpatch_handle_t *ep, const char *output_se
 		crc_64bit.length = 0ull;
 		crc_64bit.start_address = 0ull;
 
-		if (crc_data->elf_bits == 32) {
+		if (crc_data->elf_bits == 32)
 			memcpy(sec_bytes, &crc_32bit, sizeof(crc_32bit));
-		} else {
+		else
 			memcpy(sec_bytes, &crc_64bit, sizeof(crc_64bit));
-		}
 	}
 
 	/* Flag section data as invalid to trigger rewrite.
@@ -808,9 +854,8 @@ void elf_patch_close_and_free(elfpatch_handle_t *ep)
 		if (ep->readonly) {
 			print_debug("DRY RUN: File will not be updated\n");
 		} else {
-			if (elf_update(ep->elf, ELF_C_WRITE) < 0) {
+			if (elf_update(ep->elf, ELF_C_WRITE) < 0)
 				print_err("Error writing ELF file: %s\n", elf_errmsg(-1));
-			}
 		}
 	}
 

src/main.c

@@ -452,12 +452,6 @@ int main(int argc, char **argv)
 	if (!cmd_opts.output_section && cmd_opts.export_xml == NULL)
 		print_err("No output section / XML export specified. Will continue but not create any output\n");
 
-	/* Do error printing if using a reversed polynomial. It is not implemented yet! */
-	if (cmd_opts.crc.rev) {
-		print_err("Reversed polynomials are not supported yet\nExiting...\n");
-		goto free_cmds;
-	}
-
 	/* Prepare libelf for use with the latest ELF version */
 	elf_version(EV_CURRENT);
 

src/named_crcs.c

@@ -110,19 +110,26 @@ void list_predefined_crcs(void)
 {
 	ft_table_t *table;
 	const struct named_crc *iter;
+	struct crc_calc crc;
 
 	table = ft_create_table();
 
 	ft_set_cell_prop(table, 0, FT_ANY_COLUMN, FT_CPROP_ROW_TYPE, FT_ROW_HEADER);
-	ft_write_ln(table, "Name", "Polynomial", "Reversed", "Start Value", "Output XOR");
+	ft_write_ln(table, "Name", "Polynomial", "Reversed", "Start Value", "Output XOR", "Test Value");
 
 	for (iter = predefined_crc_table; iter->name; iter++) {
-		ft_printf_ln(table, "%s|0x%lx|%s|0x%x|0x%x",
+		crc_init(&crc, &iter->settings);
+		/* Calculate the test value */
+		crc_push_bytes(&crc, (const uint8_t *)"123456789", 9);
+		crc_finish_calc(&crc);
+		ft_printf_ln(table, "%s|0x%lx|%s|0x%x|0x%x|0x%x",
 			     iter->name,
 			     iter->settings.polynomial,
 			     iter->settings.rev ? "yes" : "no",
 			     iter->settings.start_value,
-			     iter->settings.xor);
+			     iter->settings.xor,
+			     crc_get_value(&crc));
+		crc_destroy(&crc);
 	}
 
 	printf("%s\n", ft_to_string(table));