Update ELF parser. Sectionr eading implemented

This commit is contained in:
Mario Hüttel 2022-10-18 22:33:32 +02:00
parent fb5f527f45
commit 0278cb19d4
5 changed files with 212 additions and 42 deletions

View File

@ -2,47 +2,136 @@
#include <patchelfcrc/reporting.h> #include <patchelfcrc/reporting.h>
#include <unistd.h> #include <unistd.h>
#include <stdio.h> #include <stdio.h>
#include <stdlib.h>
#include <string.h> #include <string.h>
#include <fcntl.h> #include <fcntl.h>
#include <sys/stat.h> #include <sys/stat.h>
#include <libelf.h>
#include <gelf.h>
#include <linklist-lib/singly-linked-list.h>
struct elf_section {
GElf_Shdr section_header;
Elf_Scn *scn;
char *name;
};
struct elfpatch {
uint32_t magic;
int fd;
Elf *elf;
GElf_Ehdr ehdr;
int class;
SlList *sections;
};
#define ELFPATCH_MAGIC 0x8545637Aul
#define is_elfpatch_struct(x) ((x) && (x)->magic == (ELFPATCH_MAGIC))
#define ret_if_ep_err(ep) do { \
if (!is_elfpatch_struct((ep))) { \
return; \
} \
} while(0)
#define ret_val_if_ep_err(ep, val) do { \
if (!is_elfpatch_struct((ep))) { \
return (val); \
} \
} while(0)
#define print_err(fmt, ...) fprintf(stderr, (fmt), ## __VA_ARGS__); #define print_err(fmt, ...) fprintf(stderr, (fmt), ## __VA_ARGS__);
int elf_patch_open(struct elfpatch *ep, const char *path) static void free_elf_section_element(struct elf_section *sec)
{ {
int fd; if (sec) {
Elf *elf; free(sec->name);
free(sec);
if (!ep || !path)
return -1000;
memset(ep, 0, sizeof(struct elfpatch));
fd = open(path, O_RDWR, 0);
if (fd < 0) {
print_err("Error opening file: %s\n", path);
return -1;
} }
elf = elf_begin(fd, ELF_C_RDWR, NULL);
if (!elf) {
close(fd);
print_err("[LIBELF] %s\n", elf_errmsg(-1));
return -1;
}
ep->fd = fd;
ep->elf = elf;
return 0;
} }
void elf_patch_print_stats(const struct elfpatch *ep) static const char *section_type_to_str(Elf64_Word type)
{
switch (type) {
case SHT_NULL:
return "NULL";
case SHT_PROGBITS:
return "PROGBITS";
case SHT_SYMTAB:
return "SYMTAB";
case SHT_STRTAB:
return "STRTAB";
case SHT_NOBITS:
return "NOBITS";
case SHT_ARM_EXIDX:
return "ARM_EXIDX";
case SHT_INIT_ARRAY:
return "INIT_ARRAY";
case SHT_FINI_ARRAY:
return "FINI_ARRAY";
default:
break;
}
return "unknown";
}
static SlList *elf_patch_get_sections(elfpatch_handle_t *ep)
{
SlList *ret = NULL;
Elf_Scn *scn;
struct elf_section *sec;
char *name;
size_t shstrndx;
ret_val_if_ep_err(ep, NULL);
if (ep->sections)
sl_list_free_full(ret, (void (*)(void *))free_elf_section_element);
ep->sections = NULL;
if (elf_getshdrstrndx (ep->elf , &shstrndx) != 0) {
print_err("ELF error: %s\n", elf_errmsg(-1));
goto ret_free_section_list;
}
scn = NULL;
while ((scn = elf_nextscn(ep->elf, scn)) != NULL) {
sec = (struct elf_section *)calloc(1u, sizeof(struct elf_section));
sec->name = NULL;
sec->scn = scn;
ret = sl_list_append(ret, sec);
if (gelf_getshdr(scn, &sec->section_header) != &sec->section_header) {
print_err("Error reading section header: %s\n", elf_errmsg(-1));
goto ret_free_section_list;
}
name = elf_strptr(ep->elf, shstrndx, sec->section_header.sh_name);
if (name) {
print_debug("[SEC] [%s] %s | %zu bytes at 0x%x (File offset: 0x%x) \n",
section_type_to_str(sec->section_header.sh_type),
name, (size_t)sec->section_header.sh_size,
sec->section_header.sh_addr,
sec->section_header.sh_offset);
sec->name = strdup(name);
}
}
ep->sections = ret;
return ret;
ret_free_section_list:
sl_list_free_full(ret, (void (*)(void *))free_elf_section_element);
ret = NULL;
return ret;
}
static int elf_patch_update_info(elfpatch_handle_t *ep)
{ {
Elf_Kind ek; Elf_Kind ek;
const char *type_string = "unrecognized"; const char *type_string = "unrecognized";
if (!ep || !ep->elf) ret_val_if_ep_err(ep, -1001);
return;
ek = elf_kind(ep->elf); ek = elf_kind(ep->elf);
@ -58,10 +147,83 @@ void elf_patch_print_stats(const struct elfpatch *ep)
break; break;
} }
print_debug("ELF File Type: %s\n", type_string); print_debug("ELF File Type: %s\n", type_string);
if (ek != ELF_K_ELF)
return -1;
gelf_getehdr(ep->elf, &ep->ehdr);
ep->class = gelf_getclass(ep->elf);
switch (ep->class) {
case ELFCLASS32:
print_debug("ELF class: 32 bit\n");
break;
case ELFCLASS64:
print_debug("ELF class: 64 bit\n");
break;
default:
print_err("Unsupported ELF class: %d\n", ep->class);
return -1;
}
if (!elf_patch_get_sections(ep)) {
print_err("No sections in file.\n");
return -1;
}
return 0;
} }
void elf_patch_close(struct elfpatch *ep) elfpatch_handle_t *elf_patch_open(const char *path)
{ {
struct elfpatch *ep;
if (!path) {
print_err("Internal error while opeing ELF file. No path specified\n");
return NULL;
}
ep = (struct elfpatch *)calloc(1u, sizeof(struct elfpatch));
ep->magic = ELFPATCH_MAGIC;
ep->fd = open(path, O_RDWR, 0);
if (ep->fd < 0) {
print_err("Error opening file: %s\n", path);
goto free_struct;
}
ep->elf = elf_begin(ep->fd, ELF_C_RDWR, NULL);
if (!ep->elf) {
print_err("[LIBELF] %s\n", elf_errmsg(-1));
goto close_fd;
}
if (elf_patch_update_info(ep)) {
print_err("File malformatted. Cannot use for CRC patching\n");
goto close_elf;
}
return (elfpatch_handle_t *)ep;
close_elf:
if (ep->elf) {
elf_end(ep->elf);
ep->elf = NULL;
}
close_fd:
if (ep->fd > 0) {
close(ep->fd);
}
free_struct:
free(ep);
ep = NULL;
return (elfpatch_handle_t *)ep;
}
void elf_patch_close_and_free(elfpatch_handle_t *ep)
{
ret_if_ep_err(ep);
if (!ep) if (!ep)
return; return;
if (ep->elf) if (ep->elf)
@ -70,6 +232,12 @@ void elf_patch_close(struct elfpatch *ep)
if (ep->fd > 0) if (ep->fd > 0)
close(ep->fd); close(ep->fd);
if (ep->sections)
sl_list_free_full(ep->sections, (void (*)(void *))free_elf_section_element);
ep->sections = NULL;
ep->elf = NULL; ep->elf = NULL;
ep->fd = 0; ep->fd = 0;
free(ep);
} }

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@ -1,17 +1,12 @@
#ifndef _ELFPATCH_H_ #ifndef _ELFPATCH_H_
#define _ELFPATCH_H_ #define _ELFPATCH_H_
#include <libelf.h> #include <stdint.h>
struct elfpatch { typedef struct elfpatch elfpatch_handle_t;
int fd;
Elf *elf;
};
int elf_patch_open(struct elfpatch *ep, const char *path); elfpatch_handle_t *elf_patch_open(const char *path);
void elf_patch_print_stats(const struct elfpatch *ep); void elf_patch_close_and_free(elfpatch_handle_t *ep);
void elf_patch_close(struct elfpatch *ep);
#endif /* _ELFPATCH_H_ */ #endif /* _ELFPATCH_H_ */

View File

@ -1,10 +1,14 @@
#ifndef _REPORTING_H_ #ifndef _REPORTING_H_
#define _REPORTING_H_ #define _REPORTING_H_
#include <stdbool.h>
#define print_err(fmt, ...) fprintf(stderr, (fmt), ## __VA_ARGS__); #define print_err(fmt, ...) fprintf(stderr, (fmt), ## __VA_ARGS__);
void print_debug(const char *fmt, ...); void print_debug(const char *fmt, ...);
void reporting_enable_verbose(void); void reporting_enable_verbose(void);
bool reporting_get_verbosity(void);
#endif /* _REPORTING_H_ */ #endif /* _REPORTING_H_ */

8
main.c
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@ -242,7 +242,7 @@ int main(int argc, char **argv)
{ {
struct crc_calc crc; struct crc_calc crc;
struct command_line_options cmd_opts; struct command_line_options cmd_opts;
struct elfpatch ep; elfpatch_handle_t *ep;
prepare_default_opts(&cmd_opts); prepare_default_opts(&cmd_opts);
parse_cmdline_options(&argc, &argv, &cmd_opts); parse_cmdline_options(&argc, &argv, &cmd_opts);
@ -275,11 +275,9 @@ int main(int argc, char **argv)
elf_version(EV_CURRENT); elf_version(EV_CURRENT);
/* Open the ELF file */ /* Open the ELF file */
elf_patch_open(&ep, cmd_opts.elf_path); ep = elf_patch_open(cmd_opts.elf_path);
elf_patch_print_stats(&ep); elf_patch_close_and_free(ep);
elf_patch_close(&ep);
crc_destroy(&crc); crc_destroy(&crc);
free_cmds: free_cmds:

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@ -20,3 +20,8 @@ void reporting_enable_verbose(void)
{ {
global_verbosity_state = true; global_verbosity_state = true;
} }
bool reporting_get_verbosity(void)
{
return global_verbosity_state;
}