125 lines
2.9 KiB
C
125 lines
2.9 KiB
C
/** Proof-of-concept to show different methods to load executables in the Linux kernel
|
|
*
|
|
* @copyright 2021, Steffen Vogel
|
|
* @license http://www.gnu.org/licenses/gpl.txt GNU Public License
|
|
* @author Steffen Vogel <post@steffenvogel.de>
|
|
* @link https://www.steffenvogel.de
|
|
*/
|
|
|
|
#include <linux/elf.h>
|
|
#include <linux/module.h>
|
|
#include <linux/string.h>
|
|
#include <linux/stat.h>
|
|
#include <linux/binfmts.h>
|
|
#include <linux/init.h>
|
|
#include <linux/file.h>
|
|
#include <linux/err.h>
|
|
#include <linux/fs.h>
|
|
#include <linux/module.h> /* Needed by all modules */
|
|
#include <linux/kernel.h> /* Needed for KERN_INFO */
|
|
#include <linux/init.h> /* Needed for the macros */
|
|
|
|
#include <linux/fs.h>
|
|
|
|
static int load_binary(struct linux_binprm *bprm)
|
|
{
|
|
int retval;
|
|
const char *i_name, *i_arg;
|
|
char interp[BINPRM_BUF_SIZE];
|
|
struct file *file;
|
|
struct elfhdr *hdr = (struct elfhdr *) bprm->buf;
|
|
|
|
/* Check if this is an ELF file */
|
|
if (memcmp(hdr->e_ident, ELFMAG, SELFMAG) != 0)
|
|
return -ENOEXEC;
|
|
if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN)
|
|
return -ENOEXEC;
|
|
if (!elf_check_arch(hdr))
|
|
return -ENOEXEC;
|
|
if (!bprm->file->f_op->mmap)
|
|
return -ENOEXEC;
|
|
|
|
printk(KERN_INFO "Got ELF file in binfmt_hermit\n");
|
|
|
|
if (hdr->e_ident[EI_OSABI] != 0xa1)
|
|
return -ENOEXEC;
|
|
|
|
/* Hardcoded for now */
|
|
i_name = "/custom_loader_poc/proxy";
|
|
i_arg = NULL;
|
|
|
|
strcpy (interp, i_name);
|
|
|
|
printk(KERN_INFO "It's a hermit one! Start the interpreter\n");
|
|
|
|
/*
|
|
* OK, we've parsed out the interpreter name and
|
|
* (optional) argument.
|
|
* Splice in (1) the interpreter's name for argv[0]
|
|
* (2) (optional) argument to interpreter
|
|
* (3) filename of shell script (replace argv[0])
|
|
*
|
|
* This is done in reverse order, because of how the
|
|
* user environment and arguments are stored.
|
|
*/
|
|
retval = remove_arg_zero(bprm);
|
|
if (retval)
|
|
return retval;
|
|
|
|
retval = copy_strings_kernel(1, &bprm->interp, bprm);
|
|
if (retval < 0)
|
|
return retval;
|
|
|
|
bprm->argc++;
|
|
|
|
retval = copy_strings_kernel(1, &i_name, bprm);
|
|
if (retval)
|
|
return retval;
|
|
|
|
bprm->argc++;
|
|
|
|
retval = bprm_change_interp(interp, bprm);
|
|
if (retval < 0)
|
|
return retval;
|
|
|
|
/*
|
|
* OK, now restart the process with the interpreter's dentry.
|
|
*/
|
|
file = open_exec(interp);
|
|
if (IS_ERR(file))
|
|
return PTR_ERR(file);
|
|
|
|
bprm->file = file;
|
|
retval = prepare_binprm(bprm);
|
|
if (retval < 0)
|
|
return retval;
|
|
|
|
return search_binary_handler(bprm);
|
|
}
|
|
|
|
static struct linux_binfmt script_format = {
|
|
.module = THIS_MODULE,
|
|
.load_binary = load_binary,
|
|
};
|
|
|
|
static int init(void)
|
|
{
|
|
printk(KERN_INFO "Loaded binary format for HermitCore\n");
|
|
|
|
register_binfmt(&script_format);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void cleanup(void)
|
|
{
|
|
printk(KERN_INFO "Un-loaded binary format for HermitCore\n");
|
|
|
|
unregister_binfmt(&script_format);
|
|
}
|
|
|
|
module_init(init);
|
|
module_exit(cleanup);
|
|
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_AUTHOR("Steffen Vogel <steffen.vogel@rwth-aachen.de>");
|