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/**
* Copyright (c) 2017 elttam
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <inttypes.h>
#include <sys/types.h>
#include <unistd.h>
#ifdef __x86_64__
#define canary_t uint64_t
#define INSN_READ "movq %%fs:0x28, %0;"
#define INSN_WRITE "movq %0, %%fs:0x28;"
#define FMT "[%d] Found canary: %#lx\n"
#elif __i386__
#define canary_t uint32_t
#define INSN_READ "movl %%gs:0x14, %0;"
#define INSN_WRITE "movl %0, %%gs:0x14;"
#define FMT "[%d] Found canary: %#x\n"
#endif
canary_t read_canary()
{
canary_t val = 0;
__asm__(INSN_READ
: "=r"(val)
:
:);
return val;
}
static inline void regenerate_canary()
{
canary_t val = (canary_t)0x4142434445464748;
__asm__(INSN_WRITE
:
: "r"(val)
:);
}
void __attribute__((optnone)) greetz(char* name)
{
char buf[64] = {0, };
canary_t can = read_canary();
printf(FMT, getpid(), can );
strcpy(buf, name); /* BoF is on purpose :) */
printf("[%d] Hello %s\n", getpid(), buf);
return;
}
static inline pid_t new_fork()
{
pid_t p = fork();
if(!p)
regenerate_canary();
return p;
}
int main(int argc, char** argv, char** envp)
{
int pid;
if(argc!=2){
printf("Missing argument\n");
return EXIT_FAILURE;
}
if ( (pid = new_fork()) == 0){
printf("Child is %d\n", getpid());
greetz(argv[1]);
} else{
printf("Parent is %d\n", getpid());
greetz(argv[1]);
}
return EXIT_SUCCESS;
}
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