Commit message: ROSE: prevent heap corruption with bad facilities

When parsing the FAC_NATIONAL_DIGIS facilities field, it's possible for
a remote host to provide more digipeaters than expected, resulting in
heap corruption.  Check against ROSE_MAX_DIGIS to prevent overflows, and
abort facilities parsing on failure.

Additionally, when parsing the FAC_CCITT_DEST_NSAP and
FAC_CCITT_SRC_NSAP facilities fields, a remote host can provide a length
of less than 10, resulting in an underflow in a memcpy size, causing a
kernel panic due to massive heap corruption.  A length of greater than
20 results in a stack overflow of the callsign array.  Abort facilities
parsing on these invalid length values.

Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: stable@kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
CVE: CVE-2011-4913
CWE: CWE-20
Vulnerability description: The rose_parse_ccitt function in net/rose/rose_subr.c in the Linux kernel before 2.6.39 does not validate the FAC_CCITT_DEST_NSAP and FAC_CCITT_SRC_NSAP fields, which allows remote attackers to (1) cause a denial of service (integer underflow, heap memory corruption, and panic) via a small length value in data sent to a ROSE socket, or (2) conduct stack-based buffer overflow attacks via a large length value in data sent to a ROSE socket.

Project: linux
File: rose_subr.c

static int rose_parse_ccitt(unsigned char *p, struct rose_facilities_struct *facilities, int len)
{
	unsigned char l, n = 0;
	char callsign[11];

	do {
		switch (*p & 0xC0) {
		case 0x00:
			p   += 2;
			n   += 2;
			len -= 2;
			break;

		case 0x40:
			p   += 3;
			n   += 3;
			len -= 3;
			break;

		case 0x80:
			p   += 4;
			n   += 4;
			len -= 4;
			break;
 
 		case 0xC0:
 			l = p[1];

			/* Prevent overflows*/
			if (l < 10 || l > 20)
				return -1;

 			if (*p == FAC_CCITT_DEST_NSAP) {
 				memcpy(&facilities->source_addr, p + 7, ROSE_ADDR_LEN);
 				memcpy(callsign, p + 12,   l - 10);
				callsign[l - 10] = '\0';
				asc2ax(&facilities->source_call, callsign);
			}
			if (*p == FAC_CCITT_SRC_NSAP) {
				memcpy(&facilities->dest_addr, p + 7, ROSE_ADDR_LEN);
				memcpy(callsign, p + 12, l - 10);
				callsign[l - 10] = '\0';
				asc2ax(&facilities->dest_call, callsign);
			}
			p   += l + 2;
			n   += l + 2;
			len -= l + 2;
			break;
		}
	} while (*p != 0x00 && len > 0);

	return n;
}

Project: linux
File: rose_subr.c

int rose_parse_facilities(unsigned char *p,
	struct rose_facilities_struct *facilities)
{
	int facilities_len, len;

	facilities_len = *p++;

	if (facilities_len == 0)
		return 0;

	while (facilities_len > 0) {
		if (*p == 0x00) {
			facilities_len--;
			p++;

 			switch (*p) {
 			case FAC_NATIONAL:		/* National */
 				len = rose_parse_national(p + 1, facilities, facilities_len - 1);
				if (len < 0)
					return 0;
 				facilities_len -= len + 1;
 				p += len + 1;
 				break;
 
 			case FAC_CCITT:		/* CCITT */
 				len = rose_parse_ccitt(p + 1, facilities, facilities_len - 1);
				if (len < 0)
					return 0;
 				facilities_len -= len + 1;
 				p += len + 1;
 				break;

			default:
				printk(KERN_DEBUG "ROSE: rose_parse_facilities - unknown facilities family %02X\n", *p);
				facilities_len--;
				p++;
				break;
			}
		} else
			break;	/* Error in facilities format */
	}

	return 1;
}

Project: linux
File: rose_subr.c

static int rose_parse_national(unsigned char *p, struct rose_facilities_struct *facilities, int len)
{
	unsigned char *pt;
	unsigned char l, lg, n = 0;
	int fac_national_digis_received = 0;

	do {
		switch (*p & 0xC0) {
		case 0x00:
			p   += 2;
			n   += 2;
			len -= 2;
			break;

		case 0x40:
			if (*p == FAC_NATIONAL_RAND)
				facilities->rand = ((p[1] << 8) & 0xFF00) + ((p[2] << 0) & 0x00FF);
			p   += 3;
			n   += 3;
			len -= 3;
			break;

		case 0x80:
			p   += 4;
			n   += 4;
			len -= 4;
			break;

		case 0xC0:
			l = p[1];
			if (*p == FAC_NATIONAL_DEST_DIGI) {
				if (!fac_national_digis_received) {
					memcpy(&facilities->source_digis[0], p + 2, AX25_ADDR_LEN);
					facilities->source_ndigis = 1;
				}
			}
			else if (*p == FAC_NATIONAL_SRC_DIGI) {
				if (!fac_national_digis_received) {
					memcpy(&facilities->dest_digis[0], p + 2, AX25_ADDR_LEN);
					facilities->dest_ndigis = 1;
				}
			}
			else if (*p == FAC_NATIONAL_FAIL_CALL) {
				memcpy(&facilities->fail_call, p + 2, AX25_ADDR_LEN);
			}
			else if (*p == FAC_NATIONAL_FAIL_ADD) {
				memcpy(&facilities->fail_addr, p + 3, ROSE_ADDR_LEN);
			}
			else if (*p == FAC_NATIONAL_DIGIS) {
				fac_national_digis_received = 1;
 				facilities->source_ndigis = 0;
 				facilities->dest_ndigis   = 0;
 				for (pt = p + 2, lg = 0 ; lg < l ; pt += AX25_ADDR_LEN, lg += AX25_ADDR_LEN) {
					if (pt[6] & AX25_HBIT) {
						if (facilities->dest_ndigis >= ROSE_MAX_DIGIS)
							return -1;
 						memcpy(&facilities->dest_digis[facilities->dest_ndigis++], pt, AX25_ADDR_LEN);
					} else {
						if (facilities->source_ndigis >= ROSE_MAX_DIGIS)
							return -1;
 						memcpy(&facilities->source_digis[facilities->source_ndigis++], pt, AX25_ADDR_LEN);
					}
 				}
 			}
 			p   += l + 2;
			n   += l + 2;
			len -= l + 2;
			break;
		}
	} while (*p != 0x00 && len > 0);

	return n;
}