rose: Add length checks to CALL_REQUEST parsing

Define some constant offsets for CALL_REQUEST based on the description
at <http://www.techfest.com/networking/wan/x25plp.htm> and the
definition of ROSE as using 10-digit (5-byte) addresses.  Use them
consistently.  Validate all implicit and explicit facilities lengths.
Validate the address length byte rather than either trusting or
assuming its value.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 57 insertions, 34 deletions

diff --git a/net/rose/rose_subr.c b/net/rose/rose_subr.c
index 174d51c9ce3..f6c71caa94b 100644
--- a/net/rose/rose_subr.c
+++ b/net/rose/rose_subr.c
@@ -142,7 +142,7 @@ void rose_write_internal(struct sock *sk, int frametype)
 		*dptr++ = ROSE_GFI | lci1;
 		*dptr++ = lci2;
 		*dptr++ = frametype;
-		*dptr++ = 0xAA;
+		*dptr++ = ROSE_CALL_REQ_ADDR_LEN_VAL;
 		memcpy(dptr, &rose->dest_addr,  ROSE_ADDR_LEN);
 		dptr   += ROSE_ADDR_LEN;
 		memcpy(dptr, &rose->source_addr, ROSE_ADDR_LEN);
@@ -246,12 +246,16 @@ static int rose_parse_national(unsigned char *p, struct rose_facilities_struct *
 	do {
 		switch (*p & 0xC0) {
 		case 0x00:
+			if (len < 2)
+				return -1;
 			p   += 2;
 			n   += 2;
 			len -= 2;
 			break;
 
 		case 0x40:
+			if (len < 3)
+				return -1;
 			if (*p == FAC_NATIONAL_RAND)
 				facilities->rand = ((p[1] << 8) & 0xFF00) + ((p[2] << 0) & 0x00FF);
 			p   += 3;
@@ -260,32 +264,48 @@ static int rose_parse_national(unsigned char *p, struct rose_facilities_struct *
 			break;
 
 		case 0x80:
+			if (len < 4)
+				return -1;
 			p   += 4;
 			n   += 4;
 			len -= 4;
 			break;
 
 		case 0xC0:
+			if (len < 2)
+				return -1;
 			l = p[1];
+			if (len < 2 + l)
+				return -1;
 			if (*p == FAC_NATIONAL_DEST_DIGI) {
 				if (!fac_national_digis_received) {
+					if (l < AX25_ADDR_LEN)
+						return -1;
 					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) {
+					if (l < AX25_ADDR_LEN)
+						return -1;
 					memcpy(&facilities->dest_digis[0], p + 2, AX25_ADDR_LEN);
 					facilities->dest_ndigis = 1;
 				}
 			}
 			else if (*p == FAC_NATIONAL_FAIL_CALL) {
+				if (l < AX25_ADDR_LEN)
+					return -1;
 				memcpy(&facilities->fail_call, p + 2, AX25_ADDR_LEN);
 			}
 			else if (*p == FAC_NATIONAL_FAIL_ADD) {
+				if (l < 1 + ROSE_ADDR_LEN)
+					return -1;
 				memcpy(&facilities->fail_addr, p + 3, ROSE_ADDR_LEN);
 			}
 			else if (*p == FAC_NATIONAL_DIGIS) {
+				if (l % AX25_ADDR_LEN)
+					return -1;
 				fac_national_digis_received = 1;
 				facilities->source_ndigis = 0;
 				facilities->dest_ndigis   = 0;
@@ -319,24 +339,32 @@ static int rose_parse_ccitt(unsigned char *p, struct rose_facilities_struct *fac
 	do {
 		switch (*p & 0xC0) {
 		case 0x00:
+			if (len < 2)
+				return -1;
 			p   += 2;
 			n   += 2;
 			len -= 2;
 			break;
 
 		case 0x40:
+			if (len < 3)
+				return -1;
 			p   += 3;
 			n   += 3;
 			len -= 3;
 			break;
 
 		case 0x80:
+			if (len < 4)
+				return -1;
 			p   += 4;
 			n   += 4;
 			len -= 4;
 			break;
 
 		case 0xC0:
+			if (len < 2)
+				return -1;
 			l = p[1];
 
 			/* Prevent overflows*/
@@ -365,49 +393,44 @@ static int rose_parse_ccitt(unsigned char *p, struct rose_facilities_struct *fac
 	return n;
 }
 
-int rose_parse_facilities(unsigned char *p,
+int rose_parse_facilities(unsigned char *p, unsigned packet_len,
 	struct rose_facilities_struct *facilities)
 {
 	int facilities_len, len;
 
 	facilities_len = *p++;
 
-	if (facilities_len == 0)
+	if (facilities_len == 0 || (unsigned)facilities_len > packet_len)
 		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 */
+	while (facilities_len >= 3 && *p == 0x00) {
+		facilities_len--;
+		p++;
+
+		switch (*p) {
+		case FAC_NATIONAL:		/* National */
+			len = rose_parse_national(p + 1, facilities, facilities_len - 1);
+			break;
+
+		case FAC_CCITT:		/* CCITT */
+			len = rose_parse_ccitt(p + 1, facilities, facilities_len - 1);
+			break;
+
+		default:
+			printk(KERN_DEBUG "ROSE: rose_parse_facilities - unknown facilities family %02X\n", *p);
+			len = 1;
+			break;
+		}
+
+		if (len < 0)
+			return 0;
+		if (WARN_ON(len >= facilities_len))
+			return 0;
+		facilities_len -= len + 1;
+		p += len + 1;
 	}
 
-	return 1;
+	return facilities_len == 0;
 }
 
 static int rose_create_facilities(unsigned char *buffer, struct rose_sock *rose)