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https://github.com/torvalds/linux
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5ef41308f9
Now with improved comma support. On parsing malformed X.25 facilities, decrementing the remaining length may cause it to underflow. Since the length is an unsigned integer, this will result in the loop continuing until the kernel crashes. This patch adds checks to ensure decrementing the remaining length does not cause it to wrap around. Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com> Signed-off-by: David S. Miller <davem@davemloft.net>
337 lines
8.6 KiB
C
337 lines
8.6 KiB
C
/*
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* X.25 Packet Layer release 002
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*
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* This is ALPHA test software. This code may break your machine,
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* randomly fail to work with new releases, misbehave and/or generally
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* screw up. It might even work.
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*
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* This code REQUIRES 2.1.15 or higher
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*
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* This module:
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* This module is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* History
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* X.25 001 Split from x25_subr.c
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* mar/20/00 Daniela Squassoni Disabling/enabling of facilities
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* negotiation.
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* apr/14/05 Shaun Pereira - Allow fast select with no restriction
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* on response.
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*/
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#include <linux/kernel.h>
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#include <linux/string.h>
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#include <linux/skbuff.h>
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#include <net/sock.h>
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#include <net/x25.h>
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/*
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* Parse a set of facilities into the facilities structures. Unrecognised
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* facilities are written to the debug log file.
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*/
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int x25_parse_facilities(struct sk_buff *skb, struct x25_facilities *facilities,
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struct x25_dte_facilities *dte_facs, unsigned long *vc_fac_mask)
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{
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unsigned char *p = skb->data;
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unsigned int len;
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*vc_fac_mask = 0;
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/*
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* The kernel knows which facilities were set on an incoming call but
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* currently this information is not available to userspace. Here we
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* give userspace who read incoming call facilities 0 length to indicate
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* it wasn't set.
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*/
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dte_facs->calling_len = 0;
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dte_facs->called_len = 0;
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memset(dte_facs->called_ae, '\0', sizeof(dte_facs->called_ae));
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memset(dte_facs->calling_ae, '\0', sizeof(dte_facs->calling_ae));
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if (skb->len < 1)
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return 0;
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len = *p++;
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if (len >= skb->len)
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return -1;
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while (len > 0) {
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switch (*p & X25_FAC_CLASS_MASK) {
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case X25_FAC_CLASS_A:
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if (len < 2)
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return 0;
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switch (*p) {
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case X25_FAC_REVERSE:
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if((p[1] & 0x81) == 0x81) {
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facilities->reverse = p[1] & 0x81;
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*vc_fac_mask |= X25_MASK_REVERSE;
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break;
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}
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if((p[1] & 0x01) == 0x01) {
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facilities->reverse = p[1] & 0x01;
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*vc_fac_mask |= X25_MASK_REVERSE;
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break;
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}
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if((p[1] & 0x80) == 0x80) {
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facilities->reverse = p[1] & 0x80;
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*vc_fac_mask |= X25_MASK_REVERSE;
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break;
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}
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if(p[1] == 0x00) {
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facilities->reverse
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= X25_DEFAULT_REVERSE;
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*vc_fac_mask |= X25_MASK_REVERSE;
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break;
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}
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case X25_FAC_THROUGHPUT:
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facilities->throughput = p[1];
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*vc_fac_mask |= X25_MASK_THROUGHPUT;
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break;
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case X25_MARKER:
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break;
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default:
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printk(KERN_DEBUG "X.25: unknown facility "
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"%02X, value %02X\n",
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p[0], p[1]);
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break;
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}
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p += 2;
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len -= 2;
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break;
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case X25_FAC_CLASS_B:
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if (len < 3)
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return 0;
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switch (*p) {
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case X25_FAC_PACKET_SIZE:
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facilities->pacsize_in = p[1];
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facilities->pacsize_out = p[2];
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*vc_fac_mask |= X25_MASK_PACKET_SIZE;
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break;
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case X25_FAC_WINDOW_SIZE:
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facilities->winsize_in = p[1];
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facilities->winsize_out = p[2];
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*vc_fac_mask |= X25_MASK_WINDOW_SIZE;
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break;
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default:
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printk(KERN_DEBUG "X.25: unknown facility "
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"%02X, values %02X, %02X\n",
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p[0], p[1], p[2]);
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break;
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}
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p += 3;
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len -= 3;
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break;
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case X25_FAC_CLASS_C:
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if (len < 4)
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return 0;
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printk(KERN_DEBUG "X.25: unknown facility %02X, "
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"values %02X, %02X, %02X\n",
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p[0], p[1], p[2], p[3]);
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p += 4;
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len -= 4;
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break;
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case X25_FAC_CLASS_D:
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if (len < p[1] + 2)
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return 0;
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switch (*p) {
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case X25_FAC_CALLING_AE:
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if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
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return 0;
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dte_facs->calling_len = p[2];
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memcpy(dte_facs->calling_ae, &p[3], p[1] - 1);
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*vc_fac_mask |= X25_MASK_CALLING_AE;
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break;
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case X25_FAC_CALLED_AE:
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if (p[1] > X25_MAX_DTE_FACIL_LEN || p[1] <= 1)
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return 0;
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dte_facs->called_len = p[2];
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memcpy(dte_facs->called_ae, &p[3], p[1] - 1);
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*vc_fac_mask |= X25_MASK_CALLED_AE;
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break;
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default:
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printk(KERN_DEBUG "X.25: unknown facility %02X,"
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"length %d\n", p[0], p[1]);
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break;
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}
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len -= p[1] + 2;
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p += p[1] + 2;
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break;
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}
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}
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return p - skb->data;
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}
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/*
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* Create a set of facilities.
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*/
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int x25_create_facilities(unsigned char *buffer,
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struct x25_facilities *facilities,
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struct x25_dte_facilities *dte_facs, unsigned long facil_mask)
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{
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unsigned char *p = buffer + 1;
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int len;
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if (!facil_mask) {
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/*
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* Length of the facilities field in call_req or
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* call_accept packets
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*/
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buffer[0] = 0;
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len = 1; /* 1 byte for the length field */
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return len;
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}
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if (facilities->reverse && (facil_mask & X25_MASK_REVERSE)) {
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*p++ = X25_FAC_REVERSE;
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*p++ = facilities->reverse;
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}
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if (facilities->throughput && (facil_mask & X25_MASK_THROUGHPUT)) {
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*p++ = X25_FAC_THROUGHPUT;
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*p++ = facilities->throughput;
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}
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if ((facilities->pacsize_in || facilities->pacsize_out) &&
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(facil_mask & X25_MASK_PACKET_SIZE)) {
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*p++ = X25_FAC_PACKET_SIZE;
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*p++ = facilities->pacsize_in ? : facilities->pacsize_out;
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*p++ = facilities->pacsize_out ? : facilities->pacsize_in;
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}
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if ((facilities->winsize_in || facilities->winsize_out) &&
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(facil_mask & X25_MASK_WINDOW_SIZE)) {
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*p++ = X25_FAC_WINDOW_SIZE;
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*p++ = facilities->winsize_in ? : facilities->winsize_out;
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*p++ = facilities->winsize_out ? : facilities->winsize_in;
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}
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if (facil_mask & (X25_MASK_CALLING_AE|X25_MASK_CALLED_AE)) {
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*p++ = X25_MARKER;
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*p++ = X25_DTE_SERVICES;
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}
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if (dte_facs->calling_len && (facil_mask & X25_MASK_CALLING_AE)) {
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unsigned bytecount = (dte_facs->calling_len + 1) >> 1;
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*p++ = X25_FAC_CALLING_AE;
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*p++ = 1 + bytecount;
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*p++ = dte_facs->calling_len;
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memcpy(p, dte_facs->calling_ae, bytecount);
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p += bytecount;
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}
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if (dte_facs->called_len && (facil_mask & X25_MASK_CALLED_AE)) {
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unsigned bytecount = (dte_facs->called_len % 2) ?
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dte_facs->called_len / 2 + 1 :
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dte_facs->called_len / 2;
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*p++ = X25_FAC_CALLED_AE;
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*p++ = 1 + bytecount;
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*p++ = dte_facs->called_len;
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memcpy(p, dte_facs->called_ae, bytecount);
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p+=bytecount;
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}
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len = p - buffer;
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buffer[0] = len - 1;
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return len;
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}
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/*
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* Try to reach a compromise on a set of facilities.
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*
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* The only real problem is with reverse charging.
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*/
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int x25_negotiate_facilities(struct sk_buff *skb, struct sock *sk,
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struct x25_facilities *new, struct x25_dte_facilities *dte)
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{
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struct x25_sock *x25 = x25_sk(sk);
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struct x25_facilities *ours = &x25->facilities;
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struct x25_facilities theirs;
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int len;
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memset(&theirs, 0, sizeof(theirs));
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memcpy(new, ours, sizeof(*new));
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len = x25_parse_facilities(skb, &theirs, dte, &x25->vc_facil_mask);
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if (len < 0)
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return len;
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/*
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* They want reverse charging, we won't accept it.
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*/
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if ((theirs.reverse & 0x01 ) && (ours->reverse & 0x01)) {
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SOCK_DEBUG(sk, "X.25: rejecting reverse charging request\n");
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return -1;
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}
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new->reverse = theirs.reverse;
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if (theirs.throughput) {
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int theirs_in = theirs.throughput & 0x0f;
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int theirs_out = theirs.throughput & 0xf0;
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int ours_in = ours->throughput & 0x0f;
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int ours_out = ours->throughput & 0xf0;
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if (!ours_in || theirs_in < ours_in) {
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SOCK_DEBUG(sk, "X.25: inbound throughput negotiated\n");
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new->throughput = (new->throughput & 0xf0) | theirs_in;
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}
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if (!ours_out || theirs_out < ours_out) {
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SOCK_DEBUG(sk,
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"X.25: outbound throughput negotiated\n");
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new->throughput = (new->throughput & 0x0f) | theirs_out;
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}
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}
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if (theirs.pacsize_in && theirs.pacsize_out) {
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if (theirs.pacsize_in < ours->pacsize_in) {
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SOCK_DEBUG(sk, "X.25: packet size inwards negotiated down\n");
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new->pacsize_in = theirs.pacsize_in;
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}
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if (theirs.pacsize_out < ours->pacsize_out) {
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SOCK_DEBUG(sk, "X.25: packet size outwards negotiated down\n");
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new->pacsize_out = theirs.pacsize_out;
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}
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}
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if (theirs.winsize_in && theirs.winsize_out) {
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if (theirs.winsize_in < ours->winsize_in) {
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SOCK_DEBUG(sk, "X.25: window size inwards negotiated down\n");
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new->winsize_in = theirs.winsize_in;
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}
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if (theirs.winsize_out < ours->winsize_out) {
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SOCK_DEBUG(sk, "X.25: window size outwards negotiated down\n");
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new->winsize_out = theirs.winsize_out;
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}
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}
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return len;
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}
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/*
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* Limit values of certain facilities according to the capability of the
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* currently attached x25 link.
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*/
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void x25_limit_facilities(struct x25_facilities *facilities,
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struct x25_neigh *nb)
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{
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if (!nb->extended) {
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if (facilities->winsize_in > 7) {
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printk(KERN_DEBUG "X.25: incoming winsize limited to 7\n");
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facilities->winsize_in = 7;
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}
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if (facilities->winsize_out > 7) {
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facilities->winsize_out = 7;
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printk( KERN_DEBUG "X.25: outgoing winsize limited to 7\n");
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}
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}
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}
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