--- /dev/null
+/*
+ * ==FILEVERSION 20020320==
+ *
+ * ppp_mppe_compress.c - interface MPPE to the PPP code.
+ * This version is for use with Linux kernel 2.2.x (ppp driver 2.3.x).
+ *
+ * By Frank Cusack <frank@google.com>.
+ * Copyright (c) 2002 Google, Inc.
+ * All rights reserved.
+ *
+ * Permission to use, copy, modify, and distribute this software and its
+ * documentation is hereby granted, provided that the above copyright
+ * notice appears in all copies. This software is provided without any
+ * warranty, express or implied.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/malloc.h>
+#include <linux/string.h>
+
+#include <linux/ppp_defs.h>
+#include <linux/ppp-comp.h>
+
+#include "arcfour.h"
+#include "sha1.h"
+
+/*
+ * State for an MPPE (de)compressor.
+ */
+typedef struct ppp_mppe_state {
+ unsigned char master_key[MPPE_MAX_KEY_LEN];
+ unsigned char session_key[MPPE_MAX_KEY_LEN];
+ arcfour_context arcfour_context; /* encryption state */
+ unsigned keylen; /* key length in bytes */
+ /* NB: 128-bit == 16, 40-bit == 8! */
+ /* If we want to support 56-bit, */
+ /* the unit has to change to bits */
+ unsigned char bits; /* MPPE control bits */
+ unsigned ccount; /* 12-bit coherency count (seqno) */
+ unsigned stateful; /* stateful mode flag */
+ int discard; /* stateful mode packet loss flag */
+ int sanity_errors; /* take down LCP if too many */
+ int unit;
+ int debug;
+ struct compstat stats;
+} ppp_mppe_state;
+
+/* ppp_mppe_state.bits definitions */
+#define MPPE_BIT_A 0x80 /* Encryption table were (re)inititalized */
+#define MPPE_BIT_B 0x40 /* MPPC only (not implemented) */
+#define MPPE_BIT_C 0x20 /* MPPC only (not implemented) */
+#define MPPE_BIT_D 0x10 /* This is an encrypted frame */
+
+#define MPPE_BIT_FLUSHED MPPE_BIT_A
+#define MPPE_BIT_ENCRYPTED MPPE_BIT_D
+
+#define MPPE_BITS(p) ((p)[4] & 0xf0)
+#define MPPE_CCOUNT(p) ((((p)[4] & 0x0f) << 8) + (p)[5])
+#define MPPE_CCOUNT_SPACE 0x1000 /* The size of the ccount space */
+
+/*
+ * MPPE overhead/packet.
+ * Note that we use this differently than other compressors.
+ */
+#define MPPE_OVHD 2 /* MPPE overhead/packet */
+/* Max bogon factor we will tolerate */
+#define SANITY_MAX 1600
+
+static void GetNewKeyFromSHA __P((unsigned char *StartKey,
+ unsigned char *SessionKey,
+ unsigned SessionKeyLength,
+ unsigned char *InterimKey));
+static void mppe_rekey __P((ppp_mppe_state *state, int));
+static void *mppe_alloc __P((unsigned char *options, int optlen));
+static void mppe_free __P((void *state));
+static int mppe_init __P((void *state, unsigned char *options,
+ int optlen, int unit, int debug, const char *));
+static int mppe_comp_init __P((void *state, unsigned char *options,
+ int optlen,
+ int unit, int hdrlen, int debug));
+static int mppe_decomp_init __P((void *state, unsigned char *options,
+ int optlen, int unit,
+ int hdrlen, int mru, int debug));
+static int mppe_compress __P((void *state, unsigned char *ibuf,
+ unsigned char *obuf,
+ int isize, int osize));
+static void mppe_incomp __P((void *state, unsigned char *ibuf, int icnt));
+static int mppe_decompress __P((void *state, unsigned char *ibuf,
+ int isize, unsigned char *obuf,int osize));
+static void mppe_comp_reset __P((void *state));
+static void mppe_decomp_reset __P((void *state));
+static void mppe_comp_stats __P((void *state, struct compstat *stats));
+
+
+/*
+ * Key Derivation, from RFC 3078, RFC 3079.
+ * Equivalent to Get_Key() for MS-CHAP as described in RFC 3079.
+ */
+static void
+GetNewKeyFromSHA(unsigned char *MasterKey, unsigned char *SessionKey,
+ unsigned SessionKeyLength, unsigned char *InterimKey)
+{
+ SHA1_CTX Context;
+ unsigned char Digest[SHA1_SIGNATURE_SIZE];
+
+ unsigned char SHApad1[40] =
+ { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
+ unsigned char SHApad2[40] =
+ { 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
+ 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
+ 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2,
+ 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2, 0xf2 };
+
+ /* assert(SessionKeyLength <= SHA1_SIGNATURE_SIZE); */
+
+ SHA1_Init(&Context);
+ SHA1_Update(&Context, MasterKey, SessionKeyLength);
+ SHA1_Update(&Context, SHApad1, sizeof(SHApad1));
+ SHA1_Update(&Context, SessionKey, SessionKeyLength);
+ SHA1_Update(&Context, SHApad2, sizeof(SHApad2));
+ SHA1_Final(Digest, &Context);
+
+ memcpy(InterimKey, Digest, SessionKeyLength);
+}
+
+/*
+ * Perform the MPPE rekey algorithm, from RFC 3078, sec. 7.3.
+ * Well, not what's written there, but rather what they meant.
+ */
+static void
+mppe_rekey(ppp_mppe_state *state, int initial_key)
+{
+ unsigned char InterimKey[MPPE_MAX_KEY_LEN];
+
+ GetNewKeyFromSHA(state->master_key, state->session_key,
+ state->keylen, InterimKey);
+ if (!initial_key) {
+ arcfour_setkey(&state->arcfour_context, InterimKey, state->keylen);
+ arcfour_encrypt(&state->arcfour_context, InterimKey, state->keylen,
+ state->session_key);
+ } else {
+ memcpy(state->session_key, InterimKey, state->keylen);
+ }
+ if (state->keylen == 8) {
+ /* See RFC 3078 */
+ state->session_key[0] = 0xd1;
+ state->session_key[1] = 0x26;
+ state->session_key[2] = 0x9e;
+ }
+ arcfour_setkey(&state->arcfour_context, state->session_key, state->keylen);
+}
+
+
+/*
+ * Allocate space for a (de)compressor.
+ */
+static void *
+mppe_alloc(unsigned char *options, int optlen)
+{
+ ppp_mppe_state *state;
+
+ if (optlen != CILEN_MPPE + sizeof(state->master_key)
+ || options[0] != CI_MPPE
+ || options[1] != CILEN_MPPE)
+ return NULL;
+
+ state = (ppp_mppe_state *) kmalloc(sizeof(*state), GFP_KERNEL);
+ if (state == NULL)
+ return NULL;
+
+ MOD_INC_USE_COUNT;
+ memset(state, 0, sizeof(*state));
+
+ /* Save keys. */
+ memcpy(state->master_key, &options[CILEN_MPPE], sizeof(state->master_key));
+ memcpy(state->session_key, state->master_key, sizeof(state->master_key));
+ /*
+ * We defer initial key generation until mppe_init(), as mppe_alloc()
+ * is called frequently during negotiation.
+ */
+
+ return (void *) state;
+}
+
+/*
+ * Deallocate space for a (de)compressor.
+ */
+static void
+mppe_free(void *arg)
+{
+ ppp_mppe_state *state = (ppp_mppe_state *) arg;
+
+ if (state) {
+ kfree(state);
+ MOD_DEC_USE_COUNT;
+ }
+}
+
+
+/*
+ * Initialize (de)compressor state.
+ */
+static int
+mppe_init(void *arg, unsigned char *options, int optlen, int unit, int debug,
+ const char *debugstr)
+{
+ ppp_mppe_state *state = (ppp_mppe_state *) arg;
+ unsigned char mppe_opts;
+
+ if (optlen != CILEN_MPPE
+ || options[0] != CI_MPPE
+ || options[1] != CILEN_MPPE)
+ return 0;
+
+ MPPE_CI_TO_OPTS(&options[2], mppe_opts);
+ if (mppe_opts & MPPE_OPT_128)
+ state->keylen = 16;
+ else if (mppe_opts & MPPE_OPT_40)
+ state->keylen = 8;
+ else {
+ printk(KERN_WARNING "%s[%d]: unknown key length\n", debugstr, unit);
+ return 0;
+ }
+ if (mppe_opts & MPPE_OPT_STATEFUL)
+ state->stateful = 1;
+
+ /* Generate the initial session key. */
+ mppe_rekey(state, 1);
+
+ if (debug) {
+ int i;
+ char mkey[sizeof(state->master_key) * 3 + 1];
+ char skey[sizeof(state->session_key) * 3 + 1];
+
+ printk(KERN_DEBUG "%s[%d]: initialized with %d-bit %s mode\n", debugstr,
+ unit, (state->keylen == 16)? 128: 40,
+ (state->stateful)? "stateful": "stateless");
+
+ for (i = 0; i < sizeof(state->master_key); i++)
+ sprintf(mkey + i * 2, "%.2x ", state->master_key[i]);
+ for (i = 0; i < sizeof(state->session_key); i++)
+ sprintf(skey + i * 2, "%.2x ", state->session_key[i]);
+ printk(KERN_DEBUG "%s[%d]: keys: master: %s initial session: %s\n",
+ debugstr, unit, mkey, skey);
+ }
+
+ /*
+ * Initialize the coherency count. The initial value is not specified
+ * in RFC 3078, but we can make a reasonable assumption that it will
+ * start at 0. Setting it to the max here makes the comp/decomp code
+ * do the right thing (determined through experiment).
+ */
+ state->ccount = MPPE_CCOUNT_SPACE - 1;
+
+ /*
+ * Note that even though we have initialized the key table, we don't
+ * set the FLUSHED bit. This is contrary to RFC 3078, sec. 3.1.
+ */
+ state->bits = MPPE_BIT_ENCRYPTED;
+
+ state->unit = unit;
+ state->debug = debug;
+
+ return 1;
+}
+
+
+
+static int
+mppe_comp_init(void *arg, unsigned char *options, int optlen, int unit,
+ int hdrlen, int debug)
+{
+ /* ARGSUSED */
+ return mppe_init(arg, options, optlen, unit, debug, "mppe_comp_init");
+}
+
+/*
+ * We received a CCP Reset-Request (actually, we are sending a Reset-Ack),
+ * tell the compressor to rekey. Note that we MUST NOT rekey for
+ * every CCP Reset-Request; we only rekey on the next xmit packet.
+ * We might get multiple CCP Reset-Requests if our CCP Reset-Ack is lost.
+ * So, rekeying for every CCP Reset-Request is broken as the peer will not
+ * know how many times we've rekeyed. (If we rekey and THEN get another
+ * CCP Reset-Request, we must rekey again.)
+ */
+static void
+mppe_comp_reset(void *arg)
+{
+ ppp_mppe_state *state = (ppp_mppe_state *) arg;
+
+ state->bits |= MPPE_BIT_FLUSHED;
+}
+
+/*
+ * Compress (encrypt) a packet.
+ * It's strange to call this a compressor, since the output is always
+ * MPPE_OVHD + 2 bytes larger than the input.
+ */
+int
+mppe_compress(void *arg, unsigned char *ibuf, unsigned char *obuf,
+ int isize, int osize)
+{
+ ppp_mppe_state *state = (ppp_mppe_state *) arg;
+ int proto;
+
+ /*
+ * Check that the protocol is in the range we handle.
+ */
+ proto = PPP_PROTOCOL(ibuf);
+ if (proto < 0x0021 || proto > 0x00fa)
+ return 0;
+
+ /* Make sure we have enough room to generate an encrypted packet. */
+ if (osize < isize + MPPE_OVHD + 2) {
+ /* Drop the packet if we should encrypt it, but can't. */
+ printk(KERN_DEBUG "mppe_compress[%d]: osize too small! "
+ "(have: %d need: %d)\n", state->unit,
+ osize, osize + MPPE_OVHD + 2);
+ return -1;
+ }
+
+ osize = isize + MPPE_OVHD + 2;
+
+ /*
+ * Copy over the PPP header and set control bits.
+ */
+ obuf[0] = PPP_ADDRESS(ibuf);
+ obuf[1] = PPP_CONTROL(ibuf);
+ obuf[2] = PPP_COMP >> 8; /* isize + MPPE_OVHD + 1 */
+ obuf[3] = PPP_COMP; /* isize + MPPE_OVHD + 2 */
+ obuf += PPP_HDRLEN;
+
+ state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
+ obuf[0] = state->ccount >> 8;
+ obuf[1] = state->ccount & 0xff;
+
+ if (!state->stateful || /* stateless mode */
+ ((state->ccount & 0xff) == 0xff) || /* "flag" packet */
+ (state->bits & MPPE_BIT_FLUSHED)) { /* CCP Reset-Request */
+ /* We must rekey */
+ if (state->debug && state->stateful)
+ printk(KERN_DEBUG "mppe_compress[%d]: rekeying\n", state->unit);
+ mppe_rekey(state, 0);
+ state->bits |= MPPE_BIT_FLUSHED;
+ }
+ obuf[0] |= state->bits;
+ state->bits &= ~MPPE_BIT_FLUSHED; /* reset for next xmit */
+
+ obuf += MPPE_OVHD;
+ ibuf += 2; /* skip to proto field */
+ isize -= 2;
+
+ /* Encrypt packet */
+ arcfour_encrypt(&state->arcfour_context, ibuf, isize, obuf);
+
+ state->stats.unc_bytes += isize;
+ state->stats.unc_packets++;
+ state->stats.comp_bytes += osize;
+ state->stats.comp_packets++;
+
+ return osize;
+}
+
+/*
+ * Since every frame grows by MPPE_OVHD + 2 bytes, this is always going
+ * to look bad ... and the longer the link is up the worse it will get.
+ */
+static void
+mppe_comp_stats(void *arg, struct compstat *stats)
+{
+ ppp_mppe_state *state = (ppp_mppe_state *) arg;
+
+ *stats = state->stats;
+}
+
+
+static int
+mppe_decomp_init(void *arg, unsigned char *options, int optlen, int unit,
+ int hdrlen, int mru, int debug)
+{
+ /* ARGSUSED */
+ return mppe_init(arg, options, optlen, unit, debug, "mppe_decomp_init");
+}
+
+/*
+ * We received a CCP Reset-Ack. Just ignore it.
+ */
+static void
+mppe_decomp_reset(void *arg)
+{
+ /* ARGSUSED */
+ return;
+}
+
+/*
+ * Decompress (decrypt) an MPPE packet.
+ */
+int
+mppe_decompress(void *arg, unsigned char *ibuf, int isize, unsigned char *obuf,
+ int osize)
+{
+ ppp_mppe_state *state = (ppp_mppe_state *) arg;
+ unsigned ccount;
+ int flushed = MPPE_BITS(ibuf) & MPPE_BIT_FLUSHED;
+ int sanity = 0;
+
+ if (isize <= PPP_HDRLEN + MPPE_OVHD) {
+ if (state->debug)
+ printk(KERN_DEBUG "mppe_decompress[%d]: short pkt (%d)\n",
+ state->unit, isize);
+ return DECOMP_ERROR;
+ }
+ /* Strange ... our output size is always LESS than the input size. */
+ /* assert(osize >= isize - MPPE_OVHD - 2); */
+
+ osize = isize - MPPE_OVHD - 2;
+
+ ccount = MPPE_CCOUNT(ibuf);
+
+ /* sanity checks -- terminate with extreme prejudice */
+ if (!(MPPE_BITS(ibuf) & MPPE_BIT_ENCRYPTED)) {
+ printk(KERN_DEBUG "mppe_decompress[%d]: ENCRYPTED bit not set!\n",
+ state->unit);
+ state->sanity_errors += 100;
+ sanity = 1;
+ }
+ if (!state->stateful && !flushed) {
+ printk(KERN_DEBUG "mppe_decompress[%d]: FLUSHED bit not set in "
+ "stateless mode!\n", state->unit);
+ state->sanity_errors += 100;
+ sanity = 1;
+ }
+ if (state->stateful && ((ccount & 0xff) == 0xff) && !flushed) {
+ printk(KERN_DEBUG "mppe_decompress[%d]: FLUSHED bit not set on "
+ "flag packet!\n", state->unit);
+ state->sanity_errors += 100;
+ sanity = 1;
+ }
+
+ if (sanity) {
+ if (state->sanity_errors < SANITY_MAX)
+ return DECOMP_ERROR;
+ else
+ /*
+ * Take LCP down if the peer is sending too many bogons.
+ * We don't want to do this for a single or just a few
+ * instances since it could just be due to packet corruption.
+ */
+ return DECOMP_FATALERROR;
+ }
+
+ /*
+ * Check the coherency count.
+ */
+
+ if (!state->stateful) {
+ /* RFC 3078, sec 8.1. Rekey for every packet. */
+ while (state->ccount != ccount) {
+ mppe_rekey(state, 0);
+ state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
+ }
+ } else {
+ /* RFC 3078, sec 8.2. */
+ if (!state->discard) {
+ /* normal state */
+ state->ccount = (state->ccount + 1) % MPPE_CCOUNT_SPACE;
+ if (ccount != state->ccount) {
+ /*
+ * (ccount > state->ccount)
+ * Packet loss detected, enter the discard state.
+ * Signal the peer to rekey (by sending a CCP Reset-Request).
+ */
+ state->discard = 1;
+ return DECOMP_ERROR;
+ }
+ } else {
+ /* discard state */
+ if (!flushed) {
+ /* ccp.c will be silent (no additional CCP Reset-Requests). */
+ return DECOMP_ERROR;
+ } else {
+ /* Rekey for every missed "flag" packet. */
+ while ((ccount & ~0xff) != (state->ccount & ~0xff)) {
+ mppe_rekey(state, 0);
+ state->ccount = (state->ccount + 256) % MPPE_CCOUNT_SPACE;
+ }
+
+ /* reset */
+ state->discard = 0;
+ state->ccount = ccount;
+ /*
+ * Another problem with RFC 3078 here. It implies that the
+ * peer need not send a Reset-Ack packet. But RFC 1962
+ * requires it. Hopefully, M$ does send a Reset-Ack; even
+ * though it isn't required for MPPE synchronization, it is
+ * required to reset CCP state.
+ */
+ }
+ }
+ if (flushed)
+ mppe_rekey(state, 0);
+ }
+
+ /*
+ * Fill in the first part of the PPP header. The protocol field
+ * comes from the decrypted data.
+ */
+ obuf[0] = PPP_ADDRESS(ibuf); /* +1 */
+ obuf[1] = PPP_CONTROL(ibuf); /* +2 */
+ obuf += 2;
+ ibuf += PPP_HDRLEN + MPPE_OVHD;
+ isize -= PPP_HDRLEN + MPPE_OVHD; /* -6 */
+ /* net: -4 */
+
+ /* And finally, decrypt the packet. */
+ arcfour_decrypt(&state->arcfour_context, ibuf, isize, obuf);
+
+ state->stats.unc_bytes += osize;
+ state->stats.unc_packets++;
+ state->stats.comp_bytes += isize;
+ state->stats.comp_packets++;
+
+ /* good packet credit */
+ state->sanity_errors >>= 1;
+
+ return osize;
+}
+
+/*
+ * Incompressible data has arrived (this should never happen!).
+ * We should probably drop the link if the protocol is in the range
+ * of what should be encrypted. At the least, we should drop this
+ * packet. (How to do this?)
+ */
+static void
+mppe_incomp(void *arg, unsigned char *ibuf, int icnt)
+{
+ ppp_mppe_state *state = (ppp_mppe_state *) arg;
+
+ if (state->debug &&
+ (PPP_PROTOCOL(ibuf) >= 0x0021 && PPP_PROTOCOL(ibuf) <= 0x00fa))
+ printk(KERN_DEBUG "mppe_incomp[%d]: incompressible (unencrypted) data! "
+ "(proto %04x)\n", state->unit, PPP_PROTOCOL(ibuf));
+
+ state->stats.inc_bytes += icnt;
+ state->stats.inc_packets++;
+ state->stats.unc_bytes += icnt;
+ state->stats.unc_packets++;
+}
+
+/*************************************************************
+ * Module interface table
+ *************************************************************/
+
+/* These are in ppp.c */
+extern int ppp_register_compressor (struct compressor *cp);
+extern void ppp_unregister_compressor (struct compressor *cp);
+
+/*
+ * Procedures exported to if_ppp.c.
+ */
+struct compressor ppp_mppe = {
+ CI_MPPE, /* compress_proto */
+ mppe_alloc, /* comp_alloc */
+ mppe_free, /* comp_free */
+ mppe_comp_init, /* comp_init */
+ mppe_comp_reset, /* comp_reset */
+ mppe_compress, /* compress */
+ mppe_comp_stats, /* comp_stat */
+ mppe_alloc, /* decomp_alloc */
+ mppe_free, /* decomp_free */
+ mppe_decomp_init, /* decomp_init */
+ mppe_decomp_reset, /* decomp_reset */
+ mppe_decompress, /* decompress */
+ mppe_incomp, /* incomp */
+ mppe_comp_stats, /* decomp_stat */
+};
+
+__initfunc(int ppp_mppe_install(void))
+{
+ int answer = ppp_register_compressor(&ppp_mppe);
+
+ if (answer == 0)
+ printk(KERN_INFO "PPP MPPE Compression module registered\n");
+ return answer;
+}
+
+#ifdef MODULE
+
+int
+init_module(void)
+{
+ return ppp_mppe_install();
+}
+
+void
+cleanup_module(void)
+{
+ if (MOD_IN_USE)
+ printk(KERN_INFO "PPP MPPE Compression module busy\n");
+ else
+ ppp_unregister_compressor(&ppp_mppe);
+}
+#endif
projects / ppp.git / blobdiff