FreeBSD/Linux Kernel Cross Reference
sys/netipsec/xform_tcp.c

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * Copyright (c) 2003 Bruce M. Simpson <bms@spc.org>
      * Copyright (c) 2016 Andrey V. Elsukov <ae@FreeBSD.org>
      *
      * Redistribution and use in source and binary forms, with or without
      * modification, are permitted provided that the following conditions
      * are met:
     *
     * 1. Redistributions of source code must retain the above copyright
     *   notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *   notice, this list of conditions and the following disclaimer in the
     *   documentation and/or other materials provided with the distribution.
     * 3. The name of the author may not be used to endorse or promote products
     *   derived from this software without specific prior written permission.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     */
    
    /* TCP MD5 Signature Option (RFC2385) */
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include "opt_inet.h"
    #include "opt_inet6.h"
    #include "opt_ipsec.h"
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/mbuf.h>
    #include <sys/lock.h>
    #include <sys/md5.h>
    #include <sys/rmlock.h>
    #include <sys/socket.h>
    #include <sys/sockopt.h>
    #include <sys/kernel.h>
    #include <sys/module.h>
    #include <sys/protosw.h>
    
    #include <netinet/in.h>
    #include <netinet/in_pcb.h>
    #include <netinet/in_systm.h>
    #include <netinet/ip.h>
    #include <netinet/ip_var.h>
    #include <netinet/tcp.h>
    #include <netinet/tcp_var.h>
    
    #include <net/vnet.h>
    
    #include <netipsec/ipsec.h>
    #include <netipsec/ipsec_support.h>
    #include <netipsec/xform.h>
    
    #ifdef INET6
    #include <netinet/ip6.h>
    #include <netipsec/ipsec6.h>
    #endif
    
    #include <netipsec/key.h>
    #include <netipsec/key_debug.h>
    
    #define TCP_SIGLEN      16      /* length of computed digest in bytes */
    #define TCP_KEYLEN_MIN  1       /* minimum length of TCP-MD5 key */
    #define TCP_KEYLEN_MAX  80      /* maximum length of TCP-MD5 key */
    
    static int
    tcp_ipsec_pcbctl(struct inpcb *inp, struct sockopt *sopt)
    {
            struct tcpcb *tp;
            int error, optval;
    
            if (sopt->sopt_name != TCP_MD5SIG) {
                    return (ENOPROTOOPT);
            }
    
            if (sopt->sopt_dir == SOPT_GET) {
                    INP_RLOCK(inp);
                    if (inp->inp_flags & INP_DROPPED) {
                            INP_RUNLOCK(inp);
                            return (ECONNRESET);
                    }
                    tp = intotcpcb(inp);
                    optval = (tp->t_flags & TF_SIGNATURE) ? 1 : 0;
                    INP_RUNLOCK(inp);
    
                    /* On success return with released INP_WLOCK */
                    return (sooptcopyout(sopt, &optval, sizeof(optval)));
            }
   
           error = sooptcopyin(sopt, &optval, sizeof(optval), sizeof(optval));
           if (error != 0)
                   return (error);
   
           /* INP_WLOCK_RECHECK */
           INP_WLOCK(inp);
           if (inp->inp_flags & INP_DROPPED) {
                   INP_WUNLOCK(inp);
                   return (ECONNRESET);
           }
           tp = intotcpcb(inp);
           if (optval > 0)
                   tp->t_flags |= TF_SIGNATURE;
           else
                   tp->t_flags &= ~TF_SIGNATURE;
   
           INP_WUNLOCK(inp);
           return (error);
   }
   
   /*
    * Callback function invoked by m_apply() to digest TCP segment data
    * contained within an mbuf chain.
    */
   static int
   tcp_signature_apply(void *fstate, void *data, u_int len)
   {
   
           MD5Update(fstate, (u_char *)data, len);
           return (0);
   }
   
   #ifdef INET
   static int
   ip_pseudo_compute(struct mbuf *m, MD5_CTX *ctx)
   {
           struct ippseudo ipp;
           struct ip *ip;
   
           ip = mtod(m, struct ip *);
           ipp.ippseudo_src.s_addr = ip->ip_src.s_addr;
           ipp.ippseudo_dst.s_addr = ip->ip_dst.s_addr;
           ipp.ippseudo_p = IPPROTO_TCP;
           ipp.ippseudo_pad = 0;
           ipp.ippseudo_len = htons(m->m_pkthdr.len - (ip->ip_hl << 2));
           MD5Update(ctx, (char *)&ipp, sizeof(ipp));
           return (ip->ip_hl << 2);
   }
   #endif
   
   #ifdef INET6
   static int
   ip6_pseudo_compute(struct mbuf *m, MD5_CTX *ctx)
   {
           struct ip6_pseudo {
                   struct in6_addr src, dst;
                   uint32_t len;
                   uint32_t nxt;
           } ip6p __aligned(4);
           struct ip6_hdr *ip6;
   
           ip6 = mtod(m, struct ip6_hdr *);
           ip6p.src = ip6->ip6_src;
           ip6p.dst = ip6->ip6_dst;
           ip6p.len = htonl(m->m_pkthdr.len - sizeof(*ip6)); /* XXX: ext headers */
           ip6p.nxt = htonl(IPPROTO_TCP);
           MD5Update(ctx, (char *)&ip6p, sizeof(ip6p));
           return (sizeof(*ip6));
   }
   #endif
   
   static int
   tcp_signature_compute(struct mbuf *m, struct tcphdr *th,
       struct secasvar *sav, u_char *buf)
   {
           MD5_CTX ctx;
           int len;
           u_short csum;
   
           MD5Init(&ctx);
            /* Step 1: Update MD5 hash with IP(v6) pseudo-header. */
           switch (sav->sah->saidx.dst.sa.sa_family) {
   #ifdef INET
           case AF_INET:
                   len = ip_pseudo_compute(m, &ctx);
                   break;
   #endif
   #ifdef INET6
           case AF_INET6:
                   len = ip6_pseudo_compute(m, &ctx);
                   break;
   #endif
           default:
                   return (EAFNOSUPPORT);
           }
           /*
            * Step 2: Update MD5 hash with TCP header, excluding options.
            * The TCP checksum must be set to zero.
            */
           csum = th->th_sum;
           th->th_sum = 0;
           MD5Update(&ctx, (char *)th, sizeof(struct tcphdr));
           th->th_sum = csum;
           /*
            * Step 3: Update MD5 hash with TCP segment data.
            * Use m_apply() to avoid an early m_pullup().
            */
           len += (th->th_off << 2);
           if (m->m_pkthdr.len - len > 0)
                   m_apply(m, len, m->m_pkthdr.len - len,
                       tcp_signature_apply, &ctx);
           /*
            * Step 4: Update MD5 hash with shared secret.
            */
           MD5Update(&ctx, sav->key_auth->key_data, _KEYLEN(sav->key_auth));
           MD5Final(buf, &ctx);
           key_sa_recordxfer(sav, m);
           return (0);
   }
   
   static void
   setsockaddrs(const struct mbuf *m, union sockaddr_union *src,
       union sockaddr_union *dst)
   {
           struct ip *ip;
   
           IPSEC_ASSERT(m->m_len >= sizeof(*ip), ("unexpected mbuf len"));
   
           ip = mtod(m, struct ip *);
           switch (ip->ip_v) {
   #ifdef INET
           case IPVERSION:
                   ipsec4_setsockaddrs(m, src, dst);
                   break;
   #endif
   #ifdef INET6
           case (IPV6_VERSION >> 4):
                   ipsec6_setsockaddrs(m, src, dst);
                   break;
   #endif
           default:
                   bzero(src, sizeof(*src));
                   bzero(dst, sizeof(*dst));
           }
   }
   
   /*
    * Compute TCP-MD5 hash of an *INBOUND* TCP segment.
    * Parameters:
    * m            pointer to head of mbuf chain
    * th           pointer to TCP header
    * buf          pointer to storage for computed MD5 digest
    *
    * Return 0 if successful, otherwise return error code.
    */
   static int
   tcp_ipsec_input(struct mbuf *m, struct tcphdr *th, u_char *buf)
   {
           char tmpdigest[TCP_SIGLEN];
           struct secasindex saidx;
           struct secasvar *sav;
   
           setsockaddrs(m, &saidx.src, &saidx.dst);
           saidx.proto = IPPROTO_TCP;
           saidx.mode = IPSEC_MODE_TCPMD5;
           saidx.reqid = 0;
           sav = key_allocsa_tcpmd5(&saidx);
           if (sav == NULL) {
                   KMOD_TCPSTAT_INC(tcps_sig_err_buildsig);
                   return (ENOENT);
           }
           if (buf == NULL) {
                   key_freesav(&sav);
                   KMOD_TCPSTAT_INC(tcps_sig_err_nosigopt);
                   return (EACCES);
           }
           /*
            * tcp_input() operates with TCP header fields in host
            * byte order. We expect them in network byte order.
            */
           tcp_fields_to_net(th);
           tcp_signature_compute(m, th, sav, tmpdigest);
           tcp_fields_to_host(th);
           key_freesav(&sav);
           if (bcmp(buf, tmpdigest, TCP_SIGLEN) != 0) {
                   KMOD_TCPSTAT_INC(tcps_sig_rcvbadsig);
                   return (EACCES);
           }
           KMOD_TCPSTAT_INC(tcps_sig_rcvgoodsig);
           return (0);
   }
   
   /*
    * Compute TCP-MD5 hash of an *OUTBOUND* TCP segment.
    * Parameters:
    * m            pointer to head of mbuf chain
    * th           pointer to TCP header
    * buf          pointer to storage for computed MD5 digest
    *
    * Return 0 if successful, otherwise return error code.
    */
   static int
   tcp_ipsec_output(struct mbuf *m, struct tcphdr *th, u_char *buf)
   {
           struct secasindex saidx;
           struct secasvar *sav;
   
           setsockaddrs(m, &saidx.src, &saidx.dst);
           saidx.proto = IPPROTO_TCP;
           saidx.mode = IPSEC_MODE_TCPMD5;
           saidx.reqid = 0;
           sav = key_allocsa_tcpmd5(&saidx);
           if (sav == NULL) {
                   KMOD_TCPSTAT_INC(tcps_sig_err_buildsig);
                   return (ENOENT);
           }
           tcp_signature_compute(m, th, sav, buf);
           key_freesav(&sav);
           return (0);
   }
   
   /*
    * Initialize a TCP-MD5 SA. Called when the SA is being set up.
    *
    * We don't need to set up the tdb prefixed fields, as we don't use the
    * opencrypto code; we just perform a key length check.
    *
    * XXX: Currently we have used single 'magic' SPI and need to still
    * support this.
    *
    * This allows per-host granularity without affecting the userland
    * interface, which is a simple socket option toggle switch,
    * TCP_SIGNATURE_ENABLE.
    *
    * To allow per-service granularity requires that we have a means
    * of mapping port to SPI. The mandated way of doing this is to
    * use SPD entries to specify packet flows which get the TCP-MD5
    * treatment, however the code to do this is currently unstable
    * and unsuitable for production use.
    *
    * Therefore we use this compromise in the meantime.
    */
   static int
   tcpsignature_init(struct secasvar *sav, struct xformsw *xsp)
   {
           int keylen;
   
           if (sav->alg_auth != SADB_X_AALG_TCP_MD5) {
                   DPRINTF(("%s: unsupported authentication algorithm %u\n",
                       __func__, sav->alg_auth));
                   return (EINVAL);
           }
           if (sav->key_auth == NULL) {
                   DPRINTF(("%s: no authentication key present\n", __func__));
                   return (EINVAL);
           }
           keylen = _KEYLEN(sav->key_auth);
           if ((keylen < TCP_KEYLEN_MIN) || (keylen > TCP_KEYLEN_MAX)) {
                   DPRINTF(("%s: invalid key length %u\n", __func__, keylen));
                   return (EINVAL);
           }
           sav->tdb_xform = xsp;
           return (0);
   }
   
   /*
    * Called when the SA is deleted.
    */
   static void
   tcpsignature_cleanup(struct secasvar *sav)
   {
   }
   
   static struct xformsw tcpsignature_xformsw = {
           .xf_type =      XF_TCPSIGNATURE,
           .xf_name =      "TCP-MD5",
           .xf_init =      tcpsignature_init,
           .xf_cleanup =   tcpsignature_cleanup,
   };
   
   static const struct tcpmd5_methods tcpmd5_methods = {
           .input = tcp_ipsec_input,
           .output = tcp_ipsec_output,
           .pcbctl = tcp_ipsec_pcbctl,
   };
   
   #ifndef KLD_MODULE
   /* TCP-MD5 support is build in the kernel */
   static const struct tcpmd5_support tcpmd5_ipsec = {
           .enabled = IPSEC_MODULE_ENABLED,
           .methods = &tcpmd5_methods
   };
   const struct tcpmd5_support * const tcp_ipsec_support = &tcpmd5_ipsec;
   #endif /* !KLD_MODULE */
   
   static int
   tcpmd5_modevent(module_t mod, int type, void *data)
   {
   
           switch (type) {
           case MOD_LOAD:
                   xform_attach(&tcpsignature_xformsw);
   #ifdef KLD_MODULE
                   tcpmd5_support_enable(&tcpmd5_methods);
   #endif
                   break;
           case MOD_UNLOAD:
   #ifdef KLD_MODULE
                   tcpmd5_support_disable();
   #endif
                   xform_detach(&tcpsignature_xformsw);
                   break;
           default:
                   return (EOPNOTSUPP);
           }
           return (0);
   }
   
   static moduledata_t tcpmd5_mod = {
           "tcpmd5",
           tcpmd5_modevent,
           0
   };
   
   DECLARE_MODULE(tcpmd5, tcpmd5_mod, SI_SUB_PROTO_DOMAIN, SI_ORDER_ANY);
   MODULE_VERSION(tcpmd5, 1);
   #ifdef KLD_MODULE
   MODULE_DEPEND(tcpmd5, ipsec_support, 1, 1, 1);
   #endif

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