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[src/trunk]: src/sys/netipsec Correctly handle the padding for IPv6-AH, as sp...



details:   https://anonhg.NetBSD.org/src/rev/f32e4b2c36a2
branches:  trunk
changeset: 832848:f32e4b2c36a2
user:      maxv <maxv%NetBSD.org@localhost>
date:      Wed May 30 18:02:40 2018 +0000

description:
Correctly handle the padding for IPv6-AH, as specified by RFC4302. Seen in
a FreeBSD bug report, by Jason Mader.

The RFC specifies that under IPv6 the complete AH header must be 64bit-
aligned, and under IPv4 32bit-aligned. That's a rule we've never respected.
The other BSDs and MacOS never have either.

So respect it now.

This makes it possible to set up IPv6-AH between Linux and NetBSD, and also
probably between Windows and NetBSD.

Until now all the tests I made were between two *BSD hosts, and everything
worked "correctly" since both hosts were speaking the same non-standard
AHv6, so they could understand each other.

Tested with Fedora<->NetBSD, hmac-sha2-384.

diffstat:

 sys/netipsec/xform_ah.c |  58 +++++++++++++++++++++++++++++++-----------------
 1 files changed, 37 insertions(+), 21 deletions(-)

diffs (185 lines):

diff -r 9d0f61f1acc7 -r f32e4b2c36a2 sys/netipsec/xform_ah.c
--- a/sys/netipsec/xform_ah.c   Wed May 30 17:48:13 2018 +0000
+++ b/sys/netipsec/xform_ah.c   Wed May 30 18:02:40 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: xform_ah.c,v 1.104 2018/05/30 17:17:11 maxv Exp $      */
+/*     $NetBSD: xform_ah.c,v 1.105 2018/05/30 18:02:40 maxv Exp $      */
 /*     $FreeBSD: xform_ah.c,v 1.1.4.1 2003/01/24 05:11:36 sam Exp $    */
 /*     $OpenBSD: ip_ah.c,v 1.63 2001/06/26 06:18:58 angelos Exp $ */
 /*
@@ -39,7 +39,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: xform_ah.c,v 1.104 2018/05/30 17:17:11 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xform_ah.c,v 1.105 2018/05/30 18:02:40 maxv Exp $");
 
 #if defined(_KERNEL_OPT)
 #include "opt_inet.h"
@@ -167,11 +167,21 @@
        size_t size;
 
        if (sav != NULL) {
-               int authsize;
+               int authsize, rplen, align;
+
                KASSERT(sav->tdb_authalgxform != NULL);
                /*XXX not right for null algorithm--does it matter??*/
+
+               /* RFC4302: use the correct alignment. */
+               align = sizeof(uint32_t);
+#ifdef INET6
+               if (sav->sah->saidx.dst.sa.sa_family == AF_INET6) {
+                       align = sizeof(uint64_t);
+               }
+#endif
+               rplen = HDRSIZE(sav);
                authsize = AUTHSIZE(sav);
-               size = roundup(authsize, sizeof(uint32_t)) + HDRSIZE(sav);
+               size = roundup(rplen + authsize, align);
        } else {
                /* default guess */
                size = sizeof(struct ah) + sizeof(uint32_t) + ah_max_authsize;
@@ -520,7 +530,7 @@
        const struct auth_hash *ahx;
        struct tdb_crypto *tc = NULL;
        struct newah *ah;
-       int hl, rplen, authsize, error, stat = AH_STAT_HDROPS;
+       int hl, rplen, authsize, ahsize, error, stat = AH_STAT_HDROPS;
        struct cryptodesc *crda;
        struct cryptop *crp = NULL;
        bool pool_used;
@@ -553,25 +563,26 @@
        }
 
        /* Verify AH header length. */
-       hl = ah->ah_len * sizeof(uint32_t);
+       hl = sizeof(struct ah) + (ah->ah_len * sizeof(uint32_t));
        ahx = sav->tdb_authalgxform;
        authsize = AUTHSIZE(sav);
-       if (hl != authsize + rplen - sizeof(struct ah)) {
+       ahsize = ah_hdrsiz(sav);
+       if (hl != ahsize) {
                char buf[IPSEC_ADDRSTRLEN];
                DPRINTF(("%s: bad authenticator length %u (expecting %lu)"
                        " for packet in SA %s/%08lx\n", __func__,
-                       hl, (u_long) (authsize + rplen - sizeof(struct ah)),
+                       hl, (u_long)ahsize,
                        ipsec_address(&sav->sah->saidx.dst, buf, sizeof(buf)),
                        (u_long) ntohl(sav->spi)));
                stat = AH_STAT_BADAUTHL;
                error = EACCES;
                goto bad;
        }
-       if (skip + authsize + rplen > m->m_pkthdr.len) {
+       if (skip + ahsize > m->m_pkthdr.len) {
                char buf[IPSEC_ADDRSTRLEN];
                DPRINTF(("%s: bad mbuf length %u (expecting >= %lu)"
                        " for packet in SA %s/%08lx\n", __func__,
-                       m->m_pkthdr.len, (u_long)(skip + authsize + rplen),
+                       m->m_pkthdr.len, (u_long)(skip + ahsize),
                        ipsec_address(&sav->sah->saidx.dst, buf, sizeof(buf)),
                        (u_long) ntohl(sav->spi)));
                stat = AH_STAT_BADAUTHL;
@@ -720,7 +731,7 @@
 ah_input_cb(struct cryptop *crp)
 {
        char buf[IPSEC_ADDRSTRLEN];
-       int rplen, error, skip, protoff;
+       int rplen, ahsize, error, skip, protoff;
        unsigned char calc[AH_ALEN_MAX];
        struct mbuf *m;
        struct tdb_crypto *tc;
@@ -751,6 +762,7 @@
        /* Figure out header size. */
        rplen = HDRSIZE(sav);
        authsize = AUTHSIZE(sav);
+       ahsize = ah_hdrsiz(sav);
 
        size = sizeof(*tc) + skip + rplen + authsize;
        if (__predict_true(size <= ah_pool_item_size))
@@ -844,7 +856,7 @@
        /*
         * Remove the AH header and authenticator from the mbuf.
         */
-       error = m_striphdr(m, skip, rplen + authsize);
+       error = m_striphdr(m, skip, ahsize);
        if (error) {
                DPRINTF(("%s: mangled mbuf chain for SA %s/%08lx\n", __func__,
                    ipsec_address(&saidx->dst, buf, sizeof(buf)),
@@ -891,7 +903,7 @@
        struct mbuf *mi;
        struct cryptop *crp;
        uint16_t iplen;
-       int error, rplen, authsize, maxpacketsize, roff;
+       int error, rplen, authsize, ahsize, maxpacketsize, roff;
        uint8_t prot;
        struct newah *ah;
        size_t ipoffs;
@@ -905,6 +917,8 @@
 
        /* Figure out header size. */
        rplen = HDRSIZE(sav);
+       authsize = AUTHSIZE(sav);
+       ahsize = ah_hdrsiz(sav);
 
        /* Check for maximum packet size violations. */
        switch (sav->sah->saidx.dst.sa.sa_family) {
@@ -930,13 +944,12 @@
                error = EPFNOSUPPORT;
                goto bad;
        }
-       authsize = AUTHSIZE(sav);
-       if (rplen + authsize + m->m_pkthdr.len > maxpacketsize) {
+       if (ahsize + m->m_pkthdr.len > maxpacketsize) {
                DPRINTF(("%s: packet in SA %s/%08lx got too big "
                    "(len %u, max len %u)\n", __func__,
                    ipsec_address(&sav->sah->saidx.dst, buf, sizeof(buf)),
                    (u_long) ntohl(sav->spi),
-                   rplen + authsize + m->m_pkthdr.len, maxpacketsize));
+                   ahsize + m->m_pkthdr.len, maxpacketsize));
                AH_STATINC(AH_STAT_TOOBIG);
                error = EMSGSIZE;
                goto bad;
@@ -956,11 +969,10 @@
        }
 
        /* Inject AH header. */
-       mi = m_makespace(m, skip, rplen + authsize, &roff);
+       mi = m_makespace(m, skip, ahsize, &roff);
        if (mi == NULL) {
                DPRINTF(("%s: failed to inject %u byte AH header for SA "
-                   "%s/%08lx\n", __func__,
-                   rplen + authsize,
+                   "%s/%08lx\n", __func__, ahsize,
                    ipsec_address(&sav->sah->saidx.dst, buf, sizeof(buf)),
                    (u_long) ntohl(sav->spi)));
                AH_STATINC(AH_STAT_HDROPS);
@@ -976,13 +988,17 @@
 
        /* Initialize the AH header. */
        m_copydata(m, protoff, sizeof(uint8_t), &ah->ah_nxt);
-       ah->ah_len = (rplen + authsize - sizeof(struct ah)) / sizeof(uint32_t);
+       ah->ah_len = (ahsize - sizeof(struct ah)) / sizeof(uint32_t);
        ah->ah_reserve = 0;
        ah->ah_spi = sav->spi;
 
        /* Zeroize authenticator. */
        m_copyback(m, skip + rplen, authsize, ipseczeroes);
 
+       /* Zeroize padding. */
+       m_copyback(m, skip + rplen + authsize, ahsize - (rplen + authsize),
+           ipseczeroes);
+
        /* Insert packet replay counter, as requested.  */
        if (sav->replay) {
                if (sav->replay->count == ~0 &&
@@ -1051,7 +1067,7 @@
         * header length as it will be fixed by our caller.
         */
        memcpy(&iplen, pext + ipoffs, sizeof(iplen));
-       iplen = htons(ntohs(iplen) + rplen + authsize);
+       iplen = htons(ntohs(iplen) + ahsize);
        m_copyback(m, ipoffs, sizeof(iplen), &iplen);
 
        /* Fix the Next Header field in saved header. */



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