[src/trunk]: src/sys/netipsec Simplify the padding computation. Until now 'pa...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/73d07542bfc2
branches:  trunk
changeset: 832842:73d07542bfc2
user:      maxv <maxv%NetBSD.org@localhost>
date:      Wed May 30 16:32:26 2018 +0000

description:
Simplify the padding computation. Until now 'padlen' contained the ESP
Trailer (two bytes), and we were doing minus two all the time.

Declare 'tlen', which contains padlen+ESP_Trailer+ICV, and use 'struct
esptail' instead of hardcoding the construction of the trailer. 'padlen'
now indicates only the length of the padding, so no need to do -2.

diffstat:

 sys/netipsec/xform_esp.c |  33 +++++++++++++++++++--------------
 1 files changed, 19 insertions(+), 14 deletions(-)

diffs (101 lines):

diff -r dd5f4fb808ae -r 73d07542bfc2 sys/netipsec/xform_esp.c
--- a/sys/netipsec/xform_esp.c  Wed May 30 16:15:19 2018 +0000
+++ b/sys/netipsec/xform_esp.c  Wed May 30 16:32:26 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: xform_esp.c,v 1.90 2018/05/30 16:15:19 maxv Exp $      */
+/*     $NetBSD: xform_esp.c,v 1.91 2018/05/30 16:32:26 maxv Exp $      */
 /*     $FreeBSD: xform_esp.c,v 1.2.2.1 2003/01/24 05:11:36 sam Exp $   */
 /*     $OpenBSD: ip_esp.c,v 1.69 2001/06/26 06:18:59 angelos Exp $ */
 
@@ -39,7 +39,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: xform_esp.c,v 1.90 2018/05/30 16:15:19 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: xform_esp.c,v 1.91 2018/05/30 16:32:26 maxv Exp $");
 
 #if defined(_KERNEL_OPT)
 #include "opt_inet.h"
@@ -687,13 +687,14 @@
        char buf[IPSEC_ADDRSTRLEN];
        const struct enc_xform *espx;
        const struct auth_hash *esph;
-       int hlen, rlen, padlen, blks, alen, i, roff;
+       int hlen, rlen, tlen, padlen, blks, alen, i, roff;
        struct mbuf *mo = NULL;
        struct tdb_crypto *tc;
        struct secasindex *saidx;
        unsigned char *tail;
        uint8_t prot;
        int error, maxpacketsize;
+       struct esptail *esptail;
 
        struct cryptodesc *crde = NULL, *crda = NULL;
        struct cryptop *crp;
@@ -721,8 +722,11 @@
        /* Raw payload length. */
        rlen = m->m_pkthdr.len - skip;
 
-       /* XXX clamp padding length a la KAME??? */
-       padlen = ((blks - ((rlen + 2) % blks)) % blks) + 2;
+       /* Encryption padding. */
+       padlen = ((blks - ((rlen + sizeof(struct esptail)) % blks)) % blks);
+
+       /* Length of what we append (tail). */
+       tlen = padlen + sizeof(struct esptail) + alen;
 
        ESP_STATINC(ESP_STAT_OUTPUT);
 
@@ -748,12 +752,12 @@
                error = EPFNOSUPPORT;
                goto bad;
        }
-       if (skip + hlen + rlen + padlen + alen > maxpacketsize) {
+       if (skip + hlen + rlen + tlen > maxpacketsize) {
                DPRINTF(("%s: packet in SA %s/%08lx got too big (len %u, "
                    "max len %u)\n", __func__,
                    ipsec_address(&saidx->dst, buf, sizeof(buf)),
                    (u_long) ntohl(sav->spi),
-                   skip + hlen + rlen + padlen + alen, maxpacketsize));
+                   skip + hlen + rlen + tlen, maxpacketsize));
                ESP_STATINC(ESP_STAT_TOOBIG);
                error = EMSGSIZE;
                goto bad;
@@ -803,7 +807,7 @@
        /*
         * Grow the mbuf, we will append data at the tail.
         */
-       tail = m_pad(m, padlen + alen);
+       tail = m_pad(m, tlen);
        if (tail == NULL) {
                DPRINTF(("%s: m_pad failed for SA %s/%08lx\n", __func__,
                    ipsec_address(&saidx->dst, buf, sizeof(buf)),
@@ -818,21 +822,22 @@
         */
        switch (sav->flags & SADB_X_EXT_PMASK) {
        case SADB_X_EXT_PSEQ:
-               for (i = 0; i < padlen - 2; i++)
+               for (i = 0; i < padlen; i++)
                        tail[i] = i + 1;
                break;
        case SADB_X_EXT_PRAND:
-               (void)cprng_fast(tail, padlen - 2);
+               (void)cprng_fast(tail, padlen);
                break;
        case SADB_X_EXT_PZERO:
        default:
-               memset(tail, 0, padlen - 2);
+               memset(tail, 0, padlen);
                break;
        }
 
-       /* Fix padding length and Next Protocol in padding itself. */
-       tail[padlen - 2] = padlen - 2;
-       m_copydata(m, protoff, sizeof(uint8_t), tail + padlen - 1);
+       /* Build the ESP Trailer. */
+       esptail = (struct esptail *)&tail[padlen];
+       esptail->esp_padlen = padlen;
+       m_copydata(m, protoff, sizeof(uint8_t), &esptail->esp_nxt);
 
        /* Fix Next Protocol in IPv4/IPv6 header. */
        prot = IPPROTO_ESP;