* Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994

/* NetBSD: print-ah.c,v 1.4 1996/05/20 00:41:16 fvdl Exp */

/*
* Copyright (c) 1988, 1989, 1990, 1991, 1992, 1993, 1994
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that: (1) source code distributions
* retain the above copyright notice and this paragraph in its entirety, (2)
* distributions including binary code include the above copyright notice and
* this paragraph in its entirety in the documentation or other materials
* provided with the distribution, and (3) all advertising materials mentioning
* features or use of this software display the following acknowledgement:
* ``This product includes software developed by the University of California,
* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
* the University nor the names of its contributors may be used to endorse
* or promote products derived from this software without specific prior
* written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/

#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: print-esp.c,v 1.13 2024/09/02 16:15:31 christos Exp $");
#endif

/* \summary: IPSEC Encapsulating Security Payload (ESP) printer */

#include <config.h>

#include "netdissect-stdinc.h"

#include <string.h>
#include <stdlib.h>

#ifdef HAVE_LIBCRYPTO
#include <openssl/evp.h>
#endif

#include "netdissect.h"
#include "extract.h"

#include "diag-control.h"

#ifdef HAVE_LIBCRYPTO
#include "strtoaddr.h"
#include "ascii_strcasecmp.h"
#endif

#include "ip.h"
#include "ip6.h"

/*
* Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
* All rights reserved.
*
* 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. Neither the name of the project nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``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 PROJECT OR CONTRIBUTORS 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.
*/

/*
* RFC1827/2406 Encapsulated Security Payload.
*/

struct newesp {
nd_uint32_t esp_spi; /* ESP */
nd_uint32_t esp_seq; /* Sequence number */
/*variable size*/ /* (IV and) Payload data */
/*variable size*/ /* padding */
/*8bit*/ /* pad size */
/*8bit*/ /* next header */
/*8bit*/ /* next header */
/*variable size, 32bit bound*/ /* Authentication data */
};

#ifdef HAVE_LIBCRYPTO
union inaddr_u {
nd_ipv4 in4;
nd_ipv6 in6;
};
struct sa_list {
struct sa_list *next;
u_int daddr_version;
union inaddr_u daddr;
uint32_t spi; /* if == 0, then IKEv2 */
int initiator;
u_char spii[8]; /* for IKEv2 */
u_char spir[8];
const EVP_CIPHER *evp;
u_int ivlen;
int authlen;
u_char authsecret[256];
int authsecret_len;
u_char secret[256]; /* is that big enough for all secrets? */
int secretlen;
};

#ifndef HAVE_EVP_CIPHER_CTX_NEW
/*
* Allocate an EVP_CIPHER_CTX.
* Used if we have an older version of OpenSSL that doesn't provide
* routines to allocate and free them.
*/
static EVP_CIPHER_CTX *
EVP_CIPHER_CTX_new(void)
{
EVP_CIPHER_CTX *ctx;

ctx = malloc(sizeof(*ctx));
if (ctx == NULL)
return (NULL);
memset(ctx, 0, sizeof(*ctx));
return (ctx);
}

static void
EVP_CIPHER_CTX_free(EVP_CIPHER_CTX *ctx)
{
EVP_CIPHER_CTX_cleanup(ctx);
free(ctx);
}
#endif

#ifdef HAVE_EVP_DECRYPTINIT_EX
/*
* Initialize the cipher by calling EVP_DecryptInit_ex(), because
* calling EVP_DecryptInit() will reset the cipher context, clearing
* the cipher, so calling it twice, with the second call having a
* null cipher, will clear the already-set cipher. EVP_DecryptInit_ex(),
* however, won't reset the cipher context, so you can use it to specify
* the IV in a second call after a first call to EVP_DecryptInit_ex()
* to set the cipher and the key.
*
* XXX - is there some reason why we need to make two calls?
*/
static int
set_cipher_parameters(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *cipher,
const unsigned char *key,
const unsigned char *iv)
{
return EVP_DecryptInit_ex(ctx, cipher, NULL, key, iv);
}
#else
/*
* Initialize the cipher by calling EVP_DecryptInit(), because we don't
* have EVP_DecryptInit_ex(); we rely on it not trashing the context.
*/
static int
set_cipher_parameters(EVP_CIPHER_CTX *ctx, const EVP_CIPHER *cipher,
const unsigned char *key,
const unsigned char *iv)
{
return EVP_DecryptInit(ctx, cipher, key, iv);
}
#endif

static u_char *
do_decrypt(netdissect_options *ndo, const char *caller, struct sa_list *sa,
const u_char *iv, const u_char *ct, unsigned int ctlen)
{
EVP_CIPHER_CTX *ctx;
unsigned int block_size;
unsigned int ptlen;
u_char *pt;
int len;

ctx = EVP_CIPHER_CTX_new();
if (ctx == NULL) {
/*
* Failed to initialize the cipher context.
* From a look at the OpenSSL code, this appears to
* mean "couldn't allocate memory for the cipher context";
* note that we're not passing any parameters, so there's
* not much else it can mean.
*/
(*ndo->ndo_error)(ndo, S_ERR_ND_MEM_ALLOC,
"%s: can't allocate memory for cipher context", caller);
return NULL;
}

if (set_cipher_parameters(ctx, sa->evp, sa->secret, NULL) < 0) {
EVP_CIPHER_CTX_free(ctx);
(*ndo->ndo_warning)(ndo, "%s: espkey init failed", caller);
return NULL;
}
if (set_cipher_parameters(ctx, NULL, NULL, iv) < 0) {
EVP_CIPHER_CTX_free(ctx);
(*ndo->ndo_warning)(ndo, "%s: IV init failed", caller);
return NULL;
}

/*
* At least as I read RFC 5996 section 3.14 and RFC 4303 section 2.4,
* if the cipher has a block size of which the ciphertext's size must
* be a multiple, the payload must be padded to make that happen, so
* the ciphertext length must be a multiple of the block size. Fail
* if that's not the case.
*/
block_size = (unsigned int)EVP_CIPHER_CTX_block_size(ctx);
if ((ctlen % block_size) != 0) {
EVP_CIPHER_CTX_free(ctx);
(*ndo->ndo_warning)(ndo,
"%s: ciphertext size %u is not a multiple of the cipher block size %u",
caller, ctlen, block_size);
return NULL;
}

/*
* Attempt to allocate a buffer for the decrypted data, because
* we can't decrypt on top of the input buffer.
*/
ptlen = ctlen;
pt = (u_char *)calloc(1, ptlen);
if (pt == NULL) {
EVP_CIPHER_CTX_free(ctx);
(*ndo->ndo_error)(ndo, S_ERR_ND_MEM_ALLOC,
"%s: can't allocate memory for decryption buffer", caller);
return NULL;
}

/*
* The size of the ciphertext handed to us is a multiple of the
* cipher block size, so we don't need to worry about padding.
*/
if (!EVP_CIPHER_CTX_set_padding(ctx, 0)) {
free(pt);
EVP_CIPHER_CTX_free(ctx);
(*ndo->ndo_warning)(ndo,
"%s: EVP_CIPHER_CTX_set_padding failed", caller);
return NULL;
}
if (!EVP_DecryptUpdate(ctx, pt, &len, ct, ctlen)) {
free(pt);
EVP_CIPHER_CTX_free(ctx);
(*ndo->ndo_warning)(ndo, "%s: EVP_DecryptUpdate failed",
caller);
return NULL;
}
EVP_CIPHER_CTX_free(ctx);
return pt;
}

/*
* This will allocate a new buffer containing the decrypted data.
* It returns 1 on success and 0 on failure.
*
* It will push the new buffer and the values of ndo->ndo_packetp and
* ndo->ndo_snapend onto the buffer stack, and change ndo->ndo_packetp
* and ndo->ndo_snapend to refer to the new buffer.
*
* Our caller must pop the buffer off the stack when it's finished
* dissecting anything in it and before it does any dissection of
* anything in the old buffer. That will free the new buffer.
*/
DIAG_OFF_DEPRECATION
int esp_decrypt_buffer_by_ikev2_print(netdissect_options *ndo,
int initiator,
const u_char spii[8],
const u_char spir[8],
const u_char *buf, const u_char *end)
{
struct sa_list *sa;
const u_char *iv;
const u_char *ct;
unsigned int ctlen;
u_char *pt;

/* initiator arg is any non-zero value */
if(initiator) initiator=1;

/* see if we can find the SA, and if so, decode it */
for (sa = ndo->ndo_sa_list_head; sa != NULL; sa = sa->next) {
if (sa->spi == 0
&& initiator == sa->initiator
&& memcmp(spii, sa->spii, 8) == 0
&& memcmp(spir, sa->spir, 8) == 0)
break;
}

if(sa == NULL) return 0;
if(sa->evp == NULL) return 0;

/*
* remove authenticator, and see if we still have something to
* work with
*/
end = end - sa->authlen;
iv = buf;
ct = iv + sa->ivlen;
ctlen = end-ct;

if(end <= ct) return 0;

pt = do_decrypt(ndo, __func__, sa, iv,
ct, ctlen);
if (pt == NULL)
return 0;

/*
* Switch to the output buffer for dissection, and save it
* on the buffer stack so it can be freed; our caller must
* pop it when done.
*/
if (!nd_push_buffer(ndo, pt, pt, ctlen)) {
free(pt);
(*ndo->ndo_error)(ndo, S_ERR_ND_MEM_ALLOC,
"%s: can't push buffer on buffer stack", __func__);
}

return 1;
}
DIAG_ON_DEPRECATION

static void esp_print_addsa(netdissect_options *ndo,
const struct sa_list *sa, int sa_def)
{
/* copy the "sa" */

struct sa_list *nsa;

/* malloc() return used in a 'struct sa_list': do not free() */
nsa = (struct sa_list *)malloc(sizeof(struct sa_list));
if (nsa == NULL)
(*ndo->ndo_error)(ndo, S_ERR_ND_MEM_ALLOC,
"%s: malloc", __func__);

*nsa = *sa;

if (sa_def)
ndo->ndo_sa_default = nsa;

nsa->next = ndo->ndo_sa_list_head;
ndo->ndo_sa_list_head = nsa;
}

static u_int hexdigit(netdissect_options *ndo, char hex)
{
if (hex >= '0' && hex <= '9')
return (hex - '0');
else if (hex >= 'A' && hex <= 'F')
return (hex - 'A' + 10);
else if (hex >= 'a' && hex <= 'f')
return (hex - 'a' + 10);
else {
(*ndo->ndo_error)(ndo, S_ERR_ND_ESP_SECRET,
"invalid hex digit %c in espsecret\n", hex);
}
}

static u_int hex2byte(netdissect_options *ndo, char *hexstring)
{
u_int byte;

byte = (hexdigit(ndo, hexstring[0]) << 4) + hexdigit(ndo, hexstring[1]);
return byte;
}

/*
* returns size of binary, 0 on failure.
*/
static int
espprint_decode_hex(netdissect_options *ndo,
u_char *binbuf, unsigned int binbuf_len, char *hex)
{
unsigned int len;
int i;

len = strlen(hex) / 2;

if (len > binbuf_len) {
(*ndo->ndo_warning)(ndo, "secret is too big: %u\n", len);
return 0;
}

i = 0;
while (hex[0] != '\0' && hex[1]!='\0') {
binbuf[i] = hex2byte(ndo, hex);
hex += 2;
i++;
}

return i;
}

/*
* decode the form: SPINUM@IP <tab> ALGONAME:0xsecret
*/

DIAG_OFF_DEPRECATION
static int
espprint_decode_encalgo(netdissect_options *ndo,
char *decode, struct sa_list *sa)
{
size_t i;
const EVP_CIPHER *evp;
int authlen = 0;
char *colon, *p;
const char *real_decode;

colon = strchr(decode, ':');
if (colon == NULL) {
(*ndo->ndo_warning)(ndo, "failed to decode espsecret: %s\n", decode);
return 0;
}
*colon = '\0';

if (strlen(decode) > strlen("-hmac96") &&
!strcmp(decode + strlen(decode) - strlen("-hmac96"),
"-hmac96")) {
p = strstr(decode, "-hmac96");
*p = '\0';
authlen = 12;
}
if (strlen(decode) > strlen("-cbc") &&
!strcmp(decode + strlen(decode) - strlen("-cbc"), "-cbc")) {
p = strstr(decode, "-cbc");
*p = '\0';
}
/*
* Not all versions of libcrypto support calls to add aliases
* to ciphers - newer versions of libressl don't - so, instead
* of making "3des" an alias for "des_ede3_cbc", if attempting
* to get the cipher fails and the name is "3des", we try
* "des_ede3_cbc".
*/
real_decode = decode;
if (strcmp(real_decode, "3des") == 0)
real_decode = "des-ede3-cbc";
evp = EVP_get_cipherbyname(real_decode);

if (!evp) {
if (decode != real_decode)
(*ndo->ndo_warning)(ndo, "failed to find cipher algo %s (%s)\n", real_decode, decode);
else
(*ndo->ndo_warning)(ndo, "failed to find cipher algo %s\n", decode);
sa->evp = NULL;
sa->authlen = 0;
sa->ivlen = 0;
return 0;
}

sa->evp = evp;
sa->authlen = authlen;
/* This returns an int, but it should never be negative */
sa->ivlen = EVP_CIPHER_iv_length(evp);

colon++;
if (colon[0] == '0' && colon[1] == 'x') {
/* decode some hex! */

colon += 2;
sa->secretlen = espprint_decode_hex(ndo, sa->secret, sizeof(sa->secret), colon);
if(sa->secretlen == 0) return 0;
} else {
i = strlen(colon);

if (i < sizeof(sa->secret)) {
memcpy(sa->secret, colon, i);
sa->secretlen = i;
} else {
memcpy(sa->secret, colon, sizeof(sa->secret));
sa->secretlen = sizeof(sa->secret);
}
}

return 1;
}
DIAG_ON_DEPRECATION

/*
* for the moment, ignore the auth algorithm, just hard code the authenticator
* length. Need to research how openssl looks up HMAC stuff.
*/
static int
espprint_decode_authalgo(netdissect_options *ndo,
char *decode, struct sa_list *sa)
{
char *colon;

colon = strchr(decode, ':');
if (colon == NULL) {
(*ndo->ndo_warning)(ndo, "failed to decode espsecret: %s\n", decode);
return 0;
}
*colon = '\0';

if(ascii_strcasecmp(decode,"sha1") == 0 ||
ascii_strcasecmp(decode,"md5") == 0) {
sa->authlen = 12;
}
return 1;
}

static void esp_print_decode_ikeline(netdissect_options *ndo, char *line,
const char *file, int lineno)
{
/* it's an IKEv2 secret, store it instead */
struct sa_list sa1;

char *init;
char *icookie, *rcookie;
int ilen, rlen;
char *authkey;
char *enckey;

init = strsep(&line, " \t");
icookie = strsep(&line, " \t");
rcookie = strsep(&line, " \t");
authkey = strsep(&line, " \t");
enckey = strsep(&line, " \t");

/* if any fields are missing */
if(!init || !icookie || !rcookie || !authkey || !enckey) {
(*ndo->ndo_warning)(ndo, "print_esp: failed to find all fields for ikev2 at %s:%u",
file, lineno);

return;
}

ilen = strlen(icookie);
rlen = strlen(rcookie);

if((init[0]!='I' && init[0]!='R')
|| icookie[0]!='0' || icookie[1]!='x'
|| rcookie[0]!='0' || rcookie[1]!='x'
|| ilen!=18
|| rlen!=18) {
(*ndo->ndo_warning)(ndo, "print_esp: line %s:%u improperly formatted.",
file, lineno);

(*ndo->ndo_warning)(ndo, "init=%s icookie=%s(%u) rcookie=%s(%u)",
init, icookie, ilen, rcookie, rlen);

return;
}

sa1.spi = 0;
sa1.initiator = (init[0] == 'I');
if(espprint_decode_hex(ndo, sa1.spii, sizeof(sa1.spii), icookie+2)!=8)
return;

if(espprint_decode_hex(ndo, sa1.spir, sizeof(sa1.spir), rcookie+2)!=8)
return;

if(!espprint_decode_encalgo(ndo, enckey, &sa1)) return;

if(!espprint_decode_authalgo(ndo, authkey, &sa1)) return;

esp_print_addsa(ndo, &sa1, FALSE);
}

/*
*
* special form: file /name
* causes us to go read from this file instead.
*
*/
static void esp_print_decode_onesecret(netdissect_options *ndo, char *line,
const char *file, int lineno)
{
struct sa_list sa1;
int sa_def;

char *spikey;
char *decode;

spikey = strsep(&line, " \t");
sa_def = 0;
memset(&sa1, 0, sizeof(struct sa_list));

/* if there is only one token, then it is an algo:key token */
if (line == NULL) {
decode = spikey;
spikey = NULL;
/* sa1.daddr.version = 0; */
/* memset(&sa1.daddr, 0, sizeof(sa1.daddr)); */
/* sa1.spi = 0; */
sa_def = 1;
} else
decode = line;

if (spikey && ascii_strcasecmp(spikey, "file") == 0) {
/* open file and read it */
FILE *secretfile;
char fileline[1024];
int subfile_lineno=0;
char *nl;
char *filename = line;

secretfile = fopen(filename, FOPEN_READ_TXT);
if (secretfile == NULL) {
(*ndo->ndo_error)(ndo, S_ERR_ND_OPEN_FILE,
"%s: can't open %s: %s\n",
__func__, filename, strerror(errno));
}

while (fgets(fileline, sizeof(fileline)-1, secretfile) != NULL) {
subfile_lineno++;
/* remove newline from the line */
nl = strchr(fileline, '\n');
if (nl)
*nl = '\0';
if (fileline[0] == '#') continue;
if (fileline[0] == '\0') continue;

esp_print_decode_onesecret(ndo, fileline, filename, subfile_lineno);
}
fclose(secretfile);

return;
}

if (spikey && ascii_strcasecmp(spikey, "ikev2") == 0) {
esp_print_decode_ikeline(ndo, line, file, lineno);
return;
}

if (spikey) {

char *spistr, *foo;
uint32_t spino;

spistr = strsep(&spikey, "@");
if (spistr == NULL) {
(*ndo->ndo_warning)(ndo, "print_esp: failed to find the @ token");
return;
}

spino = strtoul(spistr, &foo, 0);
if (spistr == foo || !spikey) {
(*ndo->ndo_warning)(ndo, "print_esp: failed to decode spi# %s\n", foo);
return;
}

sa1.spi = spino;

if (strtoaddr6(spikey, &sa1.daddr.in6) == 1) {
sa1.daddr_version = 6;
} else if (strtoaddr(spikey, &sa1.daddr.in4) == 1) {
sa1.daddr_version = 4;
} else {
(*ndo->ndo_warning)(ndo, "print_esp: can not decode IP# %s\n", spikey);
return;
}
}

if (decode) {
/* skip any blank spaces */
while (*decode == ' ' || *decode == '\t' || *decode == '\r' || *decode == '\n')
decode++;

if(!espprint_decode_encalgo(ndo, decode, &sa1)) {
return;
}
}

esp_print_addsa(ndo, &sa1, sa_def);
}

DIAG_OFF_DEPRECATION
static void esp_init(netdissect_options *ndo _U_)
{
/*
* 0.9.6 doesn't appear to define OPENSSL_API_COMPAT, so
* we check whether it's undefined or it's less than the
* value for 1.1.0.
*/
#if !defined(OPENSSL_API_COMPAT) || OPENSSL_API_COMPAT < 0x10100000L
OpenSSL_add_all_algorithms();
#endif
}
DIAG_ON_DEPRECATION

void esp_decodesecret_print(netdissect_options *ndo)
{
char *line;
char *p;
static int initialized = 0;

if (!initialized) {
esp_init(ndo);
initialized = 1;
}

p = ndo->ndo_espsecret;

while (p && p[0] != '\0') {
/* pick out the first line or first thing until a comma */
if ((line = strsep(&p, "\n,")) == NULL) {
line = p;
p = NULL;
}

esp_print_decode_onesecret(ndo, line, "cmdline", 0);
}

ndo->ndo_espsecret = NULL;
}

#endif

#ifdef HAVE_LIBCRYPTO
#define USED_IF_LIBCRYPTO
#else
#define USED_IF_LIBCRYPTO _U_
#endif

#ifdef HAVE_LIBCRYPTO
DIAG_OFF_DEPRECATION
#endif
void
esp_print(netdissect_options *ndo,
const u_char *bp, u_int length,
const u_char *bp2 USED_IF_LIBCRYPTO,
u_int ver USED_IF_LIBCRYPTO,
int fragmented USED_IF_LIBCRYPTO,
u_int ttl_hl USED_IF_LIBCRYPTO)
{
const struct newesp *esp;
const u_char *ep;
#ifdef HAVE_LIBCRYPTO
const struct ip *ip;
struct sa_list *sa = NULL;
const struct ip6_hdr *ip6 = NULL;
const u_char *iv;
u_int ivlen;
u_int payloadlen;
const u_char *ct;
u_char *pt;
u_int padlen;
u_int nh;
#endif

ndo->ndo_protocol = "esp";
esp = (const struct newesp *)bp;

/* 'ep' points to the end of available data. */
ep = ndo->ndo_snapend;

if ((const u_char *)(esp + 1) >= ep) {
nd_print_trunc(ndo);
return;
}
ND_PRINT("ESP(spi=0x%08x", GET_BE_U_4(esp->esp_spi));
ND_PRINT(",seq=0x%x)", GET_BE_U_4(esp->esp_seq));
ND_PRINT(", length %u", length);

#ifdef HAVE_LIBCRYPTO
/* initialize SAs */
if (ndo->ndo_sa_list_head == NULL) {
if (!ndo->ndo_espsecret)
return;

esp_decodesecret_print(ndo);
}

if (ndo->ndo_sa_list_head == NULL)
return;

ip = (const struct ip *)bp2;
switch (ver) {
case 6:
ip6 = (const struct ip6_hdr *)bp2;
/* we do not attempt to decrypt jumbograms */
if (!GET_BE_U_2(ip6->ip6_plen))
return;
/* XXX - check whether it's fragmented? */
/* if we can't get nexthdr, we do not need to decrypt it */

/* see if we can find the SA, and if so, decode it */
for (sa = ndo->ndo_sa_list_head; sa != NULL; sa = sa->next) {
if (sa->spi == GET_BE_U_4(esp->esp_spi) &&
sa->daddr_version == 6 &&
UNALIGNED_MEMCMP(&sa->daddr.in6, &ip6->ip6_dst,
sizeof(nd_ipv6)) == 0) {
break;
}
}
break;
case 4:
/* nexthdr & padding are in the last fragment */
if (fragmented)
return;

/* see if we can find the SA, and if so, decode it */
for (sa = ndo->ndo_sa_list_head; sa != NULL; sa = sa->next) {
if (sa->spi == GET_BE_U_4(esp->esp_spi) &&
sa->daddr_version == 4 &&
UNALIGNED_MEMCMP(&sa->daddr.in4, &ip->ip_dst,
sizeof(nd_ipv4)) == 0) {
break;
}
}
break;
default:
return;
}

/* if we didn't find the specific one, then look for
* an unspecified one.
*/
if (sa == NULL)
sa = ndo->ndo_sa_default;

/* if not found fail */
if (sa == NULL)
return;

/* pointer to the IV, if there is one */
iv = (const u_char *)(esp + 1) + 0;
/* length of the IV, if there is one; 0, if there isn't */
ivlen = sa->ivlen;

/*
* Get a pointer to the ciphertext.
*
* p points to the beginning of the payload, i.e. to the
* initialization vector, so if we skip past the initialization
* vector, it points to the beginning of the ciphertext.
*/
ct = iv + ivlen;

/*
* Make sure the authentication data/integrity check value length
* isn't bigger than the total amount of data available after
* the ESP header and initialization vector is removed and,
* if not, slice the authentication data/ICV off.
*/
if (ep - ct < sa->authlen) {
nd_print_trunc(ndo);
return;
}
ep = ep - sa->authlen;

/*
* Calculate the length of the ciphertext. ep points to
* the beginning of the authentication data/integrity check
* value, i.e. right past the end of the ciphertext;
*/
payloadlen = ep - ct;

if (sa->evp == NULL)
return;

/*
* If the next header value is past the end of the available
* data, we won't be able to fetch it once we've decrypted
* the ciphertext, so there's no point in decrypting the data.
*
* Report it as truncation.
*/
if (!ND_TTEST_1(ep - 1)) {
nd_print_trunc(ndo);
return;
}

pt = do_decrypt(ndo, __func__, sa, iv, ct, payloadlen);
if (pt == NULL)
return;

/*
* Switch to the output buffer for dissection, and
* save it on the buffer stack so it can be freed.
*/
if (!nd_push_buffer(ndo, pt, pt, payloadlen)) {
free(pt);
(*ndo->ndo_error)(ndo, S_ERR_ND_MEM_ALLOC,
"%s: can't push buffer on buffer stack", __func__);
}

/*
* Sanity check for pad length; if it, plus 2 for the pad
* length and next header fields, is bigger than the ciphertext
* length (which is also the plaintext length), it's too big.
*
* XXX - the check can fail if the packet is corrupt *or* if
* it was not decrypted with the correct key, so that the
* "plaintext" is not what was being sent.
*/
padlen = GET_U_1(pt + payloadlen - 2);
if (padlen + 2 > payloadlen) {
nd_print_trunc(ndo);
return;
}

/* Get the next header */
nh = GET_U_1(pt + payloadlen - 1);

ND_PRINT(": ");

/*
* Don't put padding + padding length(1 byte) + next header(1 byte)
* in the buffer because they are not part of the plaintext to decode.
*/
if (!nd_push_snaplen(ndo, pt, payloadlen - (padlen + 2))) {
(*ndo->ndo_error)(ndo, S_ERR_ND_MEM_ALLOC,
"%s: can't push snaplen on buffer stack", __func__);
}

/* Now dissect the plaintext. */
ip_demux_print(ndo, pt, payloadlen - (padlen + 2), ver, fragmented,
ttl_hl, nh, bp2);

/* Pop the buffer, freeing it. */
nd_pop_packet_info(ndo);
/* Pop the nd_push_snaplen */
nd_pop_packet_info(ndo);
#endif
}
#ifdef HAVE_LIBCRYPTO
DIAG_ON_DEPRECATION
#endif