/*      $OpenBSD: print-ipsec.c,v 1.27 2021/11/29 18:50:16 tb Exp $     */

/*
 * Copyright (c) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999
 *      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.
 *
 * Format and print IPsec (ESP/AH) packets.
 *      By Tero Kivinen <kivinen@ssh.fi>, Tero Mononen <tmo@ssh.fi>,  
 *         Tatu Ylonen <ylo@ssh.fi> and Timo J. Rinne <tri@ssh.fi>
 *         in co-operation with SSH Communications Security, Espoo, Finland    
 */

#include <sys/time.h>
#include <sys/socket.h>

#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip6.h>
#include <netinet/ip_var.h>
#include <netinet/udp.h>
#include <netinet/udp_var.h>
#include <netinet/tcp.h>

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

#include "addrtoname.h"
#include "interface.h"
#include "extract.h"                /* must come after interface.h */

#include <openssl/evp.h>
#include <ctype.h>

/*
 * IPsec/ESP header
 */
struct esp_hdr {
        u_int esp_spi;
        u_int esp_seq;
};

static int espinit = 0;
static int espauthlen = 12;
static EVP_CIPHER_CTX *ctx;

int
esp_init (char *espspec)
{
        const EVP_CIPHER *evp;
        char *p, *espkey, s[3], name[1024];
        u_char *key;
        int i, klen, len;

        evp = EVP_aes_128_cbc();        /* default */
        espkey = espspec;
        if ((p = strchr(espspec, ':')) != NULL) {
                len = p - espspec;
                if (len >= sizeof(name))
                        error("espalg too long");
                memcpy(name, espspec, len);
                name[len] = '\0';
                espkey = p + 1;

                /* strip auth alg */
                espauthlen = 0;
                if ((p = strstr(name, "-hmac96")) != NULL) {
                        espauthlen = 12;
                        *p = '\0';
                }
                OpenSSL_add_all_algorithms();
                if ((evp = EVP_get_cipherbyname(name)) == NULL)
                        error("espalg `%s' not supported", name);
        }
        klen = EVP_CIPHER_key_length(evp);
        if (strlen(espkey) != klen * 2)
                error("espkey size mismatch, %d bytes needed", klen);
        if ((key = malloc(klen)) == NULL)
                error("malloc failed");
        for (i = 0; i < klen; i++) {
                s[0] = espkey[2*i];
                s[1] = espkey[2*i + 1];
                s[2] = 0;
                if (!isxdigit((unsigned char)s[0]) ||
                    !isxdigit((unsigned char)s[1])) {
                        free(key);
                        error("espkey must be specified in hex");
                }
                key[i] = strtoul(s, NULL, 16);
        }
        if ((ctx = EVP_CIPHER_CTX_new()) == NULL) {
                free(key);
                error("espkey init failed");
        }
        if (!EVP_CipherInit(ctx, evp, key, NULL, 0)) {
                EVP_CIPHER_CTX_free(ctx);
                free(key);
                error("espkey init failed");
        }
        free(key);
        espinit = 1;
        return (0);
}

void
esp_decrypt (const u_char *bp, u_int len, const u_char *bp2)
{
        const struct ip *ip;
        u_char *data, pad, nh;
        int blocksz;

        ip = (const struct ip *)bp2;

        blocksz = EVP_CIPHER_CTX_block_size(ctx);

        /* Skip fragments and short packets */
        if (ntohs(ip->ip_off) & 0x3fff)
                return;
        if (snapend - bp < len) {
                printf(" [|esp]");
                return;
        }
        /*
         * Skip ESP header and ignore authentication trailer.
         * For decryption we need at least 2 blocks: IV and
         * one cipher block.
         */
        if (len < sizeof(struct esp_hdr) + espauthlen + 2 * blocksz) {
                printf(" [|esp]");
                return;
        }

        data = (char *)bp;
        data += sizeof(struct esp_hdr);
        len -= sizeof(struct esp_hdr);
        len -= espauthlen;

        /* the first block contains the IV */
        if (!EVP_CipherInit(ctx, NULL, NULL, data, 0))
                return;

        len -= blocksz;
        data += blocksz;

        /* decrypt remaining payload */
        if (!EVP_Cipher(ctx, data, data, len))
                return;

        nh = data[len - 1];
        pad = data[len - 2];

        /* verify padding */
        if (pad + 2 > len)
                return;
        if (data[len - 3]  != pad)
                return;
        if (vflag > 1)
                printf(" pad %d", pad);
        len -= (pad + 2);
        printf(": ");
        switch (nh) {
        case IPPROTO_TCP:
                tcp_print(data, len, bp2);
                break;
        case IPPROTO_UDP:
                udp_print(data, len, bp2);
                break;
        case IPPROTO_IPV6:
                ip6_print(data, len);
                break;
        case IPPROTO_IPV4:
                ip_print(data, len);
                break;
        case IPPROTO_ICMP:
                icmp_print(data, len, bp2);
                break;
        case IPPROTO_ICMPV6:
                icmp6_print(data, len, bp2);
                break;
        default:
                printf("ip-proto-%d %d", nh, len);
                break;
        }
        if (vflag)
                printf(" (esp)");
}

void 
esp_print (const u_char *bp, u_int len, const u_char *bp2)
{
        const struct esp_hdr *esp;

        if (len < sizeof(struct esp_hdr)) {
                printf("[|esp]");
                return;
        }
        esp = (const struct esp_hdr *)bp;

        printf("esp spi 0x%08x seq %u len %d",
            ntohl(esp->esp_spi), ntohl(esp->esp_seq), len);

        if (espinit)
                esp_decrypt(bp, len, bp2);
}

/*
 * IPsec/AH header
 */
struct ah_hdr {
        u_char  ah_nxt_hdr;
        u_char  ah_pl_len;
        u_short ah_reserved;
        u_int   ah_spi;
        u_int   ah_seq;
};

void
ah_print (const u_char *bp, u_int len, const u_char *bp2)
{
        const struct ip *ip;
        const struct ah_hdr *ah;
        u_int pl_len = len;
        const struct ip6_hdr *ip6;

        ip = (const struct ip *)bp2;
        if (ip->ip_v == 6) {
                ip6 = (const struct ip6_hdr *)bp2;
                printf("ah %s > %s", ip6addr_string(&ip6->ip6_src),
                    ip6addr_string(&ip6->ip6_dst));
        } else
                printf("ah %s > %s",
                    ipaddr_string(&ip->ip_src), ipaddr_string(&ip->ip_dst));

        if (pl_len < sizeof(struct ah_hdr)) {
                printf("[|ah]");
                return;
        }
        ah = (const struct ah_hdr *)bp;

        printf(" spi 0x%08x seq %u len %d",
            ntohl(ah->ah_spi), ntohl(ah->ah_seq), len);

        if (vflag) {
                printf(" [ ");

                pl_len = (ah->ah_pl_len + 2) << 2; /* RFC2402, sec 2.2 */

                if (len <= pl_len) {
                        printf("truncated");
                        goto out;
                }
                
                switch (ah->ah_nxt_hdr) { 

                case IPPROTO_IPIP: /* Tunnel Mode, IP-in-IP */
                        ip_print(bp + pl_len, len - pl_len); 
                        break;

                case IPPROTO_ICMP: /* From here and down; Transport mode */
                        icmp_print(bp + pl_len, len - pl_len,
                                  (const u_char *) ip);
                        break;

                case IPPROTO_ICMPV6:
                        icmp6_print(bp + pl_len, len - pl_len,
                                  (const u_char *) ip);
                        break;

                case IPPROTO_TCP:
                        tcp_print(bp + pl_len, len - pl_len, 
                                  (const u_char *) ip);
                        break;

                case IPPROTO_UDP:
                        udp_print(bp + pl_len, len - pl_len, 
                                  (const u_char *) ip);
                        break;

                case IPPROTO_ESP:
                        esp_print(bp + pl_len, len - pl_len, 
                                  (const u_char *) ip);
                        break;

                case IPPROTO_AH:
                        ah_print(bp + pl_len, len - pl_len, 
                                 (const u_char *) ip);
                        break;

                default:
                        printf("ip-proto-%d len %d",
                            ah->ah_nxt_hdr, len - pl_len);
                }
out:
                printf(" ]");
        }

}

struct ipcomp_hdr {
        u_char  ipcomp_nxt_hdr;
        u_char  ipcomp_flags;
        u_short ipcomp_cpi;
};

void
ipcomp_print (const u_char *bp, u_int len, const u_char *bp2)
{
        const struct ip *ip;
        const struct ipcomp_hdr *ipc;
        u_int plen = len;
 
        ip = (const struct ip *)bp2;

        printf("ipcomp %s > %s",
            ipaddr_string(&ip->ip_src),
            ipaddr_string(&ip->ip_dst));

        if (plen < sizeof(struct ipcomp_hdr)) {
                printf("[|ipcomp]");
                return;
        }
        ipc = (const struct ipcomp_hdr *)bp;

        printf(" cpi 0x%04X flags %x next %x",
            ntohs(ipc->ipcomp_cpi), ipc->ipcomp_flags, ipc->ipcomp_nxt_hdr);
}