/*
 * $Id: nemesis-dns.c,v 1.1.1.1 2003/10/31 21:29:36 jnathan Exp $
 *
 * THE NEMESIS PROJECT
 * Copyright (C) 1999, 2000, 2001 Mark Grimes <mark@stateful.net>
 * Copyright (C) 2001 - 2003 Jeff Nathan <jeff@snort.org>
 *
 * nemesis-dns.c (DNS Packet Injector)
 *
 */

#include "nemesis-dns.h"
#include "nemesis.h"
#if defined(WIN32)
    #include <pcap.h>
#endif

static ETHERhdr etherhdr;
static IPhdr iphdr;
static TCPhdr tcphdr;
static UDPhdr udphdr;
static DNShdr dnshdr;
static FileData pd, ipod, tcpod;
static int got_payload;
static char *payloadfile = NULL;       /* payload file name */
static char *ipoptionsfile = NULL;     /* TCP options file name */
static char *tcpoptionsfile = NULL;    /* IP options file name */
static char *device = NULL;            /* Ethernet device */
#if defined(WIN32)
    static char *ifacetmp = NULL;
#endif

static void dns_cmdline(int, char **);
static int dns_exit(int);
static void dns_initdata(void);
static void dns_usage(char *);
static void dns_validatedata(void);
static void dns_verbose(void);

void nemesis_dns(int argc, char **argv)
{
    const char *module = "DNS Packet Injection";

    nemesis_maketitle(title, module, version);

    if (argc > 1 && !strncmp(argv[1], "help", 4))
        dns_usage(argv[0]);

    if (nemesis_seedrand() < 0)
        fprintf(stderr, "ERROR: Unable to seed random number generator.\n");

    dns_initdata();
    dns_cmdline(argc, argv);
    dns_validatedata();
    dns_verbose();

    if (got_payload)
    {
        if (state)
        {
#if defined(WIN32)
            if (builddatafromfile(DNSTCP_LINKBUFFSIZE, &pd,
                    (const char *)payloadfile, 
                    (const u_int32_t)PAYLOADMODE) < 0)
#else
            if (builddatafromfile(((got_link == 1) ? DNSTCP_LINKBUFFSIZE :
                    DNSTCP_RAWBUFFSIZE), &pd, (const char *)payloadfile, 
                    (const u_int32_t)PAYLOADMODE) < 0)
#endif
                dns_exit(1);
        }
        else
        {
#if defined(WIN32)
            if (builddatafromfile(DNSUDP_LINKBUFFSIZE, &pd, 
                    (const char *)payloadfile, 
                    (const u_int32_t)PAYLOADMODE) < 0)
#else
            if (builddatafromfile(((got_link == 1) ? DNSUDP_LINKBUFFSIZE :
                    DNSUDP_RAWBUFFSIZE), &pd, (const char *)payloadfile, 
                    (const u_int32_t)PAYLOADMODE) < 0)
#endif
                dns_exit(1);
        }
    }

    if (got_ipoptions)
    {
        if (builddatafromfile(OPTIONSBUFFSIZE, &ipod, 
                (const char *)ipoptionsfile, (const u_int32_t)OPTIONSMODE) < 0)
            dns_exit(1);
    }

    if (state && got_tcpoptions)
    {
        if (builddatafromfile(OPTIONSBUFFSIZE, &tcpod, 
                (const char *)tcpoptionsfile, (const u_int32_t)OPTIONSMODE) < 0)
            dns_exit(1);
    }
       
    if (builddns(&etherhdr, &iphdr, &tcphdr, &udphdr, &dnshdr, &pd, &ipod, 
                &tcpod, device) < 0)
    {
        puts("\nDNS Injection Failure");
        dns_exit(1);
    }
    else
    {
        puts("\nDNS Packet Injected");
        dns_exit(0);
    }
}

static void dns_initdata(void)
{
    /* defaults */
    etherhdr.ether_type = ETHERTYPE_IP;     /* Ethernet type IP */
    memset(etherhdr.ether_shost, 0, 6);     /* Ethernet source address */
    memset(etherhdr.ether_dhost, 0xff, 6);  /* Ethernet destination address */
    memset(&iphdr.ip_src.s_addr, 0, 4);     /* IP source address */
    memset(&iphdr.ip_dst.s_addr, 0, 4);     /* IP destination address */
    iphdr.ip_tos = IPTOS_LOWDELAY;          /* IP type of service */
    iphdr.ip_id = (u_int16_t)libnet_get_prand(PRu16);   /* IP ID */
    iphdr.ip_p = IPPROTO_UDP;
    iphdr.ip_off = 0;                       /* IP fragmentation offset */
    iphdr.ip_ttl = 255;                     /* IP TTL */
    tcphdr.th_sport = (u_int16_t)libnet_get_prand(PRu16);
                                            /* TCP source port */
    tcphdr.th_dport = 53;                   /* TCP destination port */
    tcphdr.th_seq = (u_int32_t)libnet_get_prand(PRu32);
                                            /* randomize sequence number */
    tcphdr.th_ack = (u_int32_t)libnet_get_prand(PRu32);
                                            /* randomize ack number */
    tcphdr.th_flags = 0;                    /* TCP flags */
    tcphdr.th_win = 4096;                   /* TCP window size */
    udphdr.uh_sport = (u_int16_t)libnet_get_prand(PRu16);
                                            /* UDP source port */
    udphdr.uh_dport = 53;                   /* UDP destination port */
    pd.file_mem = NULL;
    pd.file_s = 0;
    ipod.file_mem = NULL;
    ipod.file_s = 0;
    tcpod.file_mem = NULL;
    tcpod.file_s = 0;
    return;
}

static void dns_validatedata(void)
{
    struct sockaddr_in sin;

    /* validation tests */
    if (iphdr.ip_src.s_addr == 0)
        iphdr.ip_src.s_addr = (u_int32_t)libnet_get_prand(PRu32);
    if (iphdr.ip_dst.s_addr == 0)
        iphdr.ip_dst.s_addr = (u_int32_t)libnet_get_prand(PRu32);

    /* if the user has supplied a source hardware addess but not a device
     * try to select a device automatically
     */
    if (memcmp(etherhdr.ether_shost, zero, 6) && !got_link && !device)
    {
        if (libnet_select_device(&sin, &device, (char *)&errbuf) < 0)
        {
            fprintf(stderr, "ERROR: Device not specified and unable to "
                    "automatically select a device.\n");
            dns_exit(1);
        }
        else
        {
#ifdef DEBUG
            printf("DEBUG: automatically selected device: "
                    "       %s\n", device);
#endif
            got_link = 1;
        }
    }

    /* if a device was specified and the user has not specified a source 
     * hardware address, try to determine the source address automatically
     */
    if (got_link)
    {
        if ((nemesis_check_link(&etherhdr, device)) < 0)
        {
            fprintf(stderr, "ERROR: cannot retrieve hardware address of %s.\n",
                    device);
            dns_exit(1);
        }
    }

    /* Attempt to send valid packets if the user hasn't decided to craft an
     * anomolous packet
     */
    if (state && tcphdr.th_flags == 0)
        tcphdr.th_flags |= TH_SYN;
    return;
}

static void dns_usage(char *arg)
{
    nemesis_printtitle((const char *)title);

    printf("DNS usage:\n  %s [-v (verbose)] [options]\n\n", arg);
    printf("DNS options: \n"
           "  -i <DNS ID>\n"
           "  -g <DNS flags>\n"
           "  -q <# of Questions>\n"
           "  -W <# of Answer RRs>\n"
           "  -A <# of Authority RRs>\n"
           "  -r <# of Additional RRs>\n"
           "  -P <Payload file>\n"
           "  -k (Enable TCP transport)\n\n");
    printf("TCP options (with -k): \n"
           "  -x <Source port>\n"
           "  -y <Destination port>\n"
           "  -f <TCP flags>\n"
           "     -fS (SYN), -fA (ACK), -fR (RST), -fP (PSH), -fF (FIN),"
           " -fU (URG)\n"
           "     -fE (ECE), -fC (CWR)\n"
           "  -w <Window size>\n"
           "  -s <SEQ number>\n"
           "  -a <ACK number>\n"
           "  -u <Urgent pointer offset>\n"
           "  -o <TCP options file>\n\n");
    printf("UDP options (without -k): \n"
           "  -x <Source port>\n"
           "  -y <Destination port>\n\n");
    printf("IP options: \n"
           "  -S <Source IP address>\n"
           "  -D <Destination IP address>\n"
           "  -I <IP ID>\n"
           "  -T <IP TTL>\n"
           "  -t <IP TOS>\n"
           "  -F <IP fragmentation options>\n"
           "     -F[D],[M],[R],[offset]\n"
           "  -O <IP options file>\n\n");
    printf("Data Link Options: \n"
#if defined(WIN32)
           "  -d <Ethernet device number>\n"
#else
           "  -d <Ethernet device name>\n"
#endif
           "  -H <Source MAC address>\n"
           "  -M <Destination MAC address>\n");
#if defined(WIN32)
    printf("  -Z (List available network interfaces by number)\n");
#endif
    putchar('\n');
    dns_exit(1);
}

static void dns_cmdline(int argc, char **argv)
{
    int opt, i, flag;
    u_int32_t addr_tmp[6];
    char *dns_options;
    char *p, c;
    extern char *optarg;
    extern int optind;

#if defined(ENABLE_PCAPOUTPUT)
  #if defined(WIN32)
    dns_options = "a:A:b:d:D:f:F:g:H:i:I:M:o:O:P:q:r:s:S:t:T:u:w:W:x:y:kvZ?";
  #else
    dns_options = "a:A:b:d:D:f:F:g:H:i:I:M:o:O:P:q:r:s:S:t:T:u:w:W:x:y:kv?";
  #endif
#else
  #if defined(WIN32)
    dns_options = "a:A:b:d:D:f:F:g:H:i:I:M:o:O:P:q:r:s:S:t:T:u:w:x:y:kvZ?";
  #else
    dns_options = "a:A:b:d:D:f:F:g:H:i:I:M:o:O:P:q:r:s:S:t:T:u:w:x:y:kv?";
  #endif
#endif

    while ((opt = getopt(argc, argv, dns_options)) != -1) {
        switch (opt)
        {
            case 'a':    /* ACK window */
                tcphdr.th_ack = xgetint32(optarg);
                break;
            case 'A':    /* number of authoritative resource records */
                dnshdr.num_auth_rr = xgetint16(optarg);
                break;
            case 'b':    /* number of answers */
                dnshdr.num_answ_rr = xgetint16(optarg);
                break;
            case 'd':    /* Ethernet device */
#if defined(WIN32)
                if (nemesis_getdev(atoi(optarg), &device) < 0)
                {
                    fprintf(stderr, "ERROR: Unable to lookup device: '%d'.\n", 
                            atoi(optarg));
                    dns_exit(1);
                }
#else
                if (strlen(optarg) < 256)
                {
                    device = strdup(optarg);
                    got_link = 1;
                }
                else
                {
                    fprintf(stderr, "ERROR: device %s > 256 characters.\n", 
                            optarg);
                    dns_exit(1);
                }
#endif
                break;
            case 'D':    /* destination IP address */
                if ((nemesis_name_resolve(optarg, 
                        (u_int32_t *)&iphdr.ip_dst.s_addr)) < 0)
                {
                    fprintf(stderr, "ERROR: Invalid destination IP address: "
                            "\"%s\".\n", optarg);
                    dns_exit(1);
                }
                break;
            case 'f':    /* TCP flags */
                p = optarg;
                while (*p != '\0')
                {
                    c = *p;
                    flag = strchr(validtcpflags, c) - validtcpflags;
                    if (flag < 0 || flag > 7)
                    {
                        printf("ERROR: Invalid TCP flag: %c.\n", c);
                        dns_exit(1);
                    }
                    else
                    {
                        tcphdr.th_flags |= 1 << flag;
                        p++;
                    }
                }
                break;
            case 'F':    /* IP fragmentation options */
                if (parsefragoptions(&iphdr, optarg) < 0)
                    dns_exit(1);
                break;
            case 'g':   /* DNS flags */
                dnshdr.flags = xgetint16(optarg);
                break;
            case 'H':    /* Ethernet source address */
                memset(addr_tmp, 0, sizeof(addr_tmp));
                sscanf(optarg, "%02X:%02X:%02X:%02X:%02X:%02X", &addr_tmp[0],
                        &addr_tmp[1], &addr_tmp[2], &addr_tmp[3], &addr_tmp[4],
                        &addr_tmp[5]);
                for (i = 0; i < 6; i++)
                    etherhdr.ether_shost[i] = (u_int8_t)addr_tmp[i];
                break;
            case 'i':   /* DNS ID */
                dnshdr.id = xgetint16(optarg);
                break;
            case 'I':   /* IP ID */
                iphdr.ip_id = xgetint16(optarg);
                break;
            case 'k':    /* use TCP */
                iphdr.ip_tos = 0;
                iphdr.ip_p = IPPROTO_TCP;
                state = 1;
                break;
            case 'M':    /* Ethernet destination address */
                memset(addr_tmp, 0, sizeof(addr_tmp));
                sscanf(optarg, "%02X:%02X:%02X:%02X:%02X:%02X", &addr_tmp[0],
                        &addr_tmp[1], &addr_tmp[2], &addr_tmp[3], &addr_tmp[4],
                        &addr_tmp[5]);
                for (i = 0; i < 6; i++)
                    etherhdr.ether_dhost[i] = (u_int8_t)addr_tmp[i]; 
                break;
            case 'o':   /* TCP options file */
                if (strlen(optarg) < 256)
                {
                    tcpoptionsfile = strdup(optarg);
                    got_tcpoptions = 1;
                }
                else
                {
                    fprintf(stderr, "ERROR: TCP options file %s > 256 "
                            "characters.\n", optarg);
                    dns_exit(1);
                }
                break;
            case 'O':   /* IP options file */
                if (strlen(optarg) < 256)
                {
                    ipoptionsfile = strdup(optarg);
                    got_ipoptions = 1;
                }
                else
                {
                    fprintf(stderr, "ERROR: IP options file %s > 256 "
                            "characters.\n", optarg);
                    dns_exit(1);
                }
                break;
            case 'P':   /* payload file */
                if (strlen(optarg) < 256)
                {
                    payloadfile = strdup(optarg);
                    got_payload = 1;
                }
                else
                {
                    fprintf(stderr, "ERROR: payload file %s > 256 "
                            "characters.\n", optarg);
                    dns_exit(1);
                }
                break;
            case 'q':    /* number of questions */
                dnshdr.num_q = xgetint16(optarg);
                break;
            case 'r':    /* number of additional resource records */
                dnshdr.num_addi_rr = xgetint16(optarg);
                break;
            case 's':    /* TCP sequence number */
                tcphdr.th_seq = xgetint32(optarg);
                break;
            case 'S':    /* source IP address */
                if ((nemesis_name_resolve(optarg, 
                        (u_int32_t *)&iphdr.ip_src.s_addr)) < 0)
                {
                    fprintf(stderr, "ERROR: Invalid source IP address: \"%s\"."
                            "\n", optarg);
                    dns_exit(1);
                }
                break;
            case 't':   /* IP type of service */
                iphdr.ip_tos = xgetint8(optarg);
                break;
            case 'T':   /* IP time to live */
                iphdr.ip_ttl = xgetint8(optarg);
                break;
            case 'u':  /* TCP urgent pointer */
                tcphdr.th_urp = xgetint16(optarg);
                break;
            case 'v':
                verbose++;
                if (verbose == 1)
                    nemesis_printtitle((const char *)title);
                break;
            case 'w':    /* TCP window size */
                tcphdr.th_win = xgetint16(optarg);
                break;

            case 'x':    /* TCP/UDP source port */
                tcphdr.th_sport = xgetint16(optarg);
                udphdr.uh_sport = xgetint16(optarg);
                break;
            case 'y':    /* TCP/UDP destination port */
                tcphdr.th_dport = xgetint16(optarg);
                udphdr.uh_dport = xgetint16(optarg);
                break;
#if defined(WIN32)
            case 'Z':
                if ((ifacetmp = pcap_lookupdev(errbuf)) == NULL)
                    perror(errbuf);

                PrintDeviceList(ifacetmp);
                dns_exit(1);
#endif
            case '?':   /* FALLTHROUGH */
            default:
                dns_usage(argv[0]);
                break;
        }
    }
    argc -= optind;
    argv += optind;
    return;
}

static int dns_exit(int code)
{
    if (got_payload)
        free(pd.file_mem);

    if (got_ipoptions)
        free(ipod.file_mem);

    if (got_tcpoptions)
        free(tcpod.file_mem);

    if (device != NULL)
        free(device);

    if (tcpoptionsfile != NULL)
        free(tcpoptionsfile);

    if (ipoptionsfile != NULL)
        free (ipoptionsfile);

    if (payloadfile != NULL);
        free(payloadfile);

#if defined(WIN32)
    if (ifacetmp != NULL)
        free(ifacetmp);
#endif

    exit(code);
}

static void dns_verbose(void)
{
    if (verbose)
    {
        if (got_link)
            nemesis_printeth(&etherhdr);

        nemesis_printip(&iphdr);

        if (state)
            nemesis_printtcp(&tcphdr);
        else
            nemesis_printudp(&udphdr);

        printf("   [DNS # Questions] %hu\n", dnshdr.num_q);
        printf("  [DNS # Answer RRs] %hu\n", dnshdr.num_answ_rr);
        printf("    [DNS # Auth RRs] %hu\n", dnshdr.num_auth_rr);
        printf("  [DNS # Addtnl RRs] %hu\n\n", dnshdr.num_addi_rr);
    }
    return;
}