SGX实践

# 2.ocall 获取外部参数

> edl 定义
```
[cdecl] void ocall_get_buf([in,size=len] void* buf1,[in,out,size=len] void* buf,size_t len);
```
> app.cpp定义
```
void ocall_get_buf(void* buf1,void* buf,size_t len)
{
//	buf=(char*)malloc(10);
	memcpy(buf,buf1,len);
}
```
> enclave调用
```
    sgx_status_t ret = SGX_ERROR_UNEXPECTED;

char s1[]="1234567890";
    //char s2[]="0987654321";
    char *s2=NULL;
    size_t len=10;

ret=ocall_get_buf(s1,s2,len);
    if (ret != SGX_SUCCESS)
        abort();

show("!!!!!!!!!!!!ocall!!!!! %s\n",s2);
```

# 3. user_datatype（ocall）

> enclave.edl

```
   include "user_types.h" /* buffer_t */
    include "flk_types.h"
    untrusted {
   
        void ocall_print_string([in, string] const char *str);
        
        [cdecl] void ocall_get_buf([in,size=len] void* buf1,[in,out,size=len] void* buf,size_t len);
        
        void ocall_get_flk_struct([in,string] const char *name,[out]struct flk_test* ptest );
        
        /*
        *[cdecl, dllimport] void *memccpy([in, out, size=len] void *dest, [in, size=len] const void *src, int val, size_t len);*/
    };
```

> flk_types.h

```
#include <stdio.h>
#include <string.h>

struct flk_test
{
	int age;
	int salary;

};
```

> ocall_get_flk_struct(const char*name,struct flk_test* ptest) definition

```
void ocall_get_flk_struct(const char *name,flk_test* ptest )
{
	printf("ocall_get_flk_struct is %s\n",name);
	ptest->age=20;
	ptest->salary=200;

printf("ocall_get_flk_struct ptest.age is %d\n",ptest->age);

}
```

# 4. user_data_type(Ecall)

# 5.关于time

``` SealedData/DRM_enclave/DRM_enclave.cpp
do{
 ret = sgx_create_pse_session();
}while(ret ==SGX_ERROR_BUSY && busy_retry_times--);
if(ret != SGX_SUCCESS)
    abort();

sgx_time_source_nonce_t nonce={0};    
sgx_time_t current_timestamp;
ret=sgx_get_trusted_time(¤t_timestamp,&nonce);
if(ret != SGX_SUCCESS)
{
    switch(ret)
    {
          case SGX_ERROR_SERVICE_UNAVAILABLE:
                /* Architecture Enclave Service Manager is not installed or not
                working properly.*/
                break;
         case SGX_ERROR_SERVICE_TIMEOUT:
                /* retry the operation*/
                break;
                
         case SGX_ERROR_BUSY:
                /* retry the operation later*/
                break;
         default:
                /*other errors*/
                break;

}
    break;
}

sgx_close_pse_session();

```
# 6 关于string to int (not atoi)
```
#include <stdio.h>
#include <stdlib.h>

typedef unsigned char  byte;

int bytesToInt(byte* bytes,int size) 
{
    int addr=0;
    for(int i=0;i<size;i++){
    if(i==0)
    {
        printf("i=0\n");
        printf("bytes[0] is %d\n",bytes[0]);
        addr = bytes[0] & 0xFF;
        printf("i=0,add is %d\n",addr);
    }
    if(i==1)
    {
        printf("i=1\n");
        addr |= ((bytes[1] << 8) & 0xFF00);
    }
    if(i==2)
    {
        printf("i=2\n");
        addr |= ((bytes[2] << 16) & 0xFF0000);
    }
    if(i==3)
    {
        printf("i=3\n");
        addr |= ((bytes[3] << 24) & 0xFF000000);
    }
    }
    return addr;
 }
 
int main(void)
{
   char * p="zzz";
   
   int t= bytesToInt((byte*) p,4);
   
   printf("t is %d\n",t);
   
   return 0;
}
```

# 7 ocall_get

> edl
```
int  ocall_flk_getTimeDiffForLocal([in,out,string] char *str);
```

> ocall use in enclave
```
  strncpy(str, "0987654321", strlen(str));

int flk_time_diff=0;
 	ocall_flk_getTimeDiffForLocal(&flk_time_diff,str);

printf("flk time return code is %d\n",flk_time_diff);
 	printf("flk time ocall str is %s\n",str);
```

>ocall definition
```
int ocall_flk_getTimeDiffForLocal(char *str)
{
	printf("flk_getTimeDiffForLocal is %s\n",str);
	memcpy(str,"123",strlen(str));

return 1234;

}
```

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