DEV-APP.md

Interface Design

Argument style

pass by pointer

• original: foo(){ void* ptr = data; ... }
• enclave: foo1(){ ec_foo(&data); }
  • ec_foo(long vaddr) @App.cpp
    • ec_foo(long vaddr){ void* ptr = (void *) vaddr; ... } @Enclave.cpp

pass by value

• original: foo(){ int[] data; ... data[0];}
• enclave: foo(){ ec_foo(data); }
  • ec_foo(int data[10]) @App.cpp
    • ec_foo(int data[10]){ ... data[0];} @Enclave.cpp

The case of leveldb iterator (per next() partitioning)

U labels untrusted memory, T lables Enclave.

U: Elem next(Iterator* it){...;SYSCALL;...;}

merge(Iterator* it){
    ...
T:  next(it);
    ...
}

main(){
    Iterator* it;
U:  merge(it);
}

==>

/////////// @Enclave.cpp /////////////

oc_next(long addr_it) @Enclave.cpp
{
    oc_next(vaddr_it); @App.cpp
}

ec_merge(long vaddr_it) @Enclave.cpp
{
    Iterator* it = vaddr_it;
    ...
    oc_next(it);
    ...
}   

/////////// @App.cpp /////////////
oc_next(long vaddr_it) @App.cpp
{
   Iterator* it = vaddr_it;
   ...
   SYSCALL;
   ...
}

ec_merge(long vaddr_it) @ App.cpp
{
   ec_merge(vaddr_it); @Enclave.cpp
}
   
main(){
   Iterator* it;
   ec_merge(it);
}

code-partition	argument pass-by	ocall freq.	copy #
it->next	value	per next()	>=3
SYSCALL	value	per syscall	>=3
it->next	pointer	per next()	1
SYSCALL	pointer	per syscall	1

Partitioning

The case of secure-channel establishment

class secureChannel_AliceToBob{
  void setup(){
    SSL_new(socket);
  }
  
  void communicate(plaintext{S}){
    SSL_write(plaintext);
    plaintext2 = SSL_read();
  }
}

void SSL_new(){
T: public_key_Bob=CA.getKey("Bob");
T: <public_key_Alice, private_key_Alice{S}>=ssl_genkey_RSA();
T: key_session{S}=ssl_genkey_ATS();
}

SSL_write(message plaintext{S}){
  T: digest=sha1(plaintext,40);
  T: sig=ssl_MAC_sign(plaintext,digest,key_session);
  T: ciphertext=ssl_aes_enc(plaintext,key_session);
  U: ssl_send(ciphertext||sig, Bob);
}

SSL_read(){
  U: <ciphertext,sig>=ssl_recv();
  T: plaintext=ssl_aes_dec(ciphertext,key_session);
  if(ssl_MAC_verify(plaintext,sig,key_session)){
    return plaintext;
  }
}

Misc issues

1. clear data before free()
2. in-Enclave key management
3. syscall while sensitive data?
   • e.g. load existing secret key from *.pem
   • random number generator (from /dev/rand/ in Unix)
4. interface: prepended compilation
   • SGXP gcc src/main.c
   • ./a.out