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CryptoBAP

This is an implementation of our CryptoBAP toolchain. This implementation includes

  • The crypto-aware symbolic execution engine on top of the proof-producing platform named HolBA
  • The extension of HolBA with the syntax of intermediate model language (IML)
  • The translation of the symbolic tree into the IML
  • The modification of the Csec-modex toolchain for getting IML files as inputs

Folders and organization

Our toolchain includes the following:

HolBA/src/tools/symbexec/examples/binaries/balrob/
A directory contains the source code of the protocols we analysed: simple mac, simple xor, RPC, RPC-enc, NSL, CSur, TinySSH and WireGuard at ARMv8 binary code.

HolBA/src/tools/symbexec/examples/PreProcess/
A directory consists of the source codes for preprocessing the BIR program before executing by our symbolic execution, e.g., finding addresses of function calls, entry and exit to/from loops.

HolBA/src/tools/symbexec/examples/IML/
A directory includes the intermediate model language (IML) syntax implemented on top of the theorem prover HOL4.

HolBA/src/tools/symbexec/examples/libload/
A directory contains the source codes of our crypto-aware symbolic execution.

HolBA/src/tools/symbexec/examples/Tests/
A directory includes extracted IML models and the input files for each of our use-cases, such as :

  • The function names used in the protocol implementation
  • The names of cryptographic functions used in the protocol implementation
  • The name of functions used for network communications in the protocol implementation and we anoint them adversary function names
  • The number of entries for cryptographic functions used in the protocol implementation
  • The number of entries for adversary functions used in the protocol implementation
  • The name of events we release during the execution of the protocol

Csec-modex/src/symtrace/
A directory contains the source code of the Csec-modex verification toolchain, which we modified to start the analysis from IML.

Csec-modex/mk/
A directory includes the make files of the Csec-modex verification toolchain, which we modified to start from IML.

Csec-modex/tests/
A directory includes subdirectories that start the analysis of our use cases from IML input files. These subdirectories contain CryptoVerif and ProVerif template files which include :

  • The cryptographic assumptions used by the protocol implementation
  • The process which generates shared cryptographic material and breeds the protocol participants
  • Queries for the property that the protocol implementation attempt to satisfy

How to setup and compile

HolBA

  1. Set up HolBA framework using HolBA/README.md
  2. Specify which binary file and which blocks inside it you want to transpile into the binary intermediate representation (BIR) in HolBA/src/tools/symbexec/examples/binaries/balrob/binariesBalrobDefsLib.sml
  3. In order to generate a BIR program of your specified binary file, execute the following lines :

You can find the BIR program stored in binariesTheory.sig file in HolBA/src/tools/symbexec/examples/binaries/balrob/ directory

  1. Now you can go to HolBA/ directory and verify your desired use-case with the following command :

    • make src/tools/symbexec/examples/Tests/subdirectory/your-desired-use-case.sml_run

  2. You can find the IML result in IML_Translation.txt file in subdirectory of the HolBA/src/tools/symbexec/examples/Tests/ directory

Csec-modex

  1. Set up Csec-modex verification toolchain using Csec-modex/README.markdown
  2. Place your derived IML file in the related subdirectory in Csec-modex/tests/
  3. Run verification via the following command :
    • make -f Makefile.csec when you are in the related subdirectory in Csec-modex/tests/

Running example

Consider a client-side of the implementation of simple XOR as described in [1].

The client_xor.da, client_xor.da.plus, and client_xor.mem are the implementation of client-side of simple XOR at ARMv8 binary in HolBA/src/tools/symbexec/examples/binaries/balrob/ directory.

You need to configure these files as input files at ARMv8 binary in file HolBA/src/tools/symbexec/examples/binaries/balrob/binariesBalrobDefsLib.sml as follows:

val configs              = [ ("client", 
                           ("client_xor.da", "balrob/client_xor.da.plus", "balrob/client_xor.mem"),
                           "client_THM",
                           ((Arbnum.fromInt 0x00000000, Arbnum.fromInt 0xffffffff),
                            (Arbnum.fromInt 0x10000000, Arbnum.fromInt (0x00000018 + 0x30d)),
                            (Arbnum.fromInt 0x10001000, Arbnum.fromInt 0x00000ff0))
			     ) ];

And then, specify which code fragments you want to transpile to BIR, like below :

val symbs_sec_text = [
    "__libc_malloc",
    "memcpy",
    "otp",
    "xor",
    "socket_connect",
    "send",
    "RAND_bytes",
    "client",
    "main"
];

You can find the BIR program in binariesTheory.sig file in HolBA/src/tools/symbexec/examples/binaries/balrob/ directory and it contains BIR blocks like as follow : 

		...
		bb_last_statement :=
                  BStmt_Jmp (BLE_Label (BL_Address (Imm64 4203720w)))|>;
 <|bb_label :=
                  BL_Address_HC (Imm64 4203720w)
                    "9400014B (bl 4029f4 <xor>)";
                  bb_statements :=
                  [BStmt_Assign (BVar "R30" (BType_Imm Bit64))
                     (BExp_Const (Imm64 4203724w))];
                  bb_last_statement :=
                  BStmt_Jmp (BLE_Label (BL_Address (Imm64 4205044w)))|>;
<|bb_label :=
                  BL_Address_HC (Imm64 4203724w)
                    "F94017A0 (ldr x0, [x29,#40])";
                    ...

Moreover, you require to set the entry and exit points of the derived BIR program in HolBA/src/tools/symbexec/examples/Tests/XOR/Combination-XOR.sml as follows : 

val lbl_tm = ``BL_Address (Imm64 4203632w)``;

val stop_lbl_tms = [``BL_Address (Imm64 4203756w)``];

And then run the following command when you are in HolBA/ directory :

  • make src/tools/symbexec/examples/Tests/XOR/Combination-XOR.sml_run

The derived IML model can be found in IML_Translation.txt file in HolBA/src/tools/symbexec/examples/Tests/XOR/ directory and is presented below : 

new OTP_48 fixed_64 
let Conc1_66 = conc1(OTP_48) in
let XOR_70 = exclusive_or(Conc1_66,pad) in
out c, XOR_70

Considering that the IML model is associated with the client side of our running example, you need to place it within the IML_client.txt file located in subdirectory Csec-modex/tests/Simple_Xor from IML.

Then, you require to perform all the aforementioned steps for the server-side implementation of the simple XOR and put the derived model into the IML_server.txt file in subdirectory Csec-modex/tests/Simple_Xor from IML.

While you are in subdirectory Csec-modex/tests/Simple_Xor from IML, execute the following command:

  • make -f Makefile.csec

You can see the result of the analysis with CryptoVerif ends with these two following lines:

RESULT Proved secrecy of OTP_48_0
All queries proved.

References

[1] Aizatulin, Mihhail, Andrew D. Gordon, and Jan Jürjens. "Computational verification of C protocol implementations by symbolic execution." Proceedings of the 2012 ACM conference on Computer and communications security. 2012.