Blowfish results are different between OpenSSL and Golang

Question

I want to read VIM encoded files in Go. This code works good enough for small file so I've decided to convert it to Go. Key generation works fine, but Blowfish encoding does not. I've traced the problem to different outcome from BF_encrypt and cipher.Encrypt(...).

Input

key: c904a7a85bbd975324c5083ed96ff022f25e062da1d575b2462c2c98d8d64d9d
data: 538b7759834d3418

Output

Golang: b5cf33144acbc794
C:      90baa70ec3e44867

Golang code:

package main

import (
    "fmt"
    "golang.org/x/crypto/blowfish"
)

func main() {
    key := []byte{0xc9, 0x04, 0xa7, 0xa8, 0x5b, 0xbd, 0x97, 0x53, 0x24, 0xc5, 0x08, 0x3e, 0xd9, 0x6f, 0xf0, 0x22, 0xf2, 0x5e, 0x06, 0x2d, 0xa1, 0xd5, 0x75, 0xb2, 0x46, 0x2c, 0x2c, 0x98, 0xd8, 0xd6, 0x4d, 0x9d}
    data := []byte{0x53, 0x8b, 0x77, 0x59, 0x83, 0x4d, 0x34, 0x18}

    cipher, err := blowfish.NewCipher(key)
    if err != nil {
        panic(err)
    }

    fmt.Printf("key: %x\n", key)
    fmt.Printf("data: %x\n", data)

    encrypted := make([]byte, 8)
    cipher.Encrypt(encrypted, data)
    fmt.Printf("encrypted: %x\n", encrypted)
}

C code:

#include <stdio.h>
#include <string.h>
#include <openssl/blowfish.h>
#include <openssl/sha.h>

/*
clang test1.c -o test1 \
-I/usr/local/Cellar/openssl/1.0.2k/include \
-L/usr/local/Cellar/openssl/1.0.2k/lib \
-lcrypto
./test1
*/

int main(int argc, char *argv[]) {
    unsigned char key[32] = {0xc9, 0x04, 0xa7, 0xa8, 0x5b, 0xbd, 0x97, 0x53, 0x24, 0xc5, 0x08, 0x3e, 0xd9, 0x6f, 0xf0, 0x22, 0xf2, 0x5e, 0x06, 0x2d, 0xa1, 0xd5, 0x75, 0xb2, 0x46, 0x2c, 0x2c, 0x98, 0xd8, 0xd6, 0x4d, 0x9d};
    unsigned char data[8] = {0x53, 0x8b, 0x77, 0x59, 0x83, 0x4d, 0x34, 0x18};

    BF_KEY bf_key;
    BF_set_key(&bf_key, 32, key);

    printf("key: ");
    for (int j = 0; j < 32; j++) printf("%02x", key[j]);
    printf("\n");
    printf("data: ");
    for (int j = 0; j < 8; j++) printf("%02x", data[j]);
    printf("\n");

    BF_encrypt((unsigned int*)data, &bf_key);

    printf("encrypted: ");
    for (int j = 0; j < 8; j++) printf("%02x", data[j]);
    printf("\n");

    return 0;
}

Can you see where the problem is?

Answer 1

The problem is in the endianness of variable data and encrypted. In the C code, data (8-bytes) is converted from byte array to unsigned int(32-bit little-endian), then being encrypted in place. It affects the endianness of both input and encrypted result. To get same result in Golang, you must perform endian conversion, e.g.

package main

import (
    "bytes"
    "fmt"

    "encoding/binary"

    "golang.org/x/crypto/blowfish"
)

func convertEndian(in []byte) ([]byte, error) {
    //Read byte array as uint32 (little-endian)
    var v1, v2 uint32
    buf := bytes.NewReader(in)
    if err := binary.Read(buf, binary.LittleEndian, &v1); err != nil {
        return nil, err
    }
    if err := binary.Read(buf, binary.LittleEndian, &v2); err != nil {
        return nil, err
    }

    //convert uint32 to byte array
    out := make([]byte, 8)
    binary.BigEndian.PutUint32(out, v1)
    binary.BigEndian.PutUint32(out[4:], v2)

    return out, nil
}

func main() {
    key := []byte{0xc9, 0x04, 0xa7, 0xa8, 0x5b, 0xbd, 0x97, 0x53, 0x24, 0xc5, 0x08, 0x3e, 0xd9, 0x6f, 0xf0, 0x22, 0xf2, 0x5e, 0x06, 0x2d, 0xa1, 0xd5, 0x75, 0xb2, 0x46, 0x2c, 0x2c, 0x98, 0xd8, 0xd6, 0x4d, 0x9d}
    data := []byte{0x53, 0x8b, 0x77, 0x59, 0x83, 0x4d, 0x34, 0x18}

    //Add: This is equal to: (unsigned int *)data in C
    cdata, _ := convertEndian(data)

    cipher, err := blowfish.NewCipher(key)
    if err != nil {
        panic(err)
    }

    fmt.Printf("key: %x\n", key)
    fmt.Printf("data: %x\n", cdata)

    encrypted := make([]byte, 8)
    cipher.Encrypt(encrypted, cdata)
    fmt.Printf("encrypted-1: %x\n", encrypted)

    //Add: This is equal to {uint32, uint32} --> byte array
    ce, _ := convertEndian(encrypted)
    fmt.Printf("encrypted-2: %02x\n", ce)
}