OpenSSL與CryptoAPI交互AES加密解密

繼上次只有CryptoAPI的加密後,這次要實現openssl的了。

動機:利用CryptoAPI制作windows的IE,火狐和chrome加密控件後,這次得加上與Android的加密信息交互。

先前有說openssl移植到android的過程,這裡就不再提android如何調用openssl了,而那一篇第9條提到的openssl與cryptoAPI兼容的兩種方式感覺實現都不太好用,這裡再次提出一種AES加密的實現方式。

寫這邊文章的最主要的原因,用過CryptoAPI的都知道,很多東西都封裝了,如果要與其他加密組件交互,得用其他組件來實現CryptoAPI的思路。

環境:windows visual studio 2010,openssl windows(x86)動態庫。

在CryptoAPI中進行AES加密解密,有一種實現方式是調用CryptDeriveKey通過提供的字節數組的hash值獲取key。

先來看下CryptoAPI實現AES,來個簡單點的版本。

1. void cryptoAPI_encrypt(string text,unsigned char* pwd,unsigned char** encryptText,int &out_len)
2. {
3. HCRYPTPROV hCryptProv = NULL;
4. HCRYPTKEY hKey = 0;
5. HCRYPTHASH hHash = 0;
6. int dwLength = 0;
8. if(!CryptAcquireContext(&hCryptProv,
9. NULL,
10. CSP_NAME,//CSP_NAME
11. PROV_RSA_AES,
12. CRYPT_VERIFYCONTEXT))
13. {
14. DWORD dwLastErr = GetLastError();
16. if(NTE_BAD_KEYSET == dwLastErr)
17. {
18. return;
19. }
20. else{
21. if(!CryptAcquireContext(&hCryptProv,
22. NULL,
23. CSP_NAME,
24. PROV_RSA_AES,
25. CRYPT_NEWKEYSET))
26. {
27. return;
28. }
29. }
30. }
31. if(!CryptCreateHash(hCryptProv, CALG_MD5, 0, 0, &hHash))
32. {
33. return;
34. }
36. BYTE *pPwd = pwd;
38. if(!CryptHashData(hHash, pPwd, 16, 0))
39. {
40. return;
41. }
43. if(!CryptDeriveKey(hCryptProv, CALG_AES_128, hHash, CRYPT_EXPORTABLE, &hKey))
44. {
45. return;
46. }
48. int len = text.length();
49. BYTE *pData ;
50. pData = (BYTE*)malloc(len*4);
51. memcpy(pData,text.c_str(),len);
52. DWORD dwLen = len;
54. if(!CryptEncrypt(hKey, NULL, true, 0, pData, &dwLen, len*4))
55. {
56. return;
57. }
59. cout <<"--------------------------" << endl << "cryptoAPI encrypt"<<endl;
60. printBytes(pData,dwLen);
61. *encryptText = pData;
62. out_len = dwLen;
63. CryptDestroyHash(hHash);
64. CryptDestroyKey(hKey);
65. CryptReleaseContext(hCryptProv,0);
66. }

這裡將傳進來的字節數組密鑰先進行MD5摘要後,再通過CryptoDeriveKey來得到最後用來加密的密鑰

openssl要以同樣的方式做一次這個步驟,首先是MD5摘要,相對比較簡單

1. unsigned char* openssl_md5(unsigned char*sessionKey,size_t n)
2. {
3. unsigned char *ret = (unsigned char*)malloc(MD5_DIGEST_LENGTH);
4. MD5(sessionKey,n,ret);
5. return ret;
6. }

然後再來實現CryptoDeriveKey,先來看下MSDN上對於這個函數的說明

主要看remarks裡面的實現步驟:

1. Let n be the required derived key length, in bytes. The derived key is the first n bytes of the hash value after the hash computation has been completed by CryptDeriveKey. If the hash is not a member of the SHA-2 family and the required key is for either 3DES or AES, the key is derived as follows:
3. 1.Form a 64-byte buffer by repeating the constant 0x36 64 times. Let k be the length of the hash value that is represented by the input parameter hBaseData. Set the first k bytes of the buffer to the result of an XOR operation of the first k bytes of the buffer with the hash value that is represented by the input parameter hBaseData.
4. 2.Form a 64-byte buffer by repeating the constant 0x5C 64 times. Set the first k bytes of the buffer to the result of an XOR operation of the first k bytes of the buffer with the hash value that is represented by the input parameter hBaseData.
5. 3.Hash the result of step 1 by using the same hash algorithm as that used to compute the hash value that is represented by the hBaseData parameter.
6. 4.Hash the result of step 2 by using the same hash algorithm as that used to compute the hash value that is represented by the hBaseData parameter.
7. 5.Concatenate the result of step 3 with the result of step 4.
8. 6.Use the first n bytes of the result of step 5 as the derived key.

非常簡單的英文,不做翻譯了...

直接上openssl代碼實現

1. //參見 http://msdn.microsoft.com/en-us/library/aa379916(v=vs.85).aspx remarks步驟
2. unsigned char* derivedKey(unsigned char*sessionKey/*hash後的值*/,size_t n/*密鑰長度*/)
3. {
4. /**step 1*/
5. unsigned char* buffer = (unsigned char*)malloc(64);
7. for(int i = 0 ; i < 64;i++)
8. {
9. buffer[i] = 0x36;
10. }
12. int k = n;
14. for(int i = 0 ; i < k ; i++)
15. {
16. buffer[i] = buffer[i] ^ sessionKey[i];
17. }
19. /*step 2*/
20. unsigned char* buffer2 = (unsigned char*)malloc(64);
22. for(int i = 0 ; i < 64;i++)
23. {
24. buffer2[i] = 0x5C;
25. }
27. for(int i = 0 ; i < k ; i++)
28. {
29. buffer2[i] = buffer2[i] ^ sessionKey[i];
30. }
31. /*step 3*/
32. unsigned char* ret1 = openssl_md5(buffer,64);
33. /*step 4*/
34. unsigned char* ret2 = openssl_md5(buffer2,64);
37. unsigned char* ret = (unsigned char*)malloc(128);
38. for(int i = 0 ; i < 128;i++)
39. {
40. if(i<64)
41. ret[i] = ret1[i];
42. else
43. ret[i] = ret2[i-64];
44. }
45. return ret;
46. }

最麻煩的地方解決了...剩下再按照CryptoAPI的實現順序實現吧

1. void openssl_aes_encrypt(string text,unsigned char** SessionKey_out/*這裡主要用作將產生的對稱密鑰輸出*/,unsigned char* sEncryptMsg,int &len)
2. {
3. OpenSSL_add_all_algorithms();
4. //產生會話密鑰
5. *SessionKey_out = (unsigned char*)malloc(MD5_SIZE);
6. RAND_bytes(*SessionKey_out,MD5_SIZE);//產生隨機密鑰,輸出之後可以給其他方法是用了
7. unsigned char* SessionKey = openssl_md5(*SessionKey_out,MD5_SIZE);
9. SessionKey = derivedKey(SessionKey,MD5_SIZE);
11. const unsigned char* sMsg = (const unsigned char*)text.c_str();
12. int cbMsg = text.length();
13. int cbEncryptMsg;
14. //加密
15. EVP_CIPHER_CTX ctx;
16. EVP_CIPHER_CTX_init(&ctx);
17. if(EVP_EncryptInit_ex(&ctx,EVP_get_cipherbynid(NID_aes_128_cbc),NULL,SessionKey,NULL))
18. {
19. int offseti=0;//in
20. int offseto=0;//out
21. int offsett=0;//temp
22. for(;;)
23. {
24. if(cbMsg-offseti<=MAX_ENCRYPT_LEN)
25. {
26. EVP_EncryptUpdate(&ctx, sEncryptMsg+offseto, &offsett, sMsg+offseti, cbMsg-offseti);
27. offseto+=offsett;
28. break;
29. }
30. else
31. {
32. EVP_EncryptUpdate(&ctx, sEncryptMsg+offseto, &offsett, sMsg+offseti, MAX_ENCRYPT_LEN);
33. offseti+=MAX_ENCRYPT_LEN;
34. offseto+=offsett;
35. }
36. }
37. EVP_EncryptFinal_ex(&ctx, sEncryptMsg+offseto, &offsett);
38. offseto+=offsett;
39. cbEncryptMsg=offseto;
40. }
41. EVP_CIPHER_CTX_cleanup(&ctx);
42. std::cout << "openssl encrypt:" << std::endl;
43. printBytes(sEncryptMsg,cbEncryptMsg);
44. len = cbEncryptMsg;
45. }

加密的搞定了,可以嘗試下了,同樣的密鑰和同樣的明文,密文輸出結果是一樣的就對了

下面是CrytpoAPI的解密:

1. void cryptAPI_decrypt(unsigned char* text,int len,unsigned char* pwd)
2. {
3. HCRYPTPROV hCryptProv = NULL;
4. HCRYPTKEY hKey = 0;
5. HCRYPTHASH hHash = 0;
6. int dwLength = 0;
8. if(!CryptAcquireContext(&hCryptProv,
9. NULL,
10. CSP_NAME,//CSP_NAME
11. PROV_RSA_AES,
12. CRYPT_VERIFYCONTEXT))
13. {
14. DWORD dwLastErr = GetLastError();
16. if(NTE_BAD_KEYSET == dwLastErr)
17. {
18. return;
19. }
20. else{
21. if(!CryptAcquireContext(&hCryptProv,
22. NULL,
23. CSP_NAME,
24. PROV_RSA_AES,
25. CRYPT_NEWKEYSET))
26. {
27. return;
28. }
29. }
30. }
33. if(!CryptCreateHash(hCryptProv, CALG_MD5, 0, 0, &hHash))
34. {
35. return;
36. }
38. BYTE *pPwd = pwd;
40. if(!CryptHashData(hHash, pPwd, 16, 0))
41. {
42. return;
43. }
45. if(!CryptDeriveKey(hCryptProv, CALG_AES_128, hHash, CRYPT_EXPORTABLE, &hKey))
46. {
47. return;
48. }
50. BYTE *pData = text;
51. DWORD dwLen = len;
53. if(!CryptDecrypt(hKey, NULL, true, 0, pData, &dwLen))
54. {
55. return;
56. }
58. cout <<"--------------------------" << endl << "cryptoAPI decrypt"<<endl;
59. char* plainText = (char*)malloc(dwLen + 1);
60. memcpy(plainText,pData,dwLen);
61. plainText[dwLen] = '\0';
62. cout << plainText << endl;
63. CryptDestroyHash(hHash);
64. CryptDestroyKey(hKey);
65. CryptReleaseContext(hCryptProv,0);
66. }

嘗試用這個方法解密CryptoAPI的加密和openssl的加密吧,都能輸出明文的

再來最後一個,openssl的解密

1. void openssl_aes_decrypt(unsigned char* text,int len,unsigned char* SessionKeyP)
2. {
3. unsigned char* decryptMsg = (unsigned char*)malloc(len);
5. OpenSSL_add_all_algorithms();
7. unsigned char* SessionKey = openssl_md5(SessionKeyP,MD5_SIZE);
9. SessionKey = derivedKey(SessionKey,MD5_SIZE);
11. const unsigned char* sMsg = text;
12. int cbMsg = len;
13. int cbEncryptMsg;
14. //解密
15. EVP_CIPHER_CTX ctx;
16. EVP_CIPHER_CTX_init(&ctx);
18. if(EVP_DecryptInit_ex(&ctx,EVP_get_cipherbynid(NID_aes_128_cbc),NULL,SessionKey,NULL))
19. {
20. int offseti=0;//in
21. int offseto=0;//out
22. int offsett=0;//temp
23. for(;;)
24. {
25. if(cbMsg-offseti<=MAX_ENCRYPT_LEN)
26. {
27. EVP_DecryptUpdate(&ctx, decryptMsg+offseto, &offsett, sMsg+offseti, cbMsg-offseti);
28. offseto+=offsett;
29. break;
30. }
31. else
32. {
33. EVP_DecryptUpdate(&ctx, decryptMsg+offseto, &offsett, sMsg+offseti, MAX_ENCRYPT_LEN);
34. offseti+=MAX_ENCRYPT_LEN;
35. offseto+=offsett;
36. }
37. }
38. EVP_DecryptFinal_ex(&ctx, decryptMsg+offseto, &offsett);
40. offseto+=offsett;
41. cbEncryptMsg=offseto;
42. }
43. EVP_CIPHER_CTX_cleanup(&ctx);
44. std::cout << "openssl decrypt:" << std::endl;
47. char* ret = (char*)malloc(cbEncryptMsg + 1);
48. memcpy(ret,decryptMsg,cbEncryptMsg);
49. ret[cbEncryptMsg] = '\0';
50. std::cout << ret << endl;
51. }

測試下:

1. int _tmain(int argc, _TCHAR* argv[])
2. {
3. string text = "texttexttexttexttext";
4. unsigned char* key;
5. unsigned char* sEncryptMsg = (unsigned char*)malloc(text.size() + MD5_SIZE);
6. int len;
7. openssl_aes_encrypt(text,&key,sEncryptMsg,len);
10. unsigned char** sEncryptMsg_crypto = (unsigned char**)malloc(sizeof(unsigned char*));
11. int len_crypto;
12. cryptoAPI_encrypt(text,key,sEncryptMsg_crypto,len_crypto);
13. cout << "-----------------------------" << endl<<"cryptoAPI decrypt openssl"<<endl;
14. //cryptAPI_decrypt(sEncryptMsg,len,key);
16. cout << "-----------------------------" << endl<<"cryptoAPI decrypt cryptoAPI"<<endl;
17. //cryptAPI_decrypt(*sEncryptMsg_crypto,len_crypto,key);
19. cout << "-----------------------------" << endl<<"oepnssl decrypt openssl"<<endl;
20. //openssl_aes_decrypt(sEncryptMsg,len,key);
22. cout << "-----------------------------" << endl<<"oepnssl decrypt cryptoAPI"<<endl;
23. //openssl_aes_decrypt(*sEncryptMsg_crypto,len_crypto,key);
24. return 0;
25. }