pkcs11 TLS example: how to avoid performing symmetric crypto on token?

space88man commented 2 weeks ago

Version

5.7.2

Description

Using wolfSSL TLS with a PKCS#11 private key : how can I restrict the token to asymmetric operations and perform symmetric operations in wolfSSL?

IOW: I only want to do C_Sign on token and let wolfSSL take care of any AES operations.

In two tokens I tested (libCryptoki2_64, libsoftoken3) the C_Sign succeeds but the server accept fails due to AES failures.

Using PKCS#11 server example : -https://github.com/wolfSSL/wolfssl-examples/blob/master/pkcs11/server-tls-pkcs11-ecc.c

wolfSSL also uses the token for AES-GCM:

LUNA libCryptoki2_64 fails at this AES part:

# pkcs11-spy dump
30: C_CreateObject
2024-07-09 22:50:11.314
[in] hSession = 0x1
[in] pTemplate[5]: 
    CKA_CLASS             CKO_SECRET_KEY       
    CKA_KEY_TYPE          CKK_AES            
    CKA_ENCRYPT           True
    CKA_DECRYPT           True
    CKA_VALUE             0000000000b0f66c / 32
    00000000  57 CE E3 50 D8 E0 F9 C3 2E 3F D7 83 BA 1B 5B 13  W..P.....?....[.
    00000010  0E DF 00 98 ED 2B 50 AB 72 7C CD 25 D5 10 8B 1A  .....+P.r|.%....
Returned:  209 CKR_TEMPLATE_INCONSISTENT

NSS softoken fails at this AES part:

127: C_CreateObject
2024-07-09 23:15:01.487
[in] hSession = 0x1000001
[in] pTemplate[5]: 
    CKA_CLASS             CKO_SECRET_KEY       
    CKA_KEY_TYPE          CKK_AES            
    CKA_ENCRYPT           True
    CKA_DECRYPT           True
    CKA_VALUE             000000000233bbec / 32
    00000000  A7 5F 7C 5F 20 E8 88 2F 99 03 0D 91 71 24 02 AF  ._|_ ../....q$..
    00000010  22 FC 6A 70 D7 63 4C E8 E4 B5 AC 7A 12 53 98 51  ".jp.cL....z.S.Q
[out] *phObject = 0xf
Returned:  0 CKR_OK

128: C_DecryptInit
2024-07-09 23:15:01.487
[in] hSession = 0x1000001
[in] pMechanism->type = CKM_AES_GCM                  
[in] pMechanism->pParameter->pIv[ulIvLen] 000000000233d180 / 12
    00000000  2C 4D EC 1D 18 85 0B A1 81 1C 57 90              ,M........W.    
[in] pMechanism->pParameter->ulIvBits = 0x0
[in] pMechanism->pParameter->pAAD[ulAADLen] 000000000233a560 / 13
    00000000  00 00 00 00 00 00 00 00 16 03 03 00 10           .............   
[in] pMechanism->pParameter->ulTagBits = 128
[in] hKey = 0xf
Returned:  113 CKR_MECHANISM_PARAM_INVALID

Additional Notes

with OpenSSL s_server with either 1.1.1 and openssl-pkcs11 (engine) or 3.x.x and pkcs11-provider (provider) the software library symmetric operations take precedence and only C_Sign is perfomed on token

SparkiDev commented 2 weeks ago

Hi @space88man,

If you do not want to perform symmetric algorithm operations with PKCS#11 then you can define: NO_PKCS11_AES. You may also want to define: NO_PKCS11_HMAC and NO_PKCS11_RNG.

You can also implement your own callback that calls wc_Pkcs11_CryptoDevCb for only the algorithms you want. Anything not using PKCS#11 needs to return NOT_COMPILED_IN. The devId can be used to identify where the operation is coming from. That is use a different identifier for TLS to another context.

Let me know which option you choose and whether it works.

Sean

space88man commented 2 weeks ago

Hi @SparkiDev

Thanks — I tried something like this: where 1 = real PKCS#11 devID, 2 = filter devID, and it works. Does this look correct to you?

/*
 * Filter callback that will passthrough only PK operations
 * to the real devID(== 1)
 * /
int my_FilterCb(int devId, wc_CryptoInfo* info, void* ctx)
{
        int ret = 0;
        // assert (devId == 2);
        fprintf(stderr, "[%d] filter callback -> %d\n", devId, info->algo_type);
        if (info->algo_type != WC_ALGO_TYPE_PK)
                return NOT_COMPILED_IN;
        // call the real PKCS#11 device
        return wc_Pkcs11_CryptoDevCb(1, info, ctx);
}

SparkiDev commented 2 weeks ago

Hi @space88man,

The code looks good assuming you are setting the devId for TLS connections to 2. Note: 'ret' is not needed in the function as you have it.

Is there anything more for this issue?

Thanks, Sean

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