cryptocb.h

Functions

	Name
int	wc_CryptoCb_RegisterDevice(int devId, CryptoDevCallbackFunc cb, void * ctx) This function registers a unique device identifier (devID) and callback function for offloading crypto operations to external hardware such as Key Store, Secure Element, HSM, PKCS11 or TPM.
void	wc_CryptoCb_UnRegisterDevice(int devId) This function un_registers a unique device identifier (devID) callback function.
int	wc_CryptoCb_DefaultDevID(void ) This function returns the default device ID for crypto callbacks. This is useful when you want to get the device ID that was set as the default for the library.
void	wc_CryptoCb_SetDeviceFindCb(CryptoDevCallbackFind cb) This function sets a callback for finding crypto devices. The callback is invoked when a device ID needs to be resolved to a device context. This is useful for dynamic device management.
void	wc_CryptoCb_InfoString(wc_CryptoInfo * info) This function converts a wc_CryptoInfo structure to a human-readable string for debugging purposes. The string is printed to stdout and describes the cryptographic operation being performed.
int	wc_CryptoCb_AesSetKey(Aes * aes, const byte * key, word32 keySz) Import an AES key into a CryptoCB device for hardware offload.

Functions Documentation

function wc_CryptoCb_RegisterDevice

int wc_CryptoCb_RegisterDevice(
    int devId,
    CryptoDevCallbackFunc cb,
    void * ctx
)

This function registers a unique device identifier (devID) and callback function for offloading crypto operations to external hardware such as Key Store, Secure Element, HSM, PKCS11 or TPM.

Parameters:

• devId any unique value, not -2 (INVALID_DEVID)
• cb a callback function with prototype: typedef int (CryptoDevCallbackFunc)(int devId, wc_CryptoInfo info, void* ctx);

See:

• wc_CryptoCb_UnRegisterDevice
• wolfSSL_SetDevId
• wolfSSL_CTX_SetDevId

Return:

• CRYPTOCB_UNAVAILABLE to fallback to using software crypto
• 0 for success
• negative value for failure

For STSAFE with Crypto Callbacks example see wolfcrypt/src/port/st/stsafe.c and the wolfSSL_STSAFE_CryptoDevCb function.

For TPM based crypto callbacks example see the wolfTPM2_CryptoDevCb function in wolfTPM src/tpm2_wrap.c

Example

#include <wolfssl/wolfcrypt/settings.h>
#include <wolfssl/wolfcrypt/cryptocb.h>
static int myCryptoCb_Func(int devId, wc_CryptoInfo* info, void* ctx)
{
    int ret = CRYPTOCB_UNAVAILABLE;

    if (info->algo_type == WC_ALGO_TYPE_PK) {
    #ifndef NO_RSA
        if (info->pk.type == WC_PK_TYPE_RSA) {
            switch (info->pk.rsa.type) {
                case RSA_PUBLIC_ENCRYPT:
                case RSA_PUBLIC_DECRYPT:
                    // RSA public op
                    ret = wc_RsaFunction(
                        info->pk.rsa.in, info->pk.rsa.inLen,
                        info->pk.rsa.out, info->pk.rsa.outLen,
                        info->pk.rsa.type, info->pk.rsa.key,
                        info->pk.rsa.rng);
                    break;
                case RSA_PRIVATE_ENCRYPT:
                case RSA_PRIVATE_DECRYPT:
                    // RSA private op
                    ret = wc_RsaFunction(
                        info->pk.rsa.in, info->pk.rsa.inLen,
                        info->pk.rsa.out, info->pk.rsa.outLen,
                        info->pk.rsa.type, info->pk.rsa.key,
                        info->pk.rsa.rng);
                    break;
            }
        }
    #endif
    #ifdef HAVE_ECC
        if (info->pk.type == WC_PK_TYPE_ECDSA_SIGN) {
            // ECDSA
            ret = wc_ecc_sign_hash(
                info->pk.eccsign.in, info->pk.eccsign.inlen,
                info->pk.eccsign.out, info->pk.eccsign.outlen,
                info->pk.eccsign.rng, info->pk.eccsign.key);
        }
    #endif
    #ifdef HAVE_ED25519
        if (info->pk.type == WC_PK_TYPE_ED25519_SIGN) {
            // ED25519 sign
            ret = wc_ed25519_sign_msg_ex(
                info->pk.ed25519sign.in, info->pk.ed25519sign.inLen,
                info->pk.ed25519sign.out, info->pk.ed25519sign.outLen,
                info->pk.ed25519sign.key, info->pk.ed25519sign.type,
                info->pk.ed25519sign.context,
                info->pk.ed25519sign.contextLen);
        }
    #endif
    }
    return ret;
}

int devId = 1;
wc_CryptoCb_RegisterDevice(devId, myCryptoCb_Func, &myCtx);
wolfSSL_CTX_SetDevId(ctx, devId);

function wc_CryptoCb_UnRegisterDevice

void wc_CryptoCb_UnRegisterDevice(
    int devId
)

This function un-registers a unique device identifier (devID) callback function.

Parameters:

• devId any unique value, not -2 (INVALID_DEVID)

See:

• wc_CryptoCb_RegisterDevice
• wolfSSL_SetDevId
• wolfSSL_CTX_SetDevId

Return: none No returns.

Example

wc_CryptoCb_UnRegisterDevice(devId);
devId = INVALID_DEVID;
wolfSSL_CTX_SetDevId(ctx, devId);

function wc_CryptoCb_DefaultDevID

int wc_CryptoCb_DefaultDevID(
    void 
)

This function returns the default device ID for crypto callbacks. This is useful when you want to get the device ID that was set as the default for the library.

See:

• wc_CryptoCb_RegisterDevice
• wc_CryptoCb_UnRegisterDevice

Return: The default device ID, or INVALID_DEVID if no default is set.

Example

int devId = wc_CryptoCb_DefaultDevID();
if (devId != INVALID_DEVID) {
    // default device ID is set
}

function wc_CryptoCb_SetDeviceFindCb

void wc_CryptoCb_SetDeviceFindCb(
    CryptoDevCallbackFind cb
)

This function sets a callback for finding crypto devices. The callback is invoked when a device ID needs to be resolved to a device context. This is useful for dynamic device management.

Parameters:

• cb callback function with prototype: typedef void (CryptoDevCallbackFind)(int devId);

See: wc_CryptoCb_RegisterDevice

Return: none No returns.

Example

void* myDeviceFindCb(int devId) {
    // lookup device context by ID
    return deviceContext;
}

wc_CryptoCb_SetDeviceFindCb(myDeviceFindCb);

function wc_CryptoCb_InfoString

void wc_CryptoCb_InfoString(
    wc_CryptoInfo * info
)

This function converts a wc_CryptoInfo structure to a human-readable string for debugging purposes. The string is printed to stdout and describes the cryptographic operation being performed.

Parameters:

• info pointer to the wc_CryptoInfo structure to convert

See: wc_CryptoCb_RegisterDevice

Return: none No returns.

Example

int myCryptoCb(int devId, wc_CryptoInfo* info, void* ctx) {
    // print debug info about the operation
    wc_CryptoCb_InfoString(info);

    // handle the operation
    return CRYPTOCB_UNAVAILABLE;
}

function wc_CryptoCb_AesSetKey

int wc_CryptoCb_AesSetKey(
    Aes * aes,
    const byte * key,
    word32 keySz
)

Import an AES key into a CryptoCB device for hardware offload.

Parameters:

• aes AES context
• key Pointer to raw AES key material
• keySz Size of key in bytes

See:

• wc_CryptoCb_RegisterDevice
• wc_AesInit

Return:

• 0 on success
• CRYPTOCB_UNAVAILABLE if device does not support this operation
• BAD_FUNC_ARG on invalid parameters

This function allows AES keys to be handled by an external device (e.g. Secure Element or HSM). When supported, the device callback stores the key internally and sets an opaque handle in aes->devCtx.

When CryptoCB AES SetKey support is enabled (WOLF_CRYPTO_CB_AES_SETKEY), wolfCrypt routes AES-GCM operations through the CryptoCB interface.

TLS Builds (Default):**

• Key bytes ARE stored in wolfCrypt memory (devKey) for fallback
• GCM tables ARE generated for software fallback
• Provides hardware acceleration with automatic fallback Crypto-Only Builds (–disable-tls):**
• Key bytes NOT stored in wolfCrypt memory (true key isolation)
• GCM tables skipped (true hardware offload)
• Callback must handle all GCM operations (SetKey, Encrypt, Decrypt, Free)

If the callback returns success (0), full AES-GCM offload is assumed. The callback must handle SetKey, Encrypt, Decrypt, and Free operations.

Example

#include <wolfssl/wolfcrypt/cryptocb.h>
#include <wolfssl/wolfcrypt/aes.h>

Aes aes;
byte key[32] = { /* 256-bit key */ };
int devId = 1;

/* Register your CryptoCB callback first */
wc_CryptoCb_RegisterDevice(devId, myCryptoCallback, NULL);

wc_AesInit(&aes, NULL, devId);
/* wc_AesGcmSetKey internally calls wc_CryptoCb_AesSetKey */
if (wc_CryptoCb_AesSetKey(&aes, key, sizeof(key)) == 0) {
    /* Key successfully imported to device via callback */
    /* aes.devCtx now contains device handle */
    /* Full GCM offload is assumed - callback must handle all operations */
}

Source code

int  wc_CryptoCb_RegisterDevice(int devId, CryptoDevCallbackFunc cb, void* ctx);

void wc_CryptoCb_UnRegisterDevice(int devId);

int wc_CryptoCb_DefaultDevID(void);

void wc_CryptoCb_SetDeviceFindCb(CryptoDevCallbackFind cb);

void wc_CryptoCb_InfoString(wc_CryptoInfo* info);
 };
    int devId = 1;

    /* Register your CryptoCB callback first */
    wc_CryptoCb_RegisterDevice(devId, myCryptoCallback, NULL);

    wc_AesInit(&aes, NULL, devId);
    /* wc_AesGcmSetKey internally calls wc_CryptoCb_AesSetKey */
    if (wc_CryptoCb_AesSetKey(&aes, key, sizeof(key)) == 0) {
        /* Key successfully imported to device via callback */
        /* aes.devCtx now contains device handle */
        /* Full GCM offload is assumed - callback must handle all operations */
    }
    \endcode

    \sa wc_CryptoCb_RegisterDevice
    \sa wc_AesInit
*/
int wc_CryptoCb_AesSetKey(Aes* aes, const byte* key, word32 keySz);

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Updated on 2026-02-20 at 02:00:32 +0000