Asymmetric Cipher Algorithm Definitions¶

struct akcipher_request¶: public key request

Definition:

struct akcipher_request {
    struct crypto_async_request base;
    struct scatterlist *src;
    struct scatterlist *dst;
    unsigned int src_len;
    unsigned int dst_len;
    void *__ctx[] ;
};

Members

base: Common attributes for async crypto requests
src: Source data For verify op this is signature + digest, in that case total size of src is src_len + dst_len.
dst: Destination data (Should be NULL for verify op)
src_len: Size of the input buffer For verify op it’s size of signature part of src, this part is supposed to be operated by cipher.
dst_len: Size of dst buffer (for all ops except verify). It needs to be at least as big as the expected result depending on the operation. After operation it will be updated with the actual size of the result. In case of error where the dst sgl size was insufficient, it will be updated to the size required for the operation. For verify op this is size of digest part in src.
__ctx: Start of private context data

struct akcipher_alg¶: generic public key algorithm

Definition:

struct akcipher_alg {
    int (*sign)(struct akcipher_request *req);
    int (*verify)(struct akcipher_request *req);
    int (*encrypt)(struct akcipher_request *req);
    int (*decrypt)(struct akcipher_request *req);
    int (*set_pub_key)(struct crypto_akcipher *tfm, const void *key, unsigned int keylen);
    int (*set_priv_key)(struct crypto_akcipher *tfm, const void *key, unsigned int keylen);
    unsigned int (*max_size)(struct crypto_akcipher *tfm);
    int (*init)(struct crypto_akcipher *tfm);
    void (*exit)(struct crypto_akcipher *tfm);
    struct crypto_alg base;
};

Members

sign: Function performs a sign operation as defined by public key algorithm. In case of error, where the dst_len was insufficient, the req->dst_len will be updated to the size required for the operation
verify: Function performs a complete verify operation as defined by public key algorithm, returning verification status. Requires digest value as input parameter.
encrypt: Function performs an encrypt operation as defined by public key algorithm. In case of error, where the dst_len was insufficient, the req->dst_len will be updated to the size required for the operation
decrypt: Function performs a decrypt operation as defined by public key algorithm. In case of error, where the dst_len was insufficient, the req->dst_len will be updated to the size required for the operation
set_pub_key: Function invokes the algorithm specific set public key function, which knows how to decode and interpret the BER encoded public key and parameters
set_priv_key: Function invokes the algorithm specific set private key function, which knows how to decode and interpret the BER encoded private key and parameters
max_size: Function returns dest buffer size required for a given key.
init: Initialize the cryptographic transformation object. This function is used to initialize the cryptographic transformation object. This function is called only once at the instantiation time, right after the transformation context was allocated. In case the cryptographic hardware has some special requirements which need to be handled by software, this function shall check for the precise requirement of the transformation and put any software fallbacks in place.
exit: Deinitialize the cryptographic transformation object. This is a counterpart to init, used to remove various changes set in init.
base: Common crypto API algorithm data structure

Asymmetric Cipher API¶

The Public Key API is used with the algorithms of type CRYPTO_ALG_TYPE_AKCIPHER (listed as type “akcipher” in /proc/crypto)

struct crypto_akcipher *crypto_alloc_akcipher(const char *alg_name, u32 type, u32 mask)¶: allocate AKCIPHER tfm handle

Parameters

const char *alg_name: is the cra_name / name or cra_driver_name / driver name of the public key algorithm e.g. “rsa”
u32 type: specifies the type of the algorithm
u32 mask: specifies the mask for the algorithm

Description

Allocate a handle for public key algorithm. The returned struct crypto_akcipher is the handle that is required for any subsequent API invocation for the public key operations.

Return

allocated handle in case of success; IS_ERR() is true in case: of an error, PTR_ERR() returns the error code.

void crypto_free_akcipher(struct crypto_akcipher *tfm)¶: free AKCIPHER tfm handle

Parameters

struct crypto_akcipher *tfm: AKCIPHER tfm handle allocated with crypto_alloc_akcipher()

Description

If tfm is a NULL or error pointer, this function does nothing.

unsigned int crypto_akcipher_maxsize(struct crypto_akcipher *tfm)¶: Get len for output buffer

Parameters

struct crypto_akcipher *tfm: AKCIPHER tfm handle allocated with crypto_alloc_akcipher()

Description

Function returns the dest buffer size required for a given key. Function assumes that the key is already set in the transformation. If this function is called without a setkey or with a failed setkey, you will end up in a NULL dereference.

int crypto_akcipher_encrypt(struct akcipher_request *req)¶: Invoke public key encrypt operation

Parameters

struct akcipher_request *req: asymmetric key request

Description

Function invokes the specific public key encrypt operation for a given public key algorithm

Return

zero on success; error code in case of error

int crypto_akcipher_decrypt(struct akcipher_request *req)¶: Invoke public key decrypt operation

Parameters

struct akcipher_request *req: asymmetric key request

Description

Function invokes the specific public key decrypt operation for a given public key algorithm

Return

zero on success; error code in case of error

int crypto_akcipher_sign(struct akcipher_request *req)¶: Invoke public key sign operation

Parameters

struct akcipher_request *req: asymmetric key request

Description

Function invokes the specific public key sign operation for a given public key algorithm

Return

zero on success; error code in case of error

int crypto_akcipher_verify(struct akcipher_request *req)¶: Invoke public key signature verification

Parameters

struct akcipher_request *req: asymmetric key request

Description

Function invokes the specific public key signature verification operation for a given public key algorithm.

Note

req->dst should be NULL, req->src should point to SG of size (req->src_size + req->dst_size), containing signature (of req->src_size length) with appended digest (of req->dst_size length).

Return

zero on verification success; error code in case of error.

int crypto_akcipher_set_pub_key(struct crypto_akcipher *tfm, const void *key, unsigned int keylen)¶: Invoke set public key operation

Parameters

struct crypto_akcipher *tfm: tfm handle
const void *key: BER encoded public key, algo OID, paramlen, BER encoded parameters
unsigned int keylen: length of the key (not including other data)

Description

Function invokes the algorithm specific set key function, which knows how to decode and interpret the encoded key and parameters

Return

zero on success; error code in case of error

int crypto_akcipher_set_priv_key(struct crypto_akcipher *tfm, const void *key, unsigned int keylen)¶: Invoke set private key operation

Parameters

struct crypto_akcipher *tfm: tfm handle
const void *key: BER encoded private key, algo OID, paramlen, BER encoded parameters
unsigned int keylen: length of the key (not including other data)

Description

Function invokes the algorithm specific set key function, which knows how to decode and interpret the encoded key and parameters

Return

zero on success; error code in case of error

Asymmetric Cipher Request Handle¶

struct akcipher_request *akcipher_request_alloc(struct crypto_akcipher *tfm, gfp_t gfp)¶: allocates public key request

Parameters

struct crypto_akcipher *tfm: AKCIPHER tfm handle allocated with crypto_alloc_akcipher()
gfp_t gfp: allocation flags

Return

allocated handle in case of success or NULL in case of an error.

void akcipher_request_free(struct akcipher_request *req)¶: zeroize and free public key request

Parameters

struct akcipher_request *req: request to free

void akcipher_request_set_callback(struct akcipher_request *req, u32 flgs, crypto_completion_t cmpl, void *data)¶: Sets an asynchronous callback.

Parameters

struct akcipher_request *req: request that the callback will be set for
u32 flgs: specify for instance if the operation may backlog
crypto_completion_t cmpl: callback which will be called
void *data: private data used by the caller

Description

Callback will be called when an asynchronous operation on a given request is finished.

void akcipher_request_set_crypt(struct akcipher_request *req, struct scatterlist *src, struct scatterlist *dst, unsigned int src_len, unsigned int dst_len)¶: Sets request parameters

Parameters

struct akcipher_request *req: public key request
struct scatterlist *src: ptr to input scatter list
struct scatterlist *dst: ptr to output scatter list or NULL for verify op
unsigned int src_len: size of the src input scatter list to be processed
unsigned int dst_len: size of the dst output scatter list or size of signature portion in src for verify op

Description

Sets parameters required by crypto operation