Key-agreement Protocol Primitives (KPP) Cipher Algorithm Definitions

struct kpp_request

Definition:

struct kpp_request {
    struct crypto_async_request base;
    struct scatterlist *src;
    struct scatterlist *dst;
    unsigned int src_len;
    unsigned int dst_len;
    UEK_KABI_RESERVE(1) void *__ctx[] ;
};

Members

base

Common attributes for async crypto requests

src

Source data

dst

Destination data

src_len

Size of the input buffer

dst_len

Size of the output buffer. 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.

__ctx

Start of private context data

struct crypto_kpp

user-instantiated object which encapsulate algorithms and core processing logic

Definition:

struct crypto_kpp {
    unsigned int reqsize;
    struct crypto_tfm base;
};

Members

reqsize

Request context size required by algorithm implementation

base

Common crypto API algorithm data structure

struct kpp_alg

generic key-agreement protocol primitives

Definition:

struct kpp_alg {
    int (*set_secret)(struct crypto_kpp *tfm, const void *buffer, unsigned int len);
    int (*generate_public_key)(struct kpp_request *req);
    int (*compute_shared_secret)(struct kpp_request *req);
    unsigned int (*max_size)(struct crypto_kpp *tfm);
    int (*init)(struct crypto_kpp *tfm);
    void (*exit)(struct crypto_kpp *tfm);
    UEK_KABI_RESERVE(1)UEK_KABI_RESERVE(2) struct crypto_alg base;
};

Members

set_secret

Function invokes the protocol specific function to store the secret private key along with parameters. The implementation knows how to decode the buffer

generate_public_key

Function generate the public key to be sent to the counterpart. In case of error, where output is not big enough req->dst_len will be updated to the size required

compute_shared_secret

Function compute the shared secret as defined by the algorithm. The result is given back to the user. In case of error, where output is not big enough, req->dst_len will be updated to the size required

max_size

Function returns the size of the output buffer

init

Initialize the object. This is called only once at instantiation time. In case the cryptographic hardware needs to be initialized. Software fallback should be put in place here.

exit

Undo everything init did.

base

Common crypto API algorithm data structure

struct kpp_secret

small header for packing secret buffer

Definition:

struct kpp_secret {
    unsigned short type;
    unsigned short len;
};

Members

type

define type of secret. Each kpp type will define its own

len

specify the len of the secret, include the header, that follows the struct

Key-agreement Protocol Primitives (KPP) Cipher API

The KPP API is used with the algorithm type CRYPTO_ALG_TYPE_KPP (listed as type “kpp” in /proc/crypto)

void crypto_free_kpp(struct crypto_kpp *tfm)

free KPP tfm handle

Parameters

struct crypto_kpp *tfm

KPP tfm handle allocated with crypto_alloc_kpp()

Description

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

int crypto_kpp_set_secret(struct crypto_kpp *tfm, const void *buffer, unsigned int len)

Invoke kpp operation

Parameters

struct crypto_kpp *tfm

tfm handle

const void *buffer

Buffer holding the packet representation of the private key. The structure of the packet key depends on the particular KPP implementation. Packing and unpacking helpers are provided for ECDH and DH (see the respective header files for those implementations).

unsigned int len

Length of the packet private key buffer.

Description

Function invokes the specific kpp operation for a given alg.

Return

zero on success; error code in case of error

int crypto_kpp_generate_public_key(struct kpp_request *req)

Invoke kpp operation

Parameters

struct kpp_request *req

kpp key request

Description

Function invokes the specific kpp operation for generating the public part for a given kpp algorithm.

To generate a private key, the caller should use a random number generator. The output of the requested length serves as the private key.

Return

zero on success; error code in case of error

int crypto_kpp_compute_shared_secret(struct kpp_request *req)

Invoke kpp operation

Parameters

struct kpp_request *req

kpp key request

Description

Function invokes the specific kpp operation for computing the shared secret for a given kpp algorithm.

Return

zero on success; error code in case of error

unsigned int crypto_kpp_maxsize(struct crypto_kpp *tfm)

Get len for output buffer

Parameters

struct crypto_kpp *tfm

KPP tfm handle allocated with crypto_alloc_kpp()

Description

Function returns the output 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.

Key-agreement Protocol Primitives (KPP) Cipher Request Handle

struct kpp_request *kpp_request_alloc(struct crypto_kpp *tfm, gfp_t gfp)

allocates kpp request

Parameters

struct crypto_kpp *tfm

KPP tfm handle allocated with crypto_alloc_kpp()

gfp_t gfp

allocation flags

Return

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

void kpp_request_free(struct kpp_request *req)

zeroize and free kpp request

Parameters

struct kpp_request *req

request to free

void kpp_request_set_callback(struct kpp_request *req, u32 flgs, crypto_completion_t cmpl, void *data)

Sets an asynchronous callback.

Parameters

struct kpp_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 kpp_request_set_input(struct kpp_request *req, struct scatterlist *input, unsigned int input_len)

Sets input buffer

Parameters

struct kpp_request *req

kpp request

struct scatterlist *input

ptr to input scatter list

unsigned int input_len

size of the input scatter list

Description

Sets parameters required by generate_public_key

void kpp_request_set_output(struct kpp_request *req, struct scatterlist *output, unsigned int output_len)

Sets output buffer

Parameters

struct kpp_request *req

kpp request

struct scatterlist *output

ptr to output scatter list

unsigned int output_len

size of the output scatter list

Description

Sets parameters required by kpp operation

ECDH Helper Functions

To use ECDH with the KPP cipher API, the following data structure and functions should be used.

The ECC curves known to the ECDH implementation are specified in this header file.

To use ECDH with KPP, the following functions should be used to operate on an ECDH private key. The packet private key that can be set with the KPP API function call of crypto_kpp_set_secret.

struct ecdh

define an ECDH private key

Definition:

struct ecdh {
    char *key;
    unsigned short key_size;
};

Members

key

Private ECDH key

key_size

Size of the private ECDH key

DH Helper Functions

To use DH with the KPP cipher API, the following data structure and functions should be used.

To use DH with KPP, the following functions should be used to operate on a DH private key. The packet private key that can be set with the KPP API function call of crypto_kpp_set_secret.

struct dh

define a DH private key

Definition:

struct dh {
    const void *key;
    const void *p;
    const void *g;
    unsigned int key_size;
    unsigned int p_size;
    unsigned int g_size;
    UEK_KABI_RESERVE(1)UEK_KABI_RESERVE(2)
};

Members

key

Private DH key

p

Diffie-Hellman parameter P

g

Diffie-Hellman generator G

key_size

Size of the private DH key

p_size

Size of DH parameter P

g_size

Size of DH generator G