/**
* \file lms.h
*
* \brief This file provides an API for the LMS post-quantum-safe stateful-hash
public-key signature scheme as defined in RFC8554 and NIST.SP.200-208.
* This implementation currently only supports a single parameter set
* MBEDTLS_LMS_SHA256_M32_H10 in order to reduce complexity. This is one
* of the signature schemes recommended by the IETF draft SUIT standard
* for IOT firmware upgrades (RFC9019).
*/
/*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
*/
#ifndef MBEDTLS_LMS_H
#define MBEDTLS_LMS_H
#include <stdint.h>
#include <stddef.h>
#include "mbedtls/private_access.h"
#include "mbedtls/build_info.h"
#define MBEDTLS_ERR_LMS_BAD_INPUT_DATA -0x0011 /**< Bad data has been input to an LMS function */
#define MBEDTLS_ERR_LMS_OUT_OF_PRIVATE_KEYS -0x0013 /**< Specified LMS key has utilised all of its private keys */
#define MBEDTLS_ERR_LMS_VERIFY_FAILED -0x0015 /**< LMS signature verification failed */
#define MBEDTLS_ERR_LMS_ALLOC_FAILED -0x0017 /**< LMS failed to allocate space for a private key */
#define MBEDTLS_ERR_LMS_BUFFER_TOO_SMALL -0x0019 /**< Input/output buffer is too small to contain requited data */
/* Currently only defined for SHA256, 32 is the max hash output size */
#define MBEDTLS_LMOTS_N_HASH_LEN_MAX (32u)
#define MBEDTLS_LMOTS_P_SIG_DIGIT_COUNT_MAX (34u)
#define MBEDTLS_LMOTS_N_HASH_LEN(type) ((type) == MBEDTLS_LMOTS_SHA256_N32_W8 ? 32u : 0)
#define MBEDTLS_LMOTS_I_KEY_ID_LEN (16u)
#define MBEDTLS_LMOTS_Q_LEAF_ID_LEN (4u)
#define MBEDTLS_LMOTS_TYPE_LEN (4u)
#define MBEDTLS_LMOTS_P_SIG_DIGIT_COUNT(type) ((type) == MBEDTLS_LMOTS_SHA256_N32_W8 ? 34u : 0)
#define MBEDTLS_LMOTS_C_RANDOM_VALUE_LEN(type) (MBEDTLS_LMOTS_N_HASH_LEN(type))
#define MBEDTLS_LMOTS_SIG_LEN(type) (MBEDTLS_LMOTS_TYPE_LEN + \
MBEDTLS_LMOTS_C_RANDOM_VALUE_LEN(type) + \
(MBEDTLS_LMOTS_P_SIG_DIGIT_COUNT(type) * \
MBEDTLS_LMOTS_N_HASH_LEN(type)))
#define MBEDTLS_LMS_TYPE_LEN (4)
#define MBEDTLS_LMS_H_TREE_HEIGHT(type) ((type) == MBEDTLS_LMS_SHA256_M32_H10 ? 10u : 0)
/* The length of a hash output, Currently only implemented for SHA256.
* Max is 32 bytes.
*/
#define MBEDTLS_LMS_M_NODE_BYTES(type) ((type) == MBEDTLS_LMS_SHA256_M32_H10 ? 32 : 0)
#define MBEDTLS_LMS_M_NODE_BYTES_MAX 32
#define MBEDTLS_LMS_SIG_LEN(type, otstype) (MBEDTLS_LMOTS_Q_LEAF_ID_LEN + \
MBEDTLS_LMOTS_SIG_LEN(otstype) + \
MBEDTLS_LMS_TYPE_LEN + \
(MBEDTLS_LMS_H_TREE_HEIGHT(type) * \
MBEDTLS_LMS_M_NODE_BYTES(type)))
#define MBEDTLS_LMS_PUBLIC_KEY_LEN(type) (MBEDTLS_LMS_TYPE_LEN + \
MBEDTLS_LMOTS_TYPE_LEN + \
MBEDTLS_LMOTS_I_KEY_ID_LEN + \
MBEDTLS_LMS_M_NODE_BYTES(type))
#ifdef __cplusplus
extern "C" {
#endif
/** The Identifier of the LMS parameter set, as per
* https://www.iana.org/assignments/leighton-micali-signatures/leighton-micali-signatures.xhtml
* We are only implementing a subset of the types, particularly H10, for the sake of simplicity.
*/
typedef enum {
MBEDTLS_LMS_SHA256_M32_H10 = 0x6,
} mbedtls_lms_algorithm_type_t;
/** The Identifier of the LMOTS parameter set, as per
* https://www.iana.org/assignments/leighton-micali-signatures/leighton-micali-signatures.xhtml.
* We are only implementing a subset of the types, particularly N32_W8, for the sake of simplicity.
*/
typedef enum {
MBEDTLS_LMOTS_SHA256_N32_W8 = 4
} mbedtls_lmots_algorithm_type_t;
/** LMOTS parameters structure.
*
* This contains the metadata associated with an LMOTS key, detailing the
* algorithm type, the key ID, and the leaf identifier should be key be part of
* a LMS key.
*/
typedef struct {
unsigned char MBEDTLS_PRIVATE(I_key_identifier[MBEDTLS_LMOTS_I_KEY_ID_LEN]); /*!< The key
identifier. */
unsigned char MBEDTLS_PRIVATE(q_leaf_identifier[MBEDTLS_LMOTS_Q_LEAF_ID_LEN]); /*!< Which
leaf of the LMS key this is.
0 if the key is not part of an LMS key. */
mbedtls_lmots_algorithm_type_t MBEDTLS_PRIVATE(type); /*!< The LM-OTS key type identifier as
per IANA. Only SHA256_N32_W8 is
currently supported. */
} mbedtls_lmots_parameters_t;
/** LMOTS public context structure.
*
* A LMOTS public key is a hash output, and the applicable parameter set.
*
* The context must be initialized before it is used. A public key must either
* be imported or generated from a private context.
*
* \dot
* digraph lmots_public_t {
* UNINITIALIZED -> INIT [label="init"];
* HAVE_PUBLIC_KEY -> INIT [label="free"];
* INIT -> HAVE_PUBLIC_KEY [label="import_public_key"];
* INIT -> HAVE_PUBLIC_KEY [label="calculate_public_key from private key"];
* HAVE_PUBLIC_KEY -> HAVE_PUBLIC_KEY [label="export_public_key"];
* }
* \enddot
*/
typedef struct {
mbedtls_lmots_parameters_t MBEDTLS_PRIVATE(params);
unsigned char MBEDTLS_PRIVATE(public_key)[MBEDTLS_LMOTS_N_HASH_LEN_MAX];
unsigned char MBEDTLS_PRIVATE(have_public_key); /*!< Whether the context contains a public key.
Boolean values only. */
} mbedtls_lmots_public_t;
#if defined(MBEDTLS_LMS_PRIVATE)
/** LMOTS private context structure.
*
* A LMOTS private key is one hash output for each of digit of the digest +
* checksum, and the applicable parameter set.
*
* The context must be initialized before it is used. A public key must either
* be imported or generated from a private context.
*
* \dot
* digraph lmots_public_t {
* UNINITIALIZED -> INIT [label="init"];
* HAVE_PRIVATE_KEY -> INIT [label="free"];
* INIT -> HAVE_PRIVATE_KEY [label="generate_private_key"];
* HAVE_PRIVATE_KEY -> INIT [label="sign"];
* }
* \enddot
*/
typedef struct {
mbedtls_lmots_parameters_t MBEDTLS_PRIVATE(params);
unsigned char MBEDTLS_PRIVATE(private_key)[MBEDTLS_LMOTS_P_SIG_DIGIT_COUNT_MAX][
MBEDTLS_LMOTS_N_HASH_LEN_MAX];
unsigned char MBEDTLS_PRIVATE(have_private_key); /*!< Whether the context contains a private key.
Boolean values only. */
} mbedtls_lmots_private_t;
#endif /* defined(MBEDTLS_LMS_PRIVATE) */
/** LMS parameters structure.
*
* This contains the metadata associated with an LMS key, detailing the
* algorithm type, the type of the underlying OTS algorithm, and the key ID.
*/
typedef struct {
unsigned char MBEDTLS_PRIVATE(I_key_identifier[MBEDTLS_LMOTS_I_KEY_ID_LEN]); /*!< The key
identifier. */
mbedtls_lmots_algorithm_type_t MBEDTLS_PRIVATE(otstype); /*!< The LM-OTS key type identifier as
per IANA. Only SHA256_N32_W8 is
currently supported. */
mbedtls_lms_algorithm_type_t MBEDTLS_PRIVATE(type); /*!< The LMS key type identifier as per
IANA. Only SHA256_M32_H10 is currently
supported. */
} mbedtls_lms_parameters_t;
/** LMS public context structure.
*
* A LMS public key is the hash output that is the root of the Merkle tree, and
* the applicable parameter set
*
* The context must be initialized before it is used. A public key must either
* be imported or generated from a private context.
*
* \dot
* digraph lms_public_t {
* UNINITIALIZED -> INIT [label="init"];
* HAVE_PUBLIC_KEY -> INIT [label="free"];
* INIT -> HAVE_PUBLIC_KEY [label="import_public_key"];
* INIT -> HAVE_PUBLIC_KEY [label="calculate_public_key from private key"];
* HAVE_PUBLIC_KEY -> HAVE_PUBLIC_KEY [label="export_public_key"];
* }
* \enddot
*/
typedef struct {
mbedtls_lms_parameters_t MBEDTLS_PRIVATE(params);
unsigned char MBEDTLS_PRIVATE(T_1_pub_key)[MBEDTLS_LMS_M_NODE_BYTES_MAX]; /*!< The public key, in
the form of the Merkle tree root node. */
unsigned char MBEDTLS_PRIVATE(have_public_key); /*!< Whether the context contains a public key.
Boolean values only. */
} mbedtls_lms_public_t;
#if defined(MBEDTLS_LMS_PRIVATE)
/** LMS private context structure.
*
* A LMS private key is a set of LMOTS private keys, an index to the next usable
* key, and the applicable parameter set.
*
* The context must be initialized before it is used. A public key must either
* be imported or generated from a private context.
*
* \dot
* digraph lms_public_t {
* UNINITIALIZED -> INIT [label="init"];
* HAVE_PRIVATE_KEY -> INIT [label="free"];
* INIT -> HAVE_PRIVATE_KEY [label="generate_private_key"];
* }
* \enddot
*/
typedef struct {
mbedtls_lms_parameters_t MBEDTLS_PRIVATE(params);
uint32_t MBEDTLS_PRIVATE(q_next_usable_key); /*!< The index of the next OTS key that has not
been used. */
mbedtls_lmots_private_t *MBEDTLS_PRIVATE(ots_private_keys); /*!< The private key material. One OTS key
for each leaf node in the Merkle tree. NULL
when have_private_key is 0 and non-NULL otherwise.
is 2^MBEDTLS_LMS_H_TREE_HEIGHT(type) in length. */
mbedtls_lmots_public_t *MBEDTLS_PRIVATE(ots_public_keys); /*!< The OTS key public keys, used to
build the Merkle tree. NULL
when have_private_key is 0 and
non-NULL otherwise.
Is 2^MBEDTLS_LMS_H_TREE_HEIGHT(type)
in length. */
unsigned char MBEDTLS_PRIVATE(have_private_key); /*!< Whether the context contains a private key.
Boolean values only. */
} mbedtls_lms_private_t;
#endif /* defined(MBEDTLS_LMS_PRIVATE) */
/**
* \brief This function initializes an LMS public context
*
* \param ctx The uninitialized LMS context that will then be
* initialized.
*/
void mbedtls_lms_public_init(mbedtls_lms_public_t *ctx);
/**
* \brief This function uninitializes an LMS public context
*
* \param ctx The initialized LMS context that will then be
* uninitialized.
*/
void mbedtls_lms_public_free(mbedtls_lms_public_t *ctx);
/**
* \brief This function imports an LMS public key into a
* public LMS context.
*
* \note Before this function is called, the context must
* have been initialized.
*
* \note See IETF RFC8554 for details of the encoding of
* this public key.
*
* \param ctx The initialized LMS context store the key in.
* \param key The buffer from which the key will be read.
* #MBEDTLS_LMS_PUBLIC_KEY_LEN bytes will be read from
* this.
* \param key_size The size of the key being imported.
*
* \return \c 0 on success.
* \return A non-zero error code on failure.
*/
int mbedtls_lms_import_public_key(mbedtls_lms_public_t *ctx,
const unsigned char *key, size_t key_size);
/**
* \brief This function exports an LMS public key from a
* LMS public context that already contains a public
* key.
*
* \note Before this function is called, the context must
* have been initialized and the context must contain
* a public key.
*
* \note See IETF RFC8554 for details of the encoding of
* this public key.
*
* \param ctx The initialized LMS public context that contains
* the public key.
* \param key The buffer into which the key will be output. Must
* be at least #MBEDTLS_LMS_PUBLIC_KEY_LEN in size.
* \param key_size The size of the key buffer.
* \param key_len If not NULL, will be written with the size of the
* key.
*
* \return \c 0 on success.
* \return A non-zero error code on failure.
*/
int mbedtls_lms_export_public_key(const mbedtls_lms_public_t *ctx,
unsigned char *key, size_t key_size,
size_t *key_len);
/**
* \brief This function verifies a LMS signature, using a
* LMS context that contains a public key.
*
* \note Before this function is called, the context must
* have been initialized and must contain a public key
* (either by import or generation).
*
* \param ctx The initialized LMS public context from which the
* public key will be read.
* \param msg The buffer from which the message will be read.
* \param msg_size The size of the message that will be read.
* \param sig The buf from which the signature will be read.
* #MBEDTLS_LMS_SIG_LEN bytes will be read from
* this.
* \param sig_size The size of the signature to be verified.
*
* \return \c 0 on successful verification.
* \return A non-zero error code on failure.
*/
int mbedtls_lms_verify(const mbedtls_lms_public_t *ctx,
const unsigned char *msg, size_t msg_size,
const unsigned char *sig, size_t sig_size);
#if defined(MBEDTLS_LMS_PRIVATE)
/**
* \brief This function initializes an LMS private context
*
* \param ctx The uninitialized LMS private context that will
* then be initialized. */
void mbedtls_lms_private_init(mbedtls_lms_private_t *ctx);
/**
* \brief This function uninitializes an LMS private context
*
* \param ctx The initialized LMS private context that will then
* be uninitialized.
*/
void mbedtls_lms_private_free(mbedtls_lms_private_t *ctx);
/**
* \brief This function generates an LMS private key, and
* stores in into an LMS private context.
*
* \warning This function is **not intended for use in
* production**, due to as-yet unsolved problems with
* handling stateful keys. The API for this function
* may change considerably in future versions.
*
* \note The seed must have at least 256 bits of entropy.
*
* \param ctx The initialized LMOTS context to generate the key
* into.
* \param type The LMS parameter set identifier.
* \param otstype The LMOTS parameter set identifier.
* \param f_rng The RNG function to be used to generate the key ID.
* \param p_rng The RNG context to be passed to f_rng
* \param seed The seed used to deterministically generate the
* key.
* \param seed_size The length of the seed.
*
* \return \c 0 on success.
* \return A non-zero error code on failure.
*/
int mbedtls_lms_generate_private_key(mbedtls_lms_private_t *ctx,
mbedtls_lms_algorithm_type_t type,
mbedtls_lmots_algorithm_type_t otstype,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng, const unsigned char *seed,
size_t seed_size);
/**
* \brief This function calculates an LMS public key from a
* LMS context that already contains a private key.
*
* \note Before this function is called, the context must
* have been initialized and the context must contain
* a private key.
*
* \param ctx The initialized LMS public context to calculate the key
* from and store it into.
*
* \param priv_ctx The LMS private context to read the private key
* from. This must have been initialized and contain a
* private key.
*
* \return \c 0 on success.
* \return A non-zero error code on failure.
*/
int mbedtls_lms_calculate_public_key(mbedtls_lms_public_t *ctx,
const mbedtls_lms_private_t *priv_ctx);
/**
* \brief This function creates a LMS signature, using a
* LMS context that contains unused private keys.
*
* \warning This function is **not intended for use in
* production**, due to as-yet unsolved problems with
* handling stateful keys. The API for this function
* may change considerably in future versions.
*
* \note Before this function is called, the context must
* have been initialized and must contain a private
* key.
*
* \note Each of the LMOTS private keys inside a LMS private
* key can only be used once. If they are reused, then
* attackers may be able to forge signatures with that
* key. This is all handled transparently, but it is
* important to not perform copy operations on LMS
* contexts that contain private key material.
*
* \param ctx The initialized LMS private context from which the
* private key will be read.
* \param f_rng The RNG function to be used for signature
* generation.
* \param p_rng The RNG context to be passed to f_rng
* \param msg The buffer from which the message will be read.
* \param msg_size The size of the message that will be read.
* \param sig The buf into which the signature will be stored.
* Must be at least #MBEDTLS_LMS_SIG_LEN in size.
* \param sig_size The size of the buffer the signature will be
* written into.
* \param sig_len If not NULL, will be written with the size of the
* signature.
*
* \return \c 0 on success.
* \return A non-zero error code on failure.
*/
int mbedtls_lms_sign(mbedtls_lms_private_t *ctx,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng, const unsigned char *msg,
unsigned int msg_size, unsigned char *sig, size_t sig_size,
size_t *sig_len);
#endif /* defined(MBEDTLS_LMS_PRIVATE) */
#ifdef __cplusplus
}
#endif
#endif /* MBEDTLS_LMS_H */
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