/** * \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 #include #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 */