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5d96a3dcde
In the ecdsa.c sample application we don't use hashing, we use ecdsa directly on a buffer containing plain text. Although the text explains that it should be the message hash it still can be confusing. Any misunderstandings here are potentially very dangerous, because ECDSA truncates the message hash if necessary and this can lead to trivial signature forgeries if the API is misused and the message is passed directly to the function without hashing. This commit adds a hash computation step to the ecdsa.c sample application and clarification to the doxygen documentation of the ECDSA functions involved.
268 lines
9.4 KiB
C
268 lines
9.4 KiB
C
/**
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* \file ecdsa.h
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*
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* \brief Elliptic curve DSA
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*
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* Copyright (C) 2006-2013, ARM Limited, All Rights Reserved
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*
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* This file is part of mbed TLS (https://tls.mbed.org)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#ifndef POLARSSL_ECDSA_H
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#define POLARSSL_ECDSA_H
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#include "ecp.h"
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#include "md.h"
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/*
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* RFC 4492 page 20:
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*
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* Ecdsa-Sig-Value ::= SEQUENCE {
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* r INTEGER,
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* s INTEGER
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* }
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*
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* Size is at most
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* 1 (tag) + 1 (len) + 1 (initial 0) + ECP_MAX_BYTES for each of r and s,
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* twice that + 1 (tag) + 2 (len) for the sequence
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* (assuming ECP_MAX_BYTES is less than 126 for r and s,
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* and less than 124 (total len <= 255) for the sequence)
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*
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*/
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/** Maximum size of an ECDSA signature in bytes */
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#define POLARSSL_ECDSA_MAX_LEN ( 3 + 2 * ( 3 + POLARSSL_ECP_MAX_BYTES ) )
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/**
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* \brief ECDSA context structure
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*
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* \note Purposefully begins with the same members as struct ecp_keypair.
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*/
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typedef struct
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{
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ecp_group grp; /*!< elliptic curve used */
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mpi d; /*!< secret signature key */
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ecp_point Q; /*!< public signature key */
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mpi r; /*!< first integer from signature */
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mpi s; /*!< second integer from signature */
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}
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ecdsa_context;
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* \brief Compute ECDSA signature of a previously hashed message
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*
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* \param grp ECP group
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* \param r First output integer
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* \param s Second output integer
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* \param d Private signing key
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* \param buf Message hash
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* \param blen Length of buf
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* \param f_rng RNG function
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* \param p_rng RNG parameter
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*
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* \note If the bitlength of the message hash is larger than the
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* bitlength of the group order, then the hash is truncated as
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* prescribed by SEC1 4.1.3 step 5.
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*
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* \return 0 if successful,
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* or a POLARSSL_ERR_ECP_XXX or POLARSSL_MPI_XXX error code
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*/
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int ecdsa_sign( ecp_group *grp, mpi *r, mpi *s,
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const mpi *d, const unsigned char *buf, size_t blen,
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int (*f_rng)(void *, unsigned char *, size_t), void *p_rng );
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#if defined(POLARSSL_ECDSA_DETERMINISTIC)
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/**
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* \brief Compute ECDSA signature of a previously hashed message
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* (deterministic version)
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*
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* \param grp ECP group
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* \param r First output integer
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* \param s Second output integer
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* \param d Private signing key
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* \param buf Message hash
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* \param blen Length of buf
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* \param md_alg MD algorithm used to hash the message
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*
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* \note If the bitlength of the message hash is larger than the
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* bitlength of the group order, then the hash is truncated as
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* prescribed by SEC1 4.1.3 step 5.
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*
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* \return 0 if successful,
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* or a POLARSSL_ERR_ECP_XXX or POLARSSL_MPI_XXX error code
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*/
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int ecdsa_sign_det( ecp_group *grp, mpi *r, mpi *s,
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const mpi *d, const unsigned char *buf, size_t blen,
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md_type_t md_alg );
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#endif /* POLARSSL_ECDSA_DETERMINISTIC */
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/**
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* \brief Verify ECDSA signature of a previously hashed message
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*
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* \param grp ECP group
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* \param buf Message hash
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* \param blen Length of buf
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* \param Q Public key to use for verification
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* \param r First integer of the signature
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* \param s Second integer of the signature
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*
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* \note If the bitlength of the message hash is larger than the
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* bitlength of the group order, then the hash is truncated as
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* prescribed by SEC1 4.1.4 step 3.
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*
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* \return 0 if successful,
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* POLARSSL_ERR_ECP_BAD_INPUT_DATA if signature is invalid
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* or a POLARSSL_ERR_ECP_XXX or POLARSSL_MPI_XXX error code
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*/
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int ecdsa_verify( ecp_group *grp,
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const unsigned char *buf, size_t blen,
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const ecp_point *Q, const mpi *r, const mpi *s);
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/**
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* \brief Compute ECDSA signature and write it to buffer,
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* serialized as defined in RFC 4492 page 20.
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* (Not thread-safe to use same context in multiple threads)
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*
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* \param ctx ECDSA context
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* \param hash Message hash
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* \param hlen Length of hash
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* \param sig Buffer that will hold the signature
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* \param slen Length of the signature written
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* \param f_rng RNG function
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* \param p_rng RNG parameter
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*
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* \note The "sig" buffer must be at least as large as twice the
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* size of the curve used, plus 7 (eg. 71 bytes if a 256-bit
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* curve is used).
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*
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* \note If the bitlength of the message hash is larger than the
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* bitlength of the group order, then the hash is truncated as
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* prescribed by SEC1 4.1.3 step 5.
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*
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* \return 0 if successful,
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* or a POLARSSL_ERR_ECP, POLARSSL_ERR_MPI or
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* POLARSSL_ERR_ASN1 error code
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*/
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int ecdsa_write_signature( ecdsa_context *ctx,
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const unsigned char *hash, size_t hlen,
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unsigned char *sig, size_t *slen,
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int (*f_rng)(void *, unsigned char *, size_t),
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void *p_rng );
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#if defined(POLARSSL_ECDSA_DETERMINISTIC)
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/**
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* \brief Compute ECDSA signature and write it to buffer,
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* serialized as defined in RFC 4492 page 20.
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* Deterministic version, RFC 6979.
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* (Not thread-safe to use same context in multiple threads)
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*
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* \param ctx ECDSA context
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* \param hash Message hash
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* \param hlen Length of hash
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* \param sig Buffer that will hold the signature
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* \param slen Length of the signature written
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* \param md_alg MD algorithm used to hash the message
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*
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* \note The "sig" buffer must be at least as large as twice the
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* size of the curve used, plus 7 (eg. 71 bytes if a 256-bit
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* curve is used).
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*
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* \return 0 if successful,
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* or a POLARSSL_ERR_ECP, POLARSSL_ERR_MPI or
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* POLARSSL_ERR_ASN1 error code
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*/
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int ecdsa_write_signature_det( ecdsa_context *ctx,
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const unsigned char *hash, size_t hlen,
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unsigned char *sig, size_t *slen,
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md_type_t md_alg );
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#endif /* POLARSSL_ECDSA_DETERMINISTIC */
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/**
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* \brief Read and verify an ECDSA signature
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*
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* \param ctx ECDSA context
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* \param hash Message hash
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* \param hlen Size of hash
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* \param sig Signature to read and verify
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* \param slen Size of sig
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*
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* \note If the bitlength of the message hash is larger than the
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* bitlength of the group order, then the hash is truncated as
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* prescribed by SEC1 4.1.4 step 3.
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*
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* \return 0 if successful,
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* POLARSSL_ERR_ECP_BAD_INPUT_DATA if signature is invalid,
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* POLARSSL_ERR_ECP_SIG_LEN_MISTMATCH if the signature is
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* valid but its actual length is less than siglen,
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* or a POLARSSL_ERR_ECP or POLARSSL_ERR_MPI error code
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*/
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int ecdsa_read_signature( ecdsa_context *ctx,
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const unsigned char *hash, size_t hlen,
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const unsigned char *sig, size_t slen );
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/**
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* \brief Generate an ECDSA keypair on the given curve
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*
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* \param ctx ECDSA context in which the keypair should be stored
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* \param gid Group (elliptic curve) to use. One of the various
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* POLARSSL_ECP_DP_XXX macros depending on configuration.
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* \param f_rng RNG function
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* \param p_rng RNG parameter
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*
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* \return 0 on success, or a POLARSSL_ERR_ECP code.
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*/
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int ecdsa_genkey( ecdsa_context *ctx, ecp_group_id gid,
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int (*f_rng)(void *, unsigned char *, size_t), void *p_rng );
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/**
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* \brief Set an ECDSA context from an EC key pair
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*
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* \param ctx ECDSA context to set
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* \param key EC key to use
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*
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* \return 0 on success, or a POLARSSL_ERR_ECP code.
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*/
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int ecdsa_from_keypair( ecdsa_context *ctx, const ecp_keypair *key );
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/**
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* \brief Initialize context
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*
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* \param ctx Context to initialize
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*/
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void ecdsa_init( ecdsa_context *ctx );
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/**
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* \brief Free context
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*
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* \param ctx Context to free
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*/
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void ecdsa_free( ecdsa_context *ctx );
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/**
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* \brief Checkup routine
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*
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* \return 0 if successful, or 1 if the test failed
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*/
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int ecdsa_self_test( int verbose );
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#ifdef __cplusplus
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}
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#endif
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#endif /* ecdsa.h */
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