Merge remote-tracking branch 'janos/iotssl-1156-ecdsa-sample-and-doc-clarification' into development

* janos/iotssl-1156-ecdsa-sample-and-doc-clarification:
  Clarify the use of ECDSA API
This commit is contained in:
Manuel Pégourié-Gonnard 2017-06-08 10:16:54 +02:00
commit c44c3c288d
3 changed files with 53 additions and 7 deletions

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@ -27,6 +27,9 @@ Bugfix
Changes
* Send fatal alerts in many more cases instead of dropping the connection.
* Clarify ECDSA documentation and improve the sample code to avoid
misunderstandings and potentially dangerous use of the API. Pointed out
by Jean-Philippe Aumasson.
= mbed TLS 2.5.0 branch released 2017-05-17

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@ -69,6 +69,10 @@ extern "C" {
* \param f_rng RNG function
* \param p_rng RNG parameter
*
* \note If the bitlength of the message hash is larger than the
* bitlength of the group order, then the hash is truncated as
* prescribed by SEC1 4.1.3 step 5.
*
* \return 0 if successful,
* or a MBEDTLS_ERR_ECP_XXX or MBEDTLS_MPI_XXX error code
*/
@ -89,6 +93,10 @@ int mbedtls_ecdsa_sign( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
* \param blen Length of buf
* \param md_alg MD algorithm used to hash the message
*
* \note If the bitlength of the message hash is larger than the
* bitlength of the group order, then the hash is truncated as
* prescribed by SEC1 4.1.3 step 5.
*
* \return 0 if successful,
* or a MBEDTLS_ERR_ECP_XXX or MBEDTLS_MPI_XXX error code
*/
@ -107,6 +115,10 @@ int mbedtls_ecdsa_sign_det( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi
* \param r First integer of the signature
* \param s Second integer of the signature
*
* \note If the bitlength of the message hash is larger than the
* bitlength of the group order, then the hash is truncated as
* prescribed by SEC1 4.1.4 step 3.
*
* \return 0 if successful,
* MBEDTLS_ERR_ECP_BAD_INPUT_DATA if signature is invalid
* or a MBEDTLS_ERR_ECP_XXX or MBEDTLS_MPI_XXX error code
@ -120,7 +132,7 @@ int mbedtls_ecdsa_verify( mbedtls_ecp_group *grp,
* serialized as defined in RFC 4492 page 20.
* (Not thread-safe to use same context in multiple threads)
*
* \note The deterministice version (RFC 6979) is used if
* \note The deterministic version (RFC 6979) is used if
* MBEDTLS_ECDSA_DETERMINISTIC is defined.
*
* \param ctx ECDSA context
@ -136,6 +148,10 @@ int mbedtls_ecdsa_verify( mbedtls_ecp_group *grp,
* size of the curve used, plus 9 (eg. 73 bytes if a 256-bit
* curve is used). MBEDTLS_ECDSA_MAX_LEN is always safe.
*
* \note If the bitlength of the message hash is larger than the
* bitlength of the group order, then the hash is truncated as
* prescribed by SEC1 4.1.3 step 5.
*
* \return 0 if successful,
* or a MBEDTLS_ERR_ECP_XXX, MBEDTLS_ERR_MPI_XXX or
* MBEDTLS_ERR_ASN1_XXX error code
@ -172,6 +188,10 @@ int mbedtls_ecdsa_write_signature( mbedtls_ecdsa_context *ctx, mbedtls_md_type_t
* size of the curve used, plus 9 (eg. 73 bytes if a 256-bit
* curve is used). MBEDTLS_ECDSA_MAX_LEN is always safe.
*
* \note If the bitlength of the message hash is larger than the
* bitlength of the group order, then the hash is truncated as
* prescribed by SEC1 4.1.3 step 5.
*
* \return 0 if successful,
* or a MBEDTLS_ERR_ECP_XXX, MBEDTLS_ERR_MPI_XXX or
* MBEDTLS_ERR_ASN1_XXX error code
@ -193,6 +213,10 @@ int mbedtls_ecdsa_write_signature_det( mbedtls_ecdsa_context *ctx,
* \param sig Signature to read and verify
* \param slen Size of sig
*
* \note If the bitlength of the message hash is larger than the
* bitlength of the group order, then the hash is truncated as
* prescribed by SEC1 4.1.4 step 3.
*
* \return 0 if successful,
* MBEDTLS_ERR_ECP_BAD_INPUT_DATA if signature is invalid,
* MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH if the signature is

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@ -37,6 +37,7 @@
#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"
#include "mbedtls/ecdsa.h"
#include "mbedtls/sha256.h"
#include <string.h>
#endif
@ -101,8 +102,10 @@ int main( int argc, char *argv[] )
mbedtls_ecdsa_context ctx_sign, ctx_verify;
mbedtls_entropy_context entropy;
mbedtls_ctr_drbg_context ctr_drbg;
unsigned char hash[] = "This should be the hash of a message.";
unsigned char sig[512];
mbedtls_sha256_context sha256_ctx;
unsigned char message[100];
unsigned char hash[32];
unsigned char sig[MBEDTLS_ECDSA_MAX_LEN];
size_t sig_len;
const char *pers = "ecdsa";
((void) argv);
@ -110,8 +113,10 @@ int main( int argc, char *argv[] )
mbedtls_ecdsa_init( &ctx_sign );
mbedtls_ecdsa_init( &ctx_verify );
mbedtls_ctr_drbg_init( &ctr_drbg );
mbedtls_sha256_init( &sha256_ctx );
memset(sig, 0, sizeof( sig ) );
memset( sig, 0, sizeof( sig ) );
memset( message, 0x25, sizeof( message ) );
ret = 1;
if( argc != 1 )
@ -155,9 +160,23 @@ int main( int argc, char *argv[] )
dump_pubkey( " + Public key: ", &ctx_sign );
/*
* Sign some message hash
* Compute message hash
*/
mbedtls_printf( " . Signing message..." );
mbedtls_printf( " . Computing message hash..." );
fflush( stdout );
mbedtls_sha256_starts( &sha256_ctx, 0 );
mbedtls_sha256_update( &sha256_ctx, message, sizeof( message ) );
mbedtls_sha256_finish( &sha256_ctx, hash );
mbedtls_printf( " ok\n" );
dump_buf( " + Hash: ", hash, sizeof( hash ) );
/*
* Sign message hash
*/
mbedtls_printf( " . Signing message hash..." );
fflush( stdout );
if( ( ret = mbedtls_ecdsa_write_signature( &ctx_sign, MBEDTLS_MD_SHA256,
@ -170,7 +189,6 @@ int main( int argc, char *argv[] )
}
mbedtls_printf( " ok (signature length = %u)\n", (unsigned int) sig_len );
dump_buf( " + Hash: ", hash, sizeof hash );
dump_buf( " + Signature: ", sig, sig_len );
/*
@ -224,6 +242,7 @@ exit:
mbedtls_ecdsa_free( &ctx_sign );
mbedtls_ctr_drbg_free( &ctr_drbg );
mbedtls_entropy_free( &entropy );
mbedtls_sha256_free( &sha256_ctx );
return( ret );
}