lib/mbedtls
1
0
Fork 0
mirror of https://github.com/Mbed-TLS/mbedtls.git synced 2025-08-08 17:42:09 +03:00
Code Activity

Clarify the use of ECDSA API

Browse Source 
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.
This commit is contained in:
Janos Follath
2017-03-10 11:31:41 +00:00
parent b5ba28cbea
commit 0a5154b8a1
3 changed files with 56 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
programs/pkey/ecdsa.c
View File

@@ -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 );
}