Streamline mbedtls_xxx_drbg_update_seed_file
Refactor mbedtls_ctr_drbg_update_seed_file and
mbedtls_hmac_drbg_update_seed_file to make the error logic clearer.
The new code does not use fseek, so it works with non-seekable files.
diff --git a/library/hmac_drbg.c b/library/hmac_drbg.c
index d5ac2f6..c50330e 100644
--- a/library/hmac_drbg.c
+++ b/library/hmac_drbg.c
@@ -417,35 +417,36 @@
int mbedtls_hmac_drbg_update_seed_file( mbedtls_hmac_drbg_context *ctx, const char *path )
{
int ret = 0;
- FILE *f;
+ FILE *f = NULL;
size_t n;
unsigned char buf[ MBEDTLS_HMAC_DRBG_MAX_INPUT ];
+ unsigned char c;
if( ( f = fopen( path, "rb" ) ) == NULL )
return( MBEDTLS_ERR_HMAC_DRBG_FILE_IO_ERROR );
- fseek( f, 0, SEEK_END );
- n = (size_t) ftell( f );
- fseek( f, 0, SEEK_SET );
-
- if( n > MBEDTLS_HMAC_DRBG_MAX_INPUT )
+ n = fread( buf, 1, sizeof( buf ), f );
+ if( fread( &c, 1, 1, f ) != 0 )
{
- fclose( f );
- return( MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG );
+ ret = MBEDTLS_ERR_HMAC_DRBG_INPUT_TOO_BIG;
+ goto exit;
}
-
- if( fread( buf, 1, n, f ) != n )
+ if( n == 0 || ferror( f ) )
+ {
ret = MBEDTLS_ERR_HMAC_DRBG_FILE_IO_ERROR;
- else
- ret = mbedtls_hmac_drbg_update_ret( ctx, buf, n );
-
+ goto exit;
+ }
fclose( f );
+ f = NULL;
+ ret = mbedtls_hmac_drbg_update_ret( ctx, buf, n );
+
+exit:
mbedtls_platform_zeroize( buf, sizeof( buf ) );
-
+ if( f != NULL )
+ fclose( f );
if( ret != 0 )
return( ret );
-
return( mbedtls_hmac_drbg_write_seed_file( ctx, path ) );
}
#endif /* MBEDTLS_FS_IO */