f667820c16
This commit implements coordinate blinding, i.e., it randomizes the representative of an elliptic curve point in its equivalence class, for prime curves implemented through EC_GFp_simple_method, EC_GFp_mont_method, and EC_GFp_nist_method. This commit is derived from the patch https://marc.info/?l=openssl-dev&m=131194808413635 by Billy Brumley. Coordinate blinding is a generally useful side-channel countermeasure and is (mostly) free. The function itself takes a few field multiplicationss, but is usually only necessary at the beginning of a scalar multiplication (as implemented in the patch). When used this way, it makes the values that variables take (i.e., field elements in an algorithm state) unpredictable. For instance, this mitigates chosen EC point side-channel attacks for settings such as ECDH and EC private key decryption, for the aforementioned curves. For EC_METHODs using different coordinate representations this commit does nothing, but the corresponding coordinate blinding function can be easily added in the future to extend these changes to such curves. Co-authored-by: Nicola Tuveri <nic.tuv@gmail.com> Co-authored-by: Billy Brumley <bbrumley@gmail.com> Reviewed-by: Andy Polyakov <appro@openssl.org> Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from https://github.com/openssl/openssl/pull/6501) |
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| .. | ||
| build.info | ||
| err.c | ||
| err_all.c | ||
| err_prn.c | ||
| openssl.ec | ||
| openssl.txt | ||
| README | ||
Adding new libraries
--------------------
When adding a new sub-library to OpenSSL, assign it a library number
ERR_LIB_XXX, define a macro XXXerr() (both in err.h), add its
name to ERR_str_libraries[] (in crypto/err/err.c), and add
ERR_load_XXX_strings() to the ERR_load_crypto_strings() function
(in crypto/err/err_all.c). Finally, add an entry:
L XXX xxx.h xxx_err.c
to crypto/err/openssl.ec, and add xxx_err.c to the Makefile.
Running make errors will then generate a file xxx_err.c, and
add all error codes used in the library to xxx.h.
Additionally the library include file must have a certain form.
Typically it will initially look like this:
#ifndef HEADER_XXX_H
#define HEADER_XXX_H
#ifdef __cplusplus
extern "C" {
#endif
/* Include files */
#include <openssl/bio.h>
#include <openssl/x509.h>
/* Macros, structures and function prototypes */
/* BEGIN ERROR CODES */
The BEGIN ERROR CODES sequence is used by the error code
generation script as the point to place new error codes, any text
after this point will be overwritten when make errors is run.
The closing #endif etc will be automatically added by the script.
The generated C error code file xxx_err.c will load the header
files stdio.h, openssl/err.h and openssl/xxx.h so the
header file must load any additional header files containing any
definitions it uses.