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mirror of https://git.tartarus.org/simon/putty.git synced 2025-01-09 17:38:00 +00:00
putty-source/defs.h
Simon Tatham 25b034ee39 Complete rewrite of PuTTY's bignum library.
The old 'Bignum' data type is gone completely, and so is sshbn.c. In
its place is a new thing called 'mp_int', handled by an entirely new
library module mpint.c, with API differences both large and small.

The main aim of this change is that the new library should be free of
timing- and cache-related side channels. I've written the code so that
it _should_ - assuming I haven't made any mistakes - do all of its
work without either control flow or memory addressing depending on the
data words of the input numbers. (Though, being an _arbitrary_
precision library, it does have to at least depend on the sizes of the
numbers - but there's a 'formal' size that can vary separately from
the actual magnitude of the represented integer, so if you want to
keep it secret that your number is actually small, it should work fine
to have a very long mp_int and just happen to store 23 in it.) So I've
done all my conditionalisation by means of computing both answers and
doing bit-masking to swap the right one into place, and all loops over
the words of an mp_int go up to the formal size rather than the actual
size.

I haven't actually tested the constant-time property in any rigorous
way yet (I'm still considering the best way to do it). But this code
is surely at the very least a big improvement on the old version, even
if I later find a few more things to fix.

I've also completely rewritten the low-level elliptic curve arithmetic
from sshecc.c; the new ecc.c is closer to being an adjunct of mpint.c
than it is to the SSH end of the code. The new elliptic curve code
keeps all coordinates in Montgomery-multiplication transformed form to
speed up all the multiplications mod the same prime, and only converts
them back when you ask for the affine coordinates. Also, I adopted
extended coordinates for the Edwards curve implementation.

sshecc.c has also had a near-total rewrite in the course of switching
it over to the new system. While I was there, I've separated ECDSA and
EdDSA more completely - they now have separate vtables, instead of a
single vtable in which nearly every function had a big if statement in
it - and also made the externally exposed types for an ECDSA key and
an ECDH context different.

A minor new feature: since the new arithmetic code includes a modular
square root function, we can now support the compressed point
representation for the NIST curves. We seem to have been getting along
fine without that so far, but it seemed a shame not to put it in,
since it was suddenly easy.

In sshrsa.c, one major change is that I've removed the RSA blinding
step in rsa_privkey_op, in which we randomise the ciphertext before
doing the decryption. The purpose of that was to avoid timing leaks
giving away the plaintext - but the new arithmetic code should take
that in its stride in the course of also being careful enough to avoid
leaking the _private key_, which RSA blinding had no way to do
anything about in any case.

Apart from those specific points, most of the rest of the changes are
more or less mechanical, just changing type names and translating code
into the new API.
2018-12-31 14:54:59 +00:00

133 lines
3.7 KiB
C

/*
* defs.h: initial definitions for PuTTY.
*
* The rule about this header file is that it can't depend on any
* other header file in this code base. This is where we define
* things, as much as we can, that other headers will want to refer
* to, such as opaque structure types and their associated typedefs,
* or macros that are used by other headers.
*/
#ifndef PUTTY_DEFS_H
#define PUTTY_DEFS_H
#include <stddef.h>
#include <stdint.h>
#include <stdbool.h>
#if defined _MSC_VER && _MSC_VER < 1800
/* Work around lack of inttypes.h in older MSVC */
#define PRIx32 "x"
#define PRIu64 "I64u"
#define SCNu64 "I64u"
#else
#include <inttypes.h>
#endif
typedef struct conf_tag Conf;
typedef struct terminal_tag Terminal;
typedef struct Filename Filename;
typedef struct FontSpec FontSpec;
typedef struct bufchain_tag bufchain;
typedef struct strbuf strbuf;
struct RSAKey;
typedef struct BinarySink BinarySink;
typedef struct BinarySource BinarySource;
typedef struct IdempotentCallback IdempotentCallback;
typedef struct SockAddr SockAddr;
typedef struct Socket Socket;
typedef struct Plug Plug;
typedef struct SocketPeerInfo SocketPeerInfo;
typedef struct Backend Backend;
typedef struct BackendVtable BackendVtable;
typedef struct Ldisc_tag Ldisc;
typedef struct LogContext LogContext;
typedef struct LogPolicy LogPolicy;
typedef struct LogPolicyVtable LogPolicyVtable;
typedef struct Seat Seat;
typedef struct SeatVtable SeatVtable;
typedef struct TermWin TermWin;
typedef struct TermWinVtable TermWinVtable;
typedef struct Ssh Ssh;
typedef struct mp_int mp_int;
typedef struct MontyContext MontyContext;
typedef struct WeierstrassCurve WeierstrassCurve;
typedef struct WeierstrassPoint WeierstrassPoint;
typedef struct MontgomeryCurve MontgomeryCurve;
typedef struct MontgomeryPoint MontgomeryPoint;
typedef struct EdwardsCurve EdwardsCurve;
typedef struct EdwardsPoint EdwardsPoint;
typedef struct SftpServer SftpServer;
typedef struct SftpServerVtable SftpServerVtable;
typedef struct Channel Channel;
typedef struct SshChannel SshChannel;
typedef struct mainchan mainchan;
typedef struct ssh_sharing_state ssh_sharing_state;
typedef struct ssh_sharing_connstate ssh_sharing_connstate;
typedef struct share_channel share_channel;
typedef struct PortFwdManager PortFwdManager;
typedef struct PortFwdRecord PortFwdRecord;
typedef struct ConnectionLayer ConnectionLayer;
typedef struct dlgparam dlgparam;
typedef struct settings_w settings_w;
typedef struct settings_r settings_r;
typedef struct settings_e settings_e;
typedef struct SessionSpecial SessionSpecial;
/*
* A small structure wrapping up a (pointer, length) pair so that it
* can be conveniently passed to or from a function.
*/
typedef struct ptrlen {
const void *ptr;
size_t len;
} ptrlen;
typedef struct logblank_t logblank_t;
typedef struct BinaryPacketProtocol BinaryPacketProtocol;
typedef struct PacketProtocolLayer PacketProtocolLayer;
/* Do a compile-time type-check of 'to_check' (without evaluating it),
* as a side effect of returning the value 'to_return'. Note that
* although this macro double-*expands* to_return, it always
* *evaluates* exactly one copy of it, so it's side-effect safe. */
#define TYPECHECK(to_check, to_return) \
(sizeof(to_check) ? (to_return) : (to_return))
/* Return a pointer to the object of structure type 'type' whose field
* with name 'field' is pointed at by 'object'. */
#define container_of(object, type, field) \
TYPECHECK(object == &((type *)0)->field, \
((type *)(((char *)(object)) - offsetof(type, field))))
#if defined __GNUC__ || defined __clang__
#define NORETURN __attribute__((__noreturn__))
#else
#define NORETURN
#endif
#endif /* PUTTY_DEFS_H */