696c13bd6a
Due to a copy-paste error, the call to |left_shift_3| is missing after reducing the password scalar in SPAKE2. This means that three bits of the password leak in Alice's message. (Two in Bob's message as the point N happens to have order 4l, not 8l.) The “correct” fix is to put in the missing call to |left_shift_3|, but that would be a breaking change. In order to fix this in a unilateral way, we add points of small order to the masking point to bring it into prime-order subgroup. BUG=chromium:778101 Change-Id: I440931a3df7f009b324d2a3e3af2d893a101804f Reviewed-on: https://boringssl-review.googlesource.com/22445 Reviewed-by: Adam Langley <agl@google.com> Reviewed-by: David Benjamin <davidben@google.com> Commit-Queue: Adam Langley <agl@google.com> CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>
130 lines
3.6 KiB
C
130 lines
3.6 KiB
C
/* Copyright (c) 2015, Google Inc.
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
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#ifndef OPENSSL_HEADER_CURVE25519_INTERNAL_H
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#define OPENSSL_HEADER_CURVE25519_INTERNAL_H
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#if defined(__cplusplus)
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extern "C" {
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#endif
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#if defined(OPENSSL_X86_64) && !defined(OPENSSL_SMALL) && \
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!defined(OPENSSL_WINDOWS) && !defined(OPENSSL_NO_ASM)
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#define BORINGSSL_X25519_X86_64
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void x25519_x86_64(uint8_t out[32], const uint8_t scalar[32],
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const uint8_t point[32]);
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#endif
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#if defined(OPENSSL_ARM) && !defined(OPENSSL_NO_ASM) && !defined(OPENSSL_APPLE)
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#define BORINGSSL_X25519_NEON
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// x25519_NEON is defined in asm/x25519-arm.S.
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void x25519_NEON(uint8_t out[32], const uint8_t scalar[32],
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const uint8_t point[32]);
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#endif
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// fe means field element. Here the field is \Z/(2^255-19). An element t,
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// entries t[0]...t[9], represents the integer t[0]+2^26 t[1]+2^51 t[2]+2^77
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// t[3]+2^102 t[4]+...+2^230 t[9]. Bounds on each t[i] vary depending on
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// context.
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typedef int32_t fe[10];
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/* ge means group element.
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* Here the group is the set of pairs (x,y) of field elements (see fe.h)
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* satisfying -x^2 + y^2 = 1 + d x^2y^2
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* where d = -121665/121666.
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*
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* Representations:
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* ge_p2 (projective): (X:Y:Z) satisfying x=X/Z, y=Y/Z
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* ge_p3 (extended): (X:Y:Z:T) satisfying x=X/Z, y=Y/Z, XY=ZT
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* ge_p1p1 (completed): ((X:Z),(Y:T)) satisfying x=X/Z, y=Y/T
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* ge_precomp (Duif): (y+x,y-x,2dxy) */
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typedef struct {
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fe X;
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fe Y;
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fe Z;
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} ge_p2;
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typedef struct {
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fe X;
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fe Y;
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fe Z;
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fe T;
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} ge_p3;
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typedef struct {
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fe X;
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fe Y;
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fe Z;
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fe T;
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} ge_p1p1;
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typedef struct {
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fe yplusx;
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fe yminusx;
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fe xy2d;
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} ge_precomp;
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typedef struct {
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fe YplusX;
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fe YminusX;
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fe Z;
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fe T2d;
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} ge_cached;
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void x25519_ge_tobytes(uint8_t *s, const ge_p2 *h);
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int x25519_ge_frombytes_vartime(ge_p3 *h, const uint8_t *s);
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void x25519_ge_p3_to_cached(ge_cached *r, const ge_p3 *p);
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void x25519_ge_p1p1_to_p2(ge_p2 *r, const ge_p1p1 *p);
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void x25519_ge_p1p1_to_p3(ge_p3 *r, const ge_p1p1 *p);
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void x25519_ge_add(ge_p1p1 *r, const ge_p3 *p, const ge_cached *q);
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void x25519_ge_sub(ge_p1p1 *r, const ge_p3 *p, const ge_cached *q);
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void x25519_ge_scalarmult_small_precomp(
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ge_p3 *h, const uint8_t a[32], const uint8_t precomp_table[15 * 2 * 32]);
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void x25519_ge_scalarmult_base(ge_p3 *h, const uint8_t a[32]);
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void x25519_ge_scalarmult(ge_p2 *r, const uint8_t *scalar, const ge_p3 *A);
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void x25519_sc_reduce(uint8_t *s);
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enum spake2_state_t {
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spake2_state_init = 0,
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spake2_state_msg_generated,
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spake2_state_key_generated,
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};
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struct spake2_ctx_st {
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uint8_t private_key[32];
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uint8_t my_msg[32];
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uint8_t password_scalar[32];
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uint8_t password_hash[64];
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uint8_t *my_name;
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size_t my_name_len;
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uint8_t *their_name;
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size_t their_name_len;
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enum spake2_role_t my_role;
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enum spake2_state_t state;
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char disable_password_scalar_hack;
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};
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#if defined(__cplusplus)
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} // extern C
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#endif
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#endif // OPENSSL_HEADER_CURVE25519_INTERNAL_H
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