Mercurial > dropbear
view libtommath/bn_mp_unpack.c @ 1715:3974f087d9c0
Disallow leading lines before the ident for server (#102)
Per RFC4253 4.2 clients must be able to process other lines of data
before the version string, server behavior is not defined neither
with MUST/SHOULD nor with MAY.
If server process up to 50 lines too - it may cause too long hanging
session with invalid/evil client that consume host resources and
potentially may lead to DDoS on poor embedded boxes.
Let's require first line from client to be version string and fail
early if it's not - matches both RFC and real OpenSSH behavior.
author | Vladislav Grishenko <themiron@users.noreply.github.com> |
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date | Mon, 15 Jun 2020 18:22:18 +0500 |
parents | 1051e4eea25a |
children |
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#include "tommath_private.h" #ifdef BN_MP_UNPACK_C /* LibTomMath, multiple-precision integer library -- Tom St Denis */ /* SPDX-License-Identifier: Unlicense */ /* based on gmp's mpz_import. * see http://gmplib.org/manual/Integer-Import-and-Export.html */ mp_err mp_unpack(mp_int *rop, size_t count, mp_order order, size_t size, mp_endian endian, size_t nails, const void *op) { mp_err err; size_t odd_nails, nail_bytes, i, j; unsigned char odd_nail_mask; mp_zero(rop); if (endian == MP_NATIVE_ENDIAN) { MP_GET_ENDIANNESS(endian); } odd_nails = (nails % 8u); odd_nail_mask = 0xff; for (i = 0; i < odd_nails; ++i) { odd_nail_mask ^= (unsigned char)(1u << (7u - i)); } nail_bytes = nails / 8u; for (i = 0; i < count; ++i) { for (j = 0; j < (size - nail_bytes); ++j) { unsigned char byte = *((const unsigned char *)op + (((order == MP_MSB_FIRST) ? i : ((count - 1u) - i)) * size) + ((endian == MP_BIG_ENDIAN) ? (j + nail_bytes) : (((size - 1u) - j) - nail_bytes))); if ((err = mp_mul_2d(rop, (j == 0u) ? (int)(8u - odd_nails) : 8, rop)) != MP_OKAY) { return err; } rop->dp[0] |= (j == 0u) ? (mp_digit)(byte & odd_nail_mask) : (mp_digit)byte; rop->used += 1; } } mp_clamp(rop); return MP_OKAY; } #endif