Mercurial > dropbear
view libtomcrypt/src/pk/asn1/der/sequence/der_encode_sequence_ex.c @ 1790:42745af83b7d
Introduce extra delay before closing unauthenticated sessions
To make it harder for attackers, introduce a delay to keep an
unauthenticated session open a bit longer, thus blocking a connection
slot until after the delay.
Without this, while there is a limit on the amount of attempts an attacker
can make at the same time (MAX_UNAUTH_PER_IP), the time taken by dropbear to
handle one attempt is still short and thus for each of the allowed parallel
attempts many attempts can be chained one after the other. The attempt rate
is then:
"MAX_UNAUTH_PER_IP / <process time of one attempt>".
With the delay, this rate becomes:
"MAX_UNAUTH_PER_IP / UNAUTH_CLOSE_DELAY".
author | Thomas De Schampheleire <thomas.de_schampheleire@nokia.com> |
---|---|
date | Wed, 15 Feb 2017 13:53:04 +0100 |
parents | 6dba84798cd5 |
children |
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/* LibTomCrypt, modular cryptographic library -- Tom St Denis * * LibTomCrypt is a library that provides various cryptographic * algorithms in a highly modular and flexible manner. * * The library is free for all purposes without any express * guarantee it works. */ #include "tomcrypt.h" /** @file der_encode_sequence_ex.c ASN.1 DER, encode a SEQUENCE, Tom St Denis */ #ifdef LTC_DER /** Encode a SEQUENCE @param list The list of items to encode @param inlen The number of items in the list @param out [out] The destination @param outlen [in/out] The size of the output @param type_of LTC_ASN1_SEQUENCE or LTC_ASN1_SET/LTC_ASN1_SETOF @return CRYPT_OK on success */ int der_encode_sequence_ex(ltc_asn1_list *list, unsigned long inlen, unsigned char *out, unsigned long *outlen, int type_of) { int err; ltc_asn1_type type; unsigned long size, x, y, z, i; void *data; LTC_ARGCHK(list != NULL); LTC_ARGCHK(out != NULL); LTC_ARGCHK(outlen != NULL); /* get size of output that will be required */ y = 0; z = 0; if ((err = der_length_sequence_ex(list, inlen, &y, &z)) != CRYPT_OK) return CRYPT_INVALID_ARG; /* too big ? */ if (*outlen < y) { *outlen = y; err = CRYPT_BUFFER_OVERFLOW; goto LBL_ERR; } /* store header */ x = 0; out[x++] = (type_of == LTC_ASN1_SEQUENCE) ? 0x30 : 0x31; if (z < 128) { out[x++] = (unsigned char)z; } else if (z < 256) { out[x++] = 0x81; out[x++] = (unsigned char)z; } else if (z < 65536UL) { out[x++] = 0x82; out[x++] = (unsigned char)((z>>8UL)&255); out[x++] = (unsigned char)(z&255); } else if (z < 16777216UL) { out[x++] = 0x83; out[x++] = (unsigned char)((z>>16UL)&255); out[x++] = (unsigned char)((z>>8UL)&255); out[x++] = (unsigned char)(z&255); } /* store data */ *outlen -= x; for (i = 0; i < inlen; i++) { type = list[i].type; size = list[i].size; data = list[i].data; if (type == LTC_ASN1_EOL) { break; } switch (type) { case LTC_ASN1_BOOLEAN: z = *outlen; if ((err = der_encode_boolean(*((int *)data), out + x, &z)) != CRYPT_OK) { goto LBL_ERR; } break; case LTC_ASN1_INTEGER: z = *outlen; if ((err = der_encode_integer(data, out + x, &z)) != CRYPT_OK) { goto LBL_ERR; } break; case LTC_ASN1_SHORT_INTEGER: z = *outlen; if ((err = der_encode_short_integer(*((unsigned long*)data), out + x, &z)) != CRYPT_OK) { goto LBL_ERR; } break; case LTC_ASN1_BIT_STRING: z = *outlen; if ((err = der_encode_bit_string(data, size, out + x, &z)) != CRYPT_OK) { goto LBL_ERR; } break; case LTC_ASN1_RAW_BIT_STRING: z = *outlen; if ((err = der_encode_raw_bit_string(data, size, out + x, &z)) != CRYPT_OK) { goto LBL_ERR; } break; case LTC_ASN1_OCTET_STRING: z = *outlen; if ((err = der_encode_octet_string(data, size, out + x, &z)) != CRYPT_OK) { goto LBL_ERR; } break; case LTC_ASN1_NULL: out[x] = 0x05; out[x+1] = 0x00; z = 2; break; case LTC_ASN1_OBJECT_IDENTIFIER: z = *outlen; if ((err = der_encode_object_identifier(data, size, out + x, &z)) != CRYPT_OK) { goto LBL_ERR; } break; case LTC_ASN1_IA5_STRING: z = *outlen; if ((err = der_encode_ia5_string(data, size, out + x, &z)) != CRYPT_OK) { goto LBL_ERR; } break; case LTC_ASN1_PRINTABLE_STRING: z = *outlen; if ((err = der_encode_printable_string(data, size, out + x, &z)) != CRYPT_OK) { goto LBL_ERR; } break; case LTC_ASN1_UTF8_STRING: z = *outlen; if ((err = der_encode_utf8_string(data, size, out + x, &z)) != CRYPT_OK) { goto LBL_ERR; } break; case LTC_ASN1_UTCTIME: z = *outlen; if ((err = der_encode_utctime(data, out + x, &z)) != CRYPT_OK) { goto LBL_ERR; } break; case LTC_ASN1_GENERALIZEDTIME: z = *outlen; if ((err = der_encode_generalizedtime(data, out + x, &z)) != CRYPT_OK) { goto LBL_ERR; } break; case LTC_ASN1_SET: z = *outlen; if ((err = der_encode_set(data, size, out + x, &z)) != CRYPT_OK) { goto LBL_ERR; } break; case LTC_ASN1_SETOF: z = *outlen; if ((err = der_encode_setof(data, size, out + x, &z)) != CRYPT_OK) { goto LBL_ERR; } break; case LTC_ASN1_SEQUENCE: z = *outlen; if ((err = der_encode_sequence_ex(data, size, out + x, &z, type)) != CRYPT_OK) { goto LBL_ERR; } break; case LTC_ASN1_CHOICE: case LTC_ASN1_CONSTRUCTED: case LTC_ASN1_CONTEXT_SPECIFIC: case LTC_ASN1_EOL: case LTC_ASN1_TELETEX_STRING: err = CRYPT_INVALID_ARG; goto LBL_ERR; } x += z; *outlen -= z; } *outlen = x; err = CRYPT_OK; LBL_ERR: return err; } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */