Mercurial > dropbear
view libtomcrypt/src/pk/asn1/der/ia5/der_length_ia5_string.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 |
line wrap: on
line source
/* 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_length_ia5_string.c ASN.1 DER, get length of IA5 STRING, Tom St Denis */ #ifdef LTC_DER static const struct { int code, value; } ia5_table[] = { { '\0', 0 }, { '\a', 7 }, { '\b', 8 }, { '\t', 9 }, { '\n', 10 }, { '\f', 12 }, { '\r', 13 }, { ' ', 32 }, { '!', 33 }, { '"', 34 }, { '#', 35 }, { '$', 36 }, { '%', 37 }, { '&', 38 }, { '\'', 39 }, { '(', 40 }, { ')', 41 }, { '*', 42 }, { '+', 43 }, { ',', 44 }, { '-', 45 }, { '.', 46 }, { '/', 47 }, { '0', 48 }, { '1', 49 }, { '2', 50 }, { '3', 51 }, { '4', 52 }, { '5', 53 }, { '6', 54 }, { '7', 55 }, { '8', 56 }, { '9', 57 }, { ':', 58 }, { ';', 59 }, { '<', 60 }, { '=', 61 }, { '>', 62 }, { '?', 63 }, { '@', 64 }, { 'A', 65 }, { 'B', 66 }, { 'C', 67 }, { 'D', 68 }, { 'E', 69 }, { 'F', 70 }, { 'G', 71 }, { 'H', 72 }, { 'I', 73 }, { 'J', 74 }, { 'K', 75 }, { 'L', 76 }, { 'M', 77 }, { 'N', 78 }, { 'O', 79 }, { 'P', 80 }, { 'Q', 81 }, { 'R', 82 }, { 'S', 83 }, { 'T', 84 }, { 'U', 85 }, { 'V', 86 }, { 'W', 87 }, { 'X', 88 }, { 'Y', 89 }, { 'Z', 90 }, { '[', 91 }, { '\\', 92 }, { ']', 93 }, { '^', 94 }, { '_', 95 }, { '`', 96 }, { 'a', 97 }, { 'b', 98 }, { 'c', 99 }, { 'd', 100 }, { 'e', 101 }, { 'f', 102 }, { 'g', 103 }, { 'h', 104 }, { 'i', 105 }, { 'j', 106 }, { 'k', 107 }, { 'l', 108 }, { 'm', 109 }, { 'n', 110 }, { 'o', 111 }, { 'p', 112 }, { 'q', 113 }, { 'r', 114 }, { 's', 115 }, { 't', 116 }, { 'u', 117 }, { 'v', 118 }, { 'w', 119 }, { 'x', 120 }, { 'y', 121 }, { 'z', 122 }, { '{', 123 }, { '|', 124 }, { '}', 125 }, { '~', 126 } }; int der_ia5_char_encode(int c) { int x; for (x = 0; x < (int)(sizeof(ia5_table)/sizeof(ia5_table[0])); x++) { if (ia5_table[x].code == c) { return ia5_table[x].value; } } return -1; } int der_ia5_value_decode(int v) { int x; for (x = 0; x < (int)(sizeof(ia5_table)/sizeof(ia5_table[0])); x++) { if (ia5_table[x].value == v) { return ia5_table[x].code; } } return -1; } /** Gets length of DER encoding of IA5 STRING @param octets The values you want to encode @param noctets The number of octets in the string to encode @param outlen [out] The length of the DER encoding for the given string @return CRYPT_OK if successful */ int der_length_ia5_string(const unsigned char *octets, unsigned long noctets, unsigned long *outlen) { unsigned long x; LTC_ARGCHK(outlen != NULL); LTC_ARGCHK(octets != NULL); /* scan string for validity */ for (x = 0; x < noctets; x++) { if (der_ia5_char_encode(octets[x]) == -1) { return CRYPT_INVALID_ARG; } } if (noctets < 128) { /* 16 LL DD DD DD ... */ *outlen = 2 + noctets; } else if (noctets < 256) { /* 16 81 LL DD DD DD ... */ *outlen = 3 + noctets; } else if (noctets < 65536UL) { /* 16 82 LL LL DD DD DD ... */ *outlen = 4 + noctets; } else if (noctets < 16777216UL) { /* 16 83 LL LL LL DD DD DD ... */ *outlen = 5 + noctets; } else { return CRYPT_INVALID_ARG; } return CRYPT_OK; } #endif /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */