Mercurial > dropbear
view libtomcrypt/src/pk/asn1/der/ia5/der_length_ia5_string.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> |
---|---|
date | Mon, 15 Jun 2020 18:22:18 +0500 |
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_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: $Format:%ai$ */