annotate libtomcrypt/src/pk/asn1/der/utctime/der_encode_utctime.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
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
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2 *
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3 * LibTomCrypt is a library that provides various cryptographic
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4 * algorithms in a highly modular and flexible manner.
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5 *
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6 * The library is free for all purposes without any express
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7 * guarantee it works.
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8 */
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9 #include "tomcrypt.h"
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10
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11 /**
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12 @file der_encode_utctime.c
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13 ASN.1 DER, encode a UTCTIME, Tom St Denis
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14 */
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15
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16 #ifdef LTC_DER
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17
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18 static const char * const baseten = "0123456789";
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19
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20 #define STORE_V(y) \
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21 out[x++] = der_ia5_char_encode(baseten[(y/10) % 10]); \
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22 out[x++] = der_ia5_char_encode(baseten[y % 10]);
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23
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24 /**
382
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25 Encodes a UTC time structure in DER format
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26 @param utctime The UTC time structure to encode
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27 @param out The destination of the DER encoding of the UTC time structure
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28 @param outlen [in/out] The length of the DER encoding
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29 @return CRYPT_OK if successful
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30 */
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31 int der_encode_utctime(ltc_utctime *utctime,
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32 unsigned char *out, unsigned long *outlen)
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33 {
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34 unsigned long x, tmplen;
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35 int err;
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36
285
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37 LTC_ARGCHK(utctime != NULL);
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38 LTC_ARGCHK(out != NULL);
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39 LTC_ARGCHK(outlen != NULL);
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40
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41 if ((err = der_length_utctime(utctime, &tmplen)) != CRYPT_OK) {
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42 return err;
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43 }
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44 if (tmplen > *outlen) {
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45 *outlen = tmplen;
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46 return CRYPT_BUFFER_OVERFLOW;
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47 }
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48
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49 /* store header */
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50 out[0] = 0x17;
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51
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52 /* store values */
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53 x = 2;
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54 STORE_V(utctime->YY);
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55 STORE_V(utctime->MM);
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56 STORE_V(utctime->DD);
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57 STORE_V(utctime->hh);
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58 STORE_V(utctime->mm);
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59 STORE_V(utctime->ss);
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60
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61 if (utctime->off_mm || utctime->off_hh) {
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62 out[x++] = der_ia5_char_encode(utctime->off_dir ? '-' : '+');
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63 STORE_V(utctime->off_hh);
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64 STORE_V(utctime->off_mm);
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65 } else {
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66 out[x++] = der_ia5_char_encode('Z');
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67 }
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68
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69 /* store length */
382
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70 out[1] = (unsigned char)(x - 2);
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71
285
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72 /* all good let's return */
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73 *outlen = x;
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74 return CRYPT_OK;
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75 }
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76
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77 #endif
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78
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79 /* ref: $Format:%D$ */
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80 /* git commit: $Format:%H$ */
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81 /* commit time: $Format:%ai$ */