Mercurial > dropbear

annotate libtomcrypt/src/pk/asn1/der/bit/der_encode_bit_string.c @ 1715:3974f087d9c0

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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
285
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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_bit_string.c
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13 ASN.1 DER, encode a BIT STRING, Tom St Denis
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14 */
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15
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16
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17 #ifdef LTC_DER
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18
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19 /**
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20 Store a BIT STRING
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21 @param in The array of bits to store (one per char)
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22 @param inlen The number of bits tostore
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23 @param out [out] The destination for the DER encoded BIT STRING
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24 @param outlen [in/out] The max size and resulting size of the DER BIT STRING
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25 @return CRYPT_OK if successful
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26 */
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27 int der_encode_bit_string(const unsigned char *in, unsigned long inlen,
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28 unsigned char *out, unsigned long *outlen)
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29 {
382
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30 unsigned long len, x, y;
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31 unsigned char buf;
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32 int err;
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33
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34 LTC_ARGCHK(in != NULL);
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35 LTC_ARGCHK(out != NULL);
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36 LTC_ARGCHK(outlen != NULL);
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37
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38 /* avoid overflows */
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39 if ((err = der_length_bit_string(inlen, &len)) != CRYPT_OK) {
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40 return err;
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41 }
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42
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43 if (len > *outlen) {
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44 *outlen = len;
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45 return CRYPT_BUFFER_OVERFLOW;
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46 }
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47
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48 /* store header (include bit padding count in length) */
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49 x = 0;
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50 y = (inlen >> 3) + ((inlen&7) ? 1 : 0) + 1;
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51
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52 out[x++] = 0x03;
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53 if (y < 128) {
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54 out[x++] = (unsigned char)y;
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55 } else if (y < 256) {
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56 out[x++] = 0x81;
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57 out[x++] = (unsigned char)y;
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58 } else if (y < 65536) {
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59 out[x++] = 0x82;
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60 out[x++] = (unsigned char)((y>>8)&255);
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61 out[x++] = (unsigned char)(y&255);
285
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62 }
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63
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64 /* store number of zero padding bits */
382
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65 out[x++] = (unsigned char)((8 - inlen) & 7);
285
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66
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67 /* store the bits in big endian format */
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68 for (y = buf = 0; y < inlen; y++) {
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69 buf |= (in[y] ? 1 : 0) << (7 - (y & 7));
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70 if ((y & 7) == 7) {
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71 out[x++] = buf;
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72 buf = 0;
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73 }
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74 }
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75 /* store last byte */
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76 if (inlen & 7) {
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77 out[x++] = buf;
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78 }
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79 *outlen = x;
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80 return CRYPT_OK;
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81 }
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82
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83 #endif
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84
1471
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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85 /* ref: $Format:%D$ */
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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86 /* git commit: $Format:%H$ */
6dba84798cd5 Update to libtomcrypt 1.18.1, merged with Dropbear changes
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87 /* commit time: $Format:%ai$ */