Mercurial > dropbear

annotate circbuffer.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 06d52bcb8094
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
rev   line source
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1 /*
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2 * Dropbear SSH
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3 *
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4 * Copyright (c) 2002-2004 Matt Johnston
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5 * All rights reserved.
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6 *
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7 * Permission is hereby granted, free of charge, to any person obtaining a copy
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8 * of this software and associated documentation files (the "Software"), to deal
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9 * in the Software without restriction, including without limitation the rights
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10 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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11 * copies of the Software, and to permit persons to whom the Software is
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12 * furnished to do so, subject to the following conditions:
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13 *
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14 * The above copyright notice and this permission notice shall be included in
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15 * all copies or substantial portions of the Software.
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16 *
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17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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20 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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23 * SOFTWARE. */
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24
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25 #include "includes.h"
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26 #include "dbutil.h"
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27 #include "circbuffer.h"
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28
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29 #define MAX_CBUF_SIZE 100000000
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30
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31 circbuffer * cbuf_new(unsigned int size) {
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32
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33 circbuffer *cbuf = NULL;
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34
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35 if (size > MAX_CBUF_SIZE) {
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36 dropbear_exit("Bad cbuf size");
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37 }
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38
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39 cbuf = (circbuffer*)m_malloc(sizeof(circbuffer));
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40 /* data is malloced on first write */
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41 cbuf->data = NULL;
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42 cbuf->used = 0;
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43 cbuf->readpos = 0;
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44 cbuf->writepos = 0;
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45 cbuf->size = size;
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46
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47 return cbuf;
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48 }
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49
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50 void cbuf_free(circbuffer * cbuf) {
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51
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52 if (cbuf->data) {
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53 m_burn(cbuf->data, cbuf->size);
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54 m_free(cbuf->data);
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55 }
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56 m_free(cbuf);
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57 }
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58
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59 unsigned int cbuf_getused(const circbuffer * cbuf) {
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60
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61 return cbuf->used;
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62
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63 }
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64
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65 unsigned int cbuf_getavail(const circbuffer * cbuf) {
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66
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67 return cbuf->size - cbuf->used;
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68
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69 }
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70
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71 unsigned int cbuf_writelen(const circbuffer *cbuf) {
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72
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73 dropbear_assert(cbuf->used <= cbuf->size);
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74 dropbear_assert(((2*cbuf->size)+cbuf->writepos-cbuf->readpos)%cbuf->size == cbuf->used%cbuf->size);
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75 dropbear_assert(((2*cbuf->size)+cbuf->readpos-cbuf->writepos)%cbuf->size == (cbuf->size-cbuf->used)%cbuf->size);
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76
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77 if (cbuf->used == cbuf->size) {
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78 TRACE(("cbuf_writelen: full buffer"))
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79 return 0; /* full */
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80 }
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81
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82 if (cbuf->writepos < cbuf->readpos) {
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83 return cbuf->readpos - cbuf->writepos;
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84 }
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85
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86 return cbuf->size - cbuf->writepos;
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87 }
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88
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89 void cbuf_readptrs(const circbuffer *cbuf,
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90 unsigned char **p1, unsigned int *len1,
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91 unsigned char **p2, unsigned int *len2) {
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92 *p1 = &cbuf->data[cbuf->readpos];
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93 *len1 = MIN(cbuf->used, cbuf->size - cbuf->readpos);
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94
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95 if (*len1 < cbuf->used) {
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96 *p2 = cbuf->data;
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97 *len2 = cbuf->used - *len1;
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98 } else {
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99 *p2 = NULL;
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100 *len2 = 0;
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101 }
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102 }
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103
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104 unsigned char* cbuf_writeptr(circbuffer *cbuf, unsigned int len) {
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105
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106 if (len > cbuf_writelen(cbuf)) {
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107 dropbear_exit("Bad cbuf write");
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108 }
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109
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110 if (!cbuf->data) {
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111 /* lazy allocation */
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112 cbuf->data = (unsigned char*)m_malloc(cbuf->size);
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113 }
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114
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115 return &cbuf->data[cbuf->writepos];
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116 }
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117
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118 void cbuf_incrwrite(circbuffer *cbuf, unsigned int len) {
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119 if (len > cbuf_writelen(cbuf)) {
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120 dropbear_exit("Bad cbuf write");
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121 }
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122
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123 cbuf->used += len;
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124 dropbear_assert(cbuf->used <= cbuf->size);
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125 cbuf->writepos = (cbuf->writepos + len) % cbuf->size;
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126 }
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127
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128
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129 void cbuf_incrread(circbuffer *cbuf, unsigned int len) {
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130 dropbear_assert(cbuf->used >= len);
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131 cbuf->used -= len;
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132 cbuf->readpos = (cbuf->readpos + len) % cbuf->size;
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133 }