1 | /* Copyright 1998 by the Massachusetts Institute of Technology. |
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2 | * |
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3 | * Permission to use, copy, modify, and distribute this |
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4 | * software and its documentation for any purpose and without |
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5 | * fee is hereby granted, provided that the above copyright |
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6 | * notice appear in all copies and that both that copyright |
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7 | * notice and this permission notice appear in supporting |
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8 | * documentation, and that the name of M.I.T. not be used in |
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9 | * advertising or publicity pertaining to distribution of the |
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10 | * software without specific, written prior permission. |
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11 | * M.I.T. makes no representations about the suitability of |
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12 | * this software for any purpose. It is provided "as is" |
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13 | * without express or implied warranty. |
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14 | */ |
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15 | |
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16 | static const char rcsid[] = "$Id: athinfod.c,v 1.3 1999-10-19 20:22:56 danw Exp $"; |
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17 | |
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18 | #include <sys/types.h> |
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19 | #include <sys/stat.h> |
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20 | #include <sys/socket.h> |
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21 | #include <stdio.h> |
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22 | #include <stdlib.h> |
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23 | #include <string.h> |
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24 | #include <ctype.h> |
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25 | #include <unistd.h> |
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26 | #include <fcntl.h> |
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27 | #include <dirent.h> |
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28 | #include <fnmatch.h> |
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29 | #include <errno.h> |
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30 | |
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31 | #define PATH_ATHINFO_DEFS "/etc/athena/athinfo.defs" |
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32 | #define PATH_ATHINFO_ACCESS "/etc/athena/athinfo.access" |
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33 | #define PATH_ATHINFO_DEFS_D "/etc/athena/athinfo.defs.d" |
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34 | #define ATHINFO_DEFS_D_WILDCARD "*.defs" /* Files to be read in defs.d */ |
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35 | |
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36 | static const char *read_query(void); |
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37 | static void shutdown_input(void); |
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38 | static const char *get_definition(const char *query); |
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39 | static void check_enabled(const char *query); |
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40 | static int first_field_matches(const char *s, const char *word); |
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41 | static const char *skip_spaces(const char *p); |
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42 | static const char *skip_nonspaces(const char *p); |
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43 | static int read_line(FILE *fp, char **buf, int *bufsize); |
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44 | static void *emalloc(size_t size); |
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45 | static void *erealloc(void *ptr, size_t size); |
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46 | |
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47 | int main(int argc, char **argv) |
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48 | { |
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49 | const char *query, *cmd; |
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50 | |
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51 | query = read_query(); |
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52 | shutdown_input(); |
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53 | cmd = get_definition(query); |
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54 | check_enabled(query); |
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55 | execl("/bin/sh", "sh", "-c", cmd, (char *) NULL); |
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56 | fprintf(stderr, "athinfod: cannot run shell, aborting.\n"); |
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57 | return 1; |
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58 | } |
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59 | |
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60 | /* Read the query from stdin and validate it. */ |
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61 | static const char *read_query(void) |
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62 | { |
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63 | char *line = NULL; |
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64 | int linesize; |
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65 | const char *p; |
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66 | |
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67 | if (read_line(stdin, &line, &linesize) != 0) |
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68 | { |
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69 | fprintf(stderr, "athinfod: couldn't read query.\n"); |
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70 | exit(0); |
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71 | } |
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72 | |
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73 | /* Make sure the query consists of printable nonspace characters. */ |
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74 | for (p = line; *p; p++) |
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75 | { |
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76 | if (!isprint((unsigned char)*p) || isspace((unsigned char)*p)) |
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77 | { |
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78 | fprintf(stderr, "athinfod: invalid query.\n"); |
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79 | exit(0); |
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80 | } |
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81 | } |
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82 | return line; |
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83 | } |
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84 | |
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85 | /* Shut down the input side of the inetd socket and repoint stdin at |
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86 | * /dev/null. This eliminates the possibility of malicious input |
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87 | * affecting the commands we execute. |
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88 | */ |
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89 | static void shutdown_input(void) |
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90 | { |
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91 | int fd; |
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92 | |
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93 | shutdown(STDIN_FILENO, 0); |
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94 | close(STDIN_FILENO); |
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95 | fd = open("/dev/null", O_RDONLY); |
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96 | if (fd == -1) |
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97 | { |
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98 | fprintf(stderr, "athinfod: cannot open /dev/null, aborting.\n"); |
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99 | exit(1); |
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100 | } |
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101 | if (fd != STDIN_FILENO) |
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102 | { |
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103 | dup2(fd, STDIN_FILENO); |
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104 | close(fd); |
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105 | } |
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106 | } |
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107 | |
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108 | /* Read the definition of query from the specified file. */ |
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109 | static const char *get_definition_from_file(const char *query, |
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110 | const char *filepath) |
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111 | { |
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112 | char *line = NULL; |
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113 | int linesize; |
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114 | FILE *fp; |
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115 | |
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116 | fp = fopen(filepath, "r"); |
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117 | if (!fp) |
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118 | { |
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119 | fprintf(stderr, |
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120 | "athinfod: cannot open %s (%s), aborting.\n", filepath, strerror(errno)); |
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121 | exit(1); |
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122 | } |
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123 | |
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124 | while (read_line(fp, &line, &linesize) == 0) |
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125 | { |
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126 | /* Ignore comment lines. */ |
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127 | if (*line == '#') |
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128 | continue; |
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129 | |
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130 | if (first_field_matches(line, query)) |
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131 | { |
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132 | fclose(fp); |
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133 | return skip_spaces(skip_nonspaces(line)); |
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134 | } |
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135 | } |
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136 | |
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137 | fclose(fp); |
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138 | return NULL; |
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139 | } |
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140 | |
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141 | static int defs_file_filter(const struct dirent *entry) |
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142 | { |
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143 | return fnmatch(ATHINFO_DEFS_D_WILDCARD, entry->d_name, 0) == 0; |
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144 | } |
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145 | |
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146 | static const char *get_definition(const char *query) |
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147 | { |
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148 | const char *definition; |
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149 | definition = get_definition_from_file(query, PATH_ATHINFO_DEFS); |
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150 | if (definition != NULL) |
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151 | return definition; |
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152 | |
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153 | struct dirent **namelist; |
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154 | int numfiles, i; |
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155 | numfiles = scandir(PATH_ATHINFO_DEFS_D, &namelist, |
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156 | defs_file_filter, alphasort); |
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157 | if (numfiles < 0) { |
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158 | if (errno != ENOENT) { |
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159 | fprintf(stderr, "athinfod: %s while scanning %s.\n", |
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160 | strerror(errno), PATH_ATHINFO_DEFS_D); |
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161 | exit(1); |
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162 | } |
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163 | } else { |
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164 | for (i = 0; i < numfiles; i++) { |
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165 | int len; |
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166 | char path[PATH_MAX]; |
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167 | len = snprintf(path, sizeof(path), "%s/%s", PATH_ATHINFO_DEFS_D, |
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168 | namelist[i]->d_name); |
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169 | if (len < 0 || len >= (int)sizeof(path)) |
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170 | /* Should we print an error here? I don't think so. */ |
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171 | continue; |
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172 | definition = get_definition_from_file(query, path); |
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173 | if (definition != NULL) |
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174 | break; |
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175 | } |
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176 | } |
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177 | |
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178 | for (i = 0; i < numfiles; i++) |
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179 | free(namelist[i]); |
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180 | free(namelist); |
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181 | |
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182 | if (definition != NULL) |
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183 | return definition; |
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184 | fprintf(stderr, "athinfod: unrecognized query.\n"); |
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185 | exit(0); |
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186 | } |
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187 | |
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188 | /* See if this command is enabled. */ |
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189 | static void check_enabled(const char *query) |
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190 | { |
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191 | char *line = NULL; |
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192 | int linesize, enabled = 0, val; |
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193 | FILE *fp; |
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194 | const char *p; |
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195 | |
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196 | fp = fopen(PATH_ATHINFO_ACCESS, "r"); |
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197 | if (!fp) |
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198 | { |
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199 | fprintf(stderr, |
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200 | "athinfod: cannot open athinfo access file, aborting.\n"); |
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201 | exit(1); |
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202 | } |
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203 | |
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204 | while (read_line(fp, &line, &linesize) == 0) |
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205 | { |
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206 | /* Only pay attention to lines starting with "enable" or "disable". */ |
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207 | if (first_field_matches(line, "enable")) |
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208 | val = 1; |
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209 | else if (first_field_matches(line, "disable")) |
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210 | val = 0; |
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211 | else |
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212 | continue; |
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213 | |
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214 | /* If we find an exact match, stop. If we find a glob match, |
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215 | * accept that value for now but hold out for an exact match. |
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216 | * (This means if there are conflicting lines in the config |
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217 | * file, we take the first exact match but the last glob match. |
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218 | * Oh well.) |
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219 | */ |
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220 | p = skip_spaces(skip_nonspaces(line)); |
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221 | if (first_field_matches(p, query)) |
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222 | { |
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223 | enabled = val; |
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224 | break; |
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225 | } |
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226 | else if (first_field_matches(p, "*")) |
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227 | enabled = val; |
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228 | } |
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229 | |
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230 | fclose(fp); |
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231 | free(line); |
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232 | if (!enabled) |
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233 | { |
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234 | fprintf(stderr, "athinfod: query disabled.\n"); |
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235 | exit(0); |
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236 | } |
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237 | } |
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238 | |
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239 | static int first_field_matches(const char *s, const char *word) |
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240 | { |
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241 | int len = strlen(word); |
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242 | |
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243 | return (strncasecmp(s, word, len) == 0 && |
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244 | (isspace((unsigned char)s[len]) || !s[len])); |
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245 | } |
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246 | |
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247 | static const char *skip_spaces(const char *p) |
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248 | { |
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249 | while (isspace((unsigned char)*p)) |
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250 | p++; |
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251 | return p; |
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252 | } |
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253 | |
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254 | static const char *skip_nonspaces(const char *p) |
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255 | { |
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256 | while (*p && !isspace((unsigned char)*p)) |
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257 | p++; |
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258 | return p; |
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259 | } |
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260 | |
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261 | /* Read a line from a file into a dynamically allocated buffer, |
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262 | * zeroing the trailing newline if there is one. The calling routine |
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263 | * may call read_line multiple times with the same buf and bufsize |
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264 | * pointers; *buf will be reallocated and *bufsize adjusted as |
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265 | * appropriate. The initial value of *buf should be NULL. After the |
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266 | * calling routine is done reading lines, it should free *buf. This |
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267 | * function returns 0 if a line was successfully read, 1 if the file |
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268 | * ended, and -1 if there was an I/O error. |
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269 | */ |
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270 | static int read_line(FILE *fp, char **buf, int *bufsize) |
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271 | { |
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272 | char *newbuf; |
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273 | int offset = 0, len; |
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274 | |
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275 | if (*buf == NULL) |
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276 | { |
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277 | *buf = emalloc(128); |
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278 | *bufsize = 128; |
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279 | } |
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280 | |
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281 | while (1) |
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282 | { |
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283 | if (!fgets(*buf + offset, *bufsize - offset, fp)) |
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284 | return (offset != 0) ? 0 : (ferror(fp)) ? -1 : 1; |
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285 | len = offset + strlen(*buf + offset); |
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286 | if ((*buf)[len - 1] == '\n') |
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287 | { |
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288 | (*buf)[len - 1] = 0; |
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289 | if (len > 1 && (*buf)[len - 2] == '\r') |
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290 | (*buf)[len - 2] = 0; |
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291 | return 0; |
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292 | } |
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293 | offset = len; |
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294 | |
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295 | /* Allocate more space. */ |
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296 | newbuf = erealloc(*buf, *bufsize * 2); |
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297 | *buf = newbuf; |
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298 | *bufsize *= 2; |
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299 | } |
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300 | } |
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301 | |
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302 | static void *emalloc(size_t size) |
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303 | { |
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304 | void *ptr; |
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305 | |
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306 | ptr = malloc(size); |
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307 | if (!ptr) |
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308 | { |
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309 | fprintf(stderr, "athinfod: malloc failure, aborting.\n"); |
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310 | exit(1); |
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311 | } |
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312 | return ptr; |
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313 | } |
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314 | |
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315 | void *erealloc(void *ptr, size_t size) |
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316 | { |
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317 | ptr = realloc(ptr, size); |
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318 | if (!ptr) |
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319 | { |
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320 | fprintf(stderr, "athinfod: realloc failure, aborting.\n"); |
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321 | exit(1); |
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322 | } |
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323 | return ptr; |
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324 | } |
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