1 | /* Copyright 1994, 1999 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 | /* This is the server for the lert system. */ |
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17 | |
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18 | static const char rcsid[] = "$Id: lertsrv.c,v 1.9 2006-03-10 07:07:34 ghudson Exp $"; |
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19 | |
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20 | #include <stdio.h> |
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21 | #include <unistd.h> |
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22 | #include <krb.h> |
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23 | #include <krb5.h> |
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24 | #include <des.h> |
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25 | #include <sys/types.h> |
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26 | #include <sys/stat.h> |
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27 | #include <fcntl.h> |
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28 | #include <sys/socket.h> |
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29 | #include <sys/uio.h> |
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30 | #include <netinet/in.h> |
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31 | #include <arpa/inet.h> |
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32 | #include <netdb.h> |
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33 | #include <sys/time.h> |
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34 | #include <hesiod.h> |
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35 | #include <string.h> |
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36 | #include <pwd.h> |
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37 | #include <sys/utsname.h> |
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38 | #include <errno.h> |
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39 | #include "lert.h" |
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40 | |
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41 | int get_user(char *pname, char *result, int onetime, char *ip); |
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42 | |
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43 | krb5_context context = NULL; |
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44 | |
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45 | int main(int argc, char **argv) |
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46 | { |
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47 | int s; /* The Socket */ |
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48 | struct sockaddr_in sin; |
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49 | struct sockaddr_in from; |
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50 | char packet[2048]; |
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51 | char *ip; |
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52 | char *username = NULL; |
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53 | int plen; |
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54 | char opacket[2048]; |
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55 | int fromlen; |
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56 | int status; |
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57 | int len; |
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58 | AUTH_DAT ad; |
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59 | KTEXT_ST authent; |
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60 | KTEXT_ST ktxt; |
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61 | /* for krb_mk_priv */ |
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62 | des_key_schedule sched; /* session key schedule */ |
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63 | struct hostent *hp; |
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64 | struct utsname thishost; |
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65 | char instance[INST_SZ]; |
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66 | /* for the krb5-authenticated v2 of the protocol */ |
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67 | krb5_error_code problem; |
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68 | krb5_auth_context auth_con = NULL; |
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69 | krb5_data auth, inbuf, outbuf; |
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70 | krb5_principal server = NULL, client = NULL; |
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71 | krb5_ticket *ticket; |
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72 | krb5_keytab keytab = NULL; |
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73 | |
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74 | ticket = NULL; |
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75 | memset(&outbuf, 0, sizeof(krb5_data)); |
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76 | |
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77 | #ifdef LOGGING |
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78 | setbuf(stdout, NULL); |
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79 | #endif |
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80 | |
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81 | s = socket(AF_INET, SOCK_DGRAM, 0); |
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82 | |
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83 | if (uname(&thishost) == -1) |
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84 | { |
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85 | fprintf(stderr, "%s: Unable to get system information: %s\n", |
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86 | argv[0], strerror(errno)); |
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87 | exit(1); |
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88 | } |
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89 | hp = gethostbyname(thishost.nodename); |
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90 | if (hp == NULL) { |
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91 | fprintf(stderr, "%s: Unable to get host name information: %s\n", |
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92 | argv[0], strerror(errno)); |
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93 | exit(1); |
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94 | } |
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95 | |
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96 | /* Clear the socket structure. */ |
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97 | memset(&sin, 0, sizeof(sin)); |
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98 | sin.sin_family = AF_INET; |
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99 | sin.sin_port = htons(LERT_PORT); |
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100 | memcpy(&sin.sin_addr.s_addr, hp->h_addr, hp->h_length); |
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101 | |
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102 | if (bind(s, (struct sockaddr *)&sin, sizeof(sin)) < 0) |
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103 | { |
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104 | fprintf(stderr, "%s: Unable to bind socket: %s\n", |
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105 | argv[0], strerror(errno)); |
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106 | exit(1); |
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107 | } |
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108 | |
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109 | fromlen = sizeof(from); |
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110 | |
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111 | for (;;) |
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112 | { |
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113 | plen = recvfrom(s, packet, sizeof(packet), 0, |
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114 | (struct sockaddr *)&from, &fromlen); |
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115 | if (plen < 0) |
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116 | { |
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117 | fprintf(stderr, "lertsrv: Error during recv: %s\n", |
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118 | strerror(errno)); |
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119 | sleep(1); /* Prevent infinite cpu hog loop */ |
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120 | continue; |
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121 | } |
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122 | |
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123 | #ifdef DEBUG |
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124 | fprintf(stderr, "lertsrv: Received packet of length %d\n", plen); |
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125 | #endif |
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126 | |
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127 | if (packet[0] == '1') |
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128 | { |
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129 | /* krb4-authenticated version of the protocol. */ |
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130 | |
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131 | /* Copy authenticator into aligned region. */ |
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132 | memcpy(&authent, &packet[LERT_LENGTH], sizeof(authent)); |
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133 | |
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134 | strcpy(instance, "*"); |
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135 | status = krb_rd_req(&authent, LERT_SERVICE, instance, 0, &ad, |
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136 | LERTS_SRVTAB); |
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137 | |
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138 | if (status != KSUCCESS) |
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139 | { |
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140 | fprintf(stderr, "lertsrv: Kerberos failure: %s\n", |
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141 | krb_err_txt[status]); |
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142 | continue; |
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143 | } |
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144 | |
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145 | opacket[0] = '1'; |
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146 | if ((strlen(ad.pinst) != 0) || (strcmp(ad.prealm, "ATHENA.MIT.EDU"))) |
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147 | { |
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148 | fprintf(stderr, "lertsrv: %s.%s@%s -- Not null instance ATHENA " |
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149 | "realm.\n", ad.pname, ad.pinst, ad.prealm); |
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150 | opacket[1] = LERT_NOT_IN_DB; |
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151 | opacket[2] = '\0'; |
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152 | } |
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153 | else |
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154 | get_user(ad.pname, &(opacket[1]), ad.checksum, |
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155 | inet_ntoa(from.sin_addr)); |
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156 | |
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157 | /* Prepare krb_mk_priv message */ |
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158 | des_key_sched(ad.session, sched); |
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159 | |
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160 | /* Make the encrypted message: |
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161 | * version, code, data, plus terminating '\0' |
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162 | */ |
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163 | len = krb_mk_priv(opacket, ktxt.dat, |
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164 | LERT_CHECK + strlen(opacket + LERT_CHECK) + 1, |
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165 | sched, ad.session, &sin, &from); |
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166 | |
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167 | /* Send it. */ |
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168 | if (sendto(s, ktxt.dat, len, 0, |
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169 | (struct sockaddr *) &from, sizeof(from)) < 0) |
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170 | fprintf(stderr, "lertsrv: sendto failed: %s\n", strerror(errno)); |
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171 | |
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172 | /* Avoid confusion, zeroize now */ |
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173 | memset(&from, 0, sizeof(from)); |
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174 | } |
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175 | else if (packet[0] == LERT_VERSION) |
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176 | { |
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177 | /* krb5-authenticated version of the protocol. */ |
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178 | if (!context) |
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179 | { |
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180 | problem = krb5_init_context(&context); |
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181 | if (problem) |
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182 | goto out; |
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183 | } |
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184 | problem = krb5_auth_con_init(context, &auth_con); |
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185 | if (problem) |
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186 | goto out; |
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187 | |
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188 | problem = |
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189 | krb5_auth_con_genaddrs(context, auth_con, s, |
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190 | KRB5_AUTH_CONTEXT_GENERATE_LOCAL_ADDR); |
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191 | if (problem) |
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192 | goto out; |
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193 | |
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194 | problem = krb5_sname_to_principal(context, NULL, LERT_SERVICE, |
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195 | KRB5_NT_SRV_HST, &server); |
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196 | if (problem) |
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197 | goto out; |
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198 | |
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199 | problem = krb5_kt_resolve(context, LERTS_KEYTAB, &keytab); |
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200 | if (problem) |
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201 | goto out; |
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202 | |
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203 | /* Get the authenticator. */ |
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204 | auth.data = packet + LERT_LENGTH; |
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205 | auth.length = sizeof(packet) - sizeof(int) - LERT_LENGTH; |
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206 | |
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207 | problem = krb5_rd_req(context, &auth_con, &auth, server, keytab, |
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208 | NULL, &ticket); |
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209 | if (problem) |
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210 | goto out; |
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211 | |
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212 | problem = krb5_copy_principal(context, ticket->enc_part2->client, |
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213 | &client); |
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214 | if (problem) |
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215 | goto out; |
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216 | |
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217 | opacket[0] = LERT_VERSION; |
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218 | |
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219 | /* If the client is something other than null instance principal |
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220 | * or is from a realm other than the server's local realm, punt |
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221 | * them. |
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222 | */ |
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223 | if ((krb5_princ_size(context, client) != 1) || |
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224 | krb5_realm_compare(context, client, server) == 0) |
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225 | { |
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226 | krb5_unparse_name(context, client, &username); |
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227 | if (username) |
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228 | { |
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229 | fprintf(stderr, "lertsrv: %s not null instance in realm " |
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230 | "%s.\n", username, |
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231 | krb5_princ_realm(context, server)->data); |
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232 | free(username); |
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233 | } |
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234 | opacket[1] = LERT_NOT_IN_DB; |
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235 | opacket[2] = '\0'; |
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236 | } |
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237 | else |
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238 | /* packet[1] will be a 0 or 1 depending on whether or not the |
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239 | * user called lert with the -n flag to indicate they don't |
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240 | * want to see the message anymore. |
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241 | * |
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242 | * The krb4 code passes in the checksum member of the AUTH_DAT |
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243 | * structure filled in by krb_rd_req(). While it will happen to |
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244 | * be 0 if the user didn't call lert with the -n flag, using |
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245 | * the value from the packet directly seems a bit more sane. |
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246 | */ |
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247 | { |
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248 | username = malloc(krb5_princ_component(context, client, 0)->length + 1); |
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249 | if (!username) |
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250 | goto out; |
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251 | strncpy(username, krb5_princ_component(context, client, 0)->data, |
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252 | krb5_princ_component(context, client, 0)->length); |
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253 | username[krb5_princ_component(context, client, 0)->length] = '\0'; |
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254 | |
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255 | get_user(username, &(opacket[1]), packet[1], |
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256 | inet_ntoa(from.sin_addr)); |
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257 | } |
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258 | |
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259 | inbuf.data = opacket; |
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260 | inbuf.length = strlen(opacket); |
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261 | |
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262 | problem = krb5_mk_priv(context, auth_con, &inbuf, &outbuf, NULL); |
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263 | if (problem) |
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264 | goto out; |
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265 | |
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266 | if (sendto(s, outbuf.data, outbuf.length, 0, |
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267 | (struct sockaddr *)&from, sizeof(from)) < 0) |
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268 | fprintf(stderr, "lertsrv: sendto failed: %s\n", strerror(errno)); |
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269 | |
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270 | /* Avoid confusion, zeroize now */ |
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271 | memset(&from, 0, sizeof(from)); |
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272 | |
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273 | out: |
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274 | if (problem) |
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275 | fprintf(stderr, "lertsrv: Kerberos error: %s\n", |
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276 | error_message(problem)); |
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277 | /* krb5 library checks if this is allocated for us. */ |
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278 | krb5_free_data_contents(context, &outbuf); |
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279 | memset(&outbuf, 0, sizeof(krb5_data)); |
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280 | if (client) |
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281 | krb5_free_principal(context, client); |
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282 | if (server) |
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283 | krb5_free_principal(context, server); |
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284 | if (ticket) |
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285 | krb5_free_ticket(context, ticket); |
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286 | if (auth_con) |
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287 | krb5_auth_con_free(context, auth_con); |
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288 | if (username) |
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289 | free(username); |
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290 | /* reset to NULL after freeing since we're going to go through |
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291 | * this loop again. |
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292 | */ |
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293 | client = server = NULL; |
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294 | ticket = NULL; |
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295 | auth_con = NULL; |
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296 | username = NULL; |
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297 | } |
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298 | else |
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299 | { |
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300 | fprintf(stderr, "lertsrv: Received packet with bad version: %d\n", |
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301 | packet[0]); |
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302 | } |
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303 | } |
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304 | |
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305 | return 0; |
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306 | } |
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307 | |
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308 | int get_user(char *pname, char *result, int onetime, char *ip) |
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309 | { |
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310 | DBM *db; |
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311 | DBM *db2; |
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312 | datum data; |
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313 | datum key; |
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314 | datum data2; |
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315 | char result2[128]; |
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316 | |
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317 | /* Prepare nil return. */ |
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318 | result[0] = LERT_FREE; |
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319 | result[1] = '\0'; |
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320 | |
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321 | /* Open the database. */ |
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322 | db = dbm_open(LERTS_DATA, O_RDWR, 0600); |
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323 | if (db == NULL) |
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324 | { |
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325 | fprintf(stderr, "Unable to open lert's database file %s: %s.\n", |
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326 | LERTS_DATA, strerror(errno)); |
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327 | return LERT_NO_DB; |
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328 | } |
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329 | |
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330 | key.dptr = pname; |
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331 | key.dsize = strlen(pname) + 1; |
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332 | |
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333 | /* Get the user. */ |
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334 | data = dbm_fetch(db, key); |
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335 | if (data.dptr == NULL) |
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336 | { |
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337 | /* Not in db. */ |
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338 | dbm_close(db); |
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339 | #ifdef LOGGING |
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340 | fprintf(stdout, "lertsrv: %s user %s not in db\n", ip, pname); |
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341 | #endif |
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342 | return LERT_NOT_IN_DB; |
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343 | } |
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344 | else |
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345 | { |
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346 | strncpy(&(result[1]), data.dptr, data.dsize); |
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347 | result[data.dsize + 1] = '\0'; |
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348 | |
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349 | if (onetime) |
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350 | { |
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351 | /* Add them to the log. */ |
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352 | db2 = dbm_open(LERTS_LOG, O_RDWR | O_CREAT, 0600); |
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353 | if (db2 == NULL) |
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354 | { |
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355 | fprintf(stderr, "Unable to open lert's log database %s: %s.\n", |
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356 | LERTS_LOG, strerror(errno)); |
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357 | } |
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358 | else |
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359 | { |
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360 | data2 = dbm_fetch(db2, key); |
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361 | if (data2.dptr == NULL) |
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362 | dbm_store(db2, key, data, DBM_INSERT); |
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363 | else |
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364 | { |
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365 | strncpy(result2, data2.dptr, data2.dsize); |
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366 | strncpy(&(result2[data2.dsize]), data.dptr, data.dsize); |
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367 | data2.dptr = result2; |
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368 | data2.dsize += data.dsize; |
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369 | dbm_store(db2, key, data2, DBM_REPLACE); |
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370 | } |
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371 | dbm_close(db2); |
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372 | } |
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373 | dbm_delete(db, key); |
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374 | } |
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375 | dbm_close(db); |
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376 | } |
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377 | |
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378 | result[0] = LERT_MSG; |
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379 | #ifdef LOGGING |
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380 | fprintf(stdout, "lertsrv: %s user %s in db with groups :%s:\n", ip, pname, |
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381 | result); |
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382 | #endif |
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383 | return LERT_GOTCHA; |
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384 | } |
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385 | |
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386 | |
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