1 | /* |
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2 | * Open a connection to a remote server. |
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3 | * |
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4 | * This is the client implementation of opening a connection to a remote |
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5 | * server and doing the initial GSS-API negotiation. This function is shared |
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6 | * between the v1 and v2 implementations. One of the things it establishes is |
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7 | * what protocol is being used. |
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8 | * |
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9 | * Written by Russ Allbery <rra@stanford.edu> |
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10 | * Based on work by Anton Ushakov |
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11 | * Copyright 2002, 2003, 2004, 2005, 2006, 2007, 2008 |
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12 | * Board of Trustees, Leland Stanford Jr. University |
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13 | * |
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14 | * See LICENSE for licensing terms. |
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15 | */ |
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16 | |
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17 | #include <config.h> |
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18 | #include <portable/system.h> |
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19 | #include <portable/gssapi.h> |
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20 | #include <portable/socket.h> |
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21 | |
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22 | #include <errno.h> |
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23 | |
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24 | #include <client/internal.h> |
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25 | #include <client/remctl.h> |
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26 | #include <util/util.h> |
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27 | |
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28 | |
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29 | /* |
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30 | * Given the remctl object (for error reporting), host, and port, attempt a |
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31 | * network connection. Returns the file descriptor if successful or -1 on |
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32 | * failure. |
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33 | */ |
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34 | static int |
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35 | internal_connect(struct remctl *r, const char *host, unsigned short port) |
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36 | { |
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37 | struct addrinfo hints, *ai; |
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38 | char portbuf[16]; |
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39 | int status, fd; |
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40 | |
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41 | /* |
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42 | * Look up the remote host and open a TCP connection. Call getaddrinfo |
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43 | * and network_connect instead of network_connect_host so that we can |
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44 | * report the complete error on host resolution. |
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45 | */ |
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46 | memset(&hints, 0, sizeof(hints)); |
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47 | hints.ai_family = AF_UNSPEC; |
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48 | hints.ai_socktype = SOCK_STREAM; |
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49 | snprintf(portbuf, sizeof(portbuf), "%hu", port); |
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50 | status = getaddrinfo(host, portbuf, &hints, &ai); |
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51 | if (status != 0) { |
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52 | internal_set_error(r, "unknown host %s: %s", host, |
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53 | gai_strerror(status)); |
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54 | return -1; |
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55 | } |
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56 | fd = network_connect(ai, NULL); |
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57 | freeaddrinfo(ai); |
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58 | if (fd < 0) { |
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59 | internal_set_error(r, "cannot connect to %s (port %hu): %s", host, |
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60 | port, socket_strerror(socket_errno)); |
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61 | return -1; |
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62 | } |
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63 | return fd; |
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64 | } |
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65 | |
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66 | |
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67 | /* |
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68 | * Given the remctl struct, the host to connect to, the principal name (which |
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69 | * may be NULL to use the default), and a pointer to a gss_name_t, import that |
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70 | * principal into a GSS-API name. We want to use a host-based name if |
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71 | * possible since that will trigger domain to realm mapping and name |
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72 | * canonicalization if desired, but given an arbitrary Kerberos principal, we |
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73 | * don't know whether it's host-based or not. Therefore, if the principal was |
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74 | * specified explicitly, always just use it. |
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75 | * |
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76 | * Returns true on success and false on failure. |
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77 | */ |
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78 | static bool |
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79 | internal_import_name(struct remctl *r, const char *host, |
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80 | const char *principal, gss_name_t *name) |
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81 | { |
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82 | gss_buffer_desc name_buffer; |
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83 | char *defprinc = NULL; |
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84 | size_t length; |
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85 | OM_uint32 major, minor; |
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86 | gss_OID oid; |
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87 | |
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88 | /* |
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89 | * If principal is NULL, use host@<host>. Don't use concat here since it |
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90 | * dies on failure and that's rude for a library. |
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91 | */ |
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92 | if (principal == NULL) { |
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93 | length = strlen("host@") + strlen(host) + 1; |
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94 | defprinc = malloc(length); |
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95 | if (defprinc == NULL) { |
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96 | internal_set_error(r, "cannot allocate memory: %s", |
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97 | strerror(errno)); |
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98 | return false; |
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99 | } |
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100 | strlcpy(defprinc, "host@", length); |
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101 | strlcat(defprinc, host, length); |
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102 | principal = defprinc; |
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103 | } |
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104 | |
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105 | /* |
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106 | * Import the name. If principal was null, we use a host-based OID; |
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107 | * otherwise, specify that the name is a Kerberos principal. |
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108 | */ |
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109 | name_buffer.value = (char *) principal; |
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110 | name_buffer.length = strlen(principal) + 1; |
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111 | if (defprinc == NULL) |
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112 | oid = GSS_C_NT_USER_NAME; |
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113 | else |
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114 | oid = GSS_C_NT_HOSTBASED_SERVICE; |
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115 | major = gss_import_name(&minor, &name_buffer, oid, name); |
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116 | if (defprinc != NULL) |
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117 | free(defprinc); |
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118 | if (major != GSS_S_COMPLETE) { |
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119 | internal_gssapi_error(r, "parsing name", major, minor); |
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120 | return false; |
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121 | } |
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122 | return true; |
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123 | } |
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124 | |
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125 | |
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126 | /* |
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127 | * Open a new connection to a server. Returns true on success, false on |
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128 | * failure. On failure, sets the error message appropriately. |
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129 | */ |
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130 | bool |
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131 | internal_open(struct remctl *r, const char *host, unsigned short port, |
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132 | const char *principal) |
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133 | { |
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134 | int status, flags; |
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135 | bool port_fallback = false; |
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136 | int fd = -1; |
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137 | gss_buffer_desc send_tok, recv_tok, *token_ptr; |
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138 | gss_buffer_desc empty_token = { 0, (void *) "" }; |
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139 | gss_name_t name = GSS_C_NO_NAME; |
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140 | gss_ctx_id_t gss_context = GSS_C_NO_CONTEXT; |
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141 | OM_uint32 major, minor, init_minor, gss_flags; |
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142 | static const OM_uint32 wanted_gss_flags |
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143 | = (GSS_C_MUTUAL_FLAG | GSS_C_CONF_FLAG | GSS_C_INTEG_FLAG |
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144 | | GSS_C_REPLAY_FLAG | GSS_C_SEQUENCE_FLAG); |
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145 | static const OM_uint32 req_gss_flags |
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146 | = (GSS_C_MUTUAL_FLAG | GSS_C_CONF_FLAG | GSS_C_INTEG_FLAG); |
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147 | |
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148 | /* |
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149 | * If port is 0, default to trying the standard port and then falling back |
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150 | * on the old port. |
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151 | */ |
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152 | if (port == 0) { |
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153 | port = REMCTL_PORT; |
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154 | port_fallback = true; |
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155 | } |
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156 | |
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157 | /* Make the network connection. */ |
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158 | fd = internal_connect(r, host, port); |
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159 | if (fd < 0 && port_fallback) |
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160 | fd = internal_connect(r, host, REMCTL_PORT_OLD); |
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161 | if (fd < 0) |
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162 | goto fail; |
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163 | r->fd = fd; |
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164 | |
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165 | /* Import the name. */ |
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166 | if (!internal_import_name(r, host, principal, &name)) |
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167 | goto fail; |
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168 | |
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169 | /* |
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170 | * Default to protocol version two, but if some other protocol is already |
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171 | * set in the remctl struct, don't override. This facility is used only |
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172 | * for testing currently. |
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173 | */ |
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174 | if (r->protocol == 0) |
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175 | r->protocol = 2; |
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176 | |
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177 | /* Send the initial negotiation token. */ |
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178 | status = token_send(fd, TOKEN_NOOP | TOKEN_CONTEXT_NEXT | TOKEN_PROTOCOL, |
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179 | &empty_token); |
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180 | if (status != TOKEN_OK) { |
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181 | internal_token_error(r, "sending initial token", status, 0, 0); |
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182 | goto fail; |
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183 | } |
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184 | |
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185 | /* Perform the context-establishment loop. |
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186 | * |
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187 | * On each pass through the loop, token_ptr points to the token to send to |
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188 | * the server (or GSS_C_NO_BUFFER on the first pass). Every generated |
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189 | * token is stored in send_tok which is then transmitted to the server; |
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190 | * every received token is stored in recv_tok, which token_ptr is then set |
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191 | * to, to be processed by the next call to gss_init_sec_context. |
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192 | * |
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193 | * GSS-API guarantees that send_tok's length will be non-zero if and only |
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194 | * if the server is expecting another token from us, and that |
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195 | * gss_init_sec_context returns GSS_S_CONTINUE_NEEDED if and only if the |
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196 | * server has another token to send us. |
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197 | * |
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198 | * We start with the assumption that we're going to do protocol v2, but if |
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199 | * the server ever drops TOKEN_PROTOCOL from the response, we fall back to |
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200 | * v1. |
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201 | */ |
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202 | token_ptr = GSS_C_NO_BUFFER; |
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203 | do { |
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204 | major = gss_init_sec_context(&init_minor, GSS_C_NO_CREDENTIAL, |
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205 | &gss_context, name, (const gss_OID) GSS_KRB5_MECHANISM, |
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206 | wanted_gss_flags, 0, NULL, token_ptr, NULL, &send_tok, |
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207 | &gss_flags, NULL); |
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208 | if (token_ptr != GSS_C_NO_BUFFER) |
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209 | free(recv_tok.value); |
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210 | |
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211 | /* If we have anything more to say, send it. */ |
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212 | if (send_tok.length != 0) { |
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213 | flags = TOKEN_CONTEXT; |
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214 | if (r->protocol > 1) |
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215 | flags |= TOKEN_PROTOCOL; |
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216 | status = token_send(fd, flags, &send_tok); |
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217 | if (status != TOKEN_OK) { |
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218 | internal_token_error(r, "sending token", status, major, minor); |
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219 | gss_release_buffer(&minor, &send_tok); |
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220 | goto fail; |
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221 | } |
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222 | } |
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223 | gss_release_buffer(&minor, &send_tok); |
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224 | |
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225 | /* On error, report the error and abort. */ |
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226 | if (major != GSS_S_COMPLETE && major != GSS_S_CONTINUE_NEEDED) { |
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227 | internal_gssapi_error(r, "initializing context", major, |
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228 | init_minor); |
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229 | goto fail; |
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230 | } |
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231 | |
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232 | /* |
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233 | * If the flags we get back from the server are bad and we're doing |
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234 | * protocol v2, report an error and abort. |
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235 | */ |
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236 | if (r->protocol > 1 && (gss_flags & req_gss_flags) != req_gss_flags) { |
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237 | internal_set_error(r, "server did not negotiate acceptable" |
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238 | " GSS-API flags"); |
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239 | goto fail; |
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240 | } |
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241 | |
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242 | /* If we're still expecting more, retrieve it. */ |
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243 | if (major == GSS_S_CONTINUE_NEEDED) { |
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244 | status = token_recv(fd, &flags, &recv_tok, TOKEN_MAX_LENGTH); |
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245 | if (status != TOKEN_OK) { |
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246 | internal_token_error(r, "receiving token", status, major, |
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247 | minor); |
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248 | goto fail; |
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249 | } |
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250 | if (r->protocol > 1 && (flags & TOKEN_PROTOCOL) != TOKEN_PROTOCOL) |
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251 | r->protocol = 1; |
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252 | token_ptr = &recv_tok; |
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253 | } |
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254 | } while (major == GSS_S_CONTINUE_NEEDED); |
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255 | |
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256 | r->context = gss_context; |
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257 | r->ready = 0; |
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258 | gss_release_name(&minor, &name); |
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259 | return true; |
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260 | |
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261 | fail: |
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262 | if (fd >= 0) |
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263 | socket_close(fd); |
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264 | r->fd = -1; |
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265 | if (name != GSS_C_NO_NAME) |
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266 | gss_release_name(&minor, &name); |
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267 | if (gss_context != GSS_C_NO_CONTEXT) |
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268 | gss_delete_sec_context(&minor, &gss_context, GSS_C_NO_BUFFER); |
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269 | return false; |
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270 | } |
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