| 1 | /************************************************* |
| 2 | * Exim - an Internet mail transport agent * |
| 3 | *************************************************/ |
| 4 | |
| 5 | /* Copyright (c) University of Cambridge 1995 - 2018 */ |
| 6 | /* See the file NOTICE for conditions of use and distribution. */ |
| 7 | |
| 8 | #include "../exim.h" |
| 9 | #include "plaintext.h" |
| 10 | |
| 11 | |
| 12 | /* Options specific to the plaintext authentication mechanism. */ |
| 13 | |
| 14 | optionlist auth_plaintext_options[] = { |
| 15 | { "client_ignore_invalid_base64", opt_bool, |
| 16 | (void *)(offsetof(auth_plaintext_options_block, client_ignore_invalid_base64)) }, |
| 17 | { "client_send", opt_stringptr, |
| 18 | (void *)(offsetof(auth_plaintext_options_block, client_send)) }, |
| 19 | { "server_prompts", opt_stringptr, |
| 20 | (void *)(offsetof(auth_plaintext_options_block, server_prompts)) } |
| 21 | }; |
| 22 | |
| 23 | /* Size of the options list. An extern variable has to be used so that its |
| 24 | address can appear in the tables drtables.c. */ |
| 25 | |
| 26 | int auth_plaintext_options_count = |
| 27 | sizeof(auth_plaintext_options)/sizeof(optionlist); |
| 28 | |
| 29 | /* Default private options block for the plaintext authentication method. */ |
| 30 | |
| 31 | auth_plaintext_options_block auth_plaintext_option_defaults = { |
| 32 | NULL, /* server_prompts */ |
| 33 | NULL, /* client_send */ |
| 34 | FALSE /* client_ignore_invalid_base64 */ |
| 35 | }; |
| 36 | |
| 37 | |
| 38 | #ifdef MACRO_PREDEF |
| 39 | |
| 40 | /* Dummy values */ |
| 41 | void auth_plaintext_init(auth_instance *ablock) {} |
| 42 | int auth_plaintext_server(auth_instance *ablock, uschar *data) {return 0;} |
| 43 | int auth_plaintext_client(auth_instance *ablock, void * sx, int timeout, |
| 44 | uschar *buffer, int buffsize) {return 0;} |
| 45 | |
| 46 | #else /*!MACRO_PREDEF*/ |
| 47 | |
| 48 | |
| 49 | |
| 50 | /************************************************* |
| 51 | * Initialization entry point * |
| 52 | *************************************************/ |
| 53 | |
| 54 | /* Called for each instance, after its options have been read, to |
| 55 | enable consistency checks to be done, or anything else that needs |
| 56 | to be set up. */ |
| 57 | |
| 58 | void |
| 59 | auth_plaintext_init(auth_instance *ablock) |
| 60 | { |
| 61 | auth_plaintext_options_block *ob = |
| 62 | (auth_plaintext_options_block *)(ablock->options_block); |
| 63 | if (ablock->public_name == NULL) ablock->public_name = ablock->name; |
| 64 | if (ablock->server_condition != NULL) ablock->server = TRUE; |
| 65 | if (ob->client_send != NULL) ablock->client = TRUE; |
| 66 | } |
| 67 | |
| 68 | |
| 69 | |
| 70 | /************************************************* |
| 71 | * Server entry point * |
| 72 | *************************************************/ |
| 73 | |
| 74 | /* For interface, see auths/README */ |
| 75 | |
| 76 | int |
| 77 | auth_plaintext_server(auth_instance *ablock, uschar *data) |
| 78 | { |
| 79 | auth_plaintext_options_block *ob = |
| 80 | (auth_plaintext_options_block *)(ablock->options_block); |
| 81 | const uschar *prompts = ob->server_prompts; |
| 82 | uschar *clear, *end, *s; |
| 83 | int number = 1; |
| 84 | int len, rc; |
| 85 | int sep = 0; |
| 86 | |
| 87 | /* Expand a non-empty list of prompt strings */ |
| 88 | |
| 89 | if (prompts != NULL) |
| 90 | { |
| 91 | prompts = expand_cstring(prompts); |
| 92 | if (prompts == NULL) |
| 93 | { |
| 94 | auth_defer_msg = expand_string_message; |
| 95 | return DEFER; |
| 96 | } |
| 97 | } |
| 98 | |
| 99 | /* If data was supplied on the AUTH command, decode it, and split it up into |
| 100 | multiple items at binary zeros. The strings are put into $auth1, $auth2, etc, |
| 101 | up to a maximum. To retain backwards compatibility, they are also put int $1, |
| 102 | $2, etc. If the data consists of the string "=" it indicates a single, empty |
| 103 | string. */ |
| 104 | |
| 105 | if (*data != 0) |
| 106 | { |
| 107 | if (Ustrcmp(data, "=") == 0) |
| 108 | { |
| 109 | auth_vars[0] = expand_nstring[++expand_nmax] = US""; |
| 110 | expand_nlength[expand_nmax] = 0; |
| 111 | } |
| 112 | else |
| 113 | { |
| 114 | if ((len = b64decode(data, &clear)) < 0) return BAD64; |
| 115 | end = clear + len; |
| 116 | while (clear < end && expand_nmax < EXPAND_MAXN) |
| 117 | { |
| 118 | if (expand_nmax < AUTH_VARS) auth_vars[expand_nmax] = clear; |
| 119 | expand_nstring[++expand_nmax] = clear; |
| 120 | while (*clear != 0) clear++; |
| 121 | expand_nlength[expand_nmax] = clear++ - expand_nstring[expand_nmax]; |
| 122 | } |
| 123 | } |
| 124 | } |
| 125 | |
| 126 | /* Now go through the list of prompt strings. Skip over any whose data has |
| 127 | already been provided as part of the AUTH command. For the rest, send them |
| 128 | out as prompts, and get a data item back. If the data item is "*", abandon the |
| 129 | authentication attempt. Otherwise, split it into items as above. */ |
| 130 | |
| 131 | while ((s = string_nextinlist(&prompts, &sep, big_buffer, big_buffer_size)) |
| 132 | != NULL && expand_nmax < EXPAND_MAXN) |
| 133 | { |
| 134 | if (number++ <= expand_nmax) continue; |
| 135 | if ((rc = auth_get_data(&data, s, Ustrlen(s))) != OK) return rc; |
| 136 | if ((len = b64decode(data, &clear)) < 0) return BAD64; |
| 137 | end = clear + len; |
| 138 | |
| 139 | /* This loop must run at least once, in case the length is zero */ |
| 140 | do |
| 141 | { |
| 142 | if (expand_nmax < AUTH_VARS) auth_vars[expand_nmax] = clear; |
| 143 | expand_nstring[++expand_nmax] = clear; |
| 144 | while (*clear != 0) clear++; |
| 145 | expand_nlength[expand_nmax] = clear++ - expand_nstring[expand_nmax]; |
| 146 | } |
| 147 | while (clear < end && expand_nmax < EXPAND_MAXN); |
| 148 | } |
| 149 | |
| 150 | /* We now have a number of items of data in $auth1, $auth2, etc (and also, for |
| 151 | compatibility, in $1, $2, etc). Authentication and authorization are handled |
| 152 | together for this authenticator by expanding the server_condition option. Note |
| 153 | that ablock->server_condition is always non-NULL because that's what configures |
| 154 | this authenticator as a server. */ |
| 155 | |
| 156 | return auth_check_serv_cond(ablock); |
| 157 | } |
| 158 | |
| 159 | |
| 160 | |
| 161 | /************************************************* |
| 162 | * Client entry point * |
| 163 | *************************************************/ |
| 164 | |
| 165 | /* For interface, see auths/README */ |
| 166 | |
| 167 | int |
| 168 | auth_plaintext_client( |
| 169 | auth_instance *ablock, /* authenticator block */ |
| 170 | void * sx, /* smtp connextion */ |
| 171 | int timeout, /* command timeout */ |
| 172 | uschar *buffer, /* buffer for reading response */ |
| 173 | int buffsize) /* size of buffer */ |
| 174 | { |
| 175 | auth_plaintext_options_block *ob = |
| 176 | (auth_plaintext_options_block *)(ablock->options_block); |
| 177 | const uschar *text = ob->client_send; |
| 178 | uschar *s; |
| 179 | BOOL first = TRUE; |
| 180 | int sep = 0; |
| 181 | int auth_var_idx = 0; |
| 182 | |
| 183 | /* The text is broken up into a number of different data items, which are |
| 184 | sent one by one. The first one is sent with the AUTH command; the remainder are |
| 185 | sent in response to subsequent prompts. Each is expanded before being sent. */ |
| 186 | |
| 187 | while ((s = string_nextinlist(&text, &sep, big_buffer, big_buffer_size))) |
| 188 | { |
| 189 | int len, clear_len; |
| 190 | uschar *ss = expand_string(s); |
| 191 | uschar *clear; |
| 192 | |
| 193 | /* Forced expansion failure is not an error; authentication is abandoned. On |
| 194 | all but the first string, we have to abandon the authentication attempt by |
| 195 | sending a line containing "*". Save the failed expansion string, because it |
| 196 | is in big_buffer, and that gets used by the sending function. */ |
| 197 | |
| 198 | if (!ss) |
| 199 | { |
| 200 | uschar *ssave = string_copy(s); |
| 201 | if (!first) |
| 202 | { |
| 203 | if (smtp_write_command(sx, SCMD_FLUSH, "*\r\n") >= 0) |
| 204 | (void) smtp_read_response(sx, US buffer, buffsize, '2', timeout); |
| 205 | } |
| 206 | if (f.expand_string_forcedfail) |
| 207 | { |
| 208 | *buffer = 0; /* No message */ |
| 209 | return CANCELLED; |
| 210 | } |
| 211 | string_format(buffer, buffsize, "expansion of \"%s\" failed in %s " |
| 212 | "authenticator: %s", ssave, ablock->name, expand_string_message); |
| 213 | return ERROR; |
| 214 | } |
| 215 | |
| 216 | len = Ustrlen(ss); |
| 217 | |
| 218 | /* The character ^ is used as an escape for a binary zero character, which is |
| 219 | needed for the PLAIN mechanism. It must be doubled if really needed. */ |
| 220 | |
| 221 | for (int i = 0; i < len; i++) |
| 222 | if (ss[i] == '^') |
| 223 | if (ss[i+1] != '^') |
| 224 | ss[i] = 0; |
| 225 | else |
| 226 | { |
| 227 | i++; |
| 228 | len--; |
| 229 | memmove(ss + i, ss + i + 1, len - i); |
| 230 | } |
| 231 | |
| 232 | /* The first string is attached to the AUTH command; others are sent |
| 233 | unembellished. */ |
| 234 | |
| 235 | if (first) |
| 236 | { |
| 237 | first = FALSE; |
| 238 | if (smtp_write_command(sx, SCMD_FLUSH, "AUTH %s%s%s\r\n", |
| 239 | ablock->public_name, len == 0 ? "" : " ", b64encode(ss, len)) < 0) |
| 240 | return FAIL_SEND; |
| 241 | } |
| 242 | else |
| 243 | { |
| 244 | if (smtp_write_command(sx, SCMD_FLUSH, "%s\r\n", b64encode(ss, len)) < 0) |
| 245 | return FAIL_SEND; |
| 246 | } |
| 247 | |
| 248 | /* If we receive a success response from the server, authentication |
| 249 | has succeeded. There may be more data to send, but is there any point |
| 250 | in provoking an error here? */ |
| 251 | |
| 252 | if (smtp_read_response(sx, US buffer, buffsize, '2', timeout)) return OK; |
| 253 | |
| 254 | /* Not a success response. If errno != 0 there is some kind of transmission |
| 255 | error. Otherwise, check the response code in the buffer. If it starts with |
| 256 | '3', more data is expected. */ |
| 257 | |
| 258 | if (errno != 0 || buffer[0] != '3') return FAIL; |
| 259 | |
| 260 | /* If there is no more data to send, we have to cancel the authentication |
| 261 | exchange and return ERROR. */ |
| 262 | |
| 263 | if (!text) |
| 264 | { |
| 265 | if (smtp_write_command(sx, SCMD_FLUSH, "*\r\n") >= 0) |
| 266 | (void)smtp_read_response(sx, US buffer, buffsize, '2', timeout); |
| 267 | string_format(buffer, buffsize, "Too few items in client_send in %s " |
| 268 | "authenticator", ablock->name); |
| 269 | return ERROR; |
| 270 | } |
| 271 | |
| 272 | /* Now that we know we'll continue, we put the received data into $auth<n>, |
| 273 | if possible. First, decode it: buffer+4 skips over the SMTP status code. */ |
| 274 | |
| 275 | clear_len = b64decode(buffer+4, &clear); |
| 276 | |
| 277 | /* If decoding failed, the default is to terminate the authentication, and |
| 278 | return FAIL, with the SMTP response still in the buffer. However, if client_ |
| 279 | ignore_invalid_base64 is set, we ignore the error, and put an empty string |
| 280 | into $auth<n>. */ |
| 281 | |
| 282 | if (clear_len < 0) |
| 283 | { |
| 284 | uschar *save_bad = string_copy(buffer); |
| 285 | if (!ob->client_ignore_invalid_base64) |
| 286 | { |
| 287 | if (smtp_write_command(sx, SCMD_FLUSH, "*\r\n") >= 0) |
| 288 | (void)smtp_read_response(sx, US buffer, buffsize, '2', timeout); |
| 289 | string_format(buffer, buffsize, "Invalid base64 string in server " |
| 290 | "response \"%s\"", save_bad); |
| 291 | return CANCELLED; |
| 292 | } |
| 293 | clear = US""; |
| 294 | clear_len = 0; |
| 295 | } |
| 296 | |
| 297 | if (auth_var_idx < AUTH_VARS) |
| 298 | auth_vars[auth_var_idx++] = string_copy(clear); |
| 299 | } |
| 300 | |
| 301 | /* Control should never actually get here. */ |
| 302 | |
| 303 | return FAIL; |
| 304 | } |
| 305 | |
| 306 | #endif /*!MACRO_PREDEF*/ |
| 307 | /* End of plaintext.c */ |