src/auths/plaintext.c

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1995 - 2009 */
   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 /*************************************************
  39 *          Initialization entry point            *
  40 *************************************************/
  41
  42 /* Called for each instance, after its options have been read, to
  43 enable consistency checks to be done, or anything else that needs
  44 to be set up. */
  45
  46 void
  47 auth_plaintext_init(auth_instance *ablock)
  48 {
  49 auth_plaintext_options_block *ob =
  50   (auth_plaintext_options_block *)(ablock->options_block);
  51 if (ablock->public_name == NULL) ablock->public_name = ablock->name;
  52 if (ablock->server_condition != NULL) ablock->server = TRUE;
  53 if (ob->client_send != NULL) ablock->client = TRUE;
  54 }
  55
  56
  57
  58 /*************************************************
  59 *             Server entry point                 *
  60 *************************************************/
  61
  62 /* For interface, see auths/README */
  63
  64 int
  65 auth_plaintext_server(auth_instance *ablock, uschar *data)
  66 {
  67 auth_plaintext_options_block *ob =
  68   (auth_plaintext_options_block *)(ablock->options_block);
  69 uschar *prompts = ob->server_prompts;
  70 uschar *clear, *end, *s;
  71 int number = 1;
  72 int len, rc;
  73 int sep = 0;
  74
  75 /* Expand a non-empty list of prompt strings */
  76
  77 if (prompts != NULL)
  78   {
  79   prompts = expand_string(prompts);
  80   if (prompts == NULL)
  81     {
  82     auth_defer_msg = expand_string_message;
  83     return DEFER;
  84     }
  85   }
  86
  87 /* If data was supplied on the AUTH command, decode it, and split it up into
  88 multiple items at binary zeros. The strings are put into $auth1, $auth2, etc,
  89 up to a maximum. To retain backwards compatibility, they are also put int $1,
  90 $2, etc. If the data consists of the string "=" it indicates a single, empty
  91 string. */
  92
  93 if (*data != 0)
  94   {
  95   if (Ustrcmp(data, "=") == 0)
  96     {
  97     auth_vars[0] = expand_nstring[++expand_nmax] = US"";
  98     expand_nlength[expand_nmax] = 0;
  99     }
 100   else
 101     {
 102     if ((len = auth_b64decode(data, &clear)) < 0) return BAD64;
 103     end = clear + len;
 104     while (clear < end && expand_nmax < EXPAND_MAXN)
 105       {
 106       if (expand_nmax < AUTH_VARS) auth_vars[expand_nmax] = clear;
 107       expand_nstring[++expand_nmax] = clear;
 108       while (*clear != 0) clear++;
 109       expand_nlength[expand_nmax] = clear++ - expand_nstring[expand_nmax];
 110       }
 111     }
 112   }
 113
 114 /* Now go through the list of prompt strings. Skip over any whose data has
 115 already been provided as part of the AUTH command. For the rest, send them
 116 out as prompts, and get a data item back. If the data item is "*", abandon the
 117 authentication attempt. Otherwise, split it into items as above. */
 118
 119 while ((s = string_nextinlist(&prompts, &sep, big_buffer, big_buffer_size))
 120         != NULL && expand_nmax < EXPAND_MAXN)
 121   {
 122   if (number++ <= expand_nmax) continue;
 123   if ((rc = auth_get_data(&data, s, Ustrlen(s))) != OK) return rc;
 124   if ((len = auth_b64decode(data, &clear)) < 0) return BAD64;
 125   end = clear + len;
 126
 127   /* This loop must run at least once, in case the length is zero */
 128   do
 129     {
 130     if (expand_nmax < AUTH_VARS) auth_vars[expand_nmax] = clear;
 131     expand_nstring[++expand_nmax] = clear;
 132     while (*clear != 0) clear++;
 133     expand_nlength[expand_nmax] = clear++ - expand_nstring[expand_nmax];
 134     }
 135   while (clear < end && expand_nmax < EXPAND_MAXN);
 136   }
 137
 138 /* We now have a number of items of data in $auth1, $auth2, etc (and also, for
 139 compatibility, in $1, $2, etc). Authentication and authorization are handled
 140 together for this authenticator by expanding the server_condition option. Note
 141 that ablock->server_condition is always non-NULL because that's what configures
 142 this authenticator as a server. */
 143
 144 return auth_check_serv_cond(ablock);
 145 }
 146
 147
 148
 149 /*************************************************
 150 *              Client entry point                *
 151 *************************************************/
 152
 153 /* For interface, see auths/README */
 154
 155 int
 156 auth_plaintext_client(
 157   auth_instance *ablock,                 /* authenticator block */
 158   smtp_inblock *inblock,                 /* connection inblock */
 159   smtp_outblock *outblock,               /* connection outblock */
 160   int timeout,                           /* command timeout */
 161   uschar *buffer,                        /* buffer for reading response */
 162   int buffsize)                          /* size of buffer */
 163 {
 164 auth_plaintext_options_block *ob =
 165   (auth_plaintext_options_block *)(ablock->options_block);
 166 uschar *text = ob->client_send;
 167 uschar *s;
 168 BOOL first = TRUE;
 169 int sep = 0;
 170 int auth_var_idx = 0;
 171
 172 /* The text is broken up into a number of different data items, which are
 173 sent one by one. The first one is sent with the AUTH command; the remainder are
 174 sent in response to subsequent prompts. Each is expanded before being sent. */
 175
 176 while ((s = string_nextinlist(&text, &sep, big_buffer, big_buffer_size)) != NULL)
 177   {
 178   int i, len, clear_len;
 179   uschar *ss = expand_string(s);
 180   uschar *clear;
 181
 182   /* Forced expansion failure is not an error; authentication is abandoned. On
 183   all but the first string, we have to abandon the authentication attempt by
 184   sending a line containing "*". Save the failed expansion string, because it
 185   is in big_buffer, and that gets used by the sending function. */
 186
 187   if (ss == NULL)
 188     {
 189     uschar *ssave = string_copy(s);
 190     if (!first)
 191       {
 192       if (smtp_write_command(outblock, FALSE, "*\r\n") >= 0)
 193         (void) smtp_read_response(inblock, US buffer, buffsize, '2', timeout);
 194       }
 195     if (expand_string_forcedfail)
 196       {
 197       *buffer = 0;       /* No message */
 198       return CANCELLED;
 199       }
 200     string_format(buffer, buffsize, "expansion of \"%s\" failed in %s "
 201       "authenticator: %s", ssave, ablock->name, expand_string_message);
 202     return ERROR;
 203     }
 204
 205   len = Ustrlen(ss);
 206
 207   /* The character ^ is used as an escape for a binary zero character, which is
 208   needed for the PLAIN mechanism. It must be doubled if really needed. */
 209
 210   for (i = 0; i < len; i++)
 211     {
 212     if (ss[i] == '^')
 213       {
 214       if (ss[i+1] != '^') ss[i] = 0; else
 215         {
 216         i++;
 217         len--;
 218         memmove(ss + i, ss + i + 1, len - i);
 219         }
 220       }
 221     }
 222
 223   /* The first string is attached to the AUTH command; others are sent
 224   unembelished. */
 225
 226   if (first)
 227     {
 228     first = FALSE;
 229     if (smtp_write_command(outblock, FALSE, "AUTH %s%s%s\r\n",
 230          ablock->public_name, (len == 0)? "" : " ",
 231          auth_b64encode(ss, len)) < 0)
 232       return FAIL_SEND;
 233     }
 234   else
 235     {
 236     if (smtp_write_command(outblock, FALSE, "%s\r\n",
 237           auth_b64encode(ss, len)) < 0)
 238       return FAIL_SEND;
 239     }
 240
 241   /* If we receive a success response from the server, authentication
 242   has succeeded. There may be more data to send, but is there any point
 243   in provoking an error here? */
 244
 245   if (smtp_read_response(inblock, US buffer, buffsize, '2', timeout)) return OK;
 246
 247   /* Not a success response. If errno != 0 there is some kind of transmission
 248   error. Otherwise, check the response code in the buffer. If it starts with
 249   '3', more data is expected. */
 250
 251   if (errno != 0 || buffer[0] != '3') return FAIL;
 252
 253   /* If there is no more data to send, we have to cancel the authentication
 254   exchange and return ERROR. */
 255
 256   if (text == NULL)
 257     {
 258     if (smtp_write_command(outblock, FALSE, "*\r\n") >= 0)
 259       (void)smtp_read_response(inblock, US buffer, buffsize, '2', timeout);
 260     string_format(buffer, buffsize, "Too few items in client_send in %s "
 261       "authenticator", ablock->name);
 262     return ERROR;
 263     }
 264
 265   /* Now that we know we'll continue, we put the received data into $auth<n>,
 266   if possible. First, decode it: buffer+4 skips over the SMTP status code. */
 267
 268   clear_len = auth_b64decode(buffer+4, &clear);
 269
 270   /* If decoding failed, the default is to terminate the authentication, and
 271   return FAIL, with the SMTP response still in the buffer. However, if client_
 272   ignore_invalid_base64 is set, we ignore the error, and put an empty string
 273   into $auth<n>. */
 274
 275   if (clear_len < 0)
 276     {
 277     uschar *save_bad = string_copy(buffer);
 278     if (!ob->client_ignore_invalid_base64)
 279       {
 280       if (smtp_write_command(outblock, FALSE, "*\r\n") >= 0)
 281         (void)smtp_read_response(inblock, US buffer, buffsize, '2', timeout);
 282       string_format(buffer, buffsize, "Invalid base64 string in server "
 283         "response \"%s\"", save_bad);
 284       return CANCELLED;
 285       }
 286     clear = US"";
 287     clear_len = 0;
 288     }
 289
 290   if (auth_var_idx < AUTH_VARS)
 291     auth_vars[auth_var_idx++] = string_copy(clear);
 292   }
 293
 294 /* Control should never actually get here. */
 295
 296 return FAIL;
 297 }
 298
 299 /* End of plaintext.c */