src/src/auths/get_data.c

   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
  10
  11 /****************************************************************
  12 *       Decode and split the argument of an AUTH command        *
  13 ****************************************************************/
  14
  15 /* If data was supplied on the AUTH command, decode it, and split it up into
  16 multiple items at binary zeros. The strings are put into $auth1, $auth2, etc,
  17 up to a maximum. To retain backwards compatibility, they are also put int $1,
  18 $2, etc. If the data consists of the string "=" it indicates a single, empty
  19 string. */
  20
  21 int
  22 auth_read_input(const uschar * data)
  23 {
  24 if (Ustrcmp(data, "=") == 0)
  25   {
  26   auth_vars[0] = expand_nstring[++expand_nmax] = US"";
  27   expand_nlength[expand_nmax] = 0;
  28   }
  29 else
  30   {
  31   uschar * clear, * end;
  32   int len;
  33
  34   if ((len = b64decode(data, &clear)) < 0) return BAD64;
  35   DEBUG(D_auth) debug_printf("auth input decode:");
  36   for (end = clear + len; clear < end && expand_nmax < EXPAND_MAXN; )
  37     {
  38     DEBUG(D_auth) debug_printf(" '%s'", clear);
  39     if (expand_nmax < AUTH_VARS) auth_vars[expand_nmax] = clear;
  40     expand_nstring[++expand_nmax] = clear;
  41     while (*clear != 0) clear++;
  42     expand_nlength[expand_nmax] = clear++ - expand_nstring[expand_nmax];
  43     }
  44   DEBUG(D_auth) debug_printf("\n");
  45   }
  46 return OK;
  47 }
  48
  49
  50
  51
  52 /*************************************************
  53 *      Issue a challenge and get a response      *
  54 *************************************************/
  55
  56 /* This function is used by authentication drivers to output a challenge
  57 to the SMTP client and read the response line.
  58
  59 Arguments:
  60    aptr       set to point to the response (which is in big_buffer)
  61    challenge  the challenge text (unencoded, may be binary)
  62    challen    the length of the challenge text
  63
  64 Returns:      OK on success
  65               BAD64 if response too large for buffer
  66               CANCELLED if response is "*"
  67 */
  68
  69 int
  70 auth_get_data(uschar ** aptr, const uschar * challenge, int challen)
  71 {
  72 int c;
  73 int p = 0;
  74 smtp_printf("334 %s\r\n", FALSE, b64encode(challenge, challen));
  75 while ((c = receive_getc(GETC_BUFFER_UNLIMITED)) != '\n' && c != EOF)
  76   {
  77   if (p >= big_buffer_size - 1) return BAD64;
  78   big_buffer[p++] = c;
  79   }
  80 if (p > 0 && big_buffer[p-1] == '\r') p--;
  81 big_buffer[p] = 0;
  82 DEBUG(D_receive) debug_printf("SMTP<< %s\n", big_buffer);
  83 if (Ustrcmp(big_buffer, "*") == 0) return CANCELLED;
  84 *aptr = big_buffer;
  85 return OK;
  86 }
  87
  88
  89
  90 int
  91 auth_prompt(const uschar * challenge)
  92 {
  93 int rc, len;
  94 uschar * resp, * clear, * end;
  95
  96 if ((rc = auth_get_data(&resp, challenge, Ustrlen(challenge))) != OK)
  97   return rc;
  98 if ((len = b64decode(resp, &clear)) < 0)
  99   return BAD64;
 100 end = clear + len;
 101
 102 /* This loop must run at least once, in case the length is zero */
 103 do
 104   {
 105   if (expand_nmax < AUTH_VARS) auth_vars[expand_nmax] = clear;
 106   expand_nstring[++expand_nmax] = clear;
 107   while (*clear != 0) clear++;
 108   expand_nlength[expand_nmax] = clear++ - expand_nstring[expand_nmax];
 109   }
 110 while (clear < end && expand_nmax < EXPAND_MAXN);
 111 return OK;
 112 }
 113
 114
 115 /***********************************************
 116 *       Send an AUTH-negotiation item           *
 117 ************************************************/
 118
 119 /* Expand and send one client auth item and read the response.
 120 Include the AUTH command and method if tagged as "first".  Use the given buffer
 121 for receiving the b6-encoded reply; decode it it return it in the string arg.
 122
 123 Return:
 124   OK          success
 125   FAIL_SEND   error after writing a command; errno is set
 126   FAIL        failed after reading a response;
 127               either errno is set (for timeouts, I/O failures) or
 128               the buffer contains the SMTP response line
 129   CANCELLED   the client cancelled authentication (often "fail" in expansion)
 130               the buffer may contain a message; if not, *buffer = 0
 131   ERROR       local problem (typically expansion error); message in buffer
 132   DEFER       more items expected
 133 */
 134
 135 int
 136 auth_client_item(void * sx, auth_instance * ablock, const uschar ** inout,
 137   unsigned flags, int timeout, uschar * buffer, int buffsize)
 138 {
 139 int len, clear_len;
 140 uschar * ss, * clear;
 141
 142 ss = US expand_cstring(*inout);
 143 if (ss == *inout) ss = string_copy(ss);
 144
 145 /* Forced expansion failure is not an error; authentication is abandoned. On
 146 all but the first string, we have to abandon the authentication attempt by
 147 sending a line containing "*". Save the failed expansion string, because it
 148 is in big_buffer, and that gets used by the sending function. */
 149
 150 if (!ss)
 151   {
 152   if (!(flags & AUTH_ITEM_FIRST))
 153     {
 154     if (smtp_write_command(sx, SCMD_FLUSH, "*\r\n") >= 0)
 155       (void) smtp_read_response(sx, US buffer, buffsize, '2', timeout);
 156     }
 157   if (f.expand_string_forcedfail)
 158     {
 159     *buffer = 0;       /* No message */
 160     return CANCELLED;
 161     }
 162   string_format(buffer, buffsize, "expansion of \"%s\" failed in %s "
 163     "authenticator: %s", *inout, ablock->name, expand_string_message);
 164   return ERROR;
 165   }
 166
 167 len = Ustrlen(ss);
 168
 169 /* The character ^ is used as an escape for a binary zero character, which is
 170 needed for the PLAIN mechanism. It must be doubled if really needed. */
 171
 172 for (int i = 0; i < len; i++)
 173   if (ss[i] == '^')
 174     if (ss[i+1] != '^')
 175       ss[i] = 0;
 176     else
 177       if (--len > ++i) memmove(ss + i, ss + i + 1, len - i);
 178
 179 /* The first string is attached to the AUTH command; others are sent
 180 unembellished. */
 181
 182 if (flags & AUTH_ITEM_FIRST)
 183   {
 184   if (smtp_write_command(sx, SCMD_FLUSH, "AUTH %s%s%s\r\n",
 185        ablock->public_name, len == 0 ? "" : " ", b64encode(CUS ss, len)) < 0)
 186     return FAIL_SEND;
 187   }
 188 else
 189   if (smtp_write_command(sx, SCMD_FLUSH, "%s\r\n", b64encode(CUS ss, len)) < 0)
 190     return FAIL_SEND;
 191
 192 /* If we receive a success response from the server, authentication
 193 has succeeded. There may be more data to send, but is there any point
 194 in provoking an error here? */
 195
 196 if (smtp_read_response(sx, US buffer, buffsize, '2', timeout))
 197   {
 198   *inout = NULL;
 199   return OK;
 200   }
 201
 202 /* Not a success response. If errno != 0 there is some kind of transmission
 203 error. Otherwise, check the response code in the buffer. If it starts with
 204 '3', more data is expected. */
 205
 206 if (errno != 0 || buffer[0] != '3') return FAIL;
 207
 208 /* If there is no more data to send, we have to cancel the authentication
 209 exchange and return ERROR. */
 210
 211 if (flags & AUTH_ITEM_LAST)
 212   {
 213   if (smtp_write_command(sx, SCMD_FLUSH, "*\r\n") >= 0)
 214     (void)smtp_read_response(sx, US buffer, buffsize, '2', timeout);
 215   string_format(buffer, buffsize, "Too few items in client_send in %s "
 216     "authenticator", ablock->name);
 217   return ERROR;
 218   }
 219
 220 /* Now that we know we'll continue, we put the received data into $auth<n>,
 221 if possible. First, decode it: buffer+4 skips over the SMTP status code. */
 222
 223 clear_len = b64decode(buffer+4, &clear);
 224
 225 /* If decoding failed, the default is to terminate the authentication, and
 226 return FAIL, with the SMTP response still in the buffer. However, if client_
 227 ignore_invalid_base64 is set, we ignore the error, and put an empty string
 228 into $auth<n>. */
 229
 230 if (clear_len < 0)
 231   {
 232   uschar *save_bad = string_copy(buffer);
 233   if (!(flags & AUTH_ITEM_IGN64))
 234     {
 235     if (smtp_write_command(sx, SCMD_FLUSH, "*\r\n") >= 0)
 236       (void)smtp_read_response(sx, US buffer, buffsize, '2', timeout);
 237     string_format(buffer, buffsize, "Invalid base64 string in server "
 238       "response \"%s\"", save_bad);
 239     return CANCELLED;
 240     }
 241   DEBUG(D_auth) debug_printf("bad b64 decode for '%s';"
 242        " ignoring due to client_ignore_invalid_base64\n", save_bad);
 243   clear = string_copy(US"");
 244   clear_len = 0;
 245   }
 246
 247 *inout = clear;
 248 return DEFER;
 249 }
 250
 251
 252 /* End of get_data.c */