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+/*************************************************
+* Exim - an Internet mail transport agent *
+*************************************************/
+
+/* Copyright (c) University of Cambridge 1995 - 2018 */
+/* Copyright (c) The Exim Maintainers 2020 */
+/* See the file NOTICE for conditions of use and distribution. */
+
+/* This file, which provides support for Microsoft's Secure Password
+Authentication, was contributed by Marc Prud'hommeaux. Tom Kistner added SPA
+server support. I (PH) have only modified it in very trivial ways.
+
+References:
+ http://www.innovation.ch/java/ntlm.html
+ http://www.kuro5hin.org/story/2002/4/28/1436/66154
+ http://download.microsoft.com/download/9/5/e/95ef66af-9026-4bb0-a41d-a4f81802d92c/%5bMS-SMTP%5d.pdf
+
+ * It seems that some systems have existing but different definitions of some
+ * of the following types. I received a complaint about "int16" causing
+ * compilation problems. So I (PH) have renamed them all, to be on the safe
+ * side, by adding 'x' on the end. See auths/auth-spa.h.
+
+ * typedef signed short int16;
+ * typedef unsigned short uint16;
+ * typedef unsigned uint32;
+ * typedef unsigned char uint8;
+
+07-August-2003: PH: Patched up the code to avoid assert bombouts for stupid
+ input data. Find appropriate comment by grepping for "PH".
+16-October-2006: PH: Added a call to auth_check_serv_cond() at the end
+05-June-2010: PP: handle SASL initial response
+*/
+
+
+#include "../exim.h"
+#include "spa.h"
+
+/* #define DEBUG_SPA */
+
+#ifdef DEBUG_SPA
+#define DSPA(x,y,z) debug_printf(x,y,z)
+#else
+#define DSPA(x,y,z)
+#endif
+
+/* Options specific to the spa authentication mechanism. */
+
+optionlist auth_spa_options[] = {
+ { "client_domain", opt_stringptr,
+ OPT_OFF(auth_spa_options_block, spa_domain) },
+ { "client_password", opt_stringptr,
+ OPT_OFF(auth_spa_options_block, spa_password) },
+ { "client_username", opt_stringptr,
+ OPT_OFF(auth_spa_options_block, spa_username) },
+ { "server_password", opt_stringptr,
+ OPT_OFF(auth_spa_options_block, spa_serverpassword) }
+};
+
+/* Size of the options list. An extern variable has to be used so that its
+address can appear in the tables drtables.c. */
+
+int auth_spa_options_count =
+ sizeof(auth_spa_options)/sizeof(optionlist);
+
+/* Default private options block for the condition authentication method. */
+
+auth_spa_options_block auth_spa_option_defaults = {
+ NULL, /* spa_password */
+ NULL, /* spa_username */
+ NULL, /* spa_domain */
+ NULL /* spa_serverpassword (for server side use) */
+};
+
+
+#ifdef MACRO_PREDEF
+
+/* Dummy values */
+void auth_spa_init(auth_instance *ablock) {}
+int auth_spa_server(auth_instance *ablock, uschar *data) {return 0;}
+int auth_spa_client(auth_instance *ablock, void * sx, int timeout,
+ uschar *buffer, int buffsize) {return 0;}
+
+#else /*!MACRO_PREDEF*/
+
+
+
+
+/*************************************************
+* Initialization entry point *
+*************************************************/
+
+/* Called for each instance, after its options have been read, to
+enable consistency checks to be done, or anything else that needs
+to be set up. */
+
+void
+auth_spa_init(auth_instance *ablock)
+{
+auth_spa_options_block *ob =
+ (auth_spa_options_block *)(ablock->options_block);
+
+/* The public name defaults to the authenticator name */
+
+if (ablock->public_name == NULL) ablock->public_name = ablock->name;
+
+/* Both username and password must be set for a client */
+
+if ((ob->spa_username == NULL) != (ob->spa_password == NULL))
+ log_write(0, LOG_PANIC_DIE|LOG_CONFIG_FOR, "%s authenticator:\n "
+ "one of client_username and client_password cannot be set without "
+ "the other", ablock->name);
+ablock->client = ob->spa_username != NULL;
+
+/* For a server we have just one option */
+
+ablock->server = ob->spa_serverpassword != NULL;
+}
+
+
+
+/*************************************************
+* Server entry point *
+*************************************************/
+
+/* For interface, see auths/README */
+
+#define CVAL(buf,pos) ((US (buf))[pos])
+#define PVAL(buf,pos) ((unsigned)CVAL(buf,pos))
+#define SVAL(buf,pos) (PVAL(buf,pos)|PVAL(buf,(pos)+1)<<8)
+#define IVAL(buf,pos) (SVAL(buf,pos)|SVAL(buf,(pos)+2)<<16)
+
+int
+auth_spa_server(auth_instance *ablock, uschar *data)
+{
+auth_spa_options_block *ob = (auth_spa_options_block *)(ablock->options_block);
+uint8x lmRespData[24];
+uint8x ntRespData[24];
+SPAAuthRequest request;
+SPAAuthChallenge challenge;
+SPAAuthResponse response;
+SPAAuthResponse *responseptr = &response;
+uschar msgbuf[2048];
+uschar *clearpass, *s;
+unsigned off;
+
+/* send a 334, MS Exchange style, and grab the client's request,
+unless we already have it via an initial response. */
+
+if (!*data && auth_get_no64_data(&data, US"NTLM supported") != OK)
+ return FAIL;
+
+if (spa_base64_to_bits(CS &request, sizeof(request), CCS data) < 0)
+ {
+ DEBUG(D_auth) debug_printf("auth_spa_server(): bad base64 data in "
+ "request: %s\n", data);
+ return FAIL;
+ }
+
+/* create a challenge and send it back */
+
+spa_build_auth_challenge(&request, &challenge);
+spa_bits_to_base64(msgbuf, US &challenge, spa_request_length(&challenge));
+
+if (auth_get_no64_data(&data, msgbuf) != OK)
+ return FAIL;
+
+/* dump client response */
+if (spa_base64_to_bits(CS &response, sizeof(response), CCS data) < 0)
+ {
+ DEBUG(D_auth) debug_printf("auth_spa_server(): bad base64 data in "
+ "response: %s\n", data);
+ return FAIL;
+ }
+
+/***************************************************************
+PH 07-Aug-2003: The original code here was this:
+
+Ustrcpy(msgbuf, unicodeToString(((char*)responseptr) +
+ IVAL(&responseptr->uUser.offset,0),
+ SVAL(&responseptr->uUser.len,0)/2) );
+
+However, if the response data is too long, unicodeToString bombs out on
+an assertion failure. It uses a 1024 fixed buffer. Bombing out is not a good
+idea. It's too messy to try to rework that function to return an error because
+it is called from a number of other places in the auth-spa.c module. Instead,
+since it is a very small function, I reproduce its code here, with a size check
+that causes failure if the size of msgbuf is exceeded. ****/
+
+ {
+ int i;
+ char * p;
+ int len = SVAL(&responseptr->uUser.len,0)/2;
+
+ if ( (off = IVAL(&responseptr->uUser.offset,0)) >= sizeof(SPAAuthResponse)
+ || len >= sizeof(responseptr->buffer)/2
+ || (p = (CS responseptr) + off) + len*2 >= CS (responseptr+1)
+ )
+ {
+ DEBUG(D_auth)
+ debug_printf("auth_spa_server(): bad uUser spec in response\n");
+ return FAIL;
+ }
+
+ if (len + 1 >= sizeof(msgbuf)) return FAIL;
+ for (i = 0; i < len; ++i)
+ {
+ msgbuf[i] = *p & 0x7f;
+ p += 2;
+ }
+ msgbuf[i] = 0;
+ }
+
+/***************************************************************/
+
+/* Put the username in $auth1 and $1. The former is now the preferred variable;
+the latter is the original variable. These have to be out of stack memory, and
+need to be available once known even if not authenticated, for error messages
+(server_set_id, which only makes it to authenticated_id if we return OK) */
+
+auth_vars[0] = expand_nstring[1] = string_copy(msgbuf);
+expand_nlength[1] = Ustrlen(msgbuf);
+expand_nmax = 1;
+
+debug_print_string(ablock->server_debug_string); /* customized debug */
+
+/* look up password */
+
+if (!(clearpass = expand_string(ob->spa_serverpassword)))
+ if (f.expand_string_forcedfail)
+ {
+ DEBUG(D_auth) debug_printf("auth_spa_server(): forced failure while "
+ "expanding spa_serverpassword\n");
+ return FAIL;
+ }
+ else
+ {
+ DEBUG(D_auth) debug_printf("auth_spa_server(): error while expanding "
+ "spa_serverpassword: %s\n", expand_string_message);
+ return DEFER;
+ }
+
+/* create local hash copy */
+
+spa_smb_encrypt(clearpass, challenge.challengeData, lmRespData);
+spa_smb_nt_encrypt(clearpass, challenge.challengeData, ntRespData);
+
+/* compare NT hash (LM may not be available) */
+
+off = IVAL(&responseptr->ntResponse.offset,0);
+if (off >= sizeof(SPAAuthResponse) - 24)
+ {
+ DEBUG(D_auth)
+ debug_printf("auth_spa_server(): bad ntRespData spec in response\n");
+ return FAIL;
+ }
+s = (US responseptr) + off;
+
+if (memcmp(ntRespData, s, 24) == 0)
+ return auth_check_serv_cond(ablock); /* success. we have a winner. */
+
+ /* Expand server_condition as an authorization check (PH) */
+
+return FAIL;
+}
+
+
+/*************************************************
+* Client entry point *
+*************************************************/
+
+/* For interface, see auths/README */
+
+int
+auth_spa_client(
+ auth_instance *ablock, /* authenticator block */
+ void * sx, /* connection */
+ int timeout, /* command timeout */
+ uschar *buffer, /* buffer for reading response */
+ int buffsize) /* size of buffer */
+{
+auth_spa_options_block *ob =
+ (auth_spa_options_block *)(ablock->options_block);
+SPAAuthRequest request;
+SPAAuthChallenge challenge;
+SPAAuthResponse response;
+char msgbuf[2048];
+char *domain = NULL;
+char *username, *password;
+
+/* Code added by PH to expand the options */
+
+*buffer = 0; /* Default no message when cancelled */
+
+if (!(username = CS expand_string(ob->spa_username)))
+ {
+ if (f.expand_string_forcedfail) return CANCELLED;
+ string_format(buffer, buffsize, "expansion of \"%s\" failed in %s "
+ "authenticator: %s", ob->spa_username, ablock->name,
+ expand_string_message);
+ return ERROR;
+ }
+
+if (!(password = CS expand_string(ob->spa_password)))
+ {
+ if (f.expand_string_forcedfail) return CANCELLED;
+ string_format(buffer, buffsize, "expansion of \"%s\" failed in %s "
+ "authenticator: %s", ob->spa_password, ablock->name,
+ expand_string_message);
+ return ERROR;
+ }
+
+if (ob->spa_domain)
+ if (!(domain = CS expand_string(ob->spa_domain)))
+ {
+ if (f.expand_string_forcedfail) return CANCELLED;
+ string_format(buffer, buffsize, "expansion of \"%s\" failed in %s "
+ "authenticator: %s", ob->spa_domain, ablock->name,
+ expand_string_message);
+ return ERROR;
+ }
+
+/* Original code */
+
+if (smtp_write_command(sx, SCMD_FLUSH, "AUTH %s\r\n", ablock->public_name) < 0)
+ return FAIL_SEND;
+
+/* wait for the 3XX OK message */
+if (!smtp_read_response(sx, US buffer, buffsize, '3', timeout))
+ return FAIL;
+
+DSPA("\n\n%s authenticator: using domain %s\n\n", ablock->name, domain);
+
+spa_build_auth_request(&request, CS username, domain);
+spa_bits_to_base64(US msgbuf, US &request, spa_request_length(&request));
+
+DSPA("\n\n%s authenticator: sending request (%s)\n\n", ablock->name, msgbuf);
+
+/* send the encrypted password */
+if (smtp_write_command(sx, SCMD_FLUSH, "%s\r\n", msgbuf) < 0)
+ return FAIL_SEND;
+
+/* wait for the auth challenge */
+if (!smtp_read_response(sx, US buffer, buffsize, '3', timeout))
+ return FAIL;
+
+/* convert the challenge into the challenge struct */
+DSPA("\n\n%s authenticator: challenge (%s)\n\n", ablock->name, buffer + 4);
+spa_base64_to_bits(CS (&challenge), sizeof(challenge), CCS (buffer + 4));
+
+spa_build_auth_response(&challenge, &response, CS username, CS password);
+spa_bits_to_base64(US msgbuf, US &response, spa_request_length(&response));
+DSPA("\n\n%s authenticator: challenge response (%s)\n\n", ablock->name, msgbuf);
+
+/* send the challenge response */
+if (smtp_write_command(sx, SCMD_FLUSH, "%s\r\n", msgbuf) < 0)
+ return FAIL_SEND;
+
+/* If we receive a success response from the server, authentication
+has succeeded. There may be more data to send, but is there any point
+in provoking an error here? */
+
+if (smtp_read_response(sx, US buffer, buffsize, '2', timeout))
+ return OK;
+
+/* Not a success response. If errno != 0 there is some kind of transmission
+error. Otherwise, check the response code in the buffer. If it starts with
+'3', more data is expected. */
+
+if (errno != 0 || buffer[0] != '3')
+ return FAIL;
+
+return FAIL;
+}
+
+#endif /*!MACRO_PREDEF*/
+/* End of spa.c */
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