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/* wptDNSKeys.cpp - Support for retrieving keys via DNS |
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* Copyright (C) 2006 Timo Schulz |
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* |
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* This file is part of WinPT. |
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* |
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* WinPT is free software; you can redistribute it and/or modify |
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* it under the terms of the GNU General Public License as published by |
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* the Free Software Foundation; either version 2 of the License, or |
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* (at your option) any later version. |
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* |
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* WinPT is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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* GNU General Public License for more details. |
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* |
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* You should have received a copy of the GNU General Public License |
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* along with WinPT; if not, write to the Free Software Foundation, |
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* Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA |
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*/ |
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|
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#include <windows.h> |
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#include <windns.h> |
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|
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#include "wptDNSKeys.h" |
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|
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|
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/* typedef for the function signature. */ |
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typedef DNS_STATUS (*dns_query_fnc) (LPSTR, WORD, DWORD, PIP4_ARRAY, |
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PDNS_RECORD*, PVOID *); |
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|
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typedef void (*dns_record_list_free_fnc) (PDNS_RECORD, DNS_FREE_TYPE); |
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|
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/* function pointer. */ |
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static dns_query_fnc dns_query = NULL; |
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static dns_record_list_free_fnc dns_record_free = NULL; |
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|
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/* hinstance handle to the DLL. */ |
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static HINSTANCE dns_api = NULL; |
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|
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/* 1 if the DNS api is not available. */ |
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static int dns_failed = 0; |
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|
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|
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|
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/* Initialize the DNS sub system. We do this via dynamic loading |
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because older NT/9X systems do not have this API. */ |
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static int |
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dns_init (void) |
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{ |
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if (dns_query) |
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return 0; |
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if (dns_failed) |
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return -1; |
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dns_api = LoadLibrary ("dnsapi"); |
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if (!dns_api) { |
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dns_failed = 1; |
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return -1; |
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} |
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dns_query = (dns_query_fnc)GetProcAddress (dns_api, "DnsQuery_A"); |
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if (!dns_query) { |
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dns_failed = 1; |
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return -1; |
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} |
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dns_record_free = (dns_record_list_free_fnc) |
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GetProcAddress (dns_api, "DnsRecordListFree"); |
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if (!dns_record_free) { |
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dns_failed = 1; |
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return -1; |
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} |
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return 0; |
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} |
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|
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|
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/* Cleanup static structs. */ |
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void |
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dns_cleanup (void) |
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{ |
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if (dns_api != NULL) |
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FreeLibrary (dns_api); |
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dns_api = NULL; |
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dns_failed = 0; |
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} |
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|
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|
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/* build a DNS name for the PKA lookup. */ |
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static char* |
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email_get_pka_addr (const char *uid) |
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{ |
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const char *fmt = "._pka."; |
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char *bo; |
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char *pka; |
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int pos=0; |
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|
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/* check that the @uid really contains an email address. */ |
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if ((bo=strchr (uid, '<')) && strchr (uid, '>')) |
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uid += (bo-uid+1); |
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if (!strchr (uid, '@')) |
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return NULL; |
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|
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/* create the user@_pka.domain-part.tlp string. */ |
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pka = (char*)calloc (1, strlen (uid)+strlen (fmt)+1); |
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while (uid && *uid != '@') |
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pka[pos++] = *uid++; |
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uid++; |
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strcat (pka, fmt); pos += strlen (fmt); |
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while (uid && *uid && *uid != '>') |
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pka[pos++] = *uid++; |
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return pka; |
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} |
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|
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|
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/* Convert the returned data from the PKA (txt) record. */ |
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pka_info_t |
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parse_pka_data (const char *data) |
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{ |
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enum pka_col_t { COL_VER=1, COL_FPR, COL_URI }; |
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pka_info_t pka; |
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char *p; |
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int pos = 1; |
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|
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if (strncmp (data, "v=pka1;", 8)) |
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return NULL; |
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pka = (pka_info_t)calloc (1, sizeof *pka); |
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p = strtok ((char*)data, ";"); |
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while (p != NULL) { |
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switch (pos) { |
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case COL_VER: |
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pka->ver = 1; |
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break; |
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|
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case COL_FPR: |
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pka->fpr = strdup (p+strlen ("fpr=")); |
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break; |
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|
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case COL_URI: /* optional */ |
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pka->uri = strdup (p+strlen ("uri=")); |
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break; |
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|
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default: |
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break; |
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} |
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pos++; |
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} |
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if (pos != 3) { |
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dns_free_pka_record (pka); |
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pka = NULL; |
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} |
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return pka; |
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} |
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|
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|
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/* Retrieve a PKA record from the DNS. |
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@userid is used to extract the email address. */ |
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extern "C" int |
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dns_get_pka_record (const char *userid, pka_info_t *r_pka) |
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{ |
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DNS_STATUS err; |
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DNS_RECORD *rec; |
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char *addr; |
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|
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*r_pka = NULL; |
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if (dns_init ()) |
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return -1; |
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addr = email_get_pka_addr (userid); |
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if (!addr) |
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return -1; |
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err = dns_query (addr, DNS_TYPE_TEXT, 0, NULL, &rec, NULL); |
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if (err) { |
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free (addr); |
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return -1; |
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} |
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*r_pka = parse_pka_data (rec->Data.Txt.pStringArray[0]); |
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|
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dns_record_free (rec, DnsFreeRecordList); |
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free (addr); |
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return 0; |
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} |
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|
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|
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/* Release the memory of the @pka structure. */ |
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extern "C" void |
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dns_free_pka_record (pka_info_t pka) |
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{ |
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if (pka->fpr != NULL) |
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free (pka->fpr); |
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pka->fpr = NULL; |
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if (pka->uri != NULL) |
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free (pka->uri); |
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pka->uri = NULL; |
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free (pka); |
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} |
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