diff options
Diffstat (limited to 'checkalias.c')
| -rw-r--r-- | checkalias.c | 141 |
1 files changed, 135 insertions, 6 deletions
diff --git a/checkalias.c b/checkalias.c index 1eca63da..80e3f007 100644 --- a/checkalias.c +++ b/checkalias.c @@ -4,7 +4,8 @@ * Copyright 1997 by Eric S. Raymond * For license terms, see the file COPYING in this directory. */ - +#include "config.h" +#ifdef HAVE_GETHOSTBYNAME #include <stdio.h> #include <string.h> #include <sys/types.h> @@ -12,10 +13,14 @@ #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> +#include "mx.h" #include "fetchmail.h" - -int is_ip_alias(const char *name1,const char *name2) -/* Given two hostnames as arguments, returns TRUE if they + +#define MX_RETRIES 3 + +static int is_ip_alias(const char *name1,const char *name2) +/* + * Given two hostnames as arguments, returns TRUE if they * have at least one IP address in common. * It is meant to be called by the is_host_alias() function in driver.c * No check is done on errors returned by gethostbyname, @@ -50,11 +55,9 @@ int is_ip_alias(const char *name1,const char *name2) dummy_addr = host_a_addr; } - hp = gethostbyname(name2); dummy_addr = (address_e *)NULL; - for (i=0,p = hp->h_addr_list; *p != 0; i++,p++) { struct in_addr in; @@ -80,3 +83,129 @@ int is_ip_alias(const char *name1,const char *name2) return (FALSE); } +int is_host_alias(const char *name, struct query *ctl) +/* determine whether name is a DNS alias of the hostname */ +{ + struct hostent *he,*he_st; + struct mxentry *mxp, *mxrecords; + + struct hostdata *lead_server = + ctl->server.lead_server ? ctl->server.lead_server : &ctl->server; + + /* + * The first two checks are optimizations that will catch a good + * many cases. + * + * (1) check against the `true name' deduced from the poll label + * and the via option (if present) at the beginning of the poll cycle. + * Odds are good this will either be the mailserver's FQDN or a suffix of + * it with the mailserver's domain's default host name omitted. + * + * (2) Then check the rest of the `also known as' + * cache accumulated by previous DNS checks. This cache is primed + * by the aka list option. + * + * Any of these on a mail address is definitive. Only if the + * name doesn't match any is it time to call the bind library. + * If this happens odds are good we're looking at an MX name. + */ + if (strcasecmp(lead_server->truename, name) == 0) + return(TRUE); + else if (str_in_list(&lead_server->akalist, name, TRUE)) + return(TRUE); + else if (!ctl->server.dns) + return(FALSE); + +#ifndef HAVE_RES_SEARCH + return(FALSE); +#else + /* + * The only code that calls the BIND library is here and in the + * start-of-query probe with gethostbyname(3). + * + * We know DNS service was up at the beginning of this poll cycle. + * If it's down, our nameserver has crashed. We don't want to try + * delivering the current message or anything else from this + * mailbox until it's back up. + */ + else if ((he = gethostbyname(name)) != (struct hostent *)NULL) + { + if (strcasecmp(ctl->server.truename, he->h_name) == 0) + goto match; + else if (((he_st = gethostbyname(ctl->server.truename)) != (struct hostent *)NULL) && ctl->server.checkalias) + { + if (outlevel == O_VERBOSE) + error(0, 0, "Checking if %s is really the same node as %s",ctl->server.truename,name); + if (is_ip_alias(ctl->server.truename,name) == TRUE) + { + if (outlevel == O_VERBOSE) + error(0, 0, "Yes, their IP addresses match"); + goto match; + } + if (outlevel == O_VERBOSE) + error(0, 0, "No, their IP addresses don't match"); + } + else + return(FALSE); + } + else + switch (h_errno) + { + case HOST_NOT_FOUND: /* specified host is unknown */ + case NO_ADDRESS: /* valid, but does not have an IP address */ + break; + + case NO_RECOVERY: /* non-recoverable name server error */ + case TRY_AGAIN: /* temporary error on authoritative server */ + default: + if (outlevel != O_SILENT) + putchar('\n'); /* terminate the progress message */ + error(0, 0, + "nameserver failure while looking for `%s' during poll of %s.", + name, ctl->server.pollname); + ctl->errcount++; + break; + } + + /* + * We're only here if DNS was OK but the gethostbyname() failed + * with a HOST_NOT_FOUND or NO_ADDRESS error. + * Search for a name match on MX records pointing to the server. + */ + h_errno = 0; + if ((mxrecords = getmxrecords(name)) == (struct mxentry *)NULL) + { + switch (h_errno) + { + case HOST_NOT_FOUND: /* specified host is unknown */ + case NO_ADDRESS: /* valid, but does not have an IP address */ + return(FALSE); + break; + + case NO_RECOVERY: /* non-recoverable name server error */ + case TRY_AGAIN: /* temporary error on authoritative server */ + default: + error(0, -1, + "nameserver failure while looking for `%s' during poll of %s.", + name, ctl->server.pollname); + ctl->errcount++; + break; + } + } + else + { + for (mxp = mxrecords; mxp->name; mxp++) + if (strcasecmp(ctl->server.truename, mxp->name) == 0) + goto match; + return(FALSE); + match:; + } + + /* add this name to relevant server's `also known as' list */ + save_str(&lead_server->akalist, name, 0); + return(TRUE); +#endif /* HAVE_RES_SEARCH */ +} +#endif /* HAVE_GETHOSTBYNAME */ + +/* checkalias.c ends here */ |