make hostalias more paranoid about its input

[unix-history] / usr / src / lib / libc / net / gethostnamadr.c

/*
* Copyright (c) 1985 Regents of the University of California.
* All rights reserved.  The Berkeley software License Agreement
* specifies the terms and conditions for redistribution.
*/

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)gethostnamadr.c     6.20 (Berkeley) %G%";
#endif LIBC_SCCS and not lint

#include <sys/param.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <ctype.h>
#include <netdb.h>
#include <stdio.h>
#include <errno.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <resolv.h>

#define MAXALIASES      35
#define MAXADDRS        35

static char *h_addr_ptrs[MAXADDRS + 1];

static struct hostent host;
static char *host_aliases[MAXALIASES];
static char hostbuf[BUFSIZ+1];
static struct in_addr host_addr;
static char HOSTDB[] = "/etc/hosts";
static FILE *hostf = NULL;
static char line[BUFSIZ+1];
static char hostaddr[MAXADDRS];
static char *host_addrs[2];
static int stayopen = 0;
static char *any();

typedef union {
   HEADER qb1;
   char qb2[PACKETSZ];
} querybuf;

static union {
   long al;
   char ac;
} align;


int h_errno;
extern errno;

static struct hostent *
getanswer(msg, msglen, iquery)
       char *msg;
       int msglen, iquery;
{
       register HEADER *hp;
       register char *cp;
       register int n;
       querybuf answer;
       char *eom, *bp, **ap;
       int type, class, buflen, ancount, qdcount;
       int haveanswer, getclass = C_ANY;
       char **hap;

       n = res_send(msg, msglen, (char *)&answer, sizeof(answer));
       if (n < 0) {
#ifdef DEBUG
               int terrno;
               terrno = errno;
               if (_res.options & RES_DEBUG)
                       printf("res_send failed\n");
               errno = terrno;
#endif
               h_errno = TRY_AGAIN;
               return (NULL);
       }
       eom = (char *)&answer + n;
       /*
        * find first satisfactory answer
        */
       hp = (HEADER *) &answer;
       ancount = ntohs(hp->ancount);
       qdcount = ntohs(hp->qdcount);
       if (hp->rcode != NOERROR || ancount == 0) {
#ifdef DEBUG
               if (_res.options & RES_DEBUG)
                       printf("rcode = %d, ancount=%d\n", hp->rcode, ancount);
#endif
               switch (hp->rcode) {
                       case NXDOMAIN:
                               /* Check if it's an authoritive answer */
                               if (hp->aa)
                                       h_errno = HOST_NOT_FOUND;
                               else
                                       h_errno = TRY_AGAIN;
                               break;
                       case SERVFAIL:
                               h_errno = TRY_AGAIN;
                               break;
                       case NOERROR:
                               h_errno = NO_ADDRESS;
                               break;
                       case FORMERR:
                       case NOTIMP:
                       case REFUSED:
                               h_errno = NO_RECOVERY;
               }
               return (NULL);
       }
       bp = hostbuf;
       buflen = sizeof(hostbuf);
       cp = (char *)&answer + sizeof(HEADER);
       if (qdcount) {
               if (iquery) {
                       if ((n = dn_expand((char *)&answer, eom,
                            cp, bp, buflen)) < 0) {
                               h_errno = NO_RECOVERY;
                               return (NULL);
                       }
                       cp += n + QFIXEDSZ;
                       host.h_name = bp;
                       n = strlen(bp) + 1;
                       bp += n;
                       buflen -= n;
               } else
                       cp += dn_skip(cp) + QFIXEDSZ;
               while (--qdcount > 0)
                       cp += dn_skip(cp) + QFIXEDSZ;
       } else if (iquery) {
               if (hp->aa)
                       h_errno = HOST_NOT_FOUND;
               else
                       h_errno = TRY_AGAIN;
               return (NULL);
       }
       ap = host_aliases;
       host.h_aliases = host_aliases;
       hap = h_addr_ptrs;
#if BSD >= 43
       host.h_addr_list = h_addr_ptrs;
#else
       host.h_addr = h_addr_ptrs[0];
#endif
       haveanswer = 0;
       while (--ancount >= 0 && cp < eom) {
               if ((n = dn_expand((char *)&answer, eom, cp, bp, buflen)) < 0)
                       break;
               cp += n;
               type = _getshort(cp);
               cp += sizeof(u_short);
               class = _getshort(cp);
               cp += sizeof(u_short) + sizeof(u_long);
               n = _getshort(cp);
               cp += sizeof(u_short);
               if (type == T_CNAME) {
                       cp += n;
                       if (ap >= &host_aliases[MAXALIASES-1])
                               continue;
                       *ap++ = bp;
                       n = strlen(bp) + 1;
                       bp += n;
                       buflen -= n;
                       continue;
               }
               if (type == T_PTR) {
                       if ((n = dn_expand((char *)&answer, eom,
                           cp, bp, buflen)) < 0) {
                               cp += n;
                               continue;
                       }
                       cp += n;
                       host.h_name = bp;
                       return(&host);
               }
               if (type != T_A)  {
#ifdef DEBUG
                       if (_res.options & RES_DEBUG)
                               printf("unexpected answer type %d, size %d\n",
                                       type, n);
#endif
                       cp += n;
                       continue;
               }
               if (haveanswer) {
                       if (n != host.h_length) {
                               cp += n;
                               continue;
                       }
                       if (class != getclass) {
                               cp += n;
                               continue;
                       }
               } else {
                       host.h_length = n;
                       getclass = class;
                       host.h_addrtype = (class == C_IN) ? AF_INET : AF_UNSPEC;
                       if (!iquery) {
                               host.h_name = bp;
                               bp += strlen(bp) + 1;
                       }
               }

               bp += (sizeof(align) - ((u_long)bp % sizeof(align))) &~
                   sizeof(align);

               if (bp + n >= &hostbuf[sizeof(hostbuf)]) {
#ifdef DEBUG
                       if (_res.options & RES_DEBUG)
                               printf("size (%d) too big\n", n);
#endif
                       break;
               }
               bcopy(cp, *hap++ = bp, n);
               bp +=n;
               cp += n;
               haveanswer++;
       }
       if (haveanswer) {
               *ap = NULL;
               *hap = NULL;
               return (&host);
       } else {
               h_errno = TRY_AGAIN;
               return (NULL);
       }
}

struct hostent *
gethostbyname(name)
       char *name;
{
       register char *cp, **domain;
       int n;
       struct hostent *hp, *gethostdomain();
       char *hostalias();
       extern struct hostent *_gethtbyname();

       if (!(_res.options & RES_INIT) && res_init() == -1)
               return (NULL);
       errno = 0;
       for (cp = name, n = 0; *cp; cp++)
               if (*cp == '.')
                       n++;
       if ((n && cp[-1] == '.') || (_res.options & RES_DEFNAMES) == 0) {
               cp[-1] = 0;
               hp = gethostdomain(name, (char *)NULL);
               cp[-1] = '.';
               return (hp);
       }
       if (n == 0 && (cp = hostalias(name)))
               return (gethostdomain(cp, (char *)NULL));
       for (domain = _res.dnsrch; *domain; domain++) {
               hp = gethostdomain(name, *domain);
               if (hp)
                       return (hp);
               if (errno == ECONNREFUSED)
                       return (_gethtbyname(name));
               if (h_errno != HOST_NOT_FOUND ||
                   (_res.options & RES_DNSRCH) == 0)
                       return (NULL);
               h_errno = 0;
       }
       return (gethostdomain(name, (char *)NULL));
}

static struct hostent *
gethostdomain(name, domain)
       char *name, *domain;
{
       querybuf buf;
       char nbuf[2*MAXDNAME+2];
       int n;

       sprintf(nbuf, "%.*s.%.*s", MAXDNAME, name, MAXDNAME, domain);
       n = res_mkquery(QUERY, nbuf, C_IN, T_A, (char *)NULL, 0, NULL,
               (char *)&buf, sizeof(buf));
       if (n < 0) {
#ifdef DEBUG
               if (_res.options & RES_DEBUG)
                       printf("res_mkquery failed\n");
#endif
               return (NULL);
       }
       return (getanswer((char *)&buf, n, 0));
}

struct hostent *
gethostbyaddr(addr, len, type)
       char *addr;
       int len, type;
{
       int n;
       querybuf buf;
       register struct hostent *hp;
       char qbuf[MAXDNAME];
       extern struct hostent *_gethtbyaddr();
       
       if (type != AF_INET)
               return (NULL);
       (void)sprintf(qbuf, "%d.%d.%d.%d.in-addr.arpa",
               ((unsigned)addr[3] & 0xff),
               ((unsigned)addr[2] & 0xff),
               ((unsigned)addr[1] & 0xff),
               ((unsigned)addr[0] & 0xff));
       n = res_mkquery(QUERY, qbuf, C_IN, T_PTR, (char *)NULL, 0, NULL,
               (char *)&buf, sizeof(buf));
       if (n < 0) {
#ifdef DEBUG
               if (_res.options & RES_DEBUG)
                       printf("res_mkquery failed\n");
#endif
               return (NULL);
       }
       hp = getanswer((char *)&buf, n, 1);
       if (hp == NULL && errno == ECONNREFUSED)
               hp = _gethtbyaddr(addr, len, type);
       if (hp == NULL)
               return(NULL);
       hp->h_addrtype = type;
       hp->h_length = len;
       h_addr_ptrs[0] = (char *)&host_addr;
       h_addr_ptrs[1] = (char *)0;
       host_addr = *(struct in_addr *)addr;
       return(hp);
}

char *
hostalias(name)
       register char *name;
{
       register char *C1, *C2;
       FILE *fp;
       char *file, *getenv(), *strcpy(), *strncpy();
       char buf[BUFSIZ];
       static char abuf[MAXDNAME];

       file = getenv("HOSTALIASES");
       if (file == NULL || (fp = fopen(file, "r")) == NULL)
               return (NULL);
       buf[sizeof(buf) - 1] = '\0';
       while (fgets(buf, sizeof(buf), fp)) {
               for (C1 = buf; *C1 && !isspace(*C1); ++C1);
               if (!*C1 || *C1 == '\n')
                       break;
               if (!strncmp(buf, name, C1 - buf)) {
                       while (isspace(*++C1));
                       if (!*C1)
                               break;
                       for (C2 = C1 + 1; *C2 && !isspace(*C2); ++C2);
                       abuf[sizeof(abuf) - 1] = *C2 = '\0';
                       (void)strncpy(abuf, C1, sizeof(abuf) - 1);
                       fclose(fp);
                       return (abuf);
               }
       }
       fclose(fp);
       return (NULL);
}

_sethtent(f)
       int f;
{
       if (hostf == NULL)
               hostf = fopen(HOSTDB, "r" );
       else
               rewind(hostf);
       stayopen |= f;
}

_endhtent()
{
       if (hostf && !stayopen) {
               (void) fclose(hostf);
               hostf = NULL;
       }
}

struct hostent *
_gethtent()
{
       char *p;
       register char *cp, **q;

       if (hostf == NULL && (hostf = fopen(HOSTDB, "r" )) == NULL)
               return (NULL);
again:
       if ((p = fgets(line, BUFSIZ, hostf)) == NULL)
               return (NULL);
       if (*p == '#')
               goto again;
       cp = any(p, "#\n");
       if (cp == NULL)
               goto again;
       *cp = '\0';
       cp = any(p, " \t");
       if (cp == NULL)
               goto again;
       *cp++ = '\0';
       /* THIS STUFF IS INTERNET SPECIFIC */
#if     BSD >= 43
       host.h_addr_list = host_addrs;
#endif
       host.h_addr = hostaddr;
       *((u_long *)host.h_addr) = inet_addr(p);
       host.h_length = sizeof (u_long);
       host.h_addrtype = AF_INET;
       while (*cp == ' ' || *cp == '\t')
               cp++;
       host.h_name = cp;
       q = host.h_aliases = host_aliases;
       cp = any(cp, " \t");
       if (cp != NULL) 
               *cp++ = '\0';
       while (cp && *cp) {
               if (*cp == ' ' || *cp == '\t') {
                       cp++;
                       continue;
               }
               if (q < &host_aliases[MAXALIASES - 1])
                       *q++ = cp;
               cp = any(cp, " \t");
               if (cp != NULL)
                       *cp++ = '\0';
       }
       *q = NULL;
       return (&host);
}

static char *
any(cp, match)
       register char *cp;
       char *match;
{
       register char *mp, c;

       while (c = *cp) {
               for (mp = match; *mp; mp++)
                       if (*mp == c)
                               return (cp);
               cp++;
       }
       return ((char *)0);
}

struct hostent *
_gethtbyname(name)
       char *name;
{
       register struct hostent *p;
       register char **cp;
       char lowname[128];
       register char *lp = lowname;
       
       while (*name)
               if (isupper(*name))
                       *lp++ = tolower(*name++);
               else
                       *lp++ = *name++;
       *lp = '\0';

       _sethtent(0);
       while (p = _gethtent()) {
               if (strcmp(p->h_name, lowname) == 0)
                       break;
               for (cp = p->h_aliases; *cp != 0; cp++)
                       if (strcmp(*cp, lowname) == 0)
                               goto found;
       }
found:
       _endhtent();
       return (p);
}

struct hostent *
_gethtbyaddr(addr, len, type)
       char *addr;
       int len, type;
{
       register struct hostent *p;

       _sethtent(0);
       while (p = _gethtent())
               if (p->h_addrtype == type && !bcmp(p->h_addr, addr, len))
                       break;
       _endhtent();
       return (p);
}