avoid remote buffer overrun on hostbuf[]. From: Joost Pol <joost@pine.nl>

correct bad practice in the code - it uses two changing variables
to manage buffer (buf and buflen).  we eliminate buflen and use
fixed point (ep) as the ending pointer.

this fix is critical.

2 files changed, 33 insertions, 43 deletions

diff --git a/src/lib/libc/net/gethostnamadr.c b/src/lib/libc/net/gethostnamadr.c
index cdc42c4329..3049d576e1 100644
--- a/src/lib/libc/net/gethostnamadr.c
+++ b/src/lib/libc/net/gethostnamadr.c
@@ -52,7 +52,7 @@
  */
 
 #if defined(LIBC_SCCS) && !defined(lint)
-static char rcsid[] = "$OpenBSD: gethostnamadr.c,v 1.47 2002/05/22 04:31:14 deraadt Exp $";
+static char rcsid[] = "$OpenBSD: gethostnamadr.c,v 1.48 2002/06/26 06:00:53 itojun Exp $";
 #endif /* LIBC_SCCS and not lint */
 
 #include <sys/param.h>
@@ -99,7 +99,7 @@ static FILE *hostf = NULL;
 static int stayopen = 0;
 
 static void map_v4v6_address(const char *src, char *dst);
-static void map_v4v6_hostent(struct hostent *hp, char **bp, int *len);
+static void map_v4v6_hostent(struct hostent *hp, char **bp, char *);
 
 #ifdef RESOLVSORT
 static void addrsort(char **, int);
@@ -168,8 +168,8 @@ getanswer(answer, anslen, qname, qtype)
         register const u_char *cp;
         register int n;
         const u_char *eom;
-        char *bp, **ap, **hap;
-        int type, class, buflen, ancount, qdcount;
+        char *bp, **ap, **hap, *ep;
+        int type, class, ancount, qdcount;
         int haveanswer, had_error;
         int toobig = 0;
         char tbuf[MAXDNAME];
@@ -203,13 +203,13 @@ getanswer(answer, anslen, qname, qtype)
         ancount = ntohs(hp->ancount);
         qdcount = ntohs(hp->qdcount);
         bp = hostbuf;
-        buflen = sizeof hostbuf;
+        ep = hostbuf + sizeof hostbuf;
         cp = answer->buf + HFIXEDSZ;
         if (qdcount != 1) {
                 h_errno = NO_RECOVERY;
                 return (NULL);
         }
-        n = dn_expand(answer->buf, eom, cp, bp, buflen);
+        n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
         if ((n < 0) || !(*name_ok)(bp)) {
                 h_errno = NO_RECOVERY;
                 return (NULL);
@@ -223,7 +223,6 @@ getanswer(answer, anslen, qname, qtype)
                 n = strlen(bp) + 1;             /* for the \0 */
                 host.h_name = bp;
                 bp += n;
-                buflen -= n;
                 /* The qname can be abbreviated, but h_name is now absolute. */
                 qname = host.h_name;
         }
@@ -236,7 +235,7 @@ getanswer(answer, anslen, qname, qtype)
         haveanswer = 0;
         had_error = 0;
         while (ancount-- > 0 && cp < eom && !had_error) {
-                n = dn_expand(answer->buf, eom, cp, bp, buflen);
+                n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
                 if ((n < 0) || !(*name_ok)(bp)) {
                         had_error++;
                         continue;
@@ -271,17 +270,15 @@ getanswer(answer, anslen, qname, qtype)
                         *ap++ = bp;
                         n = strlen(bp) + 1;     /* for the \0 */
                         bp += n;
-                        buflen -= n;
                         /* Get canonical name. */
                         n = strlen(tbuf) + 1;   /* for the \0 */
-                        if (n > buflen) {
+                        if (n > ep - bp) {
                                 had_error++;
                                 continue;
                         }
                         strcpy(bp, tbuf);
                         host.h_name = bp;
                         bp += n;
-                        buflen -= n;
                         continue;
                 }
                 if (qtype == T_PTR && type == T_CNAME) {
@@ -297,14 +294,13 @@ getanswer(answer, anslen, qname, qtype)
                         cp += n;
                         /* Get canonical name. */
                         n = strlen(tbuf) + 1;   /* for the \0 */
-                        if (n > buflen) {
+                        if (n > ep - bp) {
                                 had_error++;
                                 continue;
                         }
                         strcpy(bp, tbuf);
                         tname = bp;
                         bp += n;
-                        buflen -= n;
                         continue;
                 }
                 if (type != qtype) {
@@ -323,7 +319,7 @@ getanswer(answer, anslen, qname, qtype)
                                 cp += n;
                                 continue;       /* XXX - had_error++ ? */
                         }
-                        n = dn_expand(answer->buf, eom, cp, bp, buflen);
+                        n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
 #ifdef USE_RESOLV_NAME_OK
                         if ((n < 0) || !res_hnok(bp)) {
 #else
@@ -343,7 +339,6 @@ getanswer(answer, anslen, qname, qtype)
                         if (n != -1) {
                                 n = strlen(bp) + 1;     /* for the \0 */
                                 bp += n;
-                                buflen -= n;
                         }
                         break;
 #else
@@ -351,8 +346,7 @@ getanswer(answer, anslen, qname, qtype)
                         if (_res.options & RES_USE_INET6) {
                                 n = strlen(bp) + 1;     /* for the \0 */
                                 bp += n;
-                                buflen -= n;
-                                map_v4v6_hostent(&host, &bp, &buflen);
+                                map_v4v6_hostent(&host, &bp, ep);
                         }
                         h_errno = NETDB_SUCCESS;
                         return (&host);
@@ -375,7 +369,6 @@ getanswer(answer, anslen, qname, qtype)
                                 host.h_name = bp;
                                 nn = strlen(bp) + 1;    /* for the \0 */
                                 bp += nn;
-                                buflen -= nn;
                         }
 
                         bp += sizeof(align) - ((u_long)bp % sizeof(align));
@@ -399,7 +392,6 @@ getanswer(answer, anslen, qname, qtype)
                         }
                         bcopy(cp, *hap++ = bp, n);
                         bp += n;
-                        buflen -= n;
                         cp += n;
                         break;
                 }
@@ -420,15 +412,14 @@ getanswer(answer, anslen, qname, qtype)
 # endif /*RESOLVSORT*/
                 if (!host.h_name) {
                         n = strlen(qname) + 1;  /* for the \0 */
-                        if (n > buflen)
+                        if (n > ep - bp)
                                 goto try_again;
                         strcpy(bp, qname);
                         host.h_name = bp;
                         bp += n;
-                        buflen -= n;
                 }
                 if (_res.options & RES_USE_INET6)
-                        map_v4v6_hostent(&host, &bp, &buflen);
+                        map_v4v6_hostent(&host, &bp, ep);
                 h_errno = NETDB_SUCCESS;
                 return (&host);
         }
@@ -520,8 +511,8 @@ gethostbyname2(name, af)
 {
         querybuf buf;
         register const char *cp;
-        char *bp;
-        int n, size, type, len, i;
+        char *bp, *ep;
+        int n, size, type, i;
         extern struct hostent *_gethtbyname2(), *_yp_gethtbyname();
         register struct hostent *hp;
         char lookups[MAXDNSLUS];
@@ -575,7 +566,7 @@ gethostbyname2(name, af)
                                 }
                                 strlcpy(hostbuf, name, MAXHOSTNAMELEN);
                                 bp = hostbuf + MAXHOSTNAMELEN;
-                                len = sizeof hostbuf - MAXHOSTNAMELEN;
+                                ep = hostbuf + sizeof(hostbuf);
                                 host.h_name = hostbuf;
                                 host.h_aliases = host_aliases;
                                 host_aliases[0] = NULL;
@@ -583,7 +574,7 @@ gethostbyname2(name, af)
                                 h_addr_ptrs[1] = NULL;
                                 host.h_addr_list = h_addr_ptrs;
                                 if (_res.options & RES_USE_INET6)
-                                        map_v4v6_hostent(&host, &bp, &len);
+                                        map_v4v6_hostent(&host, &bp, ep);
                                 h_errno = NETDB_SUCCESS;
                                 return (&host);
                         }
@@ -607,7 +598,7 @@ gethostbyname2(name, af)
                                 }
                                 strlcpy(hostbuf, name, MAXHOSTNAMELEN);
                                 bp = hostbuf + MAXHOSTNAMELEN;
-                                len = sizeof hostbuf - MAXHOSTNAMELEN;
+                                ep = hostbuf + sizeof(hostbuf);
                                 host.h_name = hostbuf;
                                 host.h_aliases = host_aliases;
                                 host_aliases[0] = NULL;
@@ -869,9 +860,9 @@ _gethtent()
         *q = NULL;
         if (_res.options & RES_USE_INET6) {
                 char *bp = hostbuf;
-                int buflen = sizeof hostbuf;
+                char *ep = hostbuf + sizeof hostbuf;
 
-                map_v4v6_hostent(&host, &bp, &buflen);
+                map_v4v6_hostent(&host, &bp, ep);
         }
         h_errno = NETDB_SUCCESS;
         return (&host);
@@ -1085,10 +1076,10 @@ map_v4v6_address(src, dst)
 }
 
 static void
-map_v4v6_hostent(hp, bpp, lenp)
+map_v4v6_hostent(hp, bpp, ep)
         struct hostent *hp;
         char **bpp;
-        int *lenp;
+        char *ep;
 {
         char **ap;
 
@@ -1099,17 +1090,15 @@ map_v4v6_hostent(hp, bpp, lenp)
         for (ap = hp->h_addr_list; *ap; ap++) {
                 int i = sizeof(align) - ((u_long)*bpp % sizeof(align));
 
-                if (*lenp < (i + IN6ADDRSZ)) {
+                if (ep - *bpp < (i + IN6ADDRSZ)) {
                         /* Out of memory.  Truncate address list here.  XXX */
                         *ap = NULL;
                         return;
                 }
                 *bpp += i;
-                *lenp -= i;
                 map_v4v6_address(*ap, *bpp);
                 *ap = *bpp;
                 *bpp += IN6ADDRSZ;
-                *lenp -= IN6ADDRSZ;
         }
 }
 
diff --git a/src/lib/libc/net/getnetnamadr.c b/src/lib/libc/net/getnetnamadr.c
index 834ddf11ae..a5a4200acf 100644
--- a/src/lib/libc/net/getnetnamadr.c
+++ b/src/lib/libc/net/getnetnamadr.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: getnetnamadr.c,v 1.15 2002/02/16 21:27:23 millert Exp $       */
+/*      $OpenBSD: getnetnamadr.c,v 1.16 2002/06/26 06:00:54 itojun Exp $        */
 
 /*
  * Copyright (c) 1997, Jason Downs.  All rights reserved.
@@ -77,7 +77,7 @@ static char sccsid[] = "@(#)getnetbyaddr.c	8.1 (Berkeley) 6/4/93";
 static char sccsid_[] = "from getnetnamadr.c    1.4 (Coimbra) 93/06/03";
 static char rcsid[] = "$From: getnetnamadr.c,v 8.7 1996/08/05 08:31:35 vixie Exp $";
 #else
-static char rcsid[] = "$OpenBSD: getnetnamadr.c,v 1.15 2002/02/16 21:27:23 millert Exp $";
+static char rcsid[] = "$OpenBSD: getnetnamadr.c,v 1.16 2002/06/26 06:00:54 itojun Exp $";
 #endif
 #endif /* LIBC_SCCS and not lint */
 
@@ -133,9 +133,9 @@ getnetanswer(answer, anslen, net_i)
         register u_char *cp;
         register int n;
         u_char *eom;
-        int type, class, buflen, ancount, qdcount, haveanswer, i, nchar;
+        int type, class, ancount, qdcount, haveanswer, i, nchar;
         char aux1[MAXHOSTNAMELEN], aux2[MAXHOSTNAMELEN], ans[MAXHOSTNAMELEN];
-        char *in, *st, *pauxt, *bp, **ap;
+        char *in, *st, *pauxt, *bp, **ap, *ep;
         char *paux1 = &aux1[0], *paux2 = &aux2[0], flag = 0;
         static  struct netent net_entry;
         static  char *net_aliases[MAXALIASES], netbuf[BUFSIZ+1];
@@ -159,7 +159,7 @@ getnetanswer(answer, anslen, net_i)
         ancount = ntohs(hp->ancount); /* #/records in the answer section */
         qdcount = ntohs(hp->qdcount); /* #/entries in the question section */
         bp = netbuf;
-        buflen = sizeof(netbuf);
+        ep = netbuf + sizeof(netbuf);
         cp = answer->buf + HFIXEDSZ;
         if (!qdcount) {
                 if (hp->aa)
@@ -175,7 +175,7 @@ getnetanswer(answer, anslen, net_i)
         net_entry.n_aliases = net_aliases;
         haveanswer = 0;
         while (--ancount >= 0 && cp < eom) {
-                n = dn_expand(answer->buf, eom, cp, bp, buflen);
+                n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
 #ifdef USE_RESOLV_NAME_OK
                 if ((n < 0) || !res_dnok(bp))
 #else
@@ -190,12 +190,13 @@ getnetanswer(answer, anslen, net_i)
                 cp += INT32SZ;          /* TTL */
                 GETSHORT(n, cp);
                 if (class == C_IN && type == T_PTR) {
-                        n = dn_expand(answer->buf, eom, cp, bp, buflen);
+                        n = dn_expand(answer->buf, eom, cp, bp, ep - bp);
 #ifdef USE_RESOLV_NAME_OK
-                        if ((n < 0) || !res_hnok(bp)) {
+                        if ((n < 0) || !res_hnok(bp))
 #else
-                        if ((n < 0) || !_hokchar(bp)) {
+                        if ((n < 0) || !_hokchar(bp))
 #endif
+                        {
                                 cp += n;
                                 return (NULL);
                         }