From 4247dca900e08daa6a8a2333baca6136bdbba31d Mon Sep 17 00:00:00 2001
From: Elliott Hughes <enh@google.com>
Date: Fri, 6 Sep 2019 22:31:48 -0700
Subject: host: cope with large DNS responses.

DNS responses were limited to 512 bytes back when they were UDP only,
but if you have a TCP connection you can get up to 64KiB.

Also use the existing constant for the size of rrname.

Also update the help text.

Also consistently use `sizeof(T)` rather than `sizeof T`.

Also use consistently use `ARRAY_LEN`.

Fixes #56.

Test: `toybox host value.testing.express`
---
 toys/pending/host.c | 39 +++++++++++++++++++++++----------------
 1 file changed, 23 insertions(+), 16 deletions(-)

(limited to 'toys')

diff --git a/toys/pending/host.c b/toys/pending/host.c
index fe0f23aa..1610301e 100644
--- a/toys/pending/host.c
+++ b/toys/pending/host.c
@@ -16,8 +16,8 @@ config HOST
     or an IPv4 dotted or IPv6 colon-separated address to reverse lookup.
     SERVER (if present) is the DNS server to use.
 
-    -a	no idea
-    -t	not a clue
+    -a	-v -t ANY
+    -t TYPE	query records of type TYPE
     -v	verbose
 */
 
@@ -68,10 +68,13 @@ static const char rct[16][32] = {
 void host_main(void)
 {
   int verbose=(toys.optflags & (FLAG_a|FLAG_v)), type,
-      i, j, ret, sec, count, rcode, qlen, alen, pllen = 0;
+      i, j, ret, sec, count, rcode, qlen, alen, pllen = 0,
+      abuf_len = 65536; // Largest TCP response.
   unsigned ttl, pri, v[5];
-  unsigned char qbuf[280], abuf[512], *p;
-  char *name, *nsname, rrname[256], plname[640], ptrbuf[128];
+  unsigned char *abuf = xmalloc(abuf_len);
+  char *rrname = xmalloc(MAXDNAME);
+  unsigned char qbuf[280], *p;
+  char *name, *nsname, plname[640], ptrbuf[128];
   struct addrinfo *ai, iplit_hints = { .ai_flags = AI_NUMERICHOST };
 
   name = *toys.optargs;
@@ -113,7 +116,7 @@ void host_main(void)
     if (type < 0) error_exit("Invalid query type: %s", TT.type_str);
   }
 
-  qlen = res_mkquery(0, name, 1, type, 0, 0, 0, qbuf, sizeof qbuf);
+  qlen = res_mkquery(0, name, 1, type, 0, 0, 0, qbuf, sizeof(qbuf));
   if (qlen < 0) error_exit("Invalid query parameters: %s", name);
 
   if (nsname) {
@@ -127,8 +130,8 @@ void host_main(void)
       sizeof(struct timeval));
     printf("Using domain server %s:\n", nsname);
     send(s, qbuf, qlen, 0);
-    alen = recv(s, abuf, sizeof abuf, 0);
-  } else alen = res_send(qbuf, qlen, abuf, sizeof abuf);
+    alen = recv(s, abuf, abuf_len, 0);
+  } else alen = res_send(qbuf, qlen, abuf, abuf_len);
 
   if (alen < 12) error_exit("Host not found.");
 
@@ -150,7 +153,7 @@ void host_main(void)
         : "Additional information:");
 
     for (; count--; p += pllen) {
-      p += dn_expand(abuf, abuf+alen, p, rrname, sizeof(rrname));
+      p += dn_expand(abuf, abuf+alen, p, rrname, MAXDNAME);
       type = (p[0]<<8) + p[1];
       p += 4;
       if (!sec) continue;
@@ -159,18 +162,18 @@ void host_main(void)
       pllen = (p[0]<<8) + p[1];
       p += 2;
 
-      switch (type<sizeof(rrt)/sizeof(*rrt) ? rrt[type].pl : 0) {
+      switch (type<ARRAY_LEN(rrt) ? rrt[type].pl : 0) {
       case PL_IP:
-        inet_ntop(rrt[type].af, p, plname, sizeof plname);
+        inet_ntop(rrt[type].af, p, plname, sizeof(plname));
         break;
       case PL_NAME:
-        dn_expand(abuf, abuf+alen, p, plname, sizeof plname);
+        dn_expand(abuf, abuf+alen, p, plname, sizeof(plname));
         break;
       case PL_TEXT:
-        snprintf(plname, sizeof plname, "\"%.*s\"", pllen, p);
+        snprintf(plname, sizeof(plname), "\"%.*s\"", pllen, p);
         break;
       case PL_SOA:
-        i = dn_expand(abuf, abuf+alen, p, plname, sizeof plname - 1);
+        i = dn_expand(abuf, abuf+alen, p, plname, sizeof(plname) - 1);
         strcat(plname, " ");
         i += dn_expand(abuf, abuf+alen, p+i, plname+strlen(plname),
           sizeof(plname)-strlen(plname));
@@ -188,13 +191,13 @@ void host_main(void)
         pri = (p[0]<<8)+p[1];
         snprintf(plname, sizeof(plname), verbose ? "%d " : "(pri=%d) by ", pri);
         dn_expand(abuf, abuf+alen, p+2, plname+strlen(plname),
-          sizeof plname - strlen(plname));
+          sizeof(plname) - strlen(plname));
         break;
       case PL_SRV:
         for (j=0; j<3; j++) v[j] = (p[2*j]<<8) + p[1+2*j];
         snprintf(plname, sizeof(plname), "%u %u %u ", v[0], v[1], v[2]);
         dn_expand(abuf, abuf+alen, p+6, plname+strlen(plname),
-          sizeof plname - strlen(plname));
+          sizeof(plname) - strlen(plname));
         break;
       default:
         printf("%s unsupported RR type %u\n", rrname, type);
@@ -209,5 +212,9 @@ void host_main(void)
     if (!verbose && sec==1) break;
   }
 
+  if (CFG_TOYBOX_FREE) {
+    free(abuf);
+    free(rrname);
+  }
   toys.exitval = rcode;
 }
-- 
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