fix parsing of RDATA for TXT records

ok gilles@

diff --git a/usr.sbin/smtpd/spfwalk.c b/usr.sbin/smtpd/spfwalk.c
index 64de139..cab0530 100644 (file)
--- a/usr.sbin/smtpd/spfwalk.c
+++ b/usr.sbin/smtpd/spfwalk.c
@@ -23,6 +23,7 @@
 #include <asr.h>
 #include <ctype.h>
 #include <err.h>
+#include <errno.h>
 #include <event.h>
 #include <pwd.h>
 #include <stdio.h>
@@ -43,6 +44,7 @@ static void   dispatch_a(struct dns_rr *);
 static void    dispatch_aaaa(struct dns_rr *);
 static void    lookup_record(int, const char *, void (*)(struct dns_rr *));
 static void    dispatch_record(struct asr_result *, void *);
+static ssize_t parse_txt(const char *, size_t, char *, size_t);
 
 int     ip_v4 = 0;
 int     ip_v6 = 0;
@@ -140,14 +142,19 @@ dispatch_record(struct asr_result *ar, void *arg)
 void
 dispatch_txt(struct dns_rr *rr)
 {
-        char buf[512];
+        char buf[4096];
         char buf2[512];
         char *in = buf;
         char *argv[512];
         char **ap = argv;
        char *end;
-       
-       print_dname(rr->rr.other.rdata, buf, sizeof(buf));
+       ssize_t n;
+
+       n = parse_txt(rr->rr.other.rdata, rr->rr.other.rdlen, buf, sizeof(buf));
+       if (n == -1 || n == sizeof(buf))
+               return;
+       buf[n] = '\0';
+
        if (strncasecmp("v=spf1 ", buf, 7))
                return;
 
@@ -238,3 +245,38 @@ dispatch_aaaa(struct dns_rr *rr)
            buffer, sizeof buffer)))
                printf("%s\n", ptr);
 }
+
+static ssize_t
+parse_txt(const char *rdata, size_t rdatalen, char *dst, size_t dstsz)
+{
+       size_t len;
+       ssize_t r = 0;
+
+       while (rdatalen) {
+               len = *(const unsigned char *)rdata;
+               if (len >= rdatalen) {
+                       errno = EINVAL;
+                       return -1;
+               }
+
+               rdata++;
+               rdatalen--;
+
+               if (len == 0)
+                       continue;
+
+               if (len >= dstsz) {
+                       errno = EOVERFLOW;
+                       return -1;
+               }
+               memmove(dst, rdata, len);
+               dst += len;
+               dstsz -= len;
+
+               rdata += len;
+               rdatalen -= len;
+               r += len;
+       }
+
+       return r;
+}