dnsd: fixes various segfaults.

One was a lib api change that was not updated and another
is a stack buffer overflow.
It also adds support for '*' in dnsd.conf. It resolves all hostnames to
a specific ip address. This is useful if you for example want redirect
all http traffic to your first-boot-web-wizard on you router/firewall.

By Timo Teras

2 files changed, 16 insertions, 9 deletions

diff --git a/libbb/udp_io.c b/libbb/udp_io.c
index 689c39a82..c99e51643 100644
--- a/libbb/udp_io.c
+++ b/libbb/udp_io.c
@@ -36,11 +36,12 @@ send_to_from(int fd, void *buf, size_t len, int flags,
 #else
         struct iovec iov[1];
         struct msghdr msg;
-        char cbuf[sizeof(struct in_pktinfo)
+        union {
+                char cmsg[CMSG_SPACE(sizeof(struct in_pktinfo))];
 #if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
-                | sizeof(struct in6_pktinfo) /* (a|b) is poor man's max(a,b) */
+                char cmsg6[CMSG_SPACE(sizeof(struct in6_pktinfo))];
 #endif
-        ];
+        } u;
         struct cmsghdr* cmsgptr;
 
         if (from->sa_family != AF_INET
@@ -57,15 +58,15 @@ send_to_from(int fd, void *buf, size_t len, int flags,
         iov[0].iov_base = buf;
         iov[0].iov_len = len;
 
-        memset(cbuf, 0, sizeof(cbuf));
+        memset(&u, 0, sizeof(u));
 
         memset(&msg, 0, sizeof(msg));
         msg.msg_name = (void *)(struct sockaddr *)to; /* or compiler will annoy us */
         msg.msg_namelen = tolen;
         msg.msg_iov = iov;
         msg.msg_iovlen = 1;
-        msg.msg_control = cbuf;
-        msg.msg_controllen = sizeof(cbuf);
+        msg.msg_control = &u;
+        msg.msg_controllen = sizeof(u);
         msg.msg_flags = flags;
 
         cmsgptr = CMSG_FIRSTHDR(&msg);
@@ -89,6 +90,8 @@ send_to_from(int fd, void *buf, size_t len, int flags,
                 pktptr->ipi6_addr = ((struct sockaddr_in6*)from)->sin6_addr;
         }
 #endif
+        msg.msg_controllen = cmsgptr->cmsg_len;
+
         return sendmsg(fd, &msg, flags);
 #endif
 }
@@ -109,7 +112,9 @@ recv_from_to(int fd, void *buf, size_t len, int flags,
         struct iovec iov[1];
         union {
                 char cmsg[CMSG_SPACE(sizeof(struct in_pktinfo))];
+#if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
                 char cmsg6[CMSG_SPACE(sizeof(struct in6_pktinfo))];
+#endif
         } u;
         struct cmsghdr *cmsgptr;
         struct msghdr msg;
diff --git a/networking/dnsd.c b/networking/dnsd.c
index cb62d2081..97ba2dc6a 100644
--- a/networking/dnsd.c
+++ b/networking/dnsd.c
@@ -194,7 +194,8 @@ static int table_lookup(uint16_t type, uint8_t * as, uint8_t * qs)
                         for (i = 1; i <= (int)(d->name[0]); i++)
                                 if (tolower(qs[i]) != d->name[i])
                                         break;
-                        if (i > (int)(d->name[0])) {
+                        if (i > (int)(d->name[0]) ||
+                            (d->name[0] == 1 && d->name[1] == '*')) {
                                 strcpy((char *)as, d->ip);
 #if DEBUG
                                 fprintf(stderr, " OK as:%s\n", as);
@@ -202,7 +203,8 @@ static int table_lookup(uint16_t type, uint8_t * as, uint8_t * qs)
                                 return 0;
                         }
                 } else if (type == REQ_PTR) { /* search by IP-address */
-                        if (!strncmp((char*)&d->rip[1], (char*)&qs[1], strlen(d->rip)-1)) {
+                        if ((d->name[0] != 1 || d->name[1] != '*') &&
+                            !strncmp((char*)&d->rip[1], (char*)&qs[1], strlen(d->rip)-1)) {
                                 strcpy((char *)as, d->name);
                                 return 0;
                         }
@@ -401,7 +403,7 @@ int dnsd_main(int argc ATTRIBUTE_UNUSED, char **argv)
                 r = process_packet(buf);
                 if (r <= 0)
                         continue;
-                send_to_from(udps, buf, r, 0, &to->u.sa, &from->u.sa, lsa->len);
+                send_to_from(udps, buf, r, 0, &from->u.sa, &to->u.sa, lsa->len);
         }
         return 0;
 }