tftpd: Canonicalize all the addresses

We cannot canonicalize myaddr and not the from address.  We need to
canonicalize both of them, or else we'll try to create an IPv4 socket
and bind an IPv6-mapped IPv4 address to it, which is going to fail.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

3 files changed, 25 insertions, 26 deletions

diff --git a/tftpd/recvfrom.c b/tftpd/recvfrom.c
index b613823..83ef29a 100644
--- a/tftpd/recvfrom.c
+++ b/tftpd/recvfrom.c
@@ -113,14 +113,15 @@ err:
     return rv;
 }
 
-#ifdef HAVE_IPV6
 static void normalize_ip6_compat(union sock_addr *myaddr)
 {
+#ifdef HAVE_IPV6
     static const uint8_t ip6_compat_prefix[12] =
 	{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff };
     struct sockaddr_in in;
 
-    if (!memcmp(&myaddr->s6.sin6_addr, ip6_compat_prefix,
+    if (myaddr->sa.sa_family == AF_INET6 &&
+	!memcmp(&myaddr->s6.sin6_addr, ip6_compat_prefix,
 		sizeof ip6_compat_prefix)) {
 	bzero(&in, sizeof in);
 	in.sin_family = AF_INET;
@@ -129,13 +130,14 @@ static void normalize_ip6_compat(union sock_addr *myaddr)
 	       sizeof ip6_compat_prefix, sizeof in.sin_addr);
 	memcpy(&myaddr->si, &in, sizeof in);
     }
-}
+#else
+    (void)myaddr;
 #endif
+}
 
 int
 myrecvfrom(int s, void *buf, int len, unsigned int flags,
-           struct sockaddr *from, socklen_t * fromlen,
-           union sock_addr *myaddr)
+           union sock_addr *from, union sock_addr *myaddr)
 {
     struct msghdr msg;
     struct iovec iov;
@@ -168,16 +170,16 @@ myrecvfrom(int s, void *buf, int len, unsigned int flags,
 
     /* Try to enable getting the return address */
 #ifdef IP_RECVDSTADDR
-    if (from->sa_family == AF_INET)
+    if (from->sa.sa_family == AF_INET)
         setsockopt(s, IPPROTO_IP, IP_RECVDSTADDR, &on, sizeof(on));
 #endif
 #ifdef IP_PKTINFO
-    if (from->sa_family == AF_INET)
+    if (from->sa.sa_family == AF_INET)
         setsockopt(s, IPPROTO_IP, IP_PKTINFO, &on, sizeof(on));
 #endif
 #ifdef HAVE_IPV6
 #ifdef IPV6_RECVPKTINFO
-    if (from->sa_family == AF_INET6)
+    if (from->sa.sa_family == AF_INET6)
         setsockopt(s, IPPROTO_IPV6, IPV6_RECVPKTINFO, &on, sizeof(on));
 #endif
 #endif
@@ -186,8 +188,8 @@ myrecvfrom(int s, void *buf, int len, unsigned int flags,
     msg.msg_controllen = sizeof(control_un);
     msg.msg_flags = 0;
 
-    msg.msg_name = from;
-    msg.msg_namelen = *fromlen;
+    msg.msg_name = &from->sa;
+    msg.msg_namelen = sizeof(*from);
     iov.iov_base = buf;
     iov.iov_len = len;
     msg.msg_iov = &iov;
@@ -196,11 +198,9 @@ myrecvfrom(int s, void *buf, int len, unsigned int flags,
     if ((n = recvmsg(s, &msg, flags)) < 0)
         return n;               /* Error */
 
-    *fromlen = msg.msg_namelen;
-
     if (myaddr) {
         bzero(myaddr, sizeof(*myaddr));
-        myaddr->sa.sa_family = from->sa_family;
+        myaddr->sa.sa_family = from->sa.sa_family;
 
         if (msg.msg_controllen < sizeof(struct cmsghdr) ||
             (msg.msg_flags & MSG_CTRUNC))
@@ -209,7 +209,7 @@ myrecvfrom(int s, void *buf, int len, unsigned int flags,
         for (cmptr = CMSG_FIRSTHDR(&msg); cmptr != NULL;
              cmptr = CMSG_NXTHDR(&msg, cmptr)) {
 
-            if (from->sa_family == AF_INET) {
+            if (from->sa.sa_family == AF_INET) {
                 myaddr->sa.sa_family = AF_INET;
 #ifdef IP_RECVDSTADDR
                 if (cmptr->cmsg_level == IPPROTO_IP &&
@@ -230,7 +230,7 @@ myrecvfrom(int s, void *buf, int len, unsigned int flags,
 #endif
             }
 #ifdef HAVE_IPV6
-            else if (from->sa_family == AF_INET6) {
+            else if (from->sa.sa_family == AF_INET6) {
                 myaddr->sa.sa_family = AF_INET6;
 #ifdef IP6_RECVDSTADDR
                 if (cmptr->cmsg_level == IPPROTO_IPV6 &&
@@ -252,7 +252,6 @@ myrecvfrom(int s, void *buf, int len, unsigned int flags,
 			   sizeof(struct in6_addr));
                 }
 #endif
-		normalize_ip6_compat(myaddr);
             }
 #endif
         }
@@ -268,6 +267,10 @@ myrecvfrom(int s, void *buf, int len, unsigned int flags,
 #endif
         }
     }
+
+    normalize_ip6_compat(myaddr);
+    normalize_ip6_compat(from);
+
     return n;
 }
 
@@ -275,16 +278,16 @@ myrecvfrom(int s, void *buf, int len, unsigned int flags,
 
 int
 myrecvfrom(int s, void *buf, int len, unsigned int flags,
-           struct sockaddr *from, socklen_t * fromlen,
-           union sock_addr *myaddr)
+           union sock_addr *from, union sock_addr *myaddr)
 {
     /* There is no way we can get the local address, fudge it */
+    socklen_t fromlen = sizeof(*from);
 
     bzero(myaddr, sizeof(*myaddr));
-    myaddr->sa.sa_family = from->sa_family;
+    myaddr->sa.sa_family = from->sa.sa_family;
     sa_set_port(myaddr, htons(IPPORT_TFTP));
 
-    return recvfrom(s, buf, len, flags, from, fromlen);
+    return recvfrom(s, buf, len, flags, from, &fromlen);
 }
 
 #endif
diff --git a/tftpd/recvfrom.h b/tftpd/recvfrom.h
index e3c4055..7773a0d 100644
--- a/tftpd/recvfrom.h
+++ b/tftpd/recvfrom.h
@@ -19,5 +19,4 @@
 
 int
 myrecvfrom(int s, void *buf, int len, unsigned int flags,
-           struct sockaddr *from, socklen_t *fromlen,
-           union sock_addr *myaddr);
+           union sock_addr *from, union sock_addr *myaddr);
diff --git a/tftpd/tftpd.c b/tftpd/tftpd.c
index 91f5ae1..364e7d2 100644
--- a/tftpd/tftpd.c
+++ b/tftpd/tftpd.c
@@ -93,7 +93,6 @@ static unsigned int max_blksize = MAX_SEGSIZE;
 static char tmpbuf[INET6_ADDRSTRLEN], *tmp_p;
 
 static union sock_addr from;
-static socklen_t fromlen;
 static off_t tsize;
 static int tsize_ok;
 
@@ -874,9 +873,7 @@ int main(int argc, char **argv)
         set_socket_nonblock(fd, 0);
 #endif
 
-        fromlen = sizeof(from);
-        n = myrecvfrom(fd, buf, sizeof(buf), 0,
-                       (struct sockaddr *)&from, &fromlen, &myaddr);
+        n = myrecvfrom(fd, buf, sizeof(buf), 0, &from, &myaddr);
 
         if (n < 0) {
             if (E_WOULD_BLOCK(errno) || errno == EINTR) {