Fix unaligned access in DHCPv4 "get_option" on MacOS

diff --git a/src/protocols/dhcpv4/packet.c b/src/protocols/dhcpv4/packet.c
index 6d0d0d6390b915f9278e466231c4d48fa10cc6ed..41e91354b7b4ad165d149b21e3ddf4eee1209601 100644 (file)
--- a/src/protocols/dhcpv4/packet.c
+++ b/src/protocols/dhcpv4/packet.c
@@ -43,10 +43,25 @@ uint8_t const *fr_dhcpv4_packet_get_option(dhcp_packet_t const *packet, size_t p
 
        if (packet_size < MIN_PACKET_SIZE) return NULL;
 
+       /*
+        *      This is needed for UBSAN on MacOS, that doesn't
+        *      allow misaligned accesses.  Because the packet
+        *      structure is flat, we don't need to deref the
+        *      packet pointer at any point, we just need to
+        *      calculate the offsets relative to the pointer
+        *      value and use those... Whatever actually deals
+        *      with the option is just expecting a uint8_t *.
+        */
+#define ALIGNED_ACCESS(packet, field) \
+               (uint8_t const *)packet + offsetof(dhcp_packet_t, field)
+
        where = 0;
        size = packet_size - offsetof(dhcp_packet_t, options);
-       data = &packet->options[where];
 
+       /*
+        *      Alignment fix.  We can't just deref a pointer
+        */
+       data = ALIGNED_ACCESS(packet, options);
        while (where < size) {
                if (data[0] == 0) { /* padding */
                        where++;
@@ -56,14 +71,14 @@ uint8_t const *fr_dhcpv4_packet_get_option(dhcp_packet_t const *packet, size_t p
 
                if (data[0] == 255) { /* end of options */
                        if ((field == DHCP_OPTION_FIELD) && (overload & DHCP_FILE_FIELD)) {
-                               data = packet->file;
+                               data = ALIGNED_ACCESS(packet, file);
                                where = 0;
                                size = sizeof(packet->file);
                                field = DHCP_FILE_FIELD;
                                continue;
 
                        } else if ((field == DHCP_FILE_FIELD || field == DHCP_OPTION_FIELD) && (overload & DHCP_SNAME_FIELD)) {
-                               data = packet->sname;
+                               data = ALIGNED_ACCESS(packet, sname);
                                where = 0;
                                size = sizeof(packet->sname);
                                field = DHCP_SNAME_FIELD;