[master] v6 FQDN option unpacking now handles values with spaces and non-printables

    Merged in rt43592.

diff --git a/RELNOTES b/RELNOTES
index 12f34481f94501f1d57acc71e9bfe26214e6c89e..cdda8cd9e51ff4a512b349e375dacbda9d4e9851 100644 (file)
--- a/RELNOTES
+++ b/RELNOTES
@@ -172,6 +172,13 @@ by Eric Young (eay@cryptsoft.com).
   reporting the issue.
   [ISC-Bugs #28038]
 
+- DHCP6 FQDN option unpacking code now correctly handles values that contain
+  spaces, special, or non-printable characters.  Prior to this the buffer
+  size needed was underestitmate causing a conversion error message to
+  be logged and DNS updates to be skipped. Thanks to Fernando Soto at
+  BlueCat Networks for bringing the matter to our attention.
+  [ISC-Bugs #43592]
+
                        Changes since 4.3.0 (bug fixes)
 
 - Tidy up several small tickets.

diff --git a/common/options.c b/common/options.c
index 223726ca0c01fbb611a3063c785133b4c54d858b..b0dcab426e2234fa0e61bb165da9bc3af3d4015d 100644 (file)
--- a/common/options.c
+++ b/common/options.c
@@ -3594,12 +3594,17 @@ fqdn6_universe_decode(struct option_state *options,
                return 0;
 
        /* Save the contents of the option in a buffer.  There are 3
-        * one-byte values we record from the packet, so we go ahead
-        * and allocate a bigger buffer to accommodate them.  But the
-        * 'length' we got (because it is a DNS encoded string) is
-        * one longer than we need...so we only add two extra octets.
-        */
-       if (!buffer_allocate(&bp, length + 2, MDL)) {
+        * one-byte values we record from the packet. The input is
+        * DNS encoded and to be safe we'll assume that each character
+        * is non-printable and will be converted to an escaped number:
+        * "\\nnn".  Yes, we'll have dead space pretty much all the time
+        * but the alternative is to basically dry run the conversion
+        * first to calculate the precise size or reallocate to a smaller
+        * buffer later, either of which is a bigger performance hit than
+        * just doing a generous allocation. */
+       unsigned bp_size = 3 + (length * 4);
+
+       if (!buffer_allocate(&bp, bp_size, MDL)) {
                log_error("No memory for dhcp6.fqdn option buffer.");
                return 0;
        }
@@ -3611,7 +3616,6 @@ fqdn6_universe_decode(struct option_state *options,
                goto error;
 
        /* XXX: We need to process 'The "N" bit'. */
-
        if (buffer[0] & 1) /* server-update. */
                bp->data[2] = 1;
        else
@@ -3631,7 +3635,7 @@ fqdn6_universe_decode(struct option_state *options,
                goto error;
 
        /* Convert the domain name to textual representation for config. */
-       len = MRns_name_ntop(buffer + 1, (char *)bp->data + 3, length - 1);
+       len = MRns_name_ntop(buffer + 1, (char *)bp->data + 3, bp_size - 3);
        if (len == -1) {
                log_error("Unable to convert dhcp6.fqdn domain name to "
                          "printable form.");