From 3ef143022acbd46d8cb2640ad93827bbb9e60117 Mon Sep 17 00:00:00 2001 From: tmarkwalder Date: Wed, 3 May 2017 09:01:36 -0400 Subject: [PATCH] [v4_1_esv] v6 FQDN option unpacking now handles values with spaces and non-printables Merged in rt43592. --- RELNOTES | 7 +++++++ common/options.c | 20 ++++++++++++-------- 2 files changed, 19 insertions(+), 8 deletions(-) diff --git a/RELNOTES b/RELNOTES index 158eecba2..c48874637 100644 --- a/RELNOTES +++ b/RELNOTES @@ -102,6 +102,13 @@ by Eric Young (eay@cryptsoft.com). for expiry in the script environment. [ISC-Bugs #43326] +- 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 4.1-ESV-R14b1 - None diff --git a/common/options.c b/common/options.c index 0f0edbda1..8a89bce96 100644 --- a/common/options.c +++ b/common/options.c @@ -3524,12 +3524,17 @@ 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; } @@ -3541,7 +3546,6 @@ 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 @@ -3561,7 +3565,7 @@ 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."); -- 2.47.3