udhcpc: sanitize hostnames in incoming packets. Closes 3979.

The following options are replaced with string "bad" if they
contain malformed hostname:
HOST_NAME, DOMAIN_NAME, NIS_DOMAIN, TFTP_SERVER_NAME

function                                             old     new   delta
xmalloc_optname_optval                               850     888     +38
attach_option                                        440     443      +3
len_of_option_as_string                               13      14      +1
dhcp_option_lengths                                   13      14      +1
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 4/0 up/down: 43/0)               Total: 43 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/networking/udhcp/common.h b/networking/udhcp/common.h
index 479ae49f3..cfd58679a 100644
--- a/networking/udhcp/common.h
+++ b/networking/udhcp/common.h
@@ -80,6 +80,9 @@ enum {
         OPTION_IP = 1,
         OPTION_IP_PAIR,
         OPTION_STRING,
+        /* Opts of STRING_HOST type will be sanitized before they are passed
+         * to udhcpc script's environment: */
+        OPTION_STRING_HOST,
 //      OPTION_BOOLEAN,
         OPTION_U8,
         OPTION_U16,