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From 3c4de6e36c4d387a648622e7b828a05f2b1b47e6 Mon Sep 17 00:00:00 2001
From: Denys Vlasenko <vda.linux@googlemail.com>
Date: Fri, 26 Feb 2016 15:54:56 +0100
Subject: [PATCH] udhcpc: fix OPTION_6RD parsing (could overflow its malloced
buffer)
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
(cherry picked from commit 352f79acbd759c14399e39baef21fc4ffe180ac2)
---
networking/udhcp/common.c | 15 +++++++++++++--
networking/udhcp/dhcpc.c | 4 ++--
2 files changed, 15 insertions(+), 4 deletions(-)
diff --git a/networking/udhcp/common.c b/networking/udhcp/common.c
index bc41c8d..680852c 100644
--- a/networking/udhcp/common.c
+++ b/networking/udhcp/common.c
@@ -142,7 +142,7 @@ const char dhcp_option_strings[] ALIGN1 =
* udhcp_str2optset: to determine how many bytes to allocate.
* xmalloc_optname_optval: to estimate string length
* from binary option length: (option[LEN] / dhcp_option_lengths[opt_type])
- * is the number of elements, multiply in by one element's string width
+ * is the number of elements, multiply it by one element's string width
* (len_of_option_as_string[opt_type]) and you know how wide string you need.
*/
const uint8_t dhcp_option_lengths[] ALIGN1 = {
@@ -162,7 +162,18 @@ const uint8_t dhcp_option_lengths[] ALIGN1 = {
[OPTION_S32] = 4,
/* Just like OPTION_STRING, we use minimum length here */
[OPTION_STATIC_ROUTES] = 5,
- [OPTION_6RD] = 22, /* ignored by udhcp_str2optset */
+ [OPTION_6RD] = 12, /* ignored by udhcp_str2optset */
+ /* The above value was chosen as follows:
+ * len_of_option_as_string[] for this option is >60: it's a string of the form
+ * "32 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 ".
+ * Each additional ipv4 address takes 4 bytes in binary option and appends
+ * another "255.255.255.255 " 16-byte string. We can set [OPTION_6RD] = 4
+ * but this severely overestimates string length: instead of 16 bytes,
+ * it adds >60 for every 4 bytes in binary option.
+ * We cheat and declare here that option is in units of 12 bytes.
+ * This adds more than 60 bytes for every three ipv4 addresses - more than enough.
+ * (Even 16 instead of 12 should work, but let's be paranoid).
+ */
};
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index 915f659..2332b57 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -113,7 +113,7 @@ static const uint8_t len_of_option_as_string[] = {
[OPTION_IP ] = sizeof("255.255.255.255 "),
[OPTION_IP_PAIR ] = sizeof("255.255.255.255 ") * 2,
[OPTION_STATIC_ROUTES ] = sizeof("255.255.255.255/32 255.255.255.255 "),
- [OPTION_6RD ] = sizeof("32 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 "),
+ [OPTION_6RD ] = sizeof("132 128 ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff 255.255.255.255 "),
[OPTION_STRING ] = 1,
[OPTION_STRING_HOST ] = 1,
#if ENABLE_FEATURE_UDHCP_RFC3397
@@ -220,7 +220,7 @@ static NOINLINE char *xmalloc_optname_optval(uint8_t *option, const struct dhcp_
type = optflag->flags & OPTION_TYPE_MASK;
optlen = dhcp_option_lengths[type];
upper_length = len_of_option_as_string[type]
- * ((unsigned)(len + optlen - 1) / (unsigned)optlen);
+ * ((unsigned)(len + optlen) / (unsigned)optlen);
dest = ret = xmalloc(upper_length + strlen(opt_name) + 2);
dest += sprintf(ret, "%s=", opt_name);
--
2.7.4
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