From 352f79acbd759c14399e39baef21fc4ffe180ac2 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko 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 Upstream-Status: Backport CVE: CVE-2016-2148 https://git.busybox.net/busybox/commit/?id=352f79 Signed-off-by: Armin Kuster --- networking/udhcp/common.c | 15 +++++++++++++-- networking/udhcp/dhcpc.c | 4 ++-- 2 files changed, 15 insertions(+), 4 deletions(-) Index: busybox-1.23.2/networking/udhcp/common.c =================================================================== --- busybox-1.23.2.orig/networking/udhcp/common.c +++ busybox-1.23.2/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[] ALIG [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). + */ }; Index: busybox-1.23.2/networking/udhcp/dhcpc.c =================================================================== --- busybox-1.23.2.orig/networking/udhcp/dhcpc.c +++ busybox-1.23.2/networking/udhcp/dhcpc.c @@ -103,7 +103,7 @@ static const uint8_t len_of_option_as_st [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 @@ -214,7 +214,7 @@ static NOINLINE char *xmalloc_optname_op 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);