| From 352f79acbd759c14399e39baef21fc4ffe180ac2 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> |
| |
| Upstream-Status: Backport |
| CVE: CVE-2016-2148 |
| https://git.busybox.net/busybox/commit/?id=352f79 |
| |
| Signed-off-by: Armin Kuster <akuster@mvista.com> |
| |
| --- |
| 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); |