Repository : ssh://git@open-mesh.org/batctl
On branch : next
commit 140882bda39c4ab891f2981e2d07146221c664a1 Author: Sven Eckelmann sven@narfation.org Date: Wed Nov 12 18:58:25 2014 +0100
batctl: Fix crash when parsing unknown TVLVs
batctl tcpdump has an array with all known TVLVs and versions. The correct parser for the TVLV is chosen by getting the pointer from the address calculated by version and type. Unfortunately, the version and type was never validated to ensure that not an unknown TVLV (like mcast) was received.
This missing validation makes it possible to crash batctl by injecting packets with an unknown type and/or version. batctl will try to get the parser, fetch a NULL pointer or random data and then try to dereferenced it. This is usually handled by the operating system with a segfault. But this might be exploitable in rare situations.
An approach to handle this problem is by combining the simple selection step with the validation step. Only valid version+type will return a parser function pointer and the requesting function will only call the parser function pointer when it got one.
This regression was introduced by 4c39fb823b86036df40187f8bd342fe5398c28ef ("batctl: tcpdump - parse TVLV containers").
Signed-off-by: Sven Eckelmann sven@narfation.org Signed-off-by: Marek Lindner mareklindner@neomailbox.ch
140882bda39c4ab891f2981e2d07146221c664a1 tcpdump.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++------------- 1 file changed, 53 insertions(+), 14 deletions(-)
diff --git a/tcpdump.c b/tcpdump.c index ad5469b..c3c847e 100644 --- a/tcpdump.c +++ b/tcpdump.c @@ -171,16 +171,53 @@ static void batctl_tvlv_parse_roam_v1(void *buff,
typedef void (*batctl_tvlv_parser_t)(void *buff, ssize_t buff_len);
-/* location [i][j] contains the parsing function for TVLV of type 'i' and - * version 'j + 1' - */ -batctl_tvlv_parser_t tvlv_parsers[][1] = { - [BATADV_TVLV_GW][0] = batctl_tvlv_parse_gw_v1, - [BATADV_TVLV_DAT][0] = batctl_tvlv_parse_dat_v1, - [BATADV_TVLV_NC][0] = batctl_tvlv_parse_nc_v1, - [BATADV_TVLV_TT][0] = batctl_tvlv_parse_tt_v1, - [BATADV_TVLV_ROAM][0] = batctl_tvlv_parse_roam_v1, -}; +static batctl_tvlv_parser_t tvlv_parser_get(uint8_t type, uint8_t version) +{ + switch (type) { + case BATADV_TVLV_GW: + switch (version) { + case 1: + return batctl_tvlv_parse_gw_v1; + default: + return NULL; + } + + case BATADV_TVLV_DAT: + switch (version) { + case 1: + return batctl_tvlv_parse_dat_v1; + default: + return NULL; + } + + case BATADV_TVLV_NC: + switch (version) { + case 1: + return batctl_tvlv_parse_nc_v1; + default: + return NULL; + } + + case BATADV_TVLV_TT: + switch (version) { + case 1: + return batctl_tvlv_parse_tt_v1; + default: + return NULL; + } + + case BATADV_TVLV_ROAM: + switch (version) { + case 1: + return batctl_tvlv_parse_roam_v1; + default: + return NULL; + } + + default: + return NULL; + } +}
static void dump_batman_ucast_tvlv(unsigned char *packet_buff, ssize_t buff_len, int read_opt, int time_printed) @@ -223,8 +260,9 @@ static void dump_batman_ucast_tvlv(unsigned char *packet_buff, ssize_t buff_len, tvlv_hdr = (struct batadv_tvlv_hdr *)ptr; len = ntohs(tvlv_hdr->len);
- parser = tvlv_parsers[tvlv_hdr->type][tvlv_hdr->version - 1]; - parser(tvlv_hdr + 1, len); + parser = tvlv_parser_get(tvlv_hdr->type, tvlv_hdr->version); + if (parser) + parser(tvlv_hdr + 1, len);
/* go to the next container */ ptr = (uint8_t *)(tvlv_hdr + 1) + len; @@ -651,8 +689,9 @@ static void dump_batman_iv_ogm(unsigned char *packet_buff, ssize_t buff_len, int tvlv_hdr = (struct batadv_tvlv_hdr *)ptr; len = ntohs(tvlv_hdr->len);
- parser = tvlv_parsers[tvlv_hdr->type][tvlv_hdr->version - 1]; - parser(tvlv_hdr + 1, len); + parser = tvlv_parser_get(tvlv_hdr->type, tvlv_hdr->version); + if (parser) + parser(tvlv_hdr + 1, len);
/* go to the next container */ ptr = (uint8_t *)(tvlv_hdr + 1) + len;