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udhcpd: untangle incredibly messy handling of DHCPREQUEST

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Also fixes attacks possible via DHCPDECLINE / DHCPRELEASE

function                                             old     new   delta
udhcpd_main                                         1846    1949    +103
send_renew                                           105     142     +37
send_NAK                                              61       -     -61
send_ACK                                             180       -    -180
------------------------------------------------------------------------------
(add/remove: 0/2 grow/shrink: 2/0 up/down: 140/-241)         Total: -101 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
2010-03-21 06:15:28 +01:00
parent 2e7aa92836
commit c7dc79e71d
9 changed files with 268 additions and 185 deletions
Download Patch File Download Diff File Expand all files Collapse all files

75
networking/udhcp/common.h
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@@ -21,11 +21,17 @@ extern const uint8_t MAC_BCAST_ADDR[6]; /* six all-ones */
/*** packet.h ***/
#define DHCP_OPTIONS_BUFSIZE 308
/* DHCP protocol. See RFC 2131 */
#define DHCP_MAGIC 0x63825363
#define DHCP_OPTIONS_BUFSIZE 308
#define BOOTREQUEST 1
#define BOOTREPLY 2
//TODO: rename ciaddr/yiaddr/chaddr
struct dhcp_packet {
uint8_t op; /* 1 = BOOTREQUEST, 2 = BOOTREPLY */
uint8_t op; /* BOOTREQUEST or BOOTREPLY */
uint8_t htype; /* hardware address type. 1 = 10mb ethernet */
uint8_t hlen; /* hardware address length */
uint8_t hops; /* used by relay agents only */
@@ -61,6 +67,71 @@ struct BUG_bad_sizeof_struct_ip_udp_dhcp_packet {
[(sizeof(struct ip_udp_dhcp_packet) != 576 + CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS) ? -1 : 1];
};
// RFC 2131 Table 5: Fields and options used by DHCP clients
//
// Field DHCPDISCOVER DHCPREQUEST DHCPDECLINE,
// DHCPINFORM DHCPRELEASE
// ----- ------------ ----------- -----------
// 'op' BOOTREQUEST BOOTREQUEST BOOTREQUEST
// 'hops' 0 0 0
// 'xid' selected by client 'xid' from server selected by
// DHCPOFFER message client
// 'secs' 0 or seconds since 0 or seconds since 0
// DHCP process started DHCP process started
// 'flags' Set 'BROADCAST' Set 'BROADCAST' 0
// flag if client flag if client
// requires broadcast requires broadcast
// reply reply
// 'ciaddr' 0 (DHCPDISCOVER) 0 or client's 0 (DHCPDECLINE)
// client's network address client's network
// network address (BOUND/RENEW/REBIND) address
// (DHCPINFORM) (DHCPRELEASE)
// 'yiaddr' 0 0 0
// 'siaddr' 0 0 0
// 'giaddr' 0 0 0
// 'chaddr' client's hardware client's hardware client's hardware
// address address address
// 'sname' options, if options, if (unused)
// indicated in indicated in
// 'sname/file' 'sname/file'
// option; otherwise option; otherwise
// unused unused
// 'file' options, if options, if (unused)
// indicated in indicated in
// 'sname/file' 'sname/file'
// option; otherwise option; otherwise
// unused unused
// 'options' options options (unused)
//
// Option DHCPDISCOVER DHCPREQUEST DHCPDECLINE,
// DHCPINFORM DHCPRELEASE
// ------ ------------ ----------- -----------
// Requested IP address MAY MUST (in MUST
// (DISCOVER) SELECTING or (DHCPDECLINE),
// MUST NOT INIT-REBOOT) MUST NOT
// (INFORM) MUST NOT (in (DHCPRELEASE)
// BOUND or
// RENEWING)
// IP address lease time MAY MAY MUST NOT
// (DISCOVER)
// MUST NOT
// (INFORM)
// Use 'file'/'sname' fields MAY MAY MAY
// Client identifier MAY MAY MAY
// Vendor class identifier MAY MAY MUST NOT
// Server identifier MUST NOT MUST (after MUST
// SELECTING)
// MUST NOT (after
// INIT-REBOOT,
// BOUND, RENEWING
// or REBINDING)
// Parameter request list MAY MAY MUST NOT
// Maximum message size MAY MAY MUST NOT
// Message SHOULD NOT SHOULD NOT SHOULD
// Site-specific MAY MAY MUST NOT
// All others MAY MAY MUST NOT
uint16_t udhcp_checksum(void *addr, int count) FAST_FUNC;
void udhcp_init_header(struct dhcp_packet *packet, char type) FAST_FUNC;