diff options
Diffstat (limited to 'proto/babel/packets.c')
-rw-r--r-- | proto/babel/packets.c | 496 |
1 files changed, 490 insertions, 6 deletions
diff --git a/proto/babel/packets.c b/proto/babel/packets.c index 1d2f5f5b..703d4026 100644 --- a/proto/babel/packets.c +++ b/proto/babel/packets.c @@ -11,7 +11,7 @@ */ #include "babel.h" - +#include "lib/mac.h" struct babel_pkt_header { u8 magic; @@ -112,6 +112,31 @@ struct babel_subtlv_source_prefix { u8 addr[0]; } PACKED; +struct babel_tlv_pc { + u8 type; + u8 length; + u32 pc; + u8 index[0]; +} PACKED; + +struct babel_tlv_mac { + u8 type; + u8 length; + u8 mac[0]; +} PACKED; + +struct babel_tlv_challenge { + u8 type; + u8 length; + u8 nonce[0]; +} PACKED; + +struct babel_mac_pseudohdr { + u8 src_addr[16]; + u16 src_port; + u8 dst_addr[16]; + u16 dst_port; +} PACKED; /* Hello flags */ #define BABEL_HF_UNICAST 0x8000 @@ -146,6 +171,9 @@ struct babel_parse_state { u8 def_ip4_prefix_seen; /* def_ip4_prefix is valid */ u8 current_tlv_endpos; /* End of self-terminating TLVs (offset from start) */ u8 sadr_enabled; + u8 is_unicast; + + struct babel_msg_auth auth; }; enum parse_result { @@ -168,6 +196,10 @@ struct babel_write_state { #define DROP1(DSC) do { err_dsc = DSC; goto drop; } while(0) #define LOG_PKT(msg, args...) \ log_rl(&p->log_pkt_tbf, L_REMOTE "%s: " msg, p->p.name, args) +#define LOG_WARN(msg, args...) \ + log_rl(&p->log_pkt_tbf, L_WARN "%s: " msg, p->p.name, args) +#define LOG_PKT_AUTH(msg, args...) \ + log_rl(&p->log_pkt_tbf, L_AUTH "%s: " msg, p->p.name, args) #define FIRST_TLV(p) ((struct babel_tlv *) (((struct babel_pkt_header *) p) + 1)) #define NEXT_TLV(t) ((struct babel_tlv *) (((byte *) t) + TLV_LENGTH(t))) @@ -274,6 +306,17 @@ put_ip6_ll(void *p, ip6_addr addr) put_u32(p+4, _I3(addr)); } +/* + * Authentication-related functions + */ +uint babel_auth_write_challenge(struct babel_tlv *hdr, union babel_msg *msg, struct babel_write_state *state, uint max_len); +int babel_auth_add_tlvs(struct babel_iface *ifa, struct babel_tlv *tlv, int max_len); +int babel_auth_sign(struct babel_iface *ifa, ip_addr dest); +int babel_auth_check(struct babel_iface *ifa, + ip_addr saddr, u16 sport, + ip_addr daddr, u16 dport, + struct babel_pkt_header *pkt, + byte *start, uint len); /* * TLV read/write functions @@ -352,6 +395,16 @@ static const struct babel_tlv_data tlv_data[BABEL_TLV_MAX] = { babel_write_seqno_request, babel_handle_seqno_request }, + [BABEL_TLV_CHALLENGE_REQ] = { + sizeof(struct babel_tlv), + NULL, + babel_auth_write_challenge, + }, + [BABEL_TLV_CHALLENGE_REPLY] = { + sizeof(struct babel_tlv), + NULL, + babel_auth_write_challenge, + }, }; static const struct babel_tlv_data *get_packet_tlv_data(u8 type) @@ -1225,7 +1278,6 @@ babel_write_tlv(struct babel_tlv *hdr, return tlv_data[msg->type].write_tlv(hdr, msg, state, max_len); } - /* * Packet RX/TX functions */ @@ -1237,6 +1289,8 @@ babel_send_to(struct babel_iface *ifa, ip_addr dest) struct babel_pkt_header *hdr = (void *) sk->tbuf; int len = get_u16(&hdr->length) + sizeof(struct babel_pkt_header); + len += babel_auth_sign(ifa, dest); + DBG("Babel: Sending %d bytes to %I\n", len, dest); return sk_send_to(sk, len, dest, 0); } @@ -1289,6 +1343,8 @@ babel_write_queue(struct babel_iface *ifa, list *queue) sl_free(p->msg_slab, msg); } + pos += babel_auth_add_tlvs(ifa, (struct babel_tlv *) pos, end-pos); + uint plen = pos - (byte *) pkt; put_u16(&pkt->length, plen - sizeof(struct babel_pkt_header)); @@ -1367,10 +1423,13 @@ babel_enqueue(union babel_msg *msg, struct babel_iface *ifa) /** * babel_process_packet - process incoming data packet + * @ifa: Interface packet was received on. * @pkt: Pointer to the packet data * @len: Length of received packet * @saddr: Address of packet sender - * @ifa: Interface packet was received on. + * @sport: Packet source port + * @daddr: Destination address of packet + * @dport: Packet destination port * * This function is the main processing hook of incoming Babel packets. It * checks that the packet header is well-formed, then processes the TLVs @@ -1382,8 +1441,10 @@ babel_enqueue(union babel_msg *msg, struct babel_iface *ifa) * order. */ static void -babel_process_packet(struct babel_pkt_header *pkt, int len, - ip_addr saddr, struct babel_iface *ifa) +babel_process_packet(struct babel_iface *ifa, + struct babel_pkt_header *pkt, int len, + ip_addr saddr, u16 sport, + ip_addr daddr, u16 dport) { u8 frame_err UNUSED = 0; struct babel_proto *p = ifa->proto; @@ -1422,6 +1483,9 @@ babel_process_packet(struct babel_pkt_header *pkt, int len, TRACE(D_PACKETS, "Packet received from %I via %s", saddr, ifa->iface->name); + if (babel_auth_check(ifa, saddr, sport, daddr, dport, pkt, end, len-plen)) + return; + init_list(&msgs); /* First pass through the packet TLV by TLV, parsing each into internal data @@ -1512,7 +1576,10 @@ babel_rx_hook(sock *sk, uint len) if (sk->flags & SKF_TRUNCATED) DROP("truncated", len); - babel_process_packet((struct babel_pkt_header *) sk->rbuf, len, sk->faddr, ifa); + babel_process_packet(ifa, + (struct babel_pkt_header *) sk->rbuf, len, + sk->faddr, sk->fport, + sk->laddr, sk->dport); return 1; drop: @@ -1562,3 +1629,420 @@ err: rfree(sk); return 0; } + + +/* Authentication checks */ +static int +babel_read_pc(struct babel_tlv *hdr, union babel_msg *m UNUSED, + struct babel_parse_state *state) +{ + struct babel_tlv_pc *tlv = (void *) hdr; + + if (!state->auth.pc_seen) + { + state->auth.pc_seen = 1; + state->auth.pc = get_u32(&tlv->pc); + state->auth.index_len = TLV_OPT_LENGTH(tlv); + state->auth.index = tlv->index; + } + + return PARSE_IGNORE; +} + +static const struct babel_tlv_data pc_tlv_data = { + .min_length = sizeof(struct babel_tlv_pc), + .read_tlv = &babel_read_pc +}; + +static int +babel_read_challenge_req(struct babel_tlv *hdr, union babel_msg *m UNUSED, + struct babel_parse_state *state) +{ + struct babel_tlv_challenge *tlv = (void *) hdr; + + if (!state->is_unicast) + { + DBG("Ignoring non-unicast challenge request from %I\n", state->saddr); + return PARSE_IGNORE; + } + + if (tlv->length > BABEL_AUTH_MAX_NONCE_LEN) + return PARSE_IGNORE; + + state->auth.challenge_len = tlv->length; + if (state->auth.challenge_len) + memcpy(state->auth.challenge, tlv->nonce, state->auth.challenge_len); + state->auth.challenge_seen = 1; + + return PARSE_IGNORE; +} + +static const struct babel_tlv_data challenge_req_tlv_data = { + .min_length = sizeof(struct babel_tlv_challenge), + .read_tlv = &babel_read_challenge_req, +}; + +static int +babel_read_challenge_reply(struct babel_tlv *hdr, union babel_msg *m UNUSED, + struct babel_parse_state *state) +{ + struct babel_tlv_challenge *tlv = (void *) hdr; + + if (tlv->length != BABEL_AUTH_NONCE_LEN || state->auth.challenge_reply_seen) + return PARSE_IGNORE; + + state->auth.challenge_reply_seen = 1; + memcpy(state->auth.challenge_reply, tlv->nonce, BABEL_AUTH_NONCE_LEN); + + return PARSE_IGNORE; +} + +static const struct babel_tlv_data challenge_reply_tlv_data = { + .min_length = sizeof(struct babel_tlv_challenge), + .read_tlv = &babel_read_challenge_reply, +}; + +static const struct babel_tlv_data * +get_auth_tlv_data(u8 type) +{ + switch(type) + { + case BABEL_TLV_PC: + return &pc_tlv_data; + case BABEL_TLV_CHALLENGE_REQ: + return &challenge_req_tlv_data; + case BABEL_TLV_CHALLENGE_REPLY: + return &challenge_reply_tlv_data; + default: + return NULL; + } +} + +uint +babel_auth_write_challenge(struct babel_tlv *hdr, union babel_msg *m, + struct babel_write_state *state UNUSED,uint max_len) +{ + struct babel_tlv_challenge *tlv = (void *) hdr; + struct babel_msg_challenge *msg = &m->challenge; + + uint len = sizeof(struct babel_tlv_challenge) + msg->nonce_len; + + if (len > max_len) + return 0; + + TLV_HDR(tlv, msg->type, len); + memcpy(tlv->nonce, msg->nonce, msg->nonce_len); + + return len; +} + +static int +babel_mac_hash(struct password_item *pass, + struct babel_mac_pseudohdr *phdr, + byte *pkt, uint pkt_len, + byte *buf, uint *buf_len) +{ + struct mac_context ctx; + + if (mac_type_length(pass->alg) > *buf_len) + return 1; + + mac_init(&ctx, pass->alg, pass->password, pass->length); + mac_update(&ctx, (byte *)phdr, sizeof(*phdr)); + mac_update(&ctx, (byte *)pkt, pkt_len); + + *buf_len = mac_get_length(&ctx); + memcpy(buf, mac_final(&ctx), *buf_len); + + mac_cleanup(&ctx); + + return 0; +} + +static void +babel_mac_build_phdr(struct babel_mac_pseudohdr *phdr, + ip_addr saddr, u16 sport, + ip_addr daddr, u16 dport) +{ + memset(phdr, 0, sizeof(*phdr)); + put_ip6(phdr->src_addr, saddr); + put_u16(&phdr->src_port, sport); + put_ip6(phdr->dst_addr, daddr); + put_u16(&phdr->dst_port, dport); + DBG("MAC pseudo-header: %I %d %I %d\n", saddr, sport, daddr, dport); +} + +static int +babel_auth_check_mac(struct babel_iface *ifa, byte *pkt, + byte *trailer, uint trailer_len, + ip_addr saddr, u16 sport, + ip_addr daddr, u16 dport) +{ + uint hash_len = (uint)(trailer - pkt); + struct babel_proto *p = ifa->proto; + byte *end = trailer + trailer_len; + btime now_ = current_real_time(); + struct babel_mac_pseudohdr phdr; + struct password_item *pass; + struct babel_tlv *tlv; + + if (trailer_len < sizeof(*tlv)) + { + LOG_PKT_AUTH("No MAC signature on packet from %I on %s", + saddr, ifa->ifname); + return 1; + } + + babel_mac_build_phdr(&phdr, saddr, sport, daddr, dport); + + WALK_LIST(pass, *ifa->cf->passwords) + { + byte mac_res[MAX_HASH_SIZE]; + uint mac_len = MAX_HASH_SIZE; + u8 frame_err = 0; + + if (pass->accfrom > now_ || pass->accto < now_) + continue; + + if (babel_mac_hash(pass, &phdr, + pkt, hash_len, + mac_res, &mac_len)) + continue; + + WALK_TLVS((void *)trailer, end, tlv, frame_err, saddr, ifa->ifname) + { + struct babel_tlv_mac *mac = (void *)tlv; + + if (tlv->type != BABEL_TLV_MAC) + continue; + + if (tlv->length == mac_len && !memcmp(mac->mac, mac_res, mac_len)) + return 0; + + DBG("MAC mismatch key id %d pos %d len %d/%d\n", + pass->id, (byte *)tlv - (byte *)pkt, mac_len, tlv->length); + } + WALK_TLVS_END; + + if (frame_err) { + DBG("MAC trailer TLV framing error\n"); + return 1; + } + } + + LOG_PKT_AUTH("No MAC key matching packet from %I found on %s", + saddr, ifa->ifname); + return 1; +} + +/** + * babel_auth_check - Check authentication for a packet + * @ifa: Interface holding the transmission buffer + * @saddr: Source address the packet was received from + * @sport: Source port the packet was received from + * @daddr: Destination address the packet was sent to + * @dport: Destination port the packet was sent to + * @pkt: Pointer to start of the packet data + * @trailer: Pointer to the packet trailer + * @trailer_len: Length of the packet trailer + * + * This function performs any necessary authentication checks on a packet and + * returns 0 if the packet should be accepted (either because it has been + * successfully authenticated or because authentication is disabled or + * configured in permissive mode), or 1 if the packet should be dropped without + * further processing. + */ +int +babel_auth_check(struct babel_iface *ifa, + ip_addr saddr, u16 sport, + ip_addr daddr, u16 dport, + struct babel_pkt_header *pkt, + byte *trailer, uint trailer_len) +{ + u8 frame_err UNUSED = 0; + struct babel_proto *p = ifa->proto; + struct babel_tlv *tlv; + + struct babel_parse_state state = { + .get_tlv_data = &get_auth_tlv_data, + .proto = p, + .ifa = ifa, + .saddr = saddr, + .is_unicast = !(ipa_classify(daddr) & IADDR_MULTICAST), + .auth = { + .sender = saddr, + }, + }; + + if (ifa->cf->auth_type == BABEL_AUTH_NONE) + return 0; + + TRACE(D_PACKETS, "Checking packet authentication signature"); + + if (babel_auth_check_mac(ifa, (byte *)pkt, + trailer, trailer_len, + saddr, sport, + daddr, dport)) + goto fail; + + /* MAC verified; parse packet to check packet counter and challenge */ + WALK_TLVS(FIRST_TLV(pkt), trailer, tlv, frame_err, saddr, ifa->iface->name) + { + union babel_msg msg; + enum parse_result res; + + res = babel_read_tlv(tlv, &msg, &state); + if (res == PARSE_ERROR) + { + LOG_PKT_AUTH("Bad TLV from %I via %s type %d pos %d - parse error", + saddr, ifa->iface->name, tlv->type, (byte *)tlv - (byte *)pkt); + goto fail; + } + } + WALK_TLVS_END; + + if (babel_auth_check_pc(ifa, &state.auth)) + goto fail; + + TRACE(D_PACKETS, "Packet from %I via %s authenticated successfully", + saddr, ifa->ifname); + return 0; + +fail: + LOG_PKT_AUTH("Packet from %I via %s failed authentication%s", + saddr, ifa->ifname, + ifa->cf->auth_permissive ? " but accepted in permissive mode" : ""); + + return !ifa->cf->auth_permissive; +} + +/** + * babel_auth_add_tlvs - Add authentication-related TLVs to a packet + * @ifa: Interface holding the transmission buffer + * @tlv: Pointer to the place where any new TLVs should be added + * @max_len: Maximum length available for adding new TLVs + * + * This function adds any new TLVs required by the authentication mode to a + * packet before it is shipped out. For MAC authentication, this is the packet + * counter TLV that must be included in every packet. + */ +int +babel_auth_add_tlvs(struct babel_iface *ifa, struct babel_tlv *tlv, int max_len) +{ + struct babel_proto *p = ifa->proto; + struct babel_tlv_pc *msg; + int len; + + if (ifa->cf->auth_type == BABEL_AUTH_NONE) + return 0; + + msg = (void *)tlv; + len = sizeof(*msg) + BABEL_AUTH_INDEX_LEN; + max_len += ifa->auth_tx_overhead; + + if (len > max_len) + { + LOG_WARN("Insufficient space to add MAC seqno TLV on iface %s: %d < %d", + ifa->ifname, max_len, len); + return 0; + } + + msg->type = BABEL_TLV_PC; + msg->length = len - sizeof(struct babel_tlv); + put_u32(&msg->pc, ifa->auth_pc++); + memcpy(msg->index, ifa->auth_index, BABEL_AUTH_INDEX_LEN); + + /* Reset index on overflow to 0 */ + if (!ifa->auth_pc) + babel_auth_reset_index(ifa); + + return len; +} + +/** + * babel_auth_sign - Sign an outgoing packet before transmission + * @ifa: Interface holding the transmission buffer + * @dest: Destination address of the packet + * + * This function adds authentication signature(s) to the packet trailer for each + * of the configured authentication keys on the interface. + */ +int +babel_auth_sign(struct babel_iface *ifa, ip_addr dest) +{ + struct babel_proto *p = ifa->proto; + struct babel_mac_pseudohdr phdr; + struct babel_pkt_header *hdr; + struct password_item *pass; + int tot_len = 0, i = 0; + struct babel_tlv *tlv; + sock *sk = ifa->sk; + byte *pos, *end; + btime now_; + int len; + + if (ifa->cf->auth_type == BABEL_AUTH_NONE) + return 0; + + hdr = (void *) sk->tbuf; + len = get_u16(&hdr->length) + sizeof(struct babel_pkt_header); + + pos = (byte *)hdr + len; + end = (byte *)hdr + ifa->tx_length + ifa->auth_tx_overhead; + tlv = (void *)pos; + now_ = current_real_time(); + + babel_mac_build_phdr(&phdr, sk->saddr, sk->fport, dest, sk->dport); + + WALK_LIST(pass, *ifa->cf->passwords) + { + struct babel_tlv_mac *msg = (void *)tlv; + uint buf_len = (uint) (end - (byte *)msg - sizeof(*msg)); + + if (pass->genfrom > now_ || pass->gento < now_) + continue; + + if (babel_mac_hash(pass, &phdr, + (byte *)hdr, len, + msg->mac, &buf_len)) + { + LOG_WARN("Insufficient space for MAC signatures on iface %s dest %I", + ifa->ifname, dest); + break; + } + + msg->type = BABEL_TLV_MAC; + msg->length = buf_len; + + tlv = NEXT_TLV(tlv); + tot_len += buf_len + sizeof(*msg); + i++; + } + + DBG("Added %d MAC signatures (%d bytes) on ifa %s for dest %I\n", + i, tot_len, ifa->ifname, dest); + + return tot_len; +} + +/** + * babel_auth_set_tx_overhead - Set interface TX overhead for authentication + * @ifa: Interface to configure + * + * This function sets the TX overhead for an interface based on its + * authentication configuration. + */ +void +babel_auth_set_tx_overhead(struct babel_iface *ifa) +{ + if (ifa->cf->auth_type == BABEL_AUTH_NONE) + { + ifa->auth_tx_overhead = 0; + return; + } + + ifa->auth_tx_overhead = (sizeof(struct babel_tlv_pc) + + sizeof(struct babel_tlv_mac) * ifa->cf->mac_num_keys + + ifa->cf->mac_total_len); + ifa->tx_length -= ifa->auth_tx_overhead; +} |