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Diffstat (limited to '')
| -rw-r--r-- | src/resolve/test-resolved-dummy-server.c | 450 |
1 files changed, 450 insertions, 0 deletions
diff --git a/src/resolve/test-resolved-dummy-server.c b/src/resolve/test-resolved-dummy-server.c new file mode 100644 index 0000000..58257d7 --- /dev/null +++ b/src/resolve/test-resolved-dummy-server.c @@ -0,0 +1,450 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include "sd-daemon.h" + +#include "fd-util.h" +#include "iovec-util.h" +#include "log.h" +#include "main-func.h" +#include "resolved-dns-packet.h" +#include "resolved-manager.h" +#include "socket-netlink.h" +#include "socket-util.h" + +/* Taken from resolved-dns-stub.c */ +#define ADVERTISE_DATAGRAM_SIZE_MAX (65536U-14U-20U-8U) + +/* This is more or less verbatim manager_recv() from resolved-manager.c, sans the manager stuff */ +static int server_recv(int fd, DnsPacket **ret) { + _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL; + CMSG_BUFFER_TYPE(CMSG_SPACE(MAXSIZE(struct in_pktinfo, struct in6_pktinfo)) + + CMSG_SPACE(int) /* ttl/hoplimit */ + + EXTRA_CMSG_SPACE /* kernel appears to require extra buffer space */) control; + union sockaddr_union sa; + struct iovec iov; + struct msghdr mh = { + .msg_name = &sa.sa, + .msg_namelen = sizeof(sa), + .msg_iov = &iov, + .msg_iovlen = 1, + .msg_control = &control, + .msg_controllen = sizeof(control), + }; + struct cmsghdr *cmsg; + ssize_t ms, l; + int r; + + assert(fd >= 0); + assert(ret); + + ms = next_datagram_size_fd(fd); + if (ms < 0) + return ms; + + r = dns_packet_new(&p, DNS_PROTOCOL_DNS, ms, DNS_PACKET_SIZE_MAX); + if (r < 0) + return r; + + iov = IOVEC_MAKE(DNS_PACKET_DATA(p), p->allocated); + + l = recvmsg_safe(fd, &mh, 0); + if (ERRNO_IS_NEG_TRANSIENT(l)) + return 0; + if (l <= 0) + return l; + + assert(!(mh.msg_flags & MSG_TRUNC)); + + p->size = (size_t) l; + + p->family = sa.sa.sa_family; + p->ipproto = IPPROTO_UDP; + if (p->family == AF_INET) { + p->sender.in = sa.in.sin_addr; + p->sender_port = be16toh(sa.in.sin_port); + } else if (p->family == AF_INET6) { + p->sender.in6 = sa.in6.sin6_addr; + p->sender_port = be16toh(sa.in6.sin6_port); + p->ifindex = sa.in6.sin6_scope_id; + } else + return -EAFNOSUPPORT; + + p->timestamp = now(CLOCK_BOOTTIME); + + CMSG_FOREACH(cmsg, &mh) { + + if (cmsg->cmsg_level == IPPROTO_IPV6) { + assert(p->family == AF_INET6); + + switch (cmsg->cmsg_type) { + + case IPV6_PKTINFO: { + struct in6_pktinfo *i = CMSG_TYPED_DATA(cmsg, struct in6_pktinfo); + + if (p->ifindex <= 0) + p->ifindex = i->ipi6_ifindex; + + p->destination.in6 = i->ipi6_addr; + break; + } + + case IPV6_HOPLIMIT: + p->ttl = *CMSG_TYPED_DATA(cmsg, int); + break; + + case IPV6_RECVFRAGSIZE: + p->fragsize = *CMSG_TYPED_DATA(cmsg, int); + break; + } + } else if (cmsg->cmsg_level == IPPROTO_IP) { + assert(p->family == AF_INET); + + switch (cmsg->cmsg_type) { + + case IP_PKTINFO: { + struct in_pktinfo *i = CMSG_TYPED_DATA(cmsg, struct in_pktinfo); + + if (p->ifindex <= 0) + p->ifindex = i->ipi_ifindex; + + p->destination.in = i->ipi_addr; + break; + } + + case IP_TTL: + p->ttl = *CMSG_TYPED_DATA(cmsg, int); + break; + + case IP_RECVFRAGSIZE: + p->fragsize = *CMSG_TYPED_DATA(cmsg, int); + break; + } + } + } + + /* The Linux kernel sets the interface index to the loopback + * device if the packet came from the local host since it + * avoids the routing table in such a case. Let's unset the + * interface index in such a case. */ + if (p->ifindex == LOOPBACK_IFINDEX) + p->ifindex = 0; + + log_debug("Received DNS UDP packet of size %zu, ifindex=%i, ttl=%u, fragsize=%zu, sender=%s, destination=%s", + p->size, p->ifindex, p->ttl, p->fragsize, + IN_ADDR_TO_STRING(p->family, &p->sender), + IN_ADDR_TO_STRING(p->family, &p->destination)); + + *ret = TAKE_PTR(p); + return 1; +} + +/* Same as above, see manager_ipv4_send() in resolved-manager.c */ +static int server_ipv4_send( + int fd, + const struct in_addr *destination, + uint16_t port, + const struct in_addr *source, + DnsPacket *packet) { + + union sockaddr_union sa; + struct iovec iov; + struct msghdr mh = { + .msg_iov = &iov, + .msg_iovlen = 1, + .msg_name = &sa.sa, + .msg_namelen = sizeof(sa.in), + }; + + assert(fd >= 0); + assert(destination); + assert(port > 0); + assert(packet); + + iov = IOVEC_MAKE(DNS_PACKET_DATA(packet), packet->size); + + sa = (union sockaddr_union) { + .in.sin_family = AF_INET, + .in.sin_addr = *destination, + .in.sin_port = htobe16(port), + }; + + return sendmsg_loop(fd, &mh, 0); +} + +static int make_reply_packet(DnsPacket *packet, DnsPacket **ret) { + _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL; + int r; + + assert(packet); + assert(ret); + + r = dns_packet_new(&p, DNS_PROTOCOL_DNS, 0, DNS_PACKET_PAYLOAD_SIZE_MAX(packet)); + if (r < 0) + return r; + + r = dns_packet_append_question(p, packet->question); + if (r < 0) + return r; + + DNS_PACKET_HEADER(p)->id = DNS_PACKET_ID(packet); + DNS_PACKET_HEADER(p)->qdcount = htobe16(dns_question_size(packet->question)); + + *ret = TAKE_PTR(p); + return 0; +} + +static int reply_append_edns(DnsPacket *packet, DnsPacket *reply, const char *extra_text, size_t rcode, uint16_t ede_code) { + size_t saved_size; + int r; + + assert(packet); + assert(reply); + + /* Append EDNS0 stuff (inspired by dns_packet_append_opt() from resolved-dns-packet.c). + * + * Relevant headers from RFC 6891: + * + * +------------+--------------+------------------------------+ + * | Field Name | Field Type | Description | + * +------------+--------------+------------------------------+ + * | NAME | domain name | MUST be 0 (root domain) | + * | TYPE | u_int16_t | OPT (41) | + * | CLASS | u_int16_t | requestor's UDP payload size | + * | TTL | u_int32_t | extended RCODE and flags | + * | RDLEN | u_int16_t | length of all RDATA | + * | RDATA | octet stream | {attribute,value} pairs | + * +------------+--------------+------------------------------+ + * + * +0 (MSB) +1 (LSB) + * +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ + * 0: | OPTION-CODE | + * +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ + * 2: | OPTION-LENGTH | + * +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ + * 4: | | + * / OPTION-DATA / + * / / + * +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ + * + * And from RFC 8914: + * + * 1 1 1 1 1 1 + * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 + * +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ + * 0: | OPTION-CODE | + * +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ + * 2: | OPTION-LENGTH | + * +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ + * 4: | INFO-CODE | + * +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ + * 6: / EXTRA-TEXT ... / + * +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ + */ + + saved_size = reply->size; + + /* empty name */ + r = dns_packet_append_uint8(reply, 0, NULL); + if (r < 0) + return r; + + /* type */ + r = dns_packet_append_uint16(reply, DNS_TYPE_OPT, NULL); + if (r < 0) + return r; + + /* class: maximum udp packet that can be received */ + r = dns_packet_append_uint16(reply, ADVERTISE_DATAGRAM_SIZE_MAX, NULL); + if (r < 0) + return r; + + /* extended RCODE and VERSION */ + r = dns_packet_append_uint16(reply, ((uint16_t) rcode & 0x0FF0) << 4, NULL); + if (r < 0) + return r; + + /* flags: DNSSEC OK (DO), see RFC3225 */ + r = dns_packet_append_uint16(reply, 0, NULL); + if (r < 0) + return r; + + /* RDATA */ + + size_t extra_text_len = isempty(extra_text) ? 0 : strlen(extra_text); + /* RDLENGTH (OPTION CODE + OPTION LENGTH + INFO-CODE + EXTRA-TEXT) */ + r = dns_packet_append_uint16(reply, 2 + 2 + 2 + extra_text_len, NULL); + if (r < 0) + return 0; + + /* OPTION-CODE: 15 for EDE */ + r = dns_packet_append_uint16(reply, 15, NULL); + if (r < 0) + return r; + + /* OPTION-LENGTH: INFO-CODE + EXTRA-TEXT */ + r = dns_packet_append_uint16(reply, 2 + extra_text_len, NULL); + if (r < 0) + return r; + + /* INFO-CODE: EDE code */ + r = dns_packet_append_uint16(reply, ede_code, NULL); + if (r < 0) + return r; + + /* EXTRA-TEXT */ + if (extra_text_len > 0) { + /* From RFC 8914: + * EDE text may be null terminated but MUST NOT be assumed to be; the length MUST be derived + * from the OPTION-LENGTH field + * + * Let's exercise our code on the receiving side and not NUL-terminate the EXTRA-TEXT field + */ + r = dns_packet_append_blob(reply, extra_text, extra_text_len, NULL); + if (r < 0) + return r; + } + + DNS_PACKET_HEADER(reply)->arcount = htobe16(DNS_PACKET_ARCOUNT(reply) + 1); + reply->opt_start = saved_size; + reply->opt_size = reply->size - saved_size; + + /* Order: qr, opcode, aa, tc, rd, ra, ad, cd, rcode */ + DNS_PACKET_HEADER(reply)->flags = htobe16(DNS_PACKET_MAKE_FLAGS( + 1, 0, 0, 0, DNS_PACKET_RD(packet), 1, 0, 1, rcode)); + return 0; +} + +static void server_fail(DnsPacket *packet, DnsPacket *reply, int rcode) { + assert(reply); + + /* Order: qr, opcode, aa, tc, rd, ra, ad, cd, rcode */ + DNS_PACKET_HEADER(reply)->flags = htobe16(DNS_PACKET_MAKE_FLAGS( + 1, 0, 0, 0, DNS_PACKET_RD(packet), 1, 0, 1, rcode)); +} + +static int server_handle_edns_bogus_dnssec(DnsPacket *packet, DnsPacket *reply) { + assert(packet); + assert(reply); + + return reply_append_edns(packet, reply, NULL, DNS_RCODE_SERVFAIL, DNS_EDE_RCODE_DNSSEC_BOGUS); +} + +static int server_handle_edns_extra_text(DnsPacket *packet, DnsPacket *reply) { + assert(packet); + assert(reply); + + return reply_append_edns(packet, reply, "Nothing to see here!", DNS_RCODE_SERVFAIL, DNS_EDE_RCODE_CENSORED); +} + +static int server_handle_edns_invalid_code(DnsPacket *packet, DnsPacket *reply, const char *extra_text) { + assert(packet); + assert(reply); + assert_cc(_DNS_EDE_RCODE_MAX_DEFINED < UINT16_MAX); + + return reply_append_edns(packet, reply, extra_text, DNS_RCODE_SERVFAIL, _DNS_EDE_RCODE_MAX_DEFINED + 1); +} + +static int server_handle_edns_code_zero(DnsPacket *packet, DnsPacket *reply) { + assert(packet); + assert(reply); + assert_cc(DNS_EDE_RCODE_OTHER == 0); + + return reply_append_edns(packet, reply, "\xF0\x9F\x90\xB1", DNS_RCODE_SERVFAIL, DNS_EDE_RCODE_OTHER); +} + +static int on_dns_packet(sd_event_source *s, int fd, uint32_t revents, void *userdata) { + _cleanup_(dns_packet_unrefp) DnsPacket *packet = NULL; + _cleanup_(dns_packet_unrefp) DnsPacket *reply = NULL; + const char *name; + int r; + + assert(fd >= 0); + + r = server_recv(fd, &packet); + if (r < 0) { + log_debug_errno(r, "Failed to receive packet, ignoring: %m"); + return 0; + } + + r = dns_packet_validate_query(packet); + if (r < 0) { + log_debug_errno(r, "Invalid DNS UDP packet, ignoring."); + return 0; + } + + r = dns_packet_extract(packet); + if (r < 0) { + log_debug_errno(r, "Failed to extract DNS packet, ignoring: %m"); + return 0; + } + + name = dns_question_first_name(packet->question); + log_info("Processing question for name '%s'", name); + + (void) dns_question_dump(packet->question, stdout); + + r = make_reply_packet(packet, &reply); + if (r < 0) { + log_debug_errno(r, "Failed to make reply packet, ignoring: %m"); + return 0; + } + + if (streq_ptr(name, "edns-bogus-dnssec.forwarded.test")) + r = server_handle_edns_bogus_dnssec(packet, reply); + else if (streq_ptr(name, "edns-extra-text.forwarded.test")) + r = server_handle_edns_extra_text(packet, reply); + else if (streq_ptr(name, "edns-invalid-code.forwarded.test")) + r = server_handle_edns_invalid_code(packet, reply, NULL); + else if (streq_ptr(name, "edns-invalid-code-with-extra-text.forwarded.test")) + r = server_handle_edns_invalid_code(packet, reply, "Hello [#]$%~ World"); + else if (streq_ptr(name, "edns-code-zero.forwarded.test")) + r = server_handle_edns_code_zero(packet, reply); + else + r = log_debug_errno(SYNTHETIC_ERRNO(EFAULT), "Unhandled name '%s', ignoring.", name); + if (r < 0) + server_fail(packet, reply, DNS_RCODE_NXDOMAIN); + + r = server_ipv4_send(fd, &packet->sender.in, packet->sender_port, &packet->destination.in, reply); + if (r < 0) + log_debug_errno(r, "Failed to send reply, ignoring: %m"); + + return 0; +} + +static int run(int argc, char *argv[]) { + _cleanup_(sd_event_unrefp) sd_event *event = NULL; + _cleanup_close_ int fd = -EBADF; + int r; + + log_setup(); + + if (argc != 2) + return log_error_errno(SYNTHETIC_ERRNO(EINVAL), + "This program takes one argument in format ip_address:port"); + + fd = make_socket_fd(LOG_DEBUG, argv[1], SOCK_DGRAM, SOCK_CLOEXEC); + if (fd < 0) + return log_error_errno(fd, "Failed to listen on address '%s': %m", argv[1]); + + r = sd_event_default(&event); + if (r < 0) + return log_error_errno(r, "Failed to allocate event: %m"); + + r = sd_event_add_io(event, NULL, fd, EPOLLIN, on_dns_packet, NULL); + if (r < 0) + return log_error_errno(r, "Failed to add IO event source: %m"); + + r = sd_event_set_signal_exit(event, true); + if (r < 0) + return log_error_errno(r, "Failed to install SIGINT/SIGTERM handlers: %m"); + + (void) sd_notify(/* unset_environment=false */ false, "READY=1"); + + r = sd_event_loop(event); + if (r < 0) + return log_error_errno(r, "Failed to run event loop: %m"); + + return 0; +} + +DEFINE_MAIN_FUNCTION(run); |