[28450] in Source-Commits
installer commit: Add minimal DNS helper application
daemon@ATHENA.MIT.EDU (Jonathan D Reed)
Mon Sep 29 11:14:19 2014
Date: Mon, 29 Sep 2014 11:14:12 -0400
From: Jonathan D Reed <jdreed@mit.edu>
Message-Id: <201409291514.s8TFECkd010427@drugstore.mit.edu>
To: source-commits@mit.edu
https://github.com/mit-athena/installer/commit/c5ca6365ee0706df339be29c53ef4a633f03c90f
commit c5ca6365ee0706df339be29c53ef4a633f03c90f
Author: Jonathan Reed <jdreed@mit.edu>
Date: Mon Aug 11 14:45:09 2014 -0400
Add minimal DNS helper application
Add a minimal DNS resolver (built for both i386 and amd64) so that we
can stop using the dns-cgi hack. This minimal DNS resolver uses
libares (c-ares). It also capable of returning its output in a format
suitable for passing to a Bourne shell "eval". This utility can also
independently validate the syntax of an IPv4 address or a hostname.
Put the necessary targets in the Makefile to build this.
Declare the "host" target as PHONY, and while we're at it, declare
other .PHONY targets that should have already been there ("clean" and
"install")
Modify host.c to check hostnames with -h
pxe/stage1/Makefile | 18 ++++-
pxe/stage1/host/host.c | 240 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 257 insertions(+), 1 deletions(-)
diff --git a/pxe/stage1/Makefile b/pxe/stage1/Makefile
index f307165..3009347 100644
--- a/pxe/stage1/Makefile
+++ b/pxe/stage1/Makefile
@@ -4,10 +4,26 @@ d=/afs/athena.mit.edu/system/athena10/installer/stage1
default:
: Use "make install" to move this from where the installer will fetch it.
-install: ${d}/debathena.tar.gz
+install: host ${d}/debathena.tar.gz
+
+host: host.amd64 host.i386
+ mkdir -p debathena/lib
+ install -m 755 host.amd64 debathena/lib
+ install -m 755 host.i386 debathena/lib
+
+host.amd64: host/host.c
+ gcc -m64 -static host/host.c -lcares -o $@
+
+host.i386: host/host.c
+ gcc -m32 -static host/host.c -lcares -o $@
${d}/debathena.tar.gz: debathena.preseed debathena-loader.sh debathena
git rev-parse --short HEAD > debathena/version
tar czvf ${d}/debathena.tar.gz --exclude "*~" debathena
cp debathena.preseed debathena-loader.sh ${d}
rm debathena/version
+clean:
+ rm -f host.amd64 host.i386
+ rm -rf debathena/lib
+
+.PHONY: clean install host
diff --git a/pxe/stage1/host/host.c b/pxe/stage1/host/host.c
new file mode 100644
index 0000000..133b666
--- /dev/null
+++ b/pxe/stage1/host/host.c
@@ -0,0 +1,240 @@
+/* A minimal DNS resolver for the stage1 installer, needed to bootstrap
+ * network configuration.
+ *
+ * Loosely based on ahost.c from version 1.1.1 of the ares library.
+ *
+ * Copyright (c) 1987-1998, Massachusetts Institute of Technology.
+ * Copyright (c) 2014, Massachusetts Institute of Technology.
+ *
+ * The majority of this file is licensed under the license commonly
+ * known as "BSD 3-clause". The full contents of the license may be
+ * found at /usr/share/common-licenses/BSD on any Debian-based
+ * distribution or at http://opensource.org/licenses/BSD-3-Clause.
+ *
+ * hostname_check() is copied verbatim from Moira, and licensed as
+ * follows:
+ * Permission to use, copy, modify, and distribute this software and
+ * its documentation for any purpose and without fee is hereby
+ * granted, provided that the above copyright notice appear in all
+ * copies and that both that copyright notice and this permission
+ * notice appear in supporting documentation, and that the name of
+ * M.I.T. not be used in advertising or publicity pertaining to
+ * distribution of the software without specific, written prior
+ * permission. M.I.T. makes no representations about the suitability
+ * of this software for any purpose. It is provided "as is" without
+ * express or implied warranty.
+ *
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <strings.h>
+#include <string.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <netdb.h>
+#include <ares.h>
+#include <ares_dns.h>
+
+#define STATUS_ERROR 64
+#define STATUS_NOT_FOUND 128
+#define STATUS_NOT_IP 1
+#define STATUS_OK 0
+
+extern int optind;
+
+/* default DNS servers to use */
+const char *DEFAULT_NS = "18.70.0.160,18.71.0.151,18.72.0.3";
+const char *DEFAULT_DOMAIN = "mit.edu";
+
+int sh_output = 0;
+
+/* hostname_check()
+ * validate the rfc1035/rfc1123-ness of a hostname
+ */
+
+int hostname_check(char *name)
+{
+ char *p;
+ int count;
+
+ /* Sanity check name: must contain only letters, numerals, and
+ * hyphen, and not start or end with a hyphen. Also make sure no
+ * label (the thing the .s seperate) is longer than 63 characters,
+ * or empty.
+ */
+
+ for (p = name, count = 0; *p; p++)
+ {
+ count++;
+ if ((!isalnum(*p) && *p != '-' && *p != '.') ||
+ (*p == '-' && p[1] == '.'))
+ return 0;
+ if (*p == '.')
+ {
+ if (count == 1)
+ return 0;
+ count = 0;
+ }
+ if (count == 64)
+ return 0;
+ }
+ if (*(p - 1) == '-')
+ return 0;
+ return 1;
+}
+
+static void callback(void *arg, int status, int timeouts, struct hostent *host)
+{
+ char addr_buf[INET_ADDRSTRLEN] = "";
+ char *alias = "";
+ if (status != ARES_SUCCESS) {
+ *(int *)arg = status == ARES_ENOTFOUND ? STATUS_NOT_FOUND : STATUS_ERROR;
+ fprintf(stderr, "%s\n", ares_strerror(status));
+ return;
+ } else {
+ *(int *)arg = STATUS_OK;
+ }
+
+ if (host->h_addr_list[0] != NULL) {
+ ares_inet_ntop(host->h_addrtype, host->h_addr_list[0],
+ addr_buf, sizeof(addr_buf));
+ }
+ if (host->h_aliases[0] != NULL &&
+ (strcasecmp(host->h_aliases[0],
+ host->h_name) != 0)) {
+ alias = host->h_aliases[0];
+ }
+ if (sh_output) {
+ if ((strchr(host->h_name, '\'') != NULL) ||
+ (strchr(addr_buf, '\'') != NULL)) {
+ fprintf(stderr, "Unable to escape values!\n");
+ *(int *)arg = STATUS_ERROR;
+ } else {
+ printf("DAIPADDR='%s'; DAHOSTNAME='%s'\n", addr_buf, host->h_name);
+ }
+ } else {
+ printf("%s\t%s\t%s\n", addr_buf, host->h_name, alias);
+ }
+}
+
+void process_queries(ares_channel channel) {
+ int nfds;
+ fd_set read_fds, write_fds;
+ struct timeval *tvp, tv;
+ /* Wait for all queries to complete. */
+ while (1) {
+ FD_ZERO(&read_fds);
+ FD_ZERO(&write_fds);
+ nfds = ares_fds(channel, &read_fds, &write_fds);
+ if (nfds == 0)
+ break;
+ tvp = ares_timeout(channel, NULL, &tv);
+ select(nfds, &read_fds, &write_fds, NULL, tvp);
+ ares_process(channel, &read_fds, &write_fds);
+ }
+}
+
+
+int lookup_host_or_ip(char *host_or_ip, int ip_only) {
+ int is_ip;
+ int addr_family = AF_INET;
+ struct in_addr ipv4_addr;
+ int status;
+ ares_channel channel;
+ struct ares_options options;
+ char *domain;
+ char *nameservers_csv;
+
+ /* Be paranoid and initialize to zero. (Hi Ben!) */
+ memset(&options, 0, sizeof(options));
+ is_ip = inet_pton(addr_family, host_or_ip, &ipv4_addr);
+ if (is_ip < 0) {
+ perror("inet_pton");
+ return STATUS_ERROR;
+ }
+ if (ip_only) {
+ return is_ip ? STATUS_OK : STATUS_NOT_IP;
+ }
+ /* Initialize library */
+ status = ares_library_init(ARES_LIB_INIT_ALL);
+ if (status != ARES_SUCCESS) {
+ fprintf(stderr, "ares_library_init: %s\n", ares_strerror(status));
+ return 1;
+ }
+ /* Set the search domain */
+ options.ndomains = 1;
+ domain = getenv("DEBATHENA_DOMAIN");
+ if (domain == NULL) {
+ domain = (char *) DEFAULT_DOMAIN;
+ }
+ options.domains = &domain;
+ status = ares_init_options(&channel, &options, ARES_OPT_DOMAINS);
+ if (status != ARES_SUCCESS) {
+ fprintf(stderr, "ares_init_options: %s\n", ares_strerror(status));
+ return 1;
+ }
+ nameservers_csv = getenv("DEBATHENA_NAMESERVERS");
+ if (nameservers_csv == NULL) {
+ nameservers_csv = (char *) DEFAULT_NS;
+ }
+ status = ares_set_servers_csv(channel, nameservers_csv);
+ if (status != ARES_SUCCESS) {
+ fprintf(stderr, "ares_set_servers_csv: %s\n", ares_strerror(status));
+ return 1;
+ }
+
+ status = STATUS_ERROR; /* The callback must set this to something else. */
+ if (is_ip) {
+ ares_gethostbyaddr(channel, &ipv4_addr, sizeof(ipv4_addr),
+ addr_family, callback, &status);
+ } else {
+ ares_gethostbyname(channel, host_or_ip, addr_family, callback,
+ &status);
+ }
+ process_queries(channel);
+ ares_destroy(channel);
+ ares_library_cleanup();
+ return status;
+}
+
+int main(int argc, char *argv[])
+{
+ int ip_only = 0;
+ int usage = 0;
+ int check_hostname = 0;
+ int opt;
+
+ while ((opt = getopt(argc, argv, "ish")) != -1) {
+ switch (opt) {
+ case 'i':
+ ip_only = 1;
+ break;
+ case 's':
+ sh_output = 1;
+ break;
+ case 'h':
+ check_hostname = 1;
+ break;
+ default:
+ usage = 1;
+ break;
+ }
+ }
+
+ if ((ip_only + check_hostname + sh_output) > 1) {
+ usage = 1;
+ }
+
+ if ((argc - optind != 1) || usage) {
+ fprintf(stderr, "Usage: %s [-i|-s|-h] host-or-ip\n", argv[0]);
+ return STATUS_ERROR;
+ }
+
+ if (check_hostname) {
+ return !hostname_check(argv[optind]);
+ }
+
+ return lookup_host_or_ip(argv[optind], ip_only);
+}
