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-rw-r--r--programs/pluto/adns.c615
1 files changed, 615 insertions, 0 deletions
diff --git a/programs/pluto/adns.c b/programs/pluto/adns.c
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+/* Pluto Asynchronous DNS Helper Program -- for internal use only!
+ * Copyright (C) 2002 D. Hugh Redelmeier.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * for more details.
+ *
+ * RCSID $Id: adns.c,v 1.1 2004/03/15 20:35:28 as Exp $
+ */
+
+#ifndef USE_LWRES /* whole file! */
+
+/* This program executes as multiple processes. The Master process
+ * receives queries (struct adns_query messages) from Pluto and distributes
+ * them amongst Worker processes. These Worker processes are created
+ * by the Master whenever a query arrives and no existing Worker is free.
+ * At most MAX_WORKERS will be created; after that, the Master will queue
+ * queries until a Worker becomes free. When a Worker has an answer from
+ * the resolver, it sends the answer as a struct adns_answer message to the
+ * Master. The Master then forwards the answer to Pluto, noting that
+ * the Worker is free to accept another query.
+ *
+ * The protocol is simple: Pluto sends a sequence of queries and receives
+ * a sequence of answers. select(2) is used by Pluto and by the Master
+ * process to decide when to read, but writes are done without checking
+ * for readiness. Communications is via pipes. Since only one process
+ * can write to each pipe, messages will not be interleaved. Fixed length
+ * records are used for simplicity.
+ *
+ * Pluto needs a way to indicate to the Master when to shut down
+ * and the Master needs to indicate this to each worker. EOF on the pipe
+ * signifies this.
+ *
+ * The interfaces between these components are considered private to
+ * Pluto. This allows us to get away with less checking. This is a
+ * reason to use pipes instead of TCP/IP.
+ *
+ * Although the code uses plain old UNIX processes, it could be modified
+ * to use threads. That might reduce resource requirements. It would
+ * preclude running on systems without thread-safe resolvers.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <syslog.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <netinet/in.h>
+#include <arpa/nameser.h>
+#include <resolv.h>
+#include <netdb.h> /* ??? for h_errno */
+
+#include <freeswan.h>
+
+/* GCC magic! */
+#ifdef GCC_LINT
+# define UNUSED __attribute__ ((unused))
+#else
+# define UNUSED /* ignore */
+#endif
+
+#include "constants.h"
+#include "adns.h" /* needs <resolv.h> */
+
+/* shared by all processes */
+
+static const char *name; /* program name, for messages */
+
+static bool debug = FALSE;
+
+/* Read a variable-length record from a pipe (and no more!).
+ * First bytes must be a size_t containing the length.
+ * HES_CONTINUE if record read
+ * HES_OK if EOF
+ * HES_IO_ERROR_IN if errno tells the tale.
+ * Others are errors.
+ */
+static enum helper_exit_status
+read_pipe(int fd, unsigned char *stuff, size_t minlen, size_t maxlen)
+{
+ size_t n = 0;
+ size_t goal = minlen;
+
+ do {
+ ssize_t m = read(fd, stuff + n, goal - n);
+
+ if (m == -1)
+ {
+ if (errno != EINTR)
+ {
+ syslog(LOG_ERR, "Input error on pipe: %s", strerror(errno));
+ return HES_IO_ERROR_IN;
+ }
+ }
+ else if (m == 0)
+ {
+ return HES_OK; /* treat empty message as EOF */
+ }
+ else
+ {
+ n += m;
+ if (n >= sizeof(size_t))
+ {
+ goal = *(size_t *)(void *)stuff;
+ if (goal < minlen || maxlen < goal)
+ {
+ if (debug)
+ fprintf(stderr, "%lu : [%lu, %lu]\n"
+ , (unsigned long)goal
+ , (unsigned long)minlen, (unsigned long)maxlen);
+ return HES_BAD_LEN;
+ }
+ }
+ }
+ } while (n < goal);
+
+ return HES_CONTINUE;
+}
+
+/* Write a variable-length record to a pipe.
+ * First bytes must be a size_t containing the length.
+ * HES_CONTINUE if record written
+ * Others are errors.
+ */
+static enum helper_exit_status
+write_pipe(int fd, const unsigned char *stuff)
+{
+ size_t len = *(const size_t *)(const void *)stuff;
+ size_t n = 0;
+
+ do {
+ ssize_t m = write(fd, stuff + n, len - n);
+
+ if (m == -1)
+ {
+ /* error, but ignore and retry if EINTR */
+ if (errno != EINTR)
+ {
+ syslog(LOG_ERR, "Output error from master: %s", strerror(errno));
+ return HES_IO_ERROR_OUT;
+ }
+ }
+ else
+ {
+ n += m;
+ }
+ } while (n != len);
+ return HES_CONTINUE;
+}
+
+/**************** worker process ****************/
+
+/* The interface in RHL6.x and BIND distribution 8.2.2 are different,
+ * so we build some of our own :-(
+ */
+
+/* Support deprecated interface to allow for older releases of the resolver.
+ * Fake new interface!
+ * See resolver(3) bind distribution (should be in RHL6.1, but isn't).
+ * __RES was 19960801 in RHL6.2, an old resolver.
+ */
+
+#if (__RES) <= 19960801
+# define OLD_RESOLVER 1
+#endif
+
+#ifdef OLD_RESOLVER
+
+# define res_ninit(statp) res_init()
+# define res_nquery(statp, dname, class, type, answer, anslen) \
+ res_query(dname, class, type, answer, anslen)
+# define res_nclose(statp) res_close()
+
+static struct __res_state *statp = &_res;
+
+#else /* !OLD_RESOLVER */
+
+static struct __res_state my_res_state /* = { 0 } */;
+static res_state statp = &my_res_state;
+
+#endif /* !OLD_RESOLVER */
+
+static int
+worker(int qfd, int afd)
+{
+ {
+ int r = res_ninit(statp);
+
+ if (r != 0)
+ {
+ syslog(LOG_ERR, "cannot initialize resolver");
+ return HES_RES_INIT;
+ }
+#ifndef OLD_RESOLVER
+ statp->options |= RES_ROTATE;
+#endif
+ statp->options |= RES_DEBUG;
+ }
+
+ for (;;)
+ {
+ struct adns_query q;
+ struct adns_answer a;
+
+ enum helper_exit_status r = read_pipe(qfd, (unsigned char *)&q
+ , sizeof(q), sizeof(q));
+
+ if (r != HES_CONTINUE)
+ return r; /* some kind of exit */
+
+ if (q.qmagic != ADNS_Q_MAGIC)
+ {
+ syslog(LOG_ERR, "error in input from master: bad magic");
+ return HES_BAD_MAGIC;
+ }
+
+ a.amagic = ADNS_A_MAGIC;
+ a.serial = q.serial;
+
+ a.result = res_nquery(statp, q.name_buf, C_IN, q.type, a.ans, sizeof(a.ans));
+ a.h_errno_val = h_errno;
+
+ a.len = offsetof(struct adns_answer, ans) + (a.result < 0? 0 : a.result);
+
+#ifdef DEBUG
+ if (((q.debugging & IMPAIR_DELAY_ADNS_KEY_ANSWER) && q.type == T_KEY)
+ || ((q.debugging & IMPAIR_DELAY_ADNS_TXT_ANSWER) && q.type == T_TXT))
+ sleep(30); /* delay the answer */
+#endif
+
+ /* write answer, possibly a bit at a time */
+ r = write_pipe(afd, (const unsigned char *)&a);
+
+ if (r != HES_CONTINUE)
+ return r; /* some kind of exit */
+ }
+}
+
+/**************** master process ****************/
+
+bool eof_from_pluto = FALSE;
+#define PLUTO_QFD 0 /* queries come on stdin */
+#define PLUTO_AFD 1 /* answers go out on stdout */
+
+#ifndef MAX_WORKERS
+# define MAX_WORKERS 10 /* number of in-flight queries */
+#endif
+
+struct worker_info {
+ int qfd; /* query pipe's file descriptor */
+ int afd; /* answer pipe's file descriptor */
+ pid_t pid;
+ bool busy;
+ void *continuation; /* of outstanding request */
+};
+
+static struct worker_info wi[MAX_WORKERS];
+static struct worker_info *wi_roof = wi;
+
+/* request FIFO */
+
+struct query_list {
+ struct query_list *next;
+ struct adns_query aq;
+};
+
+static struct query_list *oldest_query = NULL;
+static struct query_list *newest_query; /* undefined when oldest == NULL */
+static struct query_list *free_queries = NULL;
+
+static bool
+spawn_worker(void)
+{
+ int qfds[2];
+ int afds[2];
+ pid_t p;
+
+ if (pipe(qfds) != 0 || pipe(afds) != 0)
+ {
+ syslog(LOG_ERR, "pipe(2) failed: %s", strerror(errno));
+ exit(HES_PIPE);
+ }
+
+ wi_roof->qfd = qfds[1]; /* write end of query pipe */
+ wi_roof->afd = afds[0]; /* read end of answer pipe */
+
+ p = fork();
+ if (p == -1)
+ {
+ /* fork failed: ignore if at least one worker exists */
+ if (wi_roof == wi)
+ {
+ syslog(LOG_ERR, "fork(2) error creating first worker: %s", strerror(errno));
+ exit(HES_FORK);
+ }
+ close(qfds[0]);
+ close(qfds[1]);
+ close(afds[0]);
+ close(afds[1]);
+ return FALSE;
+ }
+ else if (p == 0)
+ {
+ /* child */
+ struct worker_info *w;
+
+ close(PLUTO_QFD);
+ close(PLUTO_AFD);
+ /* close all master pipes, including ours */
+ for (w = wi; w <= wi_roof; w++)
+ {
+ close(w->qfd);
+ close(w->afd);
+ }
+ exit(worker(qfds[0], afds[1]));
+ }
+ else
+ {
+ /* parent */
+ struct worker_info *w = wi_roof++;
+
+ w->pid = p;
+ w->busy = FALSE;
+ close(qfds[0]);
+ close(afds[1]);
+ return TRUE;
+ }
+}
+
+static void
+send_eof(struct worker_info *w)
+{
+ pid_t p;
+ int status;
+
+ close(w->qfd);
+ w->qfd = NULL_FD;
+
+ close(w->afd);
+ w->afd = NULL_FD;
+
+ /* reap child */
+ p = waitpid(w->pid, &status, 0);
+ /* ignore result -- what could we do with it? */
+}
+
+static void
+forward_query(struct worker_info *w)
+{
+ struct query_list *q = oldest_query;
+
+ if (q == NULL)
+ {
+ if (eof_from_pluto)
+ send_eof(w);
+ }
+ else
+ {
+ enum helper_exit_status r
+ = write_pipe(w->qfd, (const unsigned char *) &q->aq);
+
+ if (r != HES_CONTINUE)
+ exit(r);
+
+ w->busy = TRUE;
+
+ oldest_query = q->next;
+ q->next = free_queries;
+ free_queries = q;
+ }
+}
+
+static void
+query(void)
+{
+ struct query_list *q = free_queries;
+ enum helper_exit_status r;
+
+ /* find an unused queue entry */
+ if (q == NULL)
+ {
+ q = malloc(sizeof(*q));
+ if (q == NULL)
+ {
+ syslog(LOG_ERR, "malloc(3) failed");
+ exit(HES_MALLOC);
+ }
+ }
+ else
+ {
+ free_queries = q->next;
+ }
+
+ r = read_pipe(PLUTO_QFD, (unsigned char *)&q->aq
+ , sizeof(q->aq), sizeof(q->aq));
+
+ if (r == HES_OK)
+ {
+ /* EOF: we're done, except for unanswered queries */
+ struct worker_info *w;
+
+ eof_from_pluto = TRUE;
+ q->next = free_queries;
+ free_queries = q;
+
+ /* Send bye-bye to unbusy processes.
+ * Note that if there are queued queries, there won't be
+ * any non-busy workers.
+ */
+ for (w = wi; w != wi_roof; w++)
+ if (!w->busy)
+ send_eof(w);
+ }
+ else if (r != HES_CONTINUE)
+ {
+ exit(r);
+ }
+ else if (q->aq.qmagic != ADNS_Q_MAGIC)
+ {
+ syslog(LOG_ERR, "error in query from Pluto: bad magic");
+ exit(HES_BAD_MAGIC);
+ }
+ else
+ {
+ struct worker_info *w;
+
+ /* got a query */
+
+ /* add it to FIFO */
+ q->next = NULL;
+ if (oldest_query == NULL)
+ oldest_query = q;
+ else
+ newest_query->next = q;
+ newest_query = q;
+
+ /* See if any worker available */
+ for (w = wi; ; w++)
+ {
+ if (w == wi_roof)
+ {
+ /* no free worker */
+ if (w == wi + MAX_WORKERS)
+ break; /* no more to be created */
+ /* make a new one */
+ if (!spawn_worker())
+ break; /* cannot create one at this time */
+ }
+ if (!w->busy)
+ {
+ /* assign first to free worker */
+ forward_query(w);
+ break;
+ }
+ }
+ }
+ return;
+}
+
+static void
+answer(struct worker_info *w)
+{
+ struct adns_answer a;
+ enum helper_exit_status r = read_pipe(w->afd, (unsigned char *)&a
+ , offsetof(struct adns_answer, ans), sizeof(a));
+
+ if (r == HES_OK)
+ {
+ /* unexpected EOF */
+ syslog(LOG_ERR, "unexpected EOF from worker");
+ exit(HES_IO_ERROR_IN);
+ }
+ else if (r != HES_CONTINUE)
+ {
+ exit(r);
+ }
+ else if (a.amagic != ADNS_A_MAGIC)
+ {
+ syslog(LOG_ERR, "Input from worker error: bad magic");
+ exit(HES_BAD_MAGIC);
+ }
+ else if (a.continuation != w->continuation)
+ {
+ /* answer doesn't match query */
+ syslog(LOG_ERR, "Input from worker error: continuation mismatch");
+ exit(HES_SYNC);
+ }
+ else
+ {
+ /* pass the answer on to Pluto */
+ enum helper_exit_status r
+ = write_pipe(PLUTO_AFD, (const unsigned char *) &a);
+
+ if (r != HES_CONTINUE)
+ exit(r);
+ w->busy = FALSE;
+ forward_query(w);
+ }
+}
+
+/* assumption: input limited; accept blocking on output */
+static int
+master(void)
+{
+ for (;;)
+ {
+ fd_set readfds;
+ int maxfd = PLUTO_QFD; /* approximate lower bound */
+ int ndes = 0;
+ struct worker_info *w;
+
+ FD_ZERO(&readfds);
+ if (!eof_from_pluto)
+ {
+ FD_SET(PLUTO_QFD, &readfds);
+ ndes++;
+ }
+ for (w = wi; w != wi_roof; w++)
+ {
+ if (w->busy)
+ {
+ FD_SET(w->afd, &readfds);
+ ndes++;
+ if (maxfd < w->afd)
+ maxfd = w->afd;
+ }
+ }
+
+ if (ndes == 0)
+ return HES_OK; /* done! */
+
+ do {
+ ndes = select(maxfd + 1, &readfds, NULL, NULL, NULL);
+ } while (ndes == -1 && errno == EINTR);
+ if (ndes == -1)
+ {
+ syslog(LOG_ERR, "select(2) error: %s", strerror(errno));
+ exit(HES_IO_ERROR_SELECT);
+ }
+ else if (ndes > 0)
+ {
+ if (FD_ISSET(PLUTO_QFD, &readfds))
+ {
+ query();
+ ndes--;
+ }
+ for (w = wi; ndes > 0 && w != wi_roof; w++)
+ {
+ if (w->busy && FD_ISSET(w->afd, &readfds))
+ {
+ answer(w);
+ ndes--;
+ }
+ }
+ }
+ }
+}
+
+/* Not to be invoked by strangers -- user hostile.
+ * Mandatory args: query-fd answer-fd
+ * Optional arg: -d, signifying "debug".
+ */
+
+static void
+adns_usage(const char *fmt, const char *arg)
+{
+ const char **sp = ipsec_copyright_notice();
+
+ fprintf(stderr, "INTERNAL TO PLUTO: DO NOT EXECUTE\n");
+
+ fprintf(stderr, fmt, arg);
+ fprintf(stderr, "\n%s\n", ipsec_version_string());
+
+ for (; *sp != NULL; sp++)
+ fprintf(stderr, "%s\n", *sp);
+
+ syslog(LOG_ERR, fmt, arg);
+ exit(HES_INVOCATION);
+}
+
+int
+main(int argc UNUSED, char **argv)
+{
+ int i = 1;
+
+ name = argv[0];
+
+ while (i < argc)
+ {
+ if (streq(argv[i], "-d"))
+ {
+ i++;
+ debug = TRUE;
+ }
+ else
+ {
+ adns_usage("unexpected argument \"%s\"", argv[i]);
+ /*NOTREACHED*/
+ }
+ }
+
+ return master();
+}
+
+#endif /* !USE_LWRES */
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