upstream: missing file in previous commit

OpenBSD-Commit-ID: e526c97fcb2fd9f0b7b229720972426ab437d7eb

Author: djmdjm

misc-agent.c

@@ -0,0 +1,329 @@
+/*
+ * Copyright (c) 2025 Damien Miller <djm@mindrot.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/un.h>
+
+#include <dirent.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <netdb.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "digest.h"
+#include "log.h"
+#include "misc.h"
+#include "pathnames.h"
+#include "ssh.h"
+#include "xmalloc.h"
+
+/* stuff shared by agent listeners (ssh-agent and sshd agent forwarding) */
+
+#define SOCKET_HOSTNAME_HASHLEN 10 /* length of hostname hash in socket path */
+
+/* used for presenting random strings in unix_listener_tmp and hostname_hash */
+static const char presentation_chars[] =
+    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+
+/* returns a text-encoded hash of the hostname of specified length (max 64) */
+static char *
+hostname_hash(size_t len)
+{
+	char hostname[NI_MAXHOST], p[65];
+	u_char hash[64];
+	int r;
+	size_t l, i;
+
+	l = ssh_digest_bytes(SSH_DIGEST_SHA512);
+	if (len > 64) {
+		error_f("bad length %zu > max %zd", len, l - 1);
+		return NULL;
+	}
+	if (gethostname(hostname, sizeof(hostname)) == -1) {
+		error_f("gethostname: %s", strerror(errno));
+		return NULL;
+	}
+	if ((r = ssh_digest_memory(SSH_DIGEST_SHA512,
+	    hostname, strlen(hostname), hash, sizeof(hash))) != 0) {
+		error_fr(r, "ssh_digest_memory");
+		return NULL;
+	}
+	memset(p, '\0', sizeof(p));
+	for (i = 0; i < l; i++)
+		p[i] = presentation_chars[
+		    hash[i] % (sizeof(presentation_chars) - 1)];
+	/* debug3_f("hostname \"%s\" => hash \"%s\"", hostname, p); */
+	p[len] = '\0';
+	return xstrdup(p);
+}
+
+char *
+agent_hostname_hash(void)
+{
+	return hostname_hash(SOCKET_HOSTNAME_HASHLEN);
+}
+
+/*
+ * Creates a unix listener at a mkstemp(3)-style path, e.g. "/dir/sock.XXXXXX"
+ * Supplied path is modified to the actual one used.
+ */
+static int
+unix_listener_tmp(char *path, int backlog)
+{
+	struct sockaddr_un sunaddr;
+	int good, sock = -1;
+	size_t i, xstart;
+	mode_t prev_mask;
+
+	/* Find first 'X' template character back from end of string */
+	xstart = strlen(path);
+	while (xstart > 0 && path[xstart - 1] == 'X')
+		xstart--;
+
+	memset(&sunaddr, 0, sizeof(sunaddr));
+	sunaddr.sun_family = AF_UNIX;
+	prev_mask = umask(0177);
+	for (good = 0; !good;) {
+		sock = -1;
+		/* Randomise path suffix */
+		for (i = xstart; path[i] != '\0'; i++) {
+			path[i] = presentation_chars[
+			    arc4random_uniform(sizeof(presentation_chars)-1)];
+		}
+		debug_f("trying path \"%s\"", path);
+
+		if (strlcpy(sunaddr.sun_path, path,
+		    sizeof(sunaddr.sun_path)) >= sizeof(sunaddr.sun_path)) {
+			error_f("path \"%s\" too long for Unix domain socket",
+			    path);
+			break;
+		}
+
+		if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) == -1) {
+			error_f("socket: %.100s", strerror(errno));
+			break;
+		}
+		if (bind(sock, (struct sockaddr *)&sunaddr,
+		    sizeof(sunaddr)) == -1) {
+			if (errno == EADDRINUSE) {
+				error_f("bind \"%s\": %.100s",
+				    path, strerror(errno));
+				close(sock);
+				sock = -1;
+				continue;
+			}
+			error_f("bind \"%s\": %.100s", path, strerror(errno));
+			break;
+		}
+		if (listen(sock, backlog) == -1) {
+			error_f("listen \"%s\": %s", path, strerror(errno));
+			break;
+		}
+		good = 1;
+	}
+	umask(prev_mask);
+	if (good) {
+		debug3_f("listening on unix socket \"%s\" as fd=%d",
+		    path, sock);
+	} else if (sock != -1) {
+		close(sock);
+		sock = -1;
+	}
+	return sock;
+}
+
+/*
+ * Create a subdirectory under the supplied home directory if it
+ * doesn't already exist
+ */
+static int
+ensure_mkdir(const char *homedir, const char *subdir)
+{
+	char *path;
+
+	xasprintf(&path, "%s/%s", homedir, subdir);
+	if (mkdir(path, 0700) == 0)
+		debug("created directory %s", path);
+	else if (errno != EEXIST) {
+		error_f("mkdir %s: %s", path, strerror(errno));
+		return -1;
+	}
+	free(path);
+	return 0;
+}
+
+static int
+agent_prepare_sockdir(const char *homedir)
+{
+	if (homedir == NULL || *homedir == '\0' ||
+	    ensure_mkdir(homedir, _PATH_SSH_USER_DIR) != 0 ||
+	    ensure_mkdir(homedir, _PATH_SSH_AGENT_SOCKET_DIR) != 0)
+		return -1;
+	return 0;
+}
+
+
+/* Get a path template for an agent socket in the user's homedir */
+static char *
+agent_socket_template(const char *homedir, const char *tag)
+{
+	char *hostnamehash, *ret;
+
+	if ((hostnamehash = hostname_hash(SOCKET_HOSTNAME_HASHLEN)) == NULL)
+		return NULL;
+	xasprintf(&ret, "%s/%s/s.%s.%s.XXXXXXXXXX",
+	    homedir, _PATH_SSH_AGENT_SOCKET_DIR, hostnamehash, tag);
+	free(hostnamehash);
+	return ret;
+}
+
+int
+agent_listener(const char *homedir, const char *tag, int *sockp, char **pathp)
+{
+	int sock;
+	char *path;
+
+	*sockp = -1;
+	*pathp = NULL;
+
+	if (agent_prepare_sockdir(homedir) != 0)
+		return -1; /* error already logged */
+	if ((path = agent_socket_template(homedir, tag)) == NULL)
+		return -1; /* error already logged */
+	if ((sock = unix_listener_tmp(path, SSH_LISTEN_BACKLOG)) == -1) {
+		free(path);
+		return -1; /* error already logged */
+	}
+	/* success */
+	*sockp = sock;
+	*pathp = path;
+	return 0;
+}
+
+static int
+socket_is_stale(const char *path)
+{
+	int fd, r;
+	struct sockaddr_un sun;
+	socklen_t l = sizeof(r);
+
+	/* attempt non-blocking connect on socket */
+	memset(&sun, '\0', sizeof(sun));
+	sun.sun_family = AF_UNIX;
+	if (strlcpy(sun.sun_path, path,
+	    sizeof(sun.sun_path)) >= sizeof(sun.sun_path)) {
+		debug_f("path for \"%s\" too long for sockaddr_un", path);
+		return 0;
+	}
+	if ((fd = socket(PF_UNIX, SOCK_STREAM, 0)) == -1) {
+		error_f("socket: %s", strerror(errno));
+		return 0;
+	}
+	set_nonblock(fd);
+	/* a socket without a listener should yield an error immediately */
+	if (connect(fd, (struct sockaddr *)&sun, sizeof(sun)) == -1) {
+		debug_f("connect \"%s\": %s", path, strerror(errno));
+		close(fd);
+		return 1;
+	}
+	if (getsockopt(fd, SOL_SOCKET, SO_ERROR, &r, &l) == -1) {
+		debug_f("getsockopt: %s", strerror(errno));
+		close(fd);
+		return 0;
+	}
+	if (r != 0) {
+		debug_f("socket error on %s: %s", path, strerror(errno));
+		close(fd);
+		return 1;
+	}
+	close(fd);
+	debug_f("socket %s seems still active", path);
+	return 0;
+}
+
+void
+agent_cleanup_stale(const char *homedir, int ignore_hosthash)
+{
+	DIR *d;
+	struct dirent *dp;
+	struct stat sb;
+	char *prefix = NULL, *dirpath, *path;
+	struct timespec now, sub;
+
+	/* Only consider sockets last modified > 1 hour ago */
+	if (clock_gettime(CLOCK_REALTIME, &now) != 0) {
+		error_f("clock_gettime: %s", strerror(errno));
+		return;
+	}
+	sub.tv_sec = 60 * 60;
+	sub.tv_nsec = 0;
+	timespecsub(&now, &sub, &now);
+
+	/* Only consider sockets from the same hostname */
+	if (!ignore_hosthash) {
+		if ((path = agent_hostname_hash()) == NULL) {
+			error_f("couldn't get hostname hash");
+			return;
+		}
+		xasprintf(&prefix, "s.%s.", path);
+		free(path);
+	}
+
+	xasprintf(&dirpath, "%s/%s", homedir, _PATH_SSH_AGENT_SOCKET_DIR);
+	if ((d = opendir(dirpath)) == NULL) {
+		if (errno != ENOENT)
+			error_f("opendir \"%s\": %s", dirpath, strerror(errno));
+		free(dirpath);
+		return;
+	}
+	while ((dp = readdir(d)) != NULL) {
+		if (dp->d_type != DT_SOCK && dp->d_type != DT_UNKNOWN)
+			continue;
+		if (fstatat(dirfd(d), dp->d_name,
+		    &sb, AT_SYMLINK_NOFOLLOW) != 0 && errno != ENOENT) {
+			error_f("stat \"%s/%s\": %s",
+			    dirpath, dp->d_name, strerror(errno));
+			continue;
+		}
+		if (!S_ISSOCK(sb.st_mode))
+			continue;
+		if (timespeccmp(&sb.st_mtim, &now, >)) {
+			debug3_f("Ignoring recent socket \"%s/%s\"",
+			    dirpath, dp->d_name);
+			continue;
+		}
+		if (!ignore_hosthash &&
+		    strncmp(dp->d_name, prefix, strlen(prefix)) != 0) {
+			debug3_f("Ignoring socket \"%s/%s\" "
+			    "from different host", dirpath, dp->d_name);
+			continue;
+		}
+		xasprintf(&path, "%s/%s", dirpath, dp->d_name);
+		if (socket_is_stale(path)) {
+			debug_f("cleanup stale socket %s", path);
+			unlinkat(dirfd(d), dp->d_name, 0);
+		}
+		free(path);
+	}
+	closedir(d);
+	free(dirpath);
+	free(prefix);
+}
+