Mailing List Archive

This adds support for systemd socket-based activation in the ssh-agent.
When using socket activation, the -a flag value must match the socket
path provided by systemd, as a sanity check. Support for this feature is
enabled by the --with-systemd configure flag.

---
Something tells me upstream would not be interested in this patch, but
as it may be useful on linux, I'm submitting it here.

Makefile.in | 3 ++-
configure.ac | 25 ++++++++++++++++++++++++
ssh-agent.c | 54 +++++++++++++++++++++++++++++++++++++++++++---------
3 files changed, 72 insertions(+), 10 deletions(-)

diff --git a/Makefile.in b/Makefile.in
index 70287f51fb81..9bace646fecf 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -53,6 +53,7 @@ CHANNELLIBS=@CHANNELLIBS@
K5LIBS=@K5LIBS@
GSSLIBS=@GSSLIBS@
SSHDLIBS=@SSHDLIBS@
+AGENTLIBS=@AGENTLIBS@
LIBEDIT=@LIBEDIT@
LIBFIDO2=@LIBFIDO2@
AR=@AR@
@@ -216,7 +217,7 @@ ssh-add$(EXEEXT): $(LIBCOMPAT) libssh.a $(SSHADD_OBJS)
$(LD) -o $@ $(SSHADD_OBJS) $(LDFLAGS) -lssh -lopenbsd-compat $(LIBS) $(CHANNELLIBS)

ssh-agent$(EXEEXT): $(LIBCOMPAT) libssh.a $(SSHAGENT_OBJS)
- $(LD) -o $@ $(SSHAGENT_OBJS) $(LDFLAGS) -lssh -lopenbsd-compat $(LIBS) $(CHANNELLIBS)
+ $(LD) -o $@ $(SSHAGENT_OBJS) $(LDFLAGS) -lssh -lopenbsd-compat $(AGENTLIBS) $(LIBS) $(CHANNELLIBS)

ssh-keygen$(EXEEXT): $(LIBCOMPAT) libssh.a $(SSHKEYGEN_OBJS)
$(LD) -o $@ $(SSHKEYGEN_OBJS) $(LDFLAGS) -lssh -lopenbsd-compat $(LIBS) $(CHANNELLIBS)
diff --git a/configure.ac b/configure.ac
index 07893e870659..d12b6e9c0588 100644
--- a/configure.ac
+++ b/configure.ac
@@ -147,6 +147,16 @@ else
AC_MSG_RESULT([no])
fi

+systemd=no
+AC_ARG_WITH([systemd],
+ [ --with-systemd Enable use of systemd socket-based activation ],
+ [. if test "x$withval" = "xyes" ; then
+ systemd=yes
+ AC_DEFINE([WITH_SYSTEMD], [1], [enable systemd socket-based activation])
+ fi
+ ]
+)
+
use_stack_protector=1
use_toolchain_hardening=1
AC_ARG_WITH([stackprotect],
@@ -3376,6 +3386,18 @@ AC_CHECK_LIB([crypt], [crypt], [
AC_CHECK_FUNCS([crypt])
LIBS="$saved_LIBS"

+if test "x$systemd" == "xyes" ; then
+ # Check for sd_listen_fds in libsystemd for socket activation
+ saved_LIBS="$LIBS"
+ AC_CHECK_LIB([systemd], [sd_listen_fds], [
+ LIBS="-lsystemd $LIBS"
+ AGENTLIBS="-lsystemd $AGENTLIBS"
+ ])
+ AC_CHECK_FUNCS([sd_listen_fds])
+ LIBS="$saved_LIBS"
+ AC_SUBST([AGENTLIBS])
+fi
+
# Check for PAM libs
PAM_MSG="no"
AC_ARG_WITH([pam],
@@ -5632,6 +5654,9 @@ fi
if test ! -z "${SSHDLIBS}"; then
echo " +for sshd: ${SSHDLIBS}"
fi
+if test ! -z "${AGENTLIBS}"; then
+echo " +for ssh-agent: ${AGENTLIBS}"
+fi

echo ""

diff --git a/ssh-agent.c b/ssh-agent.c
index c72518ba3537..eb3a8b022590 100644
--- a/ssh-agent.c
+++ b/ssh-agent.c
@@ -69,6 +69,9 @@
#include <stdlib.h>
#include <time.h>
#include <string.h>
+#ifdef WITH_SYSTEMD
+# include <systemd/sd-daemon.h>
+#endif
#include <unistd.h>
#ifdef HAVE_UTIL_H
# include <util.h>
@@ -166,6 +169,11 @@ pid_t cleanup_pid = 0;
char socket_name[PATH_MAX];
char socket_dir[PATH_MAX];

+#ifdef WITH_SYSTEMD
+/* tracks whether the active AUTH_SOCKET was passed to us by a third party */
+int external_socket = 0;
+#endif
+
/* Pattern-list of allowed PKCS#11/Security key paths */
static char *allowed_providers;

@@ -1946,6 +1954,10 @@ cleanup_socket(void)
{
if (cleanup_pid != 0 && getpid() != cleanup_pid)
return;
+#ifdef WITH_SYSTEMD
+ if (external_socket)
+ return;
+#endif
debug_f("cleanup");
if (socket_name[0])
unlink(socket_name);
@@ -2000,7 +2012,7 @@ int
main(int ac, char **av)
{
int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0;
- int sock, ch, result, saved_errno;
+ int sock = 0, ch, result, saved_errno;
char *shell, *format, *pidstr, *agentsocket = NULL;
#ifdef HAVE_SETRLIMIT
struct rlimit rlim;
@@ -2015,6 +2027,9 @@ main(int ac, char **av)
struct pollfd *pfd = NULL;
size_t npfd = 0;
u_int maxfds;
+#ifdef WITH_SYSTEMD
+ int nfds = 0;
+#endif

/* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
sanitise_stdfd();
@@ -2142,6 +2157,25 @@ main(int ac, char **av)

parent_pid = getpid();

+#ifdef WITH_SYSTEMD
+ nfds = sd_listen_fds(1);
+ if (nfds > 0) {
+ sock = SD_LISTEN_FDS_START;
+ if (agentsocket == NULL) {
+ fprintf(stderr, "%s not set, cannot use socket-activation",
+ SSH_AUTHSOCKET_ENV_NAME);
+ exit(1);
+ } else if (sd_is_socket_unix(sock, SOCK_STREAM, 1, agentsocket, 0) <= 0) {
+ fprintf(stderr, "Unexpected auth sock received from systemd. Expected %s\n", agentsocket);
+ exit(1);
+ } else if (nfds > 1) {
+ fprintf(stderr, "too many fds received from systemd (%d)\n", nfds);
+ exit(1);
+ }
+ strlcpy(socket_name, agentsocket, sizeof socket_name);
+ external_socket = 1;
+ }
+#endif
if (agentsocket == NULL) {
/* Create private directory for agent socket */
mktemp_proto(socket_dir, sizeof(socket_dir));
@@ -2150,7 +2184,7 @@ main(int ac, char **av)
exit(1);
}
snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir,
- (long)parent_pid);
+ (long)parent_pid);
} else {
/* Try to use specified agent socket */
socket_dir[0] = '\0';
@@ -2161,14 +2195,16 @@ main(int ac, char **av)
* Create socket early so it will exist before command gets run from
* the parent.
*/
- prev_mask = umask(0177);
- sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0);
- if (sock < 0) {
- /* XXX - unix_listener() calls error() not perror() */
- *socket_name = '\0'; /* Don't unlink any existing file */
- cleanup_exit(1);
+ if (sock == 0) {
+ prev_mask = umask(0177);
+ sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0);
+ if (sock < 0) {
+ /* XXX - unix_listener() calls error() not perror() */
+ *socket_name = '\0'; /* Don't unlink any existing file */
+ cleanup_exit(1);
+ }
+ umask(prev_mask);
}
- umask(prev_mask);

/*
* Fork, and have the parent execute the command, if any, or present
--
2.41.0

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