From c3ccaeeddc4d92bfe34cedaa6b71cb6e830fe280 Mon Sep 17 00:00:00 2001
From: "Anna (navi) Figueiredo Gomes" <navi@vlhl.dev>
Date: Thu, 18 Jul 2024 17:29:21 +0200
Subject: librc, openrc-pam: instantiate user.<username> service automatically

it's created in /run/openrc/dynamic and linked to the service in /etc at
login.

Signed-off-by: Anna (navi) Figueiredo Gomes <navi@vlhl.dev>
---
 src/librc/librc-depend.c    |  1 +
 src/librc/librc.c           | 29 +++++++++++++++++++++++++++++
 src/librc/rc.h.in           | 10 ++++++++++
 src/openrc-pam/openrc-pam.c | 14 ++++++++++++--
 src/shared/helpers.h        | 16 ++++++++++++++++
 5 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/src/librc/librc-depend.c b/src/librc/librc-depend.c
index a03e1a61..9f592cfe 100644
--- a/src/librc/librc-depend.c
+++ b/src/librc/librc-depend.c
@@ -700,6 +700,7 @@ static const char *const depdirs[] =
 	"options",
 	"exclusive",
 	"scheduled",
+	"dynamic",
 	"tmp",
 	NULL
 };
diff --git a/src/librc/librc.c b/src/librc/librc.c
index d218c8be..ee728b30 100644
--- a/src/librc/librc.c
+++ b/src/librc/librc.c
@@ -1317,6 +1317,35 @@ rc_service_delete(const char *runlevel, const char *service)
 	return (r == 0);
 }
 
+char *
+rc_service_base(const char *service)
+{
+	char *dot = strchr(service, '.');
+	if (!dot)
+		return NULL;
+	return xstrndup(service, dot - service);
+}
+
+char *
+rc_service_dylink(const char *service, const char *target)
+{
+	char *file = rc_service_resolve(service);
+	char *target_file = NULL;
+	if (!exists(file))
+		goto out;
+
+	xasprintf(&target_file, "%s/dynamic/%s", rc_service_dir(), target);
+	if (!exists(target_file) && symlink(file, target_file) == -1) {
+		free(target_file);
+		target_file = NULL;
+		goto out;
+	}
+
+out:
+	free(file);
+	return target_file;
+}
+
 RC_STRINGLIST *
 rc_services_scheduled_by(const char *service)
 {
diff --git a/src/librc/rc.h.in b/src/librc/rc.h.in
index 59fdfda3..794b4353 100644
--- a/src/librc/rc.h.in
+++ b/src/librc/rc.h.in
@@ -275,6 +275,16 @@ RC_STRINGLIST *rc_service_extra_commands(const char *);
  * @return pointer to full path of service */
 char *rc_service_resolve(const char *);
 
+/*! Gets the base service for a multiplexed service
+ * @param multiplexed service to check
+ * @return pointer to base service name or NULL if not multiplexed */
+char *rc_service_base(const char *);
+
+/*! Dynamically multiplexes a service into the runtime directory.
+ * @param service to link
+ * @param target service name */
+char *rc_service_dylink(const char *, const char *);
+
 /*! Schedule a service to be started when another service starts
  * @param service that starts the scheduled service when started
  * @param service_to_start service that will be started */
diff --git a/src/openrc-pam/openrc-pam.c b/src/openrc-pam/openrc-pam.c
index 241b123d..f0556ada 100644
--- a/src/openrc-pam/openrc-pam.c
+++ b/src/openrc-pam/openrc-pam.c
@@ -18,6 +18,7 @@ exec_openrc(pam_handle_t *pamh, bool opening)
 	char *svc_name = NULL;
 	char *pam_lock = NULL;
 	char *logins, *rundir;
+	char *file;
 	const char *username;
 	struct passwd *pw;
 	int count = 0, fd = -1;
@@ -48,17 +49,26 @@ exec_openrc(pam_handle_t *pamh, bool opening)
 		goto out;
 	}
 
+	file = rc_service_resolve(svc_name);
+	if (!file) {
+		file = rc_service_dylink("user", svc_name);
+		if (!file) {
+			svc_unlock(pam_lock, fd);
+			goto out;
+		}
+	}
+
 	logins = rc_service_value_get(svc_name, "logins");
 	if (logins)
 		sscanf(logins, "%d", &count);
 	free(logins);
 
 	if (opening && count == 0) {
-		pid = service_start(svc_name);
+		pid = service_start(file);
 		rc_service_mark(svc_name, RC_SERVICE_HOTPLUGGED);
 		count++;
 	} else if (count > 0) {
-		pid = service_stop(svc_name);
+		pid = service_stop(file);
 		count--;
 	}
 
diff --git a/src/shared/helpers.h b/src/shared/helpers.h
index dee41b75..36a25a2d 100644
--- a/src/shared/helpers.h
+++ b/src/shared/helpers.h
@@ -91,6 +91,22 @@ RC_UNUSED static char *xstrdup(const char *str)
 	/* NOTREACHED */
 }
 
+RC_UNUSED static char *xstrndup(const char *str, size_t n)
+{
+	char *value;
+
+	if (!str)
+		return (NULL);
+
+	value = strndup(str, n);
+
+	if (value)
+		return (value);
+
+	ERRX;
+	/* NOTREACHED */
+}
+
 #undef ERRX
 
 /*
-- 
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