mosquitto-auth-shadow: support libpam based authentication

mosquitto-auth-shadow/Config.in

@@ -0,0 +1,7 @@
+if PACKAGE_mosquitto-auth-shadow
+
+config MOSQUITTO_AUTH_PAM_SUPPORT
+	bool "Enable support of Linux PAM module for Authentication"
+	default y
+
+endif

mosquitto-auth-shadow/Makefile

@@ -14,12 +14,13 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=mosquitto-auth-shadow
-PKG_VERSION:=1.0.1
+PKG_VERSION:=1.1.0
 
 PKG_MAINTAINER:=Erik Karlsson <erik.karlsson@genexis.eu>
 PKG_LICENSE:=EPL-2.0
 
 PKG_BUILD_PARALLEL:=1
+PKG_CONFIG_DEPENDS:=CONFIG_MOSQUITTO_AUTH_PAM_SUPPORT
 
 include $(INCLUDE_DIR)/package.mk
 
@@ -27,7 +28,7 @@ define Package/mosquitto-auth-shadow
   SECTION:=net
   CATEGORY:=Network
   TITLE:=mosquitto - /etc/shadow authentication plugin
-  DEPENDS:=+mosquitto-ssl
+  DEPENDS:=+mosquitto-ssl +MOSQUITTO_AUTH_PAM_SUPPORT:libpam
   USERID:=mosquitto=200:mosquitto=200 mosquitto=200:shadow=11
 endef
 
@@ -36,6 +37,14 @@ define Package/mosquitto-auth-shadow/description
   users using /etc/shadow
 endef
 
+define Package/mosquitto-auth-shadow/config
+	source "$(SOURCE)/Config.in"
+endef
+
+ifeq ($(CONFIG_MOSQUITTO_AUTH_PAM_SUPPORT),y)
+TARGET_CFLAGS+=-DENABLE_PAM_SUPPORT
+endif
+
 define Package/mosquitto-auth-shadow/install
 	$(INSTALL_DIR) $(1)/usr/lib
 	$(INSTALL_BIN) $(PKG_BUILD_DIR)/mosquitto_auth_shadow.so $(1)/usr/lib/

mosquitto-auth-shadow/src/Makefile

@@ -19,7 +19,7 @@ all: $(TARGETS)
 	$(CC) $(CFLAGS) -Wall -Werror -fPIC -c -o $@ $<
 
 mosquitto_auth_shadow.so: mosquitto_auth_shadow.pic.o
-	$(CC) $(LDFLAGS) -shared -o $@ $^
+	$(CC) $(LDFLAGS) -shared -o $@ $^ $(if $(filter -DENABLE_PAM_SUPPORT,$(CFLAGS)),-lpam)
 
 clean:
 	rm -f *.o $(TARGETS)

mosquitto-auth-shadow/src/mosquitto_auth_shadow.c

@@ -15,22 +15,78 @@
 #include <string.h>
 #include <shadow.h>
 #include <crypt.h>
+#include <stdlib.h>
 #include <mosquitto.h>
 #include <mosquitto_broker.h>
 #include <mosquitto_plugin.h>
 
-static int basic_auth_callback(int event, void *event_data, void *userdata)
+#ifdef ENABLE_PAM_SUPPORT
+#include <security/pam_appl.h>
+
+static int pam_conversation(int num_msg, const struct pam_message **msg, struct pam_response **resp, void *appdata_ptr)
+{
+	int i;
+	const char *pass = (const char *)appdata_ptr;
+
+	*resp = calloc(num_msg, sizeof(struct pam_response));
+	if (*resp == NULL) {
+		mosquitto_log_printf(MOSQ_LOG_ERR, "pam failed to allocate buffer for validation");
+		return PAM_BUF_ERR;
+	}
+
+	if (pass == NULL)
+		return PAM_SUCCESS;
+
+	for (i = 0; i < num_msg; ++i) {
+		if (msg[i]->msg_style == PAM_PROMPT_ECHO_OFF) {
+			(*resp)[i].resp = strdup(pass);
+			if ((*resp)[i].resp == NULL) {
+				for (int j = 0; j < i ; j++)
+					free((*resp)[j].resp);
+
+				free(*resp);
+				*resp = NULL;
+				mosquitto_log_printf(MOSQ_LOG_ERR, "pam failed in strdup");
+				return PAM_BUF_ERR;
+			}
+		}
+	}
+	return PAM_SUCCESS;
+}
+
+static int process_pam_auth_callback(struct mosquitto_evt_basic_auth *ed)
+{
+	struct pam_conv conv;
+	int retval;
+	pam_handle_t *pamh = NULL;
+
+	conv.conv = pam_conversation;
+	conv.appdata_ptr = (void *)ed->password;
+
+	retval = pam_start("mosquitto", ed->username, &conv, &pamh);
+	if (retval != PAM_SUCCESS) {
+		mosquitto_log_printf(MOSQ_LOG_ERR, "pam start failed: %s", pam_strerror(pamh, retval));
+		return MOSQ_ERR_AUTH;
+	}
+
+	retval = pam_authenticate(pamh, 0);
+	pam_end(pamh, retval);
+	if (retval == PAM_SUCCESS) {
+		mosquitto_log_printf(MOSQ_LOG_NOTICE, "pam user [%s] logged in", ed->username);
+		return MOSQ_ERR_SUCCESS;
+	}
+
+	mosquitto_log_printf(MOSQ_LOG_NOTICE, "pam user [%s] failed authentication, err [%s]", ed->username, pam_strerror(pamh, retval));
+	return MOSQ_ERR_AUTH;
+}
+#else
+static int process_shadow_auth_callback(struct mosquitto_evt_basic_auth *ed)
 {
-	struct mosquitto_evt_basic_auth *ed = event_data;
 	struct spwd spbuf, *sp = NULL;
 	char buf[256];
 	struct crypt_data data;
 	char *hash;
 
-	/* Let other plugins or broker decide about anonymous login */
-	if (ed->username == NULL)
-		return MOSQ_ERR_PLUGIN_DEFER;
-
 	getspnam_r(ed->username, &spbuf, buf, sizeof(buf), &sp);
 
 	if (sp == NULL || sp->sp_pwdp == NULL)
@@ -54,6 +110,22 @@ static int basic_auth_callback(int event, void *event_data, void *userdata)
 
 	return MOSQ_ERR_AUTH;
 }
+#endif
+
+static int basic_auth_callback(int event, void *event_data, void *userdata)
+{
+	struct mosquitto_evt_basic_auth *ed = event_data;
+
+	/* Let other plugins or broker decide about anonymous login */
+	if (ed->username == NULL)
+		return MOSQ_ERR_PLUGIN_DEFER;
+
+#ifdef ENABLE_PAM_SUPPORT
+	return process_pam_auth_callback(ed);
+#else
+	return process_shadow_auth_callback(ed);
+#endif
+}
 
 int mosquitto_plugin_version(int supported_version_count,
 			     const int *supported_versions)