Abstract the message priority sanity checking

We needs this sanity checking in multiple places, so create a new
function internal to libpushover: `pushover_message_priority_sane`.
Signed-off-by: Shawn Webb <shawn.webb@hardenedbsd.org>

libpushover/Makefile

 SHLIB=	pushover
 SHLIB_MAJOR=	0
-SRCS=	libpushover.c
+SRCS=	libpushover.c sanity.c
 INCS=	libpushover.h
 
 CFLAGS+=	-I${.CURDIR} -I/usr/local/include

libpushover/libpushover.c

@@ -197,19 +197,7 @@ pushover_message_set_priority(pushover_message_t *msg,
 
 	assert(msg != NULL);
 
-	switch (prio) {
-	case PSH_PRIO_NONE:
-	case PSH_PRIO_QUIET:
-	case PSH_PRIO_DEF:
-	case PSH_PRIO_HIGH:
-	case PSH_PRIO_CONFIRM:
-		msg->psh_priority = prio;
-		break;
-	default:
-		return (false);
-	}
-
-	return (true);
+	return (pushover_message_priority_sane(msg->psh_priority));
 }
 
 EXPORTED_SYM
@@ -226,6 +214,7 @@ pushover_submit_message(pushover_ctx_t *ctx, pushover_message_t *msg)
 	assert(ctx->psh_token != NULL);
 	assert(msg->psh_user != NULL);
 	assert(msg->psh_msg != NULL);
+	assert(pushover_message_priority_sane(msg->psh_priority));
 
 	res = false;
 
@@ -236,10 +225,8 @@ pushover_submit_message(pushover_ctx_t *ctx, pushover_message_t *msg)
 	curl_easy_setopt(curl, CURLOPT_URL, ctx->psh_uri);
 
 	post_str = msg_to_str(ctx, msg, curl);
-	if (post_str == NULL) {
-		res = false;
+	if (post_str == NULL)
 		goto end;
-	}
 	curl_easy_setopt(curl, CURLOPT_POSTFIELDS, post_str);
 
 	curl_code = curl_easy_perform(curl);

libpushover/libpushover.h

@@ -47,4 +47,6 @@ bool pushover_message_set_priority(pushover_message_t *,
     pushover_priority_t);
 bool pushover_submit_message(pushover_ctx_t *, pushover_message_t *);
 
+bool pushover_message_priority_sane(pushover_priority_t);
+
 #endif /* !_LIBPUSHOVER_H */

libpushover/sanity.c

+/*-
+ * Copyright (c) 2020 HardenedBSD Foundation Corp.
+ * Author: Shawn Webb <shawn.webb@hardenedbsd.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "libpushover.h"
+
+bool
+pushover_message_priority_sane(pushover_priority_t prio)
+{
+
+	switch (prio) {
+	case PSH_PRIO_NONE:
+	case PSH_PRIO_QUIET:
+	case PSH_PRIO_DEF:
+	case PSH_PRIO_HIGH:
+	case PSH_PRIO_CONFIRM:
+		return (true);
+	default:
+		return (false);
+	}
+}