add --with-confdir feature

This adds support for an /etc/doas.d configuration directory as discussed in #61. It is disabled by default.

Author: kaniini

README.md

@@ -61,3 +61,12 @@ similar to sudo.
 
 See the comment block in `timestamp.c` for an in-depth description on how
 timestamps are created and checked to be as safe as possible.
+
+### `--with-doas-confdir`
+
+An optional feature can be enabled which will result in `doas` reading configuration
+snippets from `/etc/doas.d`.  These configuration snippets have the same requirements
+as `/etc/doas.conf` (owned by root, not world-writable).
+
+If this feature is enabled, only the `/etc/doas.d` directory is read, and the historical
+`/etc/doas.conf` file is ignored.

configure

@@ -27,6 +27,7 @@ usage: configure [options]
   --without-shadow       disable shadow support
 
   --with-timestamp       enable timestamp support
+  --with-doas-confdir    enable configuration directory support
 
   --uid-max=NUM          set UID_MAX (default 65535)
   --gid-max=NUM          set GID_MAX (default 65535)
@@ -38,6 +39,7 @@ EOF
 
 # defaults
 WITHOUT_TIMESTAMP=yes
+WITHOUT_CONFDIR=yes
 UID_MAX=65535
 GID_MAX=65535
 
@@ -56,6 +58,8 @@ for x; do
 	--target) TARGET=$var ;;
 	--enable-debug) DEBUG=yes ;;
 	--enable-static) BUILD_STATIC=yes ;;
+	--with-doas-confdir) WITHOUT_CONFDIR= ;;
+	--without-doas-confdir) WITHOUT_CONFDIR=yes ;;
 	--with-pam) WITHOUT_PAM=; WITHOUT_SHADOW=yes ;;
 	--with-shadow) WITHOUT_SHADOW=; WITHOUT_PAM=yes ;;
 	--without-pam) WITHOUT_PAM=yes ;;
@@ -558,4 +562,8 @@ fi
 
 printf '#define DOAS_CONF "%s/doas.conf"\n' "${SYSCONFDIR}" >>$CONFIG_H
 
+if [ -z "$WITHOUT_CONFDIR" ]; then
+	printf '#define DOAS_CONFDIR "%s/doas.d"\n' "${SYSCONFDIR}" >>$CONFIG_H
+fi
+
 printf '\n#endif /* CONFIG_H */\n' >>$CONFIG_H

doas.c

@@ -35,6 +35,7 @@
 #include <syslog.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <dirent.h>
 
 #include "openbsd.h"
 #include "doas.h"
@@ -155,6 +156,7 @@ permit(uid_t uid, gid_t *groups, int ngroups, const struct rule **lastr,
 static void
 parseconfig(const char *filename, int checkperms)
 {
+	extern const char *yyfn;
 	extern FILE *yyfp;
 	extern int yyparse(void);
 	struct stat sb;
@@ -164,6 +166,8 @@ parseconfig(const char *filename, int checkperms)
 		err(1, checkperms ? "doas is not enabled, %s" :
 		    "could not open config file %s", filename);
 
+	yyfn = filename;
+
 	if (checkperms) {
 		if (fstat(fileno(yyfp), &sb) != 0)
 			err(1, "fstat(\"%s\")", filename);
@@ -174,11 +178,67 @@ parseconfig(const char *filename, int checkperms)
 	}
 
 	yyparse();
+	yyfn = NULL;
+
 	fclose(yyfp);
 	if (parse_errors)
 		exit(1);
 }
 
+#ifdef DOAS_CONFDIR
+static int
+isconfdir(const char *dirpath)
+{
+	struct stat sb;
+
+	if (lstat(dirpath, &sb) != 0)
+		err(1, "lstat(\"%s\")", dirpath);
+
+	if ((sb.st_mode & (S_IFMT)) == S_IFDIR)
+		return 1;
+
+	errno = ENOTDIR;
+	return 0;
+}
+
+static void
+parseconfdir(const char *dirpath, int checkperms)
+{
+	struct dirent **dirent_table;
+	size_t i, dirent_count;
+	char pathbuf[PATH_MAX];
+
+	if (!isconfdir(dirpath))
+		err(1, checkperms ? "doas is not enabled, %s" :
+		    "could not open config directory %s", dirpath);
+
+	dirent_count = scandir(dirpath, &dirent_table, NULL, alphasort);
+
+	for (i = 0; i < dirent_count; i++)
+	{
+		struct stat sb;
+		size_t pathlen;
+
+		pathlen = snprintf(pathbuf, sizeof pathbuf, "%s/%s", dirpath, dirent_table[i]->d_name);
+		free(dirent_table[i]);
+
+		/* make sure path ends in .conf */
+		if (strcmp(pathbuf + (pathlen - 5), ".conf"))
+			continue;
+
+		if (stat(pathbuf, &sb) != 0)
+			err(1, "stat(\"%s\")", pathbuf);
+
+		if ((sb.st_mode & (S_IFMT)) != S_IFREG)
+			continue;
+
+		parseconfig(pathbuf, checkperms);
+	}
+
+	free(dirent_table);
+}
+#endif
+
 static void __dead
 checkconfig(const char *confpath, int argc, char **argv,
     uid_t uid, gid_t *groups, int ngroups, uid_t target)
@@ -188,7 +248,13 @@ checkconfig(const char *confpath, int argc, char **argv,
 	if (setresuid(uid, uid, uid) != 0)
 		err(1, "setresuid");
 
+#ifdef DOAS_CONFDIR
+	if (isconfdir(confpath))
+		parseconfdir(confpath, 0);
+	else
+#else
 	parseconfig(confpath, 0);
+#endif
 	if (!argc)
 		exit(0);
 
@@ -330,7 +396,13 @@ main(int argc, char **argv)
 	if (geteuid())
 		errx(1, "not installed setuid");
 
+#ifdef DOAS_CONFDIR
+	if (isconfdir(DOAS_CONFDIR))
+		parseconfdir(DOAS_CONFDIR, 1);
+	else
+#else
 	parseconfig(DOAS_CONF, 1);
+#endif
 
 	/* cmdline is used only for logging, no need to abort on truncate */
 	(void)strlcpy(cmdline, argv[0], sizeof(cmdline));

parse.y

@@ -49,6 +49,7 @@ typedef struct {
 } yystype;
 #define YYSTYPE yystype
 
+const char *yyfn;
 FILE *yyfp;
 
 struct rule **rules;
@@ -203,7 +204,7 @@ yyerror(const char *fmt, ...)
 	va_start(va, fmt);
 	vfprintf(stderr, fmt, va);
 	va_end(va);
-	fprintf(stderr, " at line %d\n", yylval.lineno + 1);
+	fprintf(stderr, " at %s, line %d\n", yyfn, yylval.lineno + 1);
 	parse_errors++;
 }