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authorTed Unangst <tedu@openbsd.org>2015-07-16 20:44:21 +0000
committerTed Unangst <tedu@openbsd.org>2015-07-16 20:44:21 +0000
commit63916476e2cfa9402bbe21be29dee2a7d60d775e (patch)
tree5a3d8c9aab57a06d538b529e1df0c1a323c2cf17
downloadopendoas-63916476e2cfa9402bbe21be29dee2a7d60d775e.tar.gz
import doas. still subject to changes, large and small.
-rw-r--r--Makefile14
-rw-r--r--doas.157
-rw-r--r--doas.c321
-rw-r--r--doas.conf.570
-rw-r--r--doas.h20
-rw-r--r--parse.y210
6 files changed, 692 insertions, 0 deletions
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..191d00f
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,14 @@
+# $OpenBSD: Makefile,v 1.9 2014/01/13 01:41:00 tedu Exp $
+
+SRCS= parse.y doas.c
+
+PROG= doas
+MAN= doas.1 doas.conf.5
+
+BINOWN= root
+BINMODE=4555
+
+CFLAGS+= -I${.CURDIR}
+COPTS+= -Wall
+
+.include <bsd.prog.mk>
diff --git a/doas.1 b/doas.1
new file mode 100644
index 0000000..d2f94ef
--- /dev/null
+++ b/doas.1
@@ -0,0 +1,57 @@
+.\" $OpenBSD$
+.\"
+.\"Copyright (c) 2015 Ted Unangst <tedu@openbsd.org>
+.\"
+.\"Permission to use, copy, modify, and distribute this software for any
+.\"purpose with or without fee is hereby granted, provided that the above
+.\"copyright notice and this permission notice appear in all copies.
+.\"
+.\"THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+.\"WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+.\"MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+.\"ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+.\"WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+.\"ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+.\"OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+.Dd $Mdocdate$
+.Dt DOAS 1
+.Os
+.Sh NAME
+.Nm doas
+.Nd execute commands as another user
+.Sh SYNOPSIS
+.Nm doas
+.Op Fl u Ar user
+command
+.Op Ar args
+.Sh DESCRIPTION
+The
+.Nm
+utility executes the given command as another user.
+.Pp
+The options are as follows:
+.Bl -tag -width tenletters
+.It Fl u Ar user
+Execute the command as
+.Ar user .
+The default is root.
+.El
+.Sh EXIT STATUS
+.Ex -std doas
+It may fail because of one of the following reasons:
+.Pp
+.Bl -bullet -compact
+.It
+The config file could not be parsed.
+.It
+The user attempted an command which is not permitted.
+.It
+Entered passphrase is incorrect.
+.El
+.Sh HISTORY
+The
+.Nm
+command first appeared in
+.Ox 5.8 .
+.Sh AUTHORS
+.An Ted Unangst Aq Mt tedu@openbsd.org
diff --git a/doas.c b/doas.c
new file mode 100644
index 0000000..7c800bd
--- /dev/null
+++ b/doas.c
@@ -0,0 +1,321 @@
+/* $OpenBSD$ */
+/*
+ * Copyright (c) 2015 Ted Unangst <tedu@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+#include <sys/types.h>
+
+#include <limits.h>
+#include <login_cap.h>
+#include <bsd_auth.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <err.h>
+#include <unistd.h>
+#include <pwd.h>
+#include <grp.h>
+#include <syslog.h>
+
+#include "doas.h"
+
+static void __dead
+usage(void)
+{
+ fprintf(stderr, "usage: doas [-u user] command [args]\n");
+ exit(1);
+}
+
+size_t
+arraylen(const char **arr)
+{
+ size_t cnt = 0;
+ while (*arr) {
+ cnt++;
+ arr++;
+ }
+ return cnt;
+}
+
+static int
+parseuid(const char *s, uid_t *uid)
+{
+ struct passwd *pw;
+ const char *errstr;
+
+ if ((pw = getpwnam(s)) != NULL) {
+ *uid = pw->pw_uid;
+ return 0;
+ }
+ *uid = strtonum(s, 0, UID_MAX, &errstr);
+ if (errstr)
+ return -1;
+ return 0;
+}
+
+static int
+uidcheck(const char *s, uid_t desired)
+{
+ uid_t uid;
+
+ if (parseuid(s, &uid) != 0)
+ return -1;
+ if (uid != desired)
+ return -1;
+ return 0;
+}
+
+static gid_t
+strtogid(const char *s)
+{
+ struct group *gr;
+ const char *errstr;
+ gid_t gid;
+
+ if ((gr = getgrnam(s)) != NULL)
+ return gr->gr_gid;
+ gid = strtonum(s, 0, GID_MAX, &errstr);
+ if (errstr)
+ return -1;
+ return gid;
+}
+
+static int
+match(uid_t uid, gid_t *groups, int ngroups, uid_t target, const char *cmd,
+ struct rule *r)
+{
+ int i;
+
+ if (r->ident[0] == ':') {
+ gid_t rgid = strtogid(r->ident + 1);
+ if (rgid == -1)
+ return 0;
+ for (i = 0; i < ngroups; i++) {
+ if (rgid == groups[i])
+ break;
+ }
+ if (i == ngroups)
+ return 0;
+ } else {
+ if (uidcheck(r->ident, uid) != 0)
+ return 0;
+ }
+ if (r->target && uidcheck(r->target, target) != 0)
+ return 0;
+ if (r->cmd && strcmp(r->cmd, cmd) != 0)
+ return 0;
+ return 1;
+}
+
+static int
+permit(uid_t uid, gid_t *groups, int ngroups, struct rule **lastr,
+ uid_t target, const char *cmd)
+{
+ int i;
+
+ *lastr = NULL;
+ for (i = 0; i < nrules; i++) {
+ if (match(uid, groups, ngroups, target, cmd, rules[i]))
+ *lastr = rules[i];
+ }
+ if (!*lastr)
+ return 0;
+ return (*lastr)->action == PERMIT;
+}
+
+static void
+parseconfig(const char *filename)
+{
+ extern FILE *yyfp;
+ extern int yyparse(void);
+
+ yyfp = fopen(filename, "r");
+ if (!yyfp) {
+ fprintf(stderr, "doas is not enabled.\n");
+ exit(1);
+ }
+ yyparse();
+ fclose(yyfp);
+}
+
+static int
+copyenvhelper(const char **oldenvp, const char **safeset, int nsafe, char **envp, int ei)
+{
+ int i;
+ for (i = 0; i < nsafe; i++) {
+ const char **oe = oldenvp;
+ while (*oe) {
+ size_t len = strlen(safeset[i]);
+ if (strncmp(*oe, safeset[i], len) == 0 &&
+ (*oe)[len] == '=') {
+ if (!(envp[ei++] = strdup(*oe)))
+ err(1, "strdup");
+ break;
+ }
+ oe++;
+ }
+ }
+ return ei;
+}
+
+static char **
+copyenv(const char **oldenvp, struct rule *rule)
+{
+ const char *safeset[] = {
+ "DISPLAY", "HOME", "LOGNAME", "MAIL", "SHELL",
+ "PATH", "TERM", "USER", "USERNAME",
+ NULL,
+ };
+ int nsafe;
+ int nextras = 0;
+ char **envp;
+ const char **extra;
+ int ei;
+ int i, j;
+
+ if ((rule->options & KEEPENV) && !rule->envlist) {
+ j = arraylen(oldenvp);
+ envp = reallocarray(NULL, j + 1, sizeof(char *));
+ for (i = 0; i < j; i++) {
+ if (!(envp[i] = strdup(oldenvp[i])))
+ err(1, "strdup");
+ }
+ envp[i] = NULL;
+ return envp;
+ }
+
+ nsafe = arraylen(safeset);
+ if ((extra = rule->envlist)) {
+ nextras = arraylen(extra);
+ for (i = 0; i < nsafe; i++) {
+ for (j = 0; j < nextras; j++) {
+ if (strcmp(extra[j], safeset[i]) == 0) {
+ extra[j--] = extra[nextras--];
+ extra[nextras] = NULL;
+ }
+ }
+ }
+ }
+
+ envp = reallocarray(NULL, nsafe + nextras + 1, sizeof(char *));
+ if (!envp)
+ err(1, "can't allocate new environment");
+
+ ei = 0;
+ ei = copyenvhelper(oldenvp, safeset, nsafe, envp, ei);
+ ei = copyenvhelper(oldenvp, rule->envlist, nextras, envp, ei);
+ envp[ei] = NULL;
+
+ return envp;
+}
+
+static void __dead
+fail(void)
+{
+ const char *msgs[] = {
+ "No lollygagging!",
+ "Better luck next time.",
+ "PEBKAC detected.",
+ "That's what happens when you're lazy.",
+ "It is clear that this has not been thought through.",
+ "That's the most ridiculous thing I've heard in the last two or three minutes!",
+ "No sane people allowed here. Go home.",
+ "I would explain, but I am too drunk.",
+ "You're not allowed to have an opinion.",
+ "Complaint forms are handled in another department.",
+ };
+ const char *m;
+
+ m = msgs[arc4random_uniform(sizeof(msgs) / sizeof(msgs[0]))];
+ fprintf(stderr, m);
+ fprintf(stderr, "\n");
+ exit(1);
+}
+
+int
+main(int argc, char **argv, char **envp)
+{
+ char cmdline[1024];
+ char myname[32];
+ uid_t uid, target = 0;
+ gid_t groups[NGROUPS_MAX + 1];
+ int ngroups;
+ struct passwd *pw;
+ struct rule *rule;
+ const char *cmd;
+ int i, ch;
+ const char *safepath = "/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin";
+
+ parseconfig("/etc/doas.conf");
+
+ while ((ch = getopt(argc, argv, "u:")) != -1) {
+ switch (ch) {
+ case 'u':
+ if (parseuid(optarg, &target) != 0)
+ errx(1, "unknown user");
+ break;
+ default:
+ usage();
+ break;
+ }
+ }
+ argv += optind;
+ argc -= optind;
+
+ if (!argc)
+ usage();
+
+ cmd = argv[0];
+ strlcpy(cmdline, argv[0], sizeof(cmdline));
+ for (i = 1; i < argc; i++) {
+ strlcat(cmdline, " ", sizeof(cmdline));
+ strlcat(cmdline, argv[i], sizeof(cmdline));
+ }
+
+ uid = getuid();
+ pw = getpwuid(uid);
+ if (!pw)
+ err(1, "getpwuid failed");
+ strlcpy(myname, pw->pw_name, sizeof(myname));
+ ngroups = getgroups(NGROUPS_MAX, groups);
+ if (ngroups == -1)
+ err(1, "can't get groups");
+ groups[ngroups++] = getgid();
+
+ if (!permit(uid, groups, ngroups, &rule, target, cmd)) {
+ syslog(LOG_AUTHPRIV | LOG_NOTICE, "failed command for %s: %s", myname, cmdline);
+ fail();
+ }
+
+ if (!(rule->options & NOPASS)) {
+ if (!auth_userokay(myname, NULL, NULL, NULL)) {
+ syslog(LOG_AUTHPRIV | LOG_NOTICE, "failed password for %s", myname);
+ fail();
+ }
+ }
+ envp = copyenv((const char **)envp, rule);
+
+ pw = getpwuid(target);
+ if (!pw)
+ errx(1, "no passwd entry for target");
+ if (setusercontext(NULL, pw, target, LOGIN_SETGROUP |
+ LOGIN_SETPRIORITY | LOGIN_SETRESOURCES | LOGIN_SETUMASK |
+ LOGIN_SETUSER) != 0)
+ errx(1, "failed to set user context for target");
+
+ syslog(LOG_AUTHPRIV | LOG_INFO, "%s ran command as %s: %s", myname, pw->pw_name, cmdline);
+ setenv("PATH", safepath, 1);
+ execvpe(cmd, argv, envp);
+ err(1, "%s", cmd);
+}
diff --git a/doas.conf.5 b/doas.conf.5
new file mode 100644
index 0000000..3f25bd1
--- /dev/null
+++ b/doas.conf.5
@@ -0,0 +1,70 @@
+.\" $OpenBSD$
+.\"
+.\"Copyright (c) 2015 Ted Unangst <tedu@openbsd.org>
+.\"
+.\"Permission to use, copy, modify, and distribute this software for any
+.\"purpose with or without fee is hereby granted, provided that the above
+.\"copyright notice and this permission notice appear in all copies.
+.\"
+.\"THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+.\"WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+.\"MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+.\"ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+.\"WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+.\"ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+.\"OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+.Dd $Mdocdate$
+.Dt DOAS.CONF 5
+.Os
+.Sh NAME
+.Nm doas.conf
+.Nd doas configuration file
+.Sh DESCRIPTION
+The
+.Xr doas 1
+utility executes commands as other users according to the rules
+in the
+.Nm
+configuration file.
+.Pp
+The rules have the following format:
+.Bd -literal -offset indent
+permit|deny [options] [identity] [as target] [cmd command]
+.Ed
+.Pp
+Rules consist of the following parts:
+.Bl -tag -width tenletters
+.It permit|deny
+The action to be taken if this rule matches.
+.It options
+Options are:
+.Bl -tag -width tenletters
+.It nopass
+The user is not required to enter a password.
+.It keepenv
+The user's environment is maintained.
+The default is to reset the environment.
+.It keepenv { [variable names] }
+Reset the environment, but keep the specified variables.
+.El
+.It identity
+The username to match.
+Groups may be specified by prepending a colon (:).
+Numeric IDs are also accepted.
+.It as target
+The target user the running user is allowed to run the command as.
+The default is root.
+.It cmd command
+The command the user is allowed or denied to run.
+The default is all commands.
+Be advised that it's best to specify absolute paths.
+.El
+.Pp
+The last matching rule determines the action taken.
+.Sh EXAMPLES
+The following example permits users in group wheel to exeucte commands as root,
+and additionally permits tedu to run procmap as root without a password.
+.Bd -literal -offset indent
+permit :wheel
+permit nopass tedu cmd /usr/sbin/procmap
+.Ed
diff --git a/doas.h b/doas.h
new file mode 100644
index 0000000..b6d0275
--- /dev/null
+++ b/doas.h
@@ -0,0 +1,20 @@
+
+struct rule {
+ int action;
+ int options;
+ const char *ident;
+ const char *target;
+ const char *cmd;
+ const char **envlist;
+};
+
+extern struct rule **rules;
+extern int nrules, maxrules;
+
+size_t arraylen(const char **);
+
+#define PERMIT 1
+#define DENY 2
+
+#define NOPASS 0x1
+#define KEEPENV 0x2
diff --git a/parse.y b/parse.y
new file mode 100644
index 0000000..4729b4e
--- /dev/null
+++ b/parse.y
@@ -0,0 +1,210 @@
+/* $OpenBSD$ */
+/*
+ * Copyright (c) 2015 Ted Unangst <tedu@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+%{
+#include <sys/types.h>
+#include <ctype.h>
+#include <unistd.h>
+#include <stdint.h>
+#include <stdarg.h>
+#include <stdio.h>
+#include <string.h>
+#include <err.h>
+
+#include "doas.h"
+
+typedef struct {
+ union {
+ struct {
+ int action;
+ int options;
+ const char **envlist;
+ };
+ const char *str;
+ };
+} yystype;
+#define YYSTYPE yystype
+
+FILE *yyfp;
+
+struct rule **rules;
+int nrules, maxrules;
+
+%}
+
+%token TPERMIT TDENY TAS TCMD
+%token TNOPASS TKEEPENV
+%token TSTRING
+
+%%
+
+grammar: /* empty */
+ | grammar '\n'
+ | grammar rule '\n'
+ ;
+
+rule: action ident target cmd {
+ struct rule *r;
+ r = calloc(1, sizeof(*r));
+ r->action = $1.action;
+ r->options = $1.options;
+ r->envlist = $1.envlist;
+ r->ident = $2.str;
+ r->target = $3.str;
+ r->cmd = $4.str;
+ if (nrules == maxrules) {
+ if (maxrules == 0)
+ maxrules = 63;
+ else
+ maxrules *= 2;
+ if (!(rules = reallocarray(rules, maxrules, sizeof(*rules))))
+ errx(1, "can't allocate rules");
+ }
+ rules[nrules++] = r;
+ } ;
+
+action: TPERMIT options {
+ $$.action = PERMIT;
+ $$.options = $2.options;
+ $$.envlist = $2.envlist;
+ } | TDENY {
+ $$.action = DENY;
+ } ;
+
+options: /* none */
+ | options option {
+ $$.options = $1.options | $2.options;
+ $$.envlist = $1.envlist;
+ if ($2.envlist) {
+ if ($$.envlist)
+ errx(1, "can't have two keepenv sections");
+ else
+ $$.envlist = $2.envlist;
+ }
+ } ;
+option: TNOPASS {
+ $$.options = NOPASS;
+ } | TKEEPENV {
+ $$.options = KEEPENV;
+ } | TKEEPENV '{' envlist '}' {
+ $$.options = KEEPENV;
+ $$.envlist = $3.envlist;
+ } ;
+
+envlist: /* empty */ {
+ if (!($$.envlist = calloc(1, sizeof(char *))))
+ errx(1, "can't allocate envlist");
+ } | envlist TSTRING {
+ int nenv = arraylen($1.envlist);
+ if (!($$.envlist = reallocarray($1.envlist, nenv + 2, sizeof(char *))))
+ errx(1, "can't allocate envlist");
+ $$.envlist[nenv] = $2.str;
+ $$.envlist[nenv + 1] = NULL;
+ }
+
+
+ident: TSTRING {
+ $$.str = $1.str;
+ } ;
+
+target: /* optional */ {
+ $$.str = NULL;
+ } | TAS TSTRING {
+ $$.str = $2.str;
+ } ;
+
+cmd: /* optional */ {
+ $$.str = NULL;
+ } | TCMD TSTRING {
+ $$.str = $2.str;
+ } ;
+
+%%
+
+void
+yyerror(const char *fmt, ...)
+{
+ va_list va;
+
+ va_start(va, fmt);
+ fprintf(stderr, "doas: ");
+ vfprintf(stderr, fmt, va);
+ fprintf(stderr, "\n");
+ va_end(va);
+ exit(1);
+}
+
+struct keyword {
+ const char *word;
+ int token;
+} keywords[] = {
+ { "deny", TDENY },
+ { "permit", TPERMIT },
+ { "as", TAS },
+ { "cmd", TCMD },
+ { "nopass", TNOPASS },
+ { "keepenv", TKEEPENV },
+};
+
+int
+yylex(void)
+{
+ char buf[1024], *ebuf, *p, *str;
+ int i, c;
+
+ p = buf;
+ ebuf = buf + sizeof(buf);
+ while ((c = getc(yyfp)) == ' ' || c == '\t')
+ ; /* skip spaces */
+ switch (c) {
+ case '\n':
+ case '{':
+ case '}':
+ return c;
+ case '#':
+ while ((c = getc(yyfp)) != '\n' && c != EOF)
+ ; /* skip comments */
+ if (c == EOF)
+ return 0;
+ return c;
+ case EOF:
+ return 0;
+ case ':':
+ *p++ = c;
+ c = getc(yyfp);
+ break;
+ default:
+ break;
+ }
+ while (isalnum(c)) {
+ *p++ = c;
+ if (p == ebuf)
+ yyerror("too much stuff");
+ c = getc(yyfp);
+ }
+ *p = 0;
+ if (c != EOF)
+ ungetc(c, yyfp);
+ for (i = 0; i < sizeof(keywords) / sizeof(keywords[0]); i++) {
+ if (strcmp(buf, keywords[i].word) == 0)
+ return keywords[i].token;
+ }
+ if ((str = strdup(buf)) == NULL)
+ err(1, "strdup");
+ yylval.str = str;
+ return TSTRING;
+}