1 files changed, 513 insertions, 0 deletions
diff --git a/source3/smbd/sec_ctx.c b/source3/smbd/sec_ctx.c
new file mode 100644
index 0000000..56fdf1f
--- /dev/null
+++ b/source3/smbd/sec_ctx.c
@@ -0,0 +1,513 @@
+/* 
+   Unix SMB/CIFS implementation.
+   uid/user handling
+   Copyright (C) Tim Potter 2000
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "includes.h"
+#include "system/passwd.h"
+#include "smbd/smbd.h"
+#include "smbd/globals.h"
+#include "libcli/security/security_token.h"
+#include "auth.h"
+#include "smbprofile.h"
+#include "../lib/util/setid.h"
+
+extern struct current_user current_user;
+
+/****************************************************************************
+ Are two UNIX tokens equal ?
+****************************************************************************/
+
+bool unix_token_equal(const struct security_unix_token *t1, const struct security_unix_token *t2)
+{
+	if (t1->uid != t2->uid || t1->gid != t2->gid ||
+			t1->ngroups != t2->ngroups) {
+		return false;
+	}
+	if (memcmp(t1->groups, t2->groups,
+			t1->ngroups*sizeof(gid_t)) != 0) {
+		return false;
+	}
+	return true;
+}
+
+/****************************************************************************
+ Become the specified uid.
+****************************************************************************/
+
+static bool become_uid(uid_t uid)
+{
+	/* Check for dodgy uid values */
+
+	if (uid == (uid_t)-1 || 
+	    ((sizeof(uid_t) == 2) && (uid == (uid_t)65535))) {
+		if (!become_uid_done) {
+			DEBUG(1,("WARNING: using uid %d is a security risk\n",
+				 (int)uid));
+			become_uid_done = true;
+		}
+	}
+
+	/* Set effective user id */
+
+	set_effective_uid(uid);
+
+	return True;
+}
+
+/****************************************************************************
+ Become the specified gid.
+****************************************************************************/
+
+static bool become_gid(gid_t gid)
+{
+	/* Check for dodgy gid values */
+
+	if (gid == (gid_t)-1 || ((sizeof(gid_t) == 2) && 
+				 (gid == (gid_t)65535))) {
+		if (!become_gid_done) {
+			DEBUG(1,("WARNING: using gid %d is a security risk\n",
+				 (int)gid));  
+			become_gid_done = true;
+		}
+	}
+
+	/* Set effective group id */
+
+	set_effective_gid(gid);
+	return True;
+}
+
+/****************************************************************************
+ Drop back to root privileges in order to change to another user.
+****************************************************************************/
+
+static void gain_root(void)
+{
+	if (non_root_mode()) {
+		return;
+	}
+
+	if (geteuid() != 0) {
+		set_effective_uid(0);
+
+		if (geteuid() != 0) {
+			DEBUG(0,
+			      ("Warning: You appear to have a trapdoor "
+			       "uid system\n"));
+		}
+	}
+
+	if (getegid() != 0) {
+		set_effective_gid(0);
+
+		if (getegid() != 0) {
+			DEBUG(0,
+			      ("Warning: You appear to have a trapdoor "
+			       "gid system\n"));
+		}
+	}
+}
+
+/****************************************************************************
+ Get the list of current groups.
+****************************************************************************/
+
+static int get_current_groups(gid_t gid, uint32_t *p_ngroups, gid_t **p_groups)
+{
+	int i;
+	int ngroups;
+	gid_t *groups = NULL;
+
+	(*p_ngroups) = 0;
+	(*p_groups) = NULL;
+
+	/* this looks a little strange, but is needed to cope with
+	   systems that put the current egid in the group list
+	   returned from getgroups() (tridge) */
+	save_re_gid();
+	set_effective_gid(gid);
+	samba_setgid(gid);
+
+	ngroups = sys_getgroups(0, NULL);
+	if (ngroups <= 0) {
+		goto fail;
+	}
+
+	if((groups = SMB_MALLOC_ARRAY(gid_t, ngroups+1)) == NULL) {
+		DEBUG(0,("setup_groups malloc fail !\n"));
+		goto fail;
+	}
+
+	if ((ngroups = sys_getgroups(ngroups,groups)) == -1) {
+		goto fail;
+	}
+
+	restore_re_gid();
+
+	(*p_ngroups) = ngroups;
+	(*p_groups) = groups;
+
+	DEBUG( 4, ( "get_current_groups: user is in %u groups: ", ngroups));
+	for (i = 0; i < ngroups; i++ ) {
+		DEBUG( 4, ( "%s%d", (i ? ", " : ""), (int)groups[i] ) );
+	}
+	DEBUG( 4, ( "\n" ) );
+
+	return ngroups;
+
+fail:
+	SAFE_FREE(groups);
+	restore_re_gid();
+	return -1;
+}
+
+/****************************************************************************
+ Create a new security context on the stack.  It is the same as the old
+ one.  User changes are done using the set_sec_ctx() function.
+****************************************************************************/
+
+bool push_sec_ctx(void)
+{
+	struct sec_ctx *ctx_p;
+
+	START_PROFILE(push_sec_ctx);
+
+	/* Check we don't overflow our stack */
+
+	if (sec_ctx_stack_ndx == MAX_SEC_CTX_DEPTH) {
+		DEBUG(0, ("Security context stack overflow!\n"));
+		smb_panic("Security context stack overflow!");
+	}
+
+	/* Store previous user context */
+
+	sec_ctx_stack_ndx++;
+
+	ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
+
+	ctx_p->ut.uid = geteuid();
+	ctx_p->ut.gid = getegid();
+
+ 	DEBUG(4, ("push_sec_ctx(%u, %u) : sec_ctx_stack_ndx = %d\n", 
+ 		  (unsigned int)ctx_p->ut.uid, (unsigned int)ctx_p->ut.gid, sec_ctx_stack_ndx ));
+
+	ctx_p->token = dup_nt_token(NULL,
+				    sec_ctx_stack[sec_ctx_stack_ndx-1].token);
+
+	ctx_p->ut.ngroups = sys_getgroups(0, NULL);
+
+	if (ctx_p->ut.ngroups != 0) {
+		if (!(ctx_p->ut.groups = SMB_MALLOC_ARRAY(gid_t, ctx_p->ut.ngroups))) {
+			DEBUG(0, ("Out of memory in push_sec_ctx()\n"));
+			TALLOC_FREE(ctx_p->token);
+			return False;
+		}
+
+		sys_getgroups(ctx_p->ut.ngroups, ctx_p->ut.groups);
+	} else {
+		ctx_p->ut.groups = NULL;
+	}
+
+	END_PROFILE(push_sec_ctx);
+
+	return True;
+}
+
+#ifndef HAVE_DARWIN_INITGROUPS
+/****************************************************************************
+ Become the specified uid and gid.
+****************************************************************************/
+
+static bool become_id(uid_t uid, gid_t gid)
+{
+	return become_gid(gid) && become_uid(uid);
+}
+
+/****************************************************************************
+ Change UNIX security context. Calls panic if not successful so no return value.
+****************************************************************************/
+/* Normal credential switch path. */
+
+static void set_unix_security_ctx(uid_t uid, gid_t gid, int ngroups, gid_t *groups)
+{
+	/* Start context switch */
+	gain_root();
+#ifdef HAVE_SETGROUPS
+	if (sys_setgroups(gid, ngroups, groups) != 0 && !non_root_mode()) {
+		smb_panic("sys_setgroups failed");
+	}
+#endif
+	become_id(uid, gid);
+	/* end context switch */
+}
+
+#else /* HAVE_DARWIN_INITGROUPS */
+
+/* The Darwin groups implementation is a little unusual. The list of
+* groups in the kernel credential is not exhaustive, but more like
+* a cache. The full group list is held in userspace and checked
+* dynamically.
+*
+* This is an optional mechanism, and setgroups(2) opts out
+* of it. That is, if you call setgroups, then the list of groups you
+* set are the only groups that are ever checked. This is not what we
+* want. We want to opt in to the dynamic resolution mechanism, so we
+* need to specify the uid of the user whose group list (cache) we are
+* setting.
+*
+* The Darwin rules are:
+*  1. Thou shalt setegid, initgroups and seteuid IN THAT ORDER
+*  2. Thou shalt not pass more that NGROUPS_MAX to initgroups
+*  3. Thou shalt leave the first entry in the groups list well alone
+*/
+
+#include <sys/syscall.h>
+
+static void set_unix_security_ctx(uid_t uid, gid_t gid, int ngroups, gid_t *groups)
+{
+	int max = NGROUPS_MAX;
+
+	/* Start context switch */
+	gain_root();
+
+	become_gid(gid);
+
+
+	if (syscall(SYS_initgroups, (ngroups > max) ? max : ngroups,
+			groups, uid) == -1 && !non_root_mode()) {
+		DEBUG(0, ("WARNING: failed to set group list "
+			"(%d groups) for UID %d: %s\n",
+			ngroups, uid, strerror(errno)));
+		smb_panic("sys_setgroups failed");
+	}
+
+	become_uid(uid);
+	/* end context switch */
+}
+
+#endif /* HAVE_DARWIN_INITGROUPS */
+
+/****************************************************************************
+ Set the current security context to a given user.
+****************************************************************************/
+
+static void set_sec_ctx_internal(uid_t uid, gid_t gid,
+				 int ngroups, gid_t *groups,
+				 const struct security_token *token)
+{
+	struct sec_ctx *ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
+
+	/* Set the security context */
+
+	DEBUG(4, ("setting sec ctx (%u, %u) - sec_ctx_stack_ndx = %d\n", 
+		(unsigned int)uid, (unsigned int)gid, sec_ctx_stack_ndx));
+
+	security_token_debug(DBGC_CLASS, 5, token);
+	debug_unix_user_token(DBGC_CLASS, 5, uid, gid, ngroups, groups);
+
+	/* Change uid, gid and supplementary group list. */
+	set_unix_security_ctx(uid, gid, ngroups, groups);
+
+	ctx_p->ut.ngroups = ngroups;
+
+	SAFE_FREE(ctx_p->ut.groups);
+	if (token && (token == ctx_p->token)) {
+		smb_panic("DUPLICATE_TOKEN");
+	}
+
+	TALLOC_FREE(ctx_p->token);
+
+	if (ngroups) {
+		ctx_p->ut.groups = (gid_t *)smb_xmemdup(groups,
+						        sizeof(gid_t) * ngroups);
+	} else {
+		ctx_p->ut.groups = NULL;
+	}
+
+	if (token) {
+		ctx_p->token = dup_nt_token(NULL, token);
+		if (!ctx_p->token) {
+			smb_panic("dup_nt_token failed");
+		}
+	} else {
+		ctx_p->token = NULL;
+	}
+
+	ctx_p->ut.uid = uid;
+	ctx_p->ut.gid = gid;
+
+	/* Update current_user stuff */
+
+	current_user.ut.uid = uid;
+	current_user.ut.gid = gid;
+	current_user.ut.ngroups = ngroups;
+	current_user.ut.groups = groups;
+	current_user.nt_user_token = ctx_p->token;
+
+	/*
+	 * Delete any ChDir cache. We can't assume
+	 * the new uid has access to current working
+	 * directory.
+	 * BUG: https://bugzilla.samba.org/show_bug.cgi?id=14682
+	 */
+	SAFE_FREE(LastDir);
+}
+
+void set_sec_ctx(uid_t uid, gid_t gid, int ngroups, gid_t *groups, const struct security_token *token)
+{
+	START_PROFILE(set_sec_ctx);
+	set_sec_ctx_internal(uid, gid, ngroups, groups, token);
+	END_PROFILE(set_sec_ctx);
+}
+
+/****************************************************************************
+ Become root context.
+****************************************************************************/
+
+void set_root_sec_ctx(void)
+{
+	/* May need to worry about supplementary groups at some stage */
+
+	START_PROFILE(set_root_sec_ctx);
+	set_sec_ctx_internal(0, 0, 0, NULL, NULL);
+	END_PROFILE(set_root_sec_ctx);
+}
+
+/****************************************************************************
+ Pop a security context from the stack.
+****************************************************************************/
+
+bool pop_sec_ctx(void)
+{
+	struct sec_ctx *ctx_p;
+	struct sec_ctx *prev_ctx_p;
+
+	START_PROFILE(pop_sec_ctx);
+
+	/* Check for stack underflow */
+
+	if (sec_ctx_stack_ndx == 0) {
+		DEBUG(0, ("Security context stack underflow!\n"));
+		smb_panic("Security context stack underflow!");
+	}
+
+	ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
+
+	/* Clear previous user info */
+
+	ctx_p->ut.uid = (uid_t)-1;
+	ctx_p->ut.gid = (gid_t)-1;
+
+	SAFE_FREE(ctx_p->ut.groups);
+	ctx_p->ut.ngroups = 0;
+
+	TALLOC_FREE(ctx_p->token);
+
+	/* Pop back previous user */
+
+	sec_ctx_stack_ndx--;
+
+	prev_ctx_p = &sec_ctx_stack[sec_ctx_stack_ndx];
+
+	/* Change uid, gid and supplementary group list. */
+	set_unix_security_ctx(prev_ctx_p->ut.uid,
+			prev_ctx_p->ut.gid,
+			prev_ctx_p->ut.ngroups,
+			prev_ctx_p->ut.groups);
+
+	/* Update current_user stuff */
+
+	current_user.ut.uid = prev_ctx_p->ut.uid;
+	current_user.ut.gid = prev_ctx_p->ut.gid;
+	current_user.ut.ngroups = prev_ctx_p->ut.ngroups;
+	current_user.ut.groups = prev_ctx_p->ut.groups;
+	current_user.nt_user_token = prev_ctx_p->token;
+
+	END_PROFILE(pop_sec_ctx);
+
+	DEBUG(4, ("pop_sec_ctx (%u, %u) - sec_ctx_stack_ndx = %d\n", 
+		(unsigned int)geteuid(), (unsigned int)getegid(), sec_ctx_stack_ndx));
+
+	return True;
+}
+
+/* Initialise the security context system */
+
+void init_sec_ctx(void)
+{
+	int i;
+	struct sec_ctx *ctx_p;
+
+	/* Initialise security context stack */
+
+	memset(sec_ctx_stack, 0, sizeof(struct sec_ctx) * MAX_SEC_CTX_DEPTH);
+
+	for (i = 0; i < MAX_SEC_CTX_DEPTH; i++) {
+		sec_ctx_stack[i].ut.uid = (uid_t)-1;
+		sec_ctx_stack[i].ut.gid = (gid_t)-1;
+	}
+
+	/* Initialise first level of stack.  It is the current context */
+	ctx_p = &sec_ctx_stack[0];
+
+	ctx_p->ut.uid = geteuid();
+	ctx_p->ut.gid = getegid();
+
+	get_current_groups(ctx_p->ut.gid, &ctx_p->ut.ngroups, &ctx_p->ut.groups);
+
+	ctx_p->token = NULL; /* Maps to guest user. */
+
+	/* Initialise current_user global */
+
+	current_user.ut.uid = ctx_p->ut.uid;
+	current_user.ut.gid = ctx_p->ut.gid;
+	current_user.ut.ngroups = ctx_p->ut.ngroups;
+	current_user.ut.groups = ctx_p->ut.groups;
+
+	/* The conn and vuid are usually taken care of by other modules.
+	   We initialise them here. */
+
+	current_user.conn = NULL;
+	current_user.vuid = UID_FIELD_INVALID;
+	current_user.nt_user_token = NULL;
+}
+
+/*************************************************************
+ Called when we're inside a become_root() temporary escalation
+ of privileges and the nt_user_token is NULL. Return the last
+ active token on the context stack. We know there is at least
+ one valid non-NULL token on the stack so panic if we underflow.
+*************************************************************/
+
+const struct security_token *sec_ctx_active_token(void)
+{
+	int stack_index = sec_ctx_stack_ndx;
+	struct sec_ctx *ctx_p = &sec_ctx_stack[stack_index];
+
+	while (ctx_p->token == NULL) {
+		stack_index--;
+		if (stack_index < 0) {
+			DEBUG(0, ("Security context active token "
+				  "stack underflow!\n"));
+			smb_panic("Security context active token "
+				  "stack underflow!");
+		}
+		ctx_p = &sec_ctx_stack[stack_index];
+	}
+	return ctx_p->token;
+}