From 62d0cd17069d26ef8cb594c92118628f26670253 Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Tue, 27 Aug 2024 22:20:22 -0300
Subject: [PATCH] auth: AUTH_ACTIONS_FILESYSTEM_RENAME

---
 kernel-src/fs/vfs.c              | 16 +++++++++++++-
 kernel-src/include/kernel/auth.h |  1 +
 kernel-src/sys/defaultauth.c     | 38 ++++++++++++++++++++------------
 3 files changed, 40 insertions(+), 15 deletions(-)

diff --git a/kernel-src/fs/vfs.c b/kernel-src/fs/vfs.c
index 602f9a8b..99df5cde 100644
--- a/kernel-src/fs/vfs.c
+++ b/kernel-src/fs/vfs.c
@@ -563,7 +563,21 @@ int vfs_rename(vnode_t *srcref, char *srcpath, vnode_t *dstref, char *dstpath, i
 	if (src != dst)
 		VOP_LOCK(src); // lock it again for the rename if they arent the same
 
-	if (0)
+	// check if we can rename the old file
+	err = auth_filesystem_check(getcred(), AUTH_ACTIONS_FILESYSTEM_RENAME, src, srcdir) ? EACCES : 0;
+	if (err)
+		goto cleanup_child;
+
+	if (dst) {
+		// and if we have a file, check if we can replace it
+		err = auth_filesystem_check(getcred(), AUTH_ACTIONS_FILESYSTEM_UNLINK, dst, dstdir) ? EACCES : 0;
+		if (err)
+			goto cleanup_child;
+	}
+
+	// and if we can then write the new link to the directory
+	err = VOP_ACCESS(dstdir, V_ACCESS_WRITE, getcred());
+	if (err)
 		goto cleanup_child;
 
 	err = VOP_RENAME(srcdir, src, srccomp, dstdir, dst, dstcomp, flags);
diff --git a/kernel-src/include/kernel/auth.h b/kernel-src/include/kernel/auth.h
index f082f094..9677d023 100644
--- a/kernel-src/include/kernel/auth.h
+++ b/kernel-src/include/kernel/auth.h
@@ -26,6 +26,7 @@
 #define AUTH_ACTIONS_FILESYSTEM_SETATTR 8
 #define AUTH_ACTIONS_FILESYSTEM_MOUNT 	16
 #define AUTH_ACTIONS_FILESYSTEM_UNLINK	32
+#define AUTH_ACTIONS_FILESYSTEM_RENAME	64
 
 #define AUTH_ACTIONS_CRED_SETRESUID	1
 #define AUTH_ACTIONS_CRED_SETRESGID	2
diff --git a/kernel-src/sys/defaultauth.c b/kernel-src/sys/defaultauth.c
index 9f2f0346..a737e426 100644
--- a/kernel-src/sys/defaultauth.c
+++ b/kernel-src/sys/defaultauth.c
@@ -8,6 +8,19 @@
 			goto done; \
 	}
 
+static inline bool writecheck(cred_t *cred, vattr_t *attr) {
+	if (CRED_IS_ESU(cred))
+		return true;
+	else if (attr->uid == cred->euid && (attr->mode & V_ATTR_MODE_USER_WRITE))
+		return true;
+	else if (attr->uid != cred->euid && attr->gid == cred->egid && (attr->mode & V_ATTR_MODE_GROUP_WRITE))
+		return true;
+	else if (attr->uid != cred->euid && attr->gid != cred->egid && (attr->mode & V_ATTR_MODE_OTHERS_WRITE))
+		return true;
+	else
+		return false;
+}
+
 static int filesystem(cred_t *cred, int actions, void *arg0, void *arg1, void *arg2) {
 	vnode_t *vnode = arg0; // expected locked
 	vnode_t *dirvnode = arg1; // expected locked
@@ -21,13 +34,7 @@ static int filesystem(cred_t *cred, int actions, void *arg0, void *arg1, void *a
 
 	int weight = 0;
 	if (actions & AUTH_ACTIONS_FILESYSTEM_WRITE) {
-		if (CRED_IS_ESU(cred))
-			weight += 1;
-		else if (attr.uid == cred->euid && (attr.mode & V_ATTR_MODE_USER_WRITE))
-			weight += 1;
-		else if (attr.uid != cred->euid && attr.gid == cred->egid && (attr.mode & V_ATTR_MODE_GROUP_WRITE))
-			weight += 1;
-		else if (attr.uid != cred->euid && attr.gid != cred->egid && (attr.mode & V_ATTR_MODE_OTHERS_WRITE))
+		if (writecheck(cred, &attr))
 			weight += 1;
 		else
 			return AUTH_DECISION_DENY;
@@ -86,23 +93,24 @@ static int filesystem(cred_t *cred, int actions, void *arg0, void *arg1, void *a
 		DONE_CHECK(actions);
 	}
 
-	if (actions & AUTH_ACTIONS_FILESYSTEM_UNLINK) {
+	if (actions & (AUTH_ACTIONS_FILESYSTEM_UNLINK | AUTH_ACTIONS_FILESYSTEM_RENAME)) {
 		__assert(dirvnode);
 
 		bool dosticky = false;
 		if (CRED_IS_ESU(cred)) {
 			dosticky = false;
-			weight += 1;
-		} else if (dirattr.uid == cred->euid && (dirattr.mode & V_ATTR_MODE_USER_WRITE)) {
-			dosticky = true;
-		} else if (dirattr.uid != cred->euid && dirattr.gid == cred->egid && (dirattr.mode & V_ATTR_MODE_GROUP_WRITE)) {
-			dosticky = true;
-		} else if (dirattr.uid != cred->euid && dirattr.gid != cred->egid && (dirattr.mode & V_ATTR_MODE_OTHERS_WRITE)) {
+		} else if (writecheck(cred, &dirattr)) {
 			dosticky = true;
 		} else {
 			return AUTH_DECISION_DENY;
 		}
 
+		// when renaming, we need to make sure we can also change the .. entry for the renamed
+		// directory when it is a directory
+		if ((actions & AUTH_ACTIONS_FILESYSTEM_RENAME) && vnode->type == V_TYPE_DIR && writecheck(cred, &attr) == false) {
+			return AUTH_DECISION_DENY;
+		}
+
 		if (dosticky && (dirattr.mode & V_ATTR_MODE_STICKY)) {
 			// sticky directory, file can only be unlinked if:
 			// - user requesting deletion is root (already checked for)
@@ -115,6 +123,8 @@ static int filesystem(cred_t *cred, int actions, void *arg0, void *arg1, void *a
 				weight += 1;
 			else
 				return AUTH_DECISION_DENY;
+		} else {
+			weight += 1;
 		}
 
 		DONE_CHECK(actions);