Attachment 10899 Details for Bug 54015

[patch] 0001-s3-smbd-Fix-mkdir-race-condition-allows-share-escape.patch

0001-s3-smbd-Fix-mkdir-race-condition-allows-share-escape.patch (text/plain), 2.64 KB, created by Arvid Requate on 2022-01-09 17:02 CET

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Creator: Arvid Requate

Created: 2022-01-09 17:02 CET

Size: 2.64 KB

patch

obsolete

>From 3e9d145e45ae4ebe1f200069414d60fea464ff55 Mon Sep 17 00:00:00 2001
>From: Jeremy Allison <jra@samba.org>
>Date: Tue, 21 Sep 2021 17:38:27 -0700
>Subject: [PATCH] s3: smbd: Fix mkdir race condition allows share escape in
> Samba 4.13.X and below: CVE-2021-43566
>
>BUG: https://bugzilla.samba.org/show_bug.cgi?id=13979
>
>Signed-off-by: Jeremy Allison <jra@samba.org>
>---
> source3/smbd/open.c | 43 ++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 40 insertions(+), 3 deletions(-)
>
>diff --git a/source3/smbd/open.c b/source3/smbd/open.c
>index ef158657684..17163e9ddea 100644
>--- a/source3/smbd/open.c
>+++ b/source3/smbd/open.c
>@@ -4255,6 +4255,8 @@ static NTSTATUS mkdir_internal(connection_struct *conn,
> 	uint32_t access_mask = SEC_DIR_ADD_SUBDIR;
> 	int ret;
> 	bool ok;
>+	struct smb_filename *oldwd_fname = NULL;
>+	struct smb_filename *smb_fname_rel = NULL;
> 
> 	SMB_ASSERT(*dirfsp == conn->cwd_fsp);
> 
>@@ -4267,7 +4269,7 @@ static NTSTATUS mkdir_internal(connection_struct *conn,
> 	ok = parent_smb_fname(talloc_tos(),
> 			      smb_dname,
> 			      &parent_dir_fname,
>-			      NULL);
>+			      &smb_fname_rel);
> 	if (!ok) {
> 		return NT_STATUS_NO_MEMORY;
> 	}
>@@ -4295,14 +4297,40 @@ static NTSTATUS mkdir_internal(connection_struct *conn,
> 		return status;
> 	}
> 
>+	oldwd_fname = vfs_GetWd(talloc_tos(), conn);
>+	if (oldwd_fname == NULL) {
>+		return NT_STATUS_NO_MEMORY;
>+	}
>+
>+	/* Pin parent directory in place. */
>+	if (vfs_ChDir(conn, parent_dir_fname) == -1) {
>+		status = map_nt_error_from_unix(errno);
>+		TALLOC_FREE(oldwd_fname);
>+		return status;
>+	}
>+
>+	/* Ensure the relative path is below the share. */
>+	status = check_reduced_name(conn, parent_dir_fname, smb_fname_rel);
>+	if (!NT_STATUS_IS_OK(status)) {
>+		goto need_chdir_err;
>+	}
>+
> 	ret = SMB_VFS_MKDIRAT(conn,
> 			      *dirfsp,
>-			      smb_dname,
>+			      smb_fname_rel,
> 			      mode);
> 	if (ret != 0) {
>-		return map_nt_error_from_unix(errno);
>+		status = map_nt_error_from_unix(errno);
>+		goto need_chdir_err;
> 	}
> 
>+	/* Return to share $cwd. */
>+	ret = vfs_ChDir(conn, oldwd_fname);
>+	if (ret == -1) {
>+		smb_panic("unable to get back to old directory\n");
>+	}
>+	TALLOC_FREE(oldwd_fname);
>+
> 	/* Ensure we're checking for a symlink here.... */
> 	/* We don't want to get caught by a symlink racer. */
> 
>@@ -4378,6 +4406,15 @@ static NTSTATUS mkdir_internal(connection_struct *conn,
> 		     smb_dname->base_name);
> 
> 	return NT_STATUS_OK;
>+
>+  need_chdir_err:
>+
>+	ret = vfs_ChDir(conn, oldwd_fname);
>+	if (ret == -1) {
>+		smb_panic("unable to get back to old directory\n");
>+	}
>+	TALLOC_FREE(oldwd_fname);
>+	return status;
> }
> 
> /****************************************************************************
>-- 
>2.30.2
>

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