From 5d4ef6ff0970c93fed49e51a01e63cb67d49d087 Mon Sep 17 00:00:00 2001 From: Jeremy Allison Date: Mon, 27 Mar 2017 10:46:47 -0700 Subject: [PATCH 1/3] s3: smbd: Fix incorrect logic exposed by fix for the security bug 12496 (CVE-2017-2619). In a UNIX filesystem, the names "." and ".." by definition can *never* be symlinks - they are already reserved names. BUG: https://bugzilla.samba.org/show_bug.cgi?id=12721 Signed-off-by: Jeremy Allison Reviewed-by: Uri Simchoni (cherry picked from commit ae17bebd250bdde5614b2ac17e53512f19fe9b68) --- source3/smbd/vfs.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/source3/smbd/vfs.c b/source3/smbd/vfs.c index 4d660122f5a..f084b1d1930 100644 --- a/source3/smbd/vfs.c +++ b/source3/smbd/vfs.c @@ -1291,8 +1291,11 @@ NTSTATUS check_reduced_name(connection_struct *conn, const char *fname) /* fname can't have changed in resolved_path. */ const char *p = &resolved_name[rootdir_len]; - /* *p can be '\0' if fname was "." */ - if (*p == '\0' && ISDOT(fname)) { + /* + * UNIX filesystem semantics, names consisting + * only of "." or ".." CANNOT be symlinks. + */ + if (ISDOT(fname) || ISDOTDOT(fname)) { goto out; } -- 2.12.2.564.g063fe858b8-goog From 71500662d1098d17657b0148a0aa06cd69482c7d Mon Sep 17 00:00:00 2001 From: Jeremy Allison Date: Mon, 27 Mar 2017 17:04:58 -0700 Subject: [PATCH 2/3] s3: smbd: Fix "follow symlink = no" regression part 2. Add an extra paramter to cwd_name to check_reduced_name(). If cwd_name == NULL then fname is a client given path relative to the root path of the share. If cwd_name != NULL then fname is a client given path relative to cwd_name. cwd_name is relative to the root path of the share. Not yet used, logic added in the next commit. BUG: https://bugzilla.samba.org/show_bug.cgi?id=12721 Signed-off-by: Jeremy Allison Reviewed-by: Ralph Boehme (cherry picked from commit 83e30cb48859b412b76572b6a3ba84d8fde167af) --- source3/smbd/filename.c | 2 +- source3/smbd/open.c | 2 +- source3/smbd/proto.h | 4 +++- source3/smbd/vfs.c | 10 +++++++++- 4 files changed, 14 insertions(+), 4 deletions(-) diff --git a/source3/smbd/filename.c b/source3/smbd/filename.c index 3593155ce4e..03773c82403 100644 --- a/source3/smbd/filename.c +++ b/source3/smbd/filename.c @@ -1222,7 +1222,7 @@ NTSTATUS check_name(connection_struct *conn, const char *name) } if (!lp_widelinks(SNUM(conn)) || !lp_follow_symlinks(SNUM(conn))) { - status = check_reduced_name(conn,name); + status = check_reduced_name(conn, NULL, name); if (!NT_STATUS_IS_OK(status)) { DEBUG(5,("check_name: name %s failed with %s\n",name, nt_errstr(status))); diff --git a/source3/smbd/open.c b/source3/smbd/open.c index 84177528511..13aaae3b023 100644 --- a/source3/smbd/open.c +++ b/source3/smbd/open.c @@ -539,7 +539,7 @@ static int non_widelink_open(struct connection_struct *conn, } /* Ensure the relative path is below the share. */ - status = check_reduced_name(conn, final_component); + status = check_reduced_name(conn, parent_dir, final_component); if (!NT_STATUS_IS_OK(status)) { saved_errno = map_errno_from_nt_status(status); goto out; diff --git a/source3/smbd/proto.h b/source3/smbd/proto.h index abfb5435493..032f75de166 100644 --- a/source3/smbd/proto.h +++ b/source3/smbd/proto.h @@ -1171,7 +1171,9 @@ const char *vfs_readdirname(connection_struct *conn, void *p, SMB_STRUCT_STAT *sbuf, char **talloced); int vfs_ChDir(connection_struct *conn, const char *path); char *vfs_GetWd(TALLOC_CTX *ctx, connection_struct *conn); -NTSTATUS check_reduced_name(connection_struct *conn, const char *fname); +NTSTATUS check_reduced_name(connection_struct *conn, + const char *cwd_name, + const char *fname); NTSTATUS check_reduced_name_with_privilege(connection_struct *conn, const char *fname, struct smb_request *smbreq); diff --git a/source3/smbd/vfs.c b/source3/smbd/vfs.c index f084b1d1930..15896f80b12 100644 --- a/source3/smbd/vfs.c +++ b/source3/smbd/vfs.c @@ -1163,9 +1163,17 @@ NTSTATUS check_reduced_name_with_privilege(connection_struct *conn, /******************************************************************* Reduce a file name, removing .. elements and checking that it is below dir in the heirachy. This uses realpath. + + If cwd_name == NULL then fname is a client given path relative + to the root path of the share. + + If cwd_name != NULL then fname is a client given path relative + to cwd_name. cwd_name is relative to the root path of the share. ********************************************************************/ -NTSTATUS check_reduced_name(connection_struct *conn, const char *fname) +NTSTATUS check_reduced_name(connection_struct *conn, + const char *cwd_name, + const char *fname) { char *resolved_name = NULL; bool allow_symlinks = true; -- 2.12.2.564.g063fe858b8-goog From e3fd46264b82ffc22424ee7364b3fd2c0fc14a7e Mon Sep 17 00:00:00 2001 From: Jeremy Allison Date: Mon, 27 Mar 2017 17:09:38 -0700 Subject: [PATCH 3/3] s3: smbd: Fix "follow symlink = no" regression part 2. Use the cwd_name parameter to reconstruct the original client name for symlink testing. BUG: https://bugzilla.samba.org/show_bug.cgi?id=12721 Signed-off-by: Jeremy Allison Reviewed-by: Ralph Boehme (cherry picked from commit e182a4d39e86c9694e255efdf6ee2ea3ccb9af4a) --- source3/smbd/vfs.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) diff --git a/source3/smbd/vfs.c b/source3/smbd/vfs.c index 15896f80b12..6c46fe54364 100644 --- a/source3/smbd/vfs.c +++ b/source3/smbd/vfs.c @@ -1176,6 +1176,7 @@ NTSTATUS check_reduced_name(connection_struct *conn, const char *fname) { char *resolved_name = NULL; + char *new_fname = NULL; bool allow_symlinks = true; bool allow_widelinks = false; @@ -1317,11 +1318,32 @@ NTSTATUS check_reduced_name(connection_struct *conn, } p++; + + /* + * If cwd_name is present and not ".", + * then fname is relative to that, not + * the root of the share. Make sure the + * path we check is the one the client + * sent (cwd_name+fname). + */ + if (cwd_name != NULL && !ISDOT(cwd_name)) { + new_fname = talloc_asprintf(talloc_tos(), + "%s/%s", + cwd_name, + fname); + if (new_fname == NULL) { + SAFE_FREE(resolved_name); + return NT_STATUS_NO_MEMORY; + } + fname = new_fname; + } + if (strcmp(fname, p)!=0) { DEBUG(2, ("check_reduced_name: Bad access " "attempt: %s is a symlink to %s\n", fname, p)); SAFE_FREE(resolved_name); + TALLOC_FREE(new_fname); return NT_STATUS_ACCESS_DENIED; } } @@ -1332,6 +1354,7 @@ NTSTATUS check_reduced_name(connection_struct *conn, DEBUG(3,("check_reduced_name: %s reduced to %s\n", fname, resolved_name)); SAFE_FREE(resolved_name); + TALLOC_FREE(new_fname); return NT_STATUS_OK; } -- 2.12.2.564.g063fe858b8-goog