When recursively copying files into OS trees, it often happens that
some subdirectory of the source directory is a symlink in the target
directory. Currently, cp will fail in that scenario with the error:
"cannot overwrite non-directory %s with directory %s"
However, we'd like cp in this scenario to follow the destination
directory symlink and copy the files into the symlinked directory
instead. Let's support this by adding a new option
--keep-directory-symlink that makes cp follow destination directory
symlinks.
We name the option --keep-directory-symlink to keep consistent with
tar which has the same option with the same effect.
---
doc/coreutils.texi | 8 ++++++++
src/copy.c | 3 ++-
src/copy.h | 3 +++
src/cp.c | 12 +++++++++++-
tests/cp/keep-directory-symlink.sh | 27 +++++++++++++++++++++++++++
5 files changed, 51 insertions(+), 2 deletions(-)
create mode 100755 tests/cp/keep-directory-symlink.sh
diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index d445ea228..07f05b8af 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -10281,6 +10281,14 @@ option is also specified.
@opindex --verbose
Print the name of each file before moving it.
+@item --keep-directory-symlink
+@opindex --keep-directory-symlink
+Follow existing symlinks to directories when copying. Note that this option
+should only be used when the contents of the destination directory are trusted
+as when this option is enabled, an attacker can place symlinks in the
+destination directory to make @command{cp} write to arbitrary directories in
the
+system.
+
@optStripTrailingSlashes
@optBackupSuffix
diff --git a/src/copy.c b/src/copy.c
index f54253e5b..bbadca293 100644
--- a/src/copy.c
+++ b/src/copy.c
@@ -2311,7 +2311,8 @@ copy_internal (char const *src_name, char const *dst_name,
bool use_lstat
= ((! S_ISREG (src_mode)
&& (! x->copy_as_regular
- || S_ISDIR (src_mode) || S_ISLNK (src_mode)))
+ || (S_ISDIR (src_mode) && !x->keep_directory_symlink)
+ || S_ISLNK (src_mode)))
|| x->move_mode || x->symbolic_link || x->hard_link
|| x->backup_type != no_backups
|| x->unlink_dest_before_opening);
diff --git a/src/copy.h b/src/copy.h
index 3809f8d23..834685c51 100644
--- a/src/copy.h
+++ b/src/copy.h
@@ -256,6 +256,9 @@ struct cp_options
/* If true, display the names of the files before copying them. */
bool verbose;
+ /* If true, follow existing symlinks to directories when copying. */
+ bool keep_directory_symlink;
+
/* If true, display details of how files were copied. */
bool debug;
diff --git a/src/cp.c b/src/cp.c
index 04a5cbee3..82c7bd964 100644
--- a/src/cp.c
+++ b/src/cp.c
@@ -68,7 +68,8 @@ enum
REFLINK_OPTION,
SPARSE_OPTION,
STRIP_TRAILING_SLASHES_OPTION,
- UNLINK_DEST_BEFORE_OPENING
+ UNLINK_DEST_BEFORE_OPENING,
+ KEEP_DIRECTORY_SYMLINK_OPTION
};
/* True if the kernel is SELinux enabled. */
@@ -141,6 +142,7 @@ static struct option const long_opts[] =
{"target-directory", required_argument, nullptr, 't'},
{"update", optional_argument, nullptr, 'u'},
{"verbose", no_argument, nullptr, 'v'},
+ {"keep-directory-symlink", no_argument, nullptr,
KEEP_DIRECTORY_SYMLINK_OPTION},
{GETOPT_SELINUX_CONTEXT_OPTION_DECL},
{GETOPT_HELP_OPTION_DECL},
{GETOPT_VERSION_OPTION_DECL},
@@ -230,6 +232,9 @@ Copy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY.\n\
"), stdout);
fputs (_("\
-v, --verbose explain what is being done\n\
+"), stdout);
+ fputs (_("\
+ --keep-directory-symlink follow existing symlinks to directories\n\
"), stdout);
fputs (_("\
-x, --one-file-system stay on this file system\n\
@@ -859,6 +864,7 @@ cp_option_init (struct cp_options *x)
x->update = false;
x->verbose = false;
+ x->keep_directory_symlink = false;
/* By default, refuse to open a dangling destination symlink, because
in general one cannot do that safely, give the current semantics of
@@ -1161,6 +1167,10 @@ main (int argc, char **argv)
x.verbose = true;
break;
+ case KEEP_DIRECTORY_SYMLINK_OPTION:
+ x.keep_directory_symlink = true;
+ break;
+
case 'x':
x.one_file_system = true;
break;
diff --git a/tests/cp/keep-directory-symlink.sh
b/tests/cp/keep-directory-symlink.sh
new file mode 100755
index 000000000..cf3918b79
--- /dev/null
+++ b/tests/cp/keep-directory-symlink.sh
@@ -0,0 +1,27 @@
+#!/bin/sh
+# Test that cp --keep-directory-symlink follows symlinks.
+
+# Copyright (C) 2024 Free Software Foundation, Inc.
+
+# 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 <https://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
+print_ver_ cp
+
+mkdir -p a/b b/d/e || framework_failure_
+ln -s b a/d || framework_failure_
+
+cp -RT --copy-contents b a || fail=1
+cp -RT --copy-contents --keep-directory-symlink b a || fail=1
+ls a/b/e || fail=1
--
2.43.0
