mirror of https://git.tukaani.org/xz.git
xz: Landlock: Fix error message if input file is a directory.
If xz is given a directory, it should look like this: $ xz /usr/bin xz: /usr/bin: Is a directory, skipping The Landlock rules didn't allow opening directories for reading: $ xz /usr/bin xz: /usr/bin: Permission denied The simplest fix was to allow opening directories for reading. While it's a bit silly to allow it solely for the error message, it shouldn't make the sandbox significantly weaker. The single-file use case (like when called from GNU tar) is still as strict as possible: all Landlock restrictions are enabled before (de)compression starts.
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@ -224,9 +224,17 @@ sandbox_init(void)
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// These are all in ABI version 1 already. We don't need truncate
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// rights because files are created with open() using O_EXCL and
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// without O_TRUNC.
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//
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// LANDLOCK_ACCESS_FS_READ_DIR is included here to get a clear error
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// message if xz is given a directory name. Without this permission
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// the message would be "Permission denied" but with this permission
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// it's "Is a directory, skipping". It could be worked around with
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// stat()/lstat() but just giving this permission is simpler and
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// shouldn't make the sandbox much weaker in practice.
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const uint64_t required_rights
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= LANDLOCK_ACCESS_FS_WRITE_FILE
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| LANDLOCK_ACCESS_FS_READ_FILE
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| LANDLOCK_ACCESS_FS_READ_DIR
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| LANDLOCK_ACCESS_FS_REMOVE_FILE
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| LANDLOCK_ACCESS_FS_MAKE_REG;
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@ -240,7 +248,9 @@ sandbox_enable_read_only(void)
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{
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// We will be opening files for reading but
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// won't create or remove any files.
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const uint64_t required_rights = LANDLOCK_ACCESS_FS_READ_FILE;
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const uint64_t required_rights
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= LANDLOCK_ACCESS_FS_READ_FILE
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| LANDLOCK_ACCESS_FS_READ_DIR;
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enable_landlock(required_rights);
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return;
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}
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@ -256,6 +266,9 @@ sandbox_enable_strict_if_allowed(int src_fd lzma_attribute((__unused__)),
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// Allow all restrictions that the kernel supports with the
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// highest Landlock ABI version that the kernel or xz supports.
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//
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// NOTE: LANDLOCK_ACCESS_FS_READ_DIR isn't needed here because
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// the only input file has already been opened.
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enable_landlock(0);
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return;
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}
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