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Date: Tue, 15 Nov 2011 09:41:57 -0600
From: Eric Sandeen <sandeen@...hat.com>
To: "Theodore Ts'o" <tytso@....edu>
CC: Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 1/2] debugfs: build read-only variant of debugfs
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On 11/14/11 11:05 PM, Theodore Ts'o wrote:
> Create a version of debugfs which only supports read-only examination
> of the file system metadata (but not the data blocks). The idea is
> that this version of debugfs might be suitable to be setuid root, and
> executable only by members of a particular group, or setgid disk, and
> globally executable, depending on the security/privacy policies in
> force at a particular site.
Just curious - what problem does this solve?
(Could the same policies simply make direct access to block devices
read-only for those users, and thus have an fs-independent solution
to whatever problem is at hand?)
- -Eric
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
> ---
> debugfs/Makefile.in | 20 ++++++++++-
> debugfs/debugfs.c | 53 ++++++++++++++++++++++++++---
> debugfs/ro_debug_cmds.ct | 85 ++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 151 insertions(+), 7 deletions(-)
> create mode 100644 debugfs/ro_debug_cmds.ct
>
> diff --git a/debugfs/Makefile.in b/debugfs/Makefile.in
> index e314b91..4674ba6 100644
> --- a/debugfs/Makefile.in
> +++ b/debugfs/Makefile.in
> @@ -11,7 +11,7 @@ INSTALL = @INSTALL@
>
> @MCONFIG@
>
> -PROGS= debugfs
> +PROGS= debugfs rdebugfs
> MANPAGES= debugfs.8
>
> MK_CMDS= _SS_DIR_OVERRIDE=../lib/ss ../lib/ss/mk_cmds
> @@ -19,6 +19,9 @@ MK_CMDS= _SS_DIR_OVERRIDE=../lib/ss ../lib/ss/mk_cmds
> DEBUG_OBJS= debug_cmds.o debugfs.o util.o ncheck.o icheck.o ls.o \
> lsdel.o dump.o set_fields.o logdump.o htree.o unused.o
>
> +RO_DEBUG_OBJS= ro_debug_cmds.o ro_debugfs.o util.o ncheck.o icheck.o ls.o \
> + lsdel.o logdump.o htree.o
> +
> SRCS= debug_cmds.c $(srcdir)/debugfs.c $(srcdir)/util.c $(srcdir)/ls.c \
> $(srcdir)/ncheck.c $(srcdir)/icheck.c $(srcdir)/lsdel.c \
> $(srcdir)/dump.c $(srcdir)/set_fields.c ${srcdir}/logdump.c \
> @@ -39,10 +42,22 @@ debugfs: $(DEBUG_OBJS) $(DEPLIBS)
> $(E) " LD $@"
> $(Q) $(CC) $(ALL_LDFLAGS) -o debugfs $(DEBUG_OBJS) $(LIBS)
>
> +rdebugfs: $(RO_DEBUG_OBJS) $(DEPLIBS)
> + $(E) " LD $@"
> + $(Q) $(CC) $(ALL_LDFLAGS) -o rdebugfs $(RO_DEBUG_OBJS) $(LIBS)
> +
> debug_cmds.c debug_cmds.h: debug_cmds.ct
> $(E) " MK_CMDS $@"
> $(Q) $(MK_CMDS) $(srcdir)/debug_cmds.ct
>
> +ro_debug_cmds.c ro_debug_cmds.h: ro_debug_cmds.ct
> + $(E) " MK_CMDS $@"
> + $(Q) $(MK_CMDS) $(srcdir)/ro_debug_cmds.ct
> +
> +ro_debugfs.o: debugfs.c
> + $(E) " CC $@"
> + $(Q) $(CC) -c $(ALL_CFLAGS) $< -DREAD_ONLY -o $@
> +
> debugfs.8: $(DEP_SUBSTITUTE) $(srcdir)/debugfs.8.in
> $(E) " SUBST $@"
> $(Q) $(SUBSTITUTE_UPTIME) $(srcdir)/debugfs.8.in debugfs.8
> @@ -80,7 +95,8 @@ uninstall:
> done
>
> clean:
> - $(RM) -f debugfs debugfs.8 \#* *.s *.o *.a *~ debug_cmds.c core
> + $(RM) -f $(PROGS) debugfs.8 \#* *.s *.o *.a *~ debug_cmds.c \
> + ro_debug_cmds.c core
>
> mostlyclean: clean
> distclean: clean
> diff --git a/debugfs/debugfs.c b/debugfs/debugfs.c
> index 1fb8f44..fda8d92 100644
> --- a/debugfs/debugfs.c
> +++ b/debugfs/debugfs.c
> @@ -140,7 +140,11 @@ void do_open_filesys(int argc, char **argv)
> open_flags |= EXT2_FLAG_IMAGE_FILE;
> break;
> case 'w':
> +#ifdef READ_ONLY
> + goto print_usage;
> +#else
> open_flags |= EXT2_FLAG_RW;
> +#endif /* READ_ONLY */
> break;
> case 'f':
> open_flags |= EXT2_FLAG_FORCE;
> @@ -184,8 +188,11 @@ void do_open_filesys(int argc, char **argv)
> return;
>
> print_usage:
> - fprintf(stderr, "%s: Usage: open [-s superblock] [-b blocksize] "
> - "[-c] [-w] <device>\n", argv[0]);
> + fprintf(stderr, "%s: Usage: open [-s superblock] [-b blocksize] [-c] "
> +#ifndef READ_ONLY
> + "[-w] "
> +#endif
> + "<device>\n", argv[0]);
> }
>
> void do_lcd(int argc, char **argv)
> @@ -251,6 +258,7 @@ void do_close_filesys(int argc, char **argv)
> close_filesystem();
> }
>
> +#ifndef READ_ONLY
> void do_init_filesys(int argc, char **argv)
> {
> struct ext2_super_block param;
> @@ -276,6 +284,7 @@ void do_init_filesys(int argc, char **argv)
> root = cwd = EXT2_ROOT_INO;
> return;
> }
> +#endif /* READ_ONLY */
>
> static void print_features(struct ext2_super_block * s, FILE *f)
> {
> @@ -393,6 +402,7 @@ print_usage:
> fprintf(stderr, "%s: Usage: show_super [-h]\n", argv[0]);
> }
>
> +#ifndef READ_ONLY
> void do_dirty_filesys(int argc EXT2FS_ATTR((unused)),
> char **argv EXT2FS_ATTR((unused)))
> {
> @@ -407,6 +417,7 @@ void do_dirty_filesys(int argc EXT2FS_ATTR((unused)),
> current_fs->super->s_state &= ~EXT2_VALID_FS;
> ext2fs_mark_super_dirty(current_fs);
> }
> +#endif /* READ_ONLY */
>
> struct list_blocks_struct {
> FILE *f;
> @@ -964,6 +975,7 @@ void do_chroot(int argc, char *argv[])
> root = inode;
> }
>
> +#ifndef READ_ONLY
> void do_clri(int argc, char *argv[])
> {
> ext2_ino_t inode;
> @@ -1006,6 +1018,7 @@ void do_seti(int argc, char *argv[])
> ext2fs_mark_inode_bitmap2(current_fs->inode_map,inode);
> ext2fs_mark_ib_dirty(current_fs);
> }
> +#endif /* READ_ONLY */
>
> void do_testi(int argc, char *argv[])
> {
> @@ -1020,6 +1033,7 @@ void do_testi(int argc, char *argv[])
> printf("Inode %u is not in use\n", inode);
> }
>
> +#ifndef READ_ONLY
> void do_freeb(int argc, char *argv[])
> {
> blk64_t block;
> @@ -1057,6 +1071,7 @@ void do_setb(int argc, char *argv[])
> }
> ext2fs_mark_bb_dirty(current_fs);
> }
> +#endif /* READ_ONLY */
>
> void do_testb(int argc, char *argv[])
> {
> @@ -1074,6 +1089,7 @@ void do_testb(int argc, char *argv[])
> }
> }
>
> +#ifndef READ_ONLY
> static void modify_u8(char *com, const char *prompt,
> const char *format, __u8 *val)
> {
> @@ -1217,6 +1233,7 @@ void do_modify_inode(int argc, char *argv[])
> if (debugfs_write_inode(inode_num, &inode, argv[1]))
> return;
> }
> +#endif /* READ_ONLY */
>
> void do_change_working_dir(int argc, char *argv[])
> {
> @@ -1298,6 +1315,7 @@ static int ext2_file_type(unsigned int mode)
> return 0;
> }
>
> +#ifndef READ_ONLY
> static void make_link(char *sourcename, char *destname)
> {
> ext2_ino_t ino;
> @@ -1445,6 +1463,7 @@ void do_unlink(int argc, char *argv[])
>
> unlink_file_by_name(argv[1]);
> }
> +#endif /* READ_ONLY */
>
> void do_find_free_block(int argc, char *argv[])
> {
> @@ -1537,6 +1556,7 @@ void do_find_free_inode(int argc, char *argv[])
> printf("Free inode found: %u\n", free_inode);
> }
>
> +#ifndef READ_ONLY
> static errcode_t copy_file(int fd, ext2_ino_t newfile)
> {
> ext2_file_t e2_file;
> @@ -1944,6 +1964,7 @@ void do_rmdir(int argc, char *argv[])
> return;
> }
> }
> +#endif /* READ_ONLY */
>
> void do_show_debugfs_params(int argc EXT2FS_ATTR((unused)),
> char *argv[] EXT2FS_ATTR((unused)))
> @@ -1957,6 +1978,7 @@ void do_show_debugfs_params(int argc EXT2FS_ATTR((unused)),
> current_fs ? current_fs->device_name : "--none--");
> }
>
> +#ifndef READ_ONLY
> void do_expand_dir(int argc, char *argv[])
> {
> ext2_ino_t inode;
> @@ -1990,6 +2012,7 @@ void do_features(int argc, char *argv[])
> }
> print_features(current_fs->super, stdout);
> }
> +#endif /* READ_ONLY */
>
> void do_bmap(int argc, char *argv[])
> {
> @@ -2047,6 +2070,7 @@ void do_imap(int argc, char *argv[])
>
> }
>
> +#ifndef READ_ONLY
> void do_set_current_time(int argc, char *argv[])
> {
> time_t now;
> @@ -2066,6 +2090,7 @@ void do_set_current_time(int argc, char *argv[])
> current_fs->now = now;
> }
> }
> +#endif /* READ_ONLY */
>
> static int find_supp_feature(__u32 *supp, int feature_type, char *name)
> {
> @@ -2132,6 +2157,7 @@ void do_supported_features(int argc, char *argv[])
> }
> }
>
> +#ifndef READ_ONLY
> void do_punch(int argc, char *argv[])
> {
> ext2_ino_t ino;
> @@ -2162,6 +2188,7 @@ void do_punch(int argc, char *argv[])
> return;
> }
> }
> +#endif /* READ_ONLY */
>
> void do_dump_mmp(int argc, char *argv[])
> {
> @@ -2256,7 +2283,13 @@ int main(int argc, char **argv)
> {
> int retval;
> int sci_idx;
> - const char *usage = "Usage: %s [-b blocksize] [-s superblock] [-f cmd_file] [-R request] [-V] [[-w] [-c] device]";
> + const char *usage =
> + "Usage: %s [-b blocksize] [-s superblock] [-f cmd_file] "
> + "[-R request] [-V] ["
> +#ifndef READ_ONLY
> + "[-w] "
> +#endif
> + "[-c] device]";
> int c;
> int open_flags = EXT2_FLAG_SOFTSUPP_FEATURES | EXT2_FLAG_64BITS;
> char *request = 0;
> @@ -2266,15 +2299,23 @@ int main(int argc, char **argv)
> blk64_t blocksize = 0;
> int catastrophic = 0;
> char *data_filename = 0;
> +#ifdef READ_ONLY
> + const char *opt_string = "iwcR:f:b:s:Vd:D";
> +#else
> + const char *opt_string = "icR:f:b:s:Vd:D";
> +#endif
>
> if (debug_prog_name == 0)
> +#ifdef READ_ONLY
> + debug_prog_name = "rdebugfs";
> +#else
> debug_prog_name = "debugfs";
> -
> +#endif
> add_error_table(&et_ext2_error_table);
> fprintf (stderr, "%s %s (%s)\n", debug_prog_name,
> E2FSPROGS_VERSION, E2FSPROGS_DATE);
>
> - while ((c = getopt (argc, argv, "iwcR:f:b:s:Vd:D")) != EOF) {
> + while ((c = getopt (argc, argv, opt_string)) != EOF) {
> switch (c) {
> case 'R':
> request = optarg;
> @@ -2288,9 +2329,11 @@ int main(int argc, char **argv)
> case 'i':
> open_flags |= EXT2_FLAG_IMAGE_FILE;
> break;
> +#ifndef READ_ONLY
> case 'w':
> open_flags |= EXT2_FLAG_RW;
> break;
> +#endif
> case 'D':
> open_flags |= EXT2_FLAG_DIRECT_IO;
> break;
> diff --git a/debugfs/ro_debug_cmds.ct b/debugfs/ro_debug_cmds.ct
> new file mode 100644
> index 0000000..4b16a67
> --- /dev/null
> +++ b/debugfs/ro_debug_cmds.ct
> @@ -0,0 +1,85 @@
> +#
> +# Restricted set of debugfs commands
> +#
> +# Copyright (C) 1993 Theodore Ts'o. This file may be redistributed
> +# under the terms of the GNU Public License.
> +#
> +command_table debug_cmds;
> +
> +request do_show_debugfs_params, "Show debugfs parameters",
> + show_debugfs_params, params;
> +
> +request do_open_filesys, "Open a filesystem",
> + open_filesys, open;
> +
> +request do_close_filesys, "Close the filesystem",
> + close_filesys, close;
> +
> +request do_show_super_stats, "Show superblock statistics",
> + show_super_stats, stats;
> +
> +request do_ncheck, "Do inode->name translation",
> + ncheck;
> +
> +request do_icheck, "Do block->inode translation",
> + icheck;
> +
> +request do_chroot, "Change root directory",
> + change_root_directory, chroot;
> +
> +request do_change_working_dir, "Change working directory",
> + change_working_directory, cd;
> +
> +request do_list_dir, "List directory",
> + list_directory, ls;
> +
> +request do_stat, "Show inode information ",
> + show_inode_info, stat;
> +
> +request do_dump_extents, "Dump extents information ",
> + dump_extents, extents, ex;
> +
> +request do_blocks, "Dump blocks used by an inode ",
> + blocks;
> +
> +request do_testi, "Test an inode's in-use flag",
> + testi;
> +
> +request do_find_free_block, "Find free block(s)",
> + find_free_block, ffb;
> +
> +request do_find_free_inode, "Find free inode(s)",
> + find_free_inode, ffi;
> +
> +request do_print_working_directory, "Print current working directory",
> + print_working_directory, pwd;
> +
> +request do_lsdel, "List deleted inodes",
> + list_deleted_inodes, lsdel;
> +
> +request do_logdump, "Dump the contents of the journal",
> + logdump;
> +
> +request do_htree_dump, "Dump a hash-indexed directory",
> + htree_dump, htree;
> +
> +request do_dx_hash, "Calculate the directory hash of a filename",
> + dx_hash, hash;
> +
> +request do_dirsearch, "Search a directory for a particular filename",
> + dirsearch;
> +
> +request do_bmap, "Calculate the logical->physical block mapping for an inode",
> + bmap;
> +
> +request do_imap, "Calculate the location of an inode",
> + imap;
> +
> +request do_supported_features, "Print features supported by this version of e2fsprogs",
> + supported_features;
> +
> +request do_dump_mmp, "Dump MMP information",
> + dump_mmp;
> +
> +end;
> +
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