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libsemanage issue with bzip-blocksize=0 and compressed modules in store 

On Mon, 2009-08-24 at 10:57 -0400, Chris PeBenito wrote:
> On Mon, 2009-08-24 at 10:04 -0400, Stephen Smalley wrote:
> > On Mon, 2009-08-24 at 09:54 -0400, Chris PeBenito wrote:
> > > I took the current release of libsemanage and added the patch to add a
> > > bzip blocksize option[1].  The modules in my store were already
> > > compressed with the stock release.  I put bzip-blocksize=0 in my
> > > semanage.conf and I do semodule -B and get:
> > >
> > > libsepol.module_package_read_offsets: wrong magic number for module
> > > package:  expected 0xf97cff8f, got 0x39685a42 (No such file or
> > > directory).
> > > libsemanage.semanage_load_module: Error while reading from module
> > > file /etc/selinux/strict/modules/tmp/modules/apm.pp. (No such file or
> > > directory).
> > > semodule:  Failed!
> > >
> > > If I do semodule -l, it will also get the magic number error.  If I
> > > remove the blocksize option, it works again.  I was able to reinsert all
> > > of the modules to get it working again with the blocksize 0 option.
> > >
> > > [1] http://userspace.selinuxproject.org/trac/changeset/ee9827000137fed2d3300124115fc1572acafe2f
> >
> > Yes, that's what I would expect.  The expectation is that either one
> > would set that option before installing the policy for the first time,
> > or that one completely re-installs the policy after setting that option.
>
> Can we have a little better handling of this case?  I don't mind
> reinstalling the policy, but the error messages aren't helpful.  In
> addition, with semodule -l being broken, I have to look into the module
> store to see what modules are installed or guess.

Seems like it is just as easy to just support pre-existing compressed
modules, see below.

Explicitly probe for the bzip2 magic string prefix and fall through to
BZ2_bzReadOpen() if the module is bzipped even if bzip-blocksize=0.
Thus bzip-blocksize=0 will prevent any further compression of
subsequently installed/updated modules, but will continue to function
with existing compressed modules.

Signed-off-by:  Stephen Smalley <sds@tycho.nsa.gov>
This commit is contained in:
Stephen Smalley 2009-08-24 14:00:27 -04:00
parent 33c961d35e
commit c3c7ef9c65
1 changed files with 10 additions and 2 deletions
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12
libsemanage/src/direct_api.c
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@ -452,6 +452,9 @@ static ssize_t bzip(semanage_handle_t *sh, const char *filename, char *data,
return total;
}
#define BZ2_MAGICSTR "BZh"
#define BZ2_MAGICLEN (sizeof(BZ2_MAGICSTR)-1)
/* bunzip() a file to '*data', returning the total number of uncompressed bytes
* in the file. Returns -1 if file could not be decompressed. */
ssize_t bunzip(semanage_handle_t *sh, FILE *f, char **data)
@ -463,8 +466,13 @@ ssize_t bunzip(semanage_handle_t *sh, FILE *f, char **data)
int bzerror;
size_t total=0;
if (!sh->conf->bzip_blocksize)
return -1;
if (!sh->conf->bzip_blocksize) {
bzerror = fread(buf, 1, BZ2_MAGICLEN, f);
rewind(f);
if ((bzerror != BZ2_MAGICLEN) || memcmp(buf, BZ2_MAGICSTR, BZ2_MAGICLEN))
return -1;
/* fall through */
}
b = BZ2_bzReadOpen ( &bzerror, f, 0, sh->conf->bzip_small, NULL, 0 );
if ( bzerror != BZ_OK ) {