Re: [PATCH] fedora: Replace pasta hard links by copies, mangle Build-IDs

["Richard W.M. Jones" <rjones@redhat.com>]

On Wed, Aug 23, 2023 at 03:48:44PM +0200, Stefano Brivio wrote:
> The hard link trick didn't actually fix the issue with SELinux file
> contexts properly: as opposed to symbolic links, SELinux now
> correctly associates types to the labels that are set -- except that
> those labels are now shared, so we can end up (depending on how
> rpm(8) extracts the archives) with /usr/bin/passt having a
> pasta_exec_t context.
> 
> This got rather confusing as running restorecon(8) seemed to fix up
> labels -- but that's simply toggling between passt_exec_t and
> pasta_exec_t for both links, because each invocation will just "fix"
> the file with the mismatching context.
> 
> Replace the hard links with copies. AppArmor's attachment, instead,
> works with hard links, and if there's no LSM, we can keep symbolic
> links, so keep symbolic links in the Makefile.
> 
> With copies, rpmbuild(8) will warn about duplicate Build-IDs in the
> same package. Mangle them in pasta binaries by summing one to the
> last byte, modulo one byte, using xxd (provided by vim-common) and
> disable the automatic rehashing by find-debuginfo(1) -- we already
> have per-release Build-IDs thanks to $VERSION passed on 'make'.

Right, this ^ was going to be my comment.  RPM doesn't like having two
identical copies of a file.  Hacking the binary to "fix" the problem
doesn't sound like a solution.

I'm CC-ing Fedora-devel-list to find out we can properly fix this issue.

Rich.

> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
> ---
>  contrib/fedora/passt.spec | 27 ++++++++++++++++++++++-----
>  1 file changed, 22 insertions(+), 5 deletions(-)
> 
> diff --git a/contrib/fedora/passt.spec b/contrib/fedora/passt.spec
> index d0c6895..51bf5a8 100644
> --- a/contrib/fedora/passt.spec
> +++ b/contrib/fedora/passt.spec
> @@ -9,6 +9,10 @@
>  
>  %global git_hash {{{ git_head }}}
>  %global selinuxtype targeted
> +# Different Build-IDs for passt and pasta: don't let find-debuginfo touch them
> +%undefine _unique_build_ids
> +%global _no_recompute_build_ids 1
> +
>  
>  Name:		passt
>  Version:	{{{ git_version }}}
> @@ -19,7 +23,7 @@ Group:		System Environment/Daemons
>  URL:		https://passt.top/
>  Source:		https://passt.top/passt/snapshot/passt-%{git_hash}.tar.xz
>  
> -BuildRequires:	gcc, make, checkpolicy, selinux-policy-devel
> +BuildRequires:	gcc, make, checkpolicy, selinux-policy-devel, binutils, vim-common
>  Requires:	(%{name}-selinux = %{version}-%{release} if selinux-policy-%{selinuxtype})
>  
>  %description
> @@ -56,15 +60,28 @@ This package adds SELinux enforcement to passt(1) and pasta(1).
>  %install
>  
>  %make_install DESTDIR=%{buildroot} prefix=%{_prefix} bindir=%{_bindir} mandir=%{_mandir} docdir=%{_docdir}/%{name}
> -# The Makefile creates symbolic links for pasta, but we need hard links for
> +# The Makefile creates symbolic links for pasta, but we need actual copies for
>  # SELinux file contexts to work as intended. Same with pasta.avx2 if present.
> -ln -f %{buildroot}%{_bindir}/passt %{buildroot}%{_bindir}/pasta
> +#
> +# To avoid duplicate Build-IDs in the same package, we increase the last byte of
> +# the value for pasta binaries by one (modulo one byte). Note that we already
> +# have differentiated Build-IDs per release, courtesy of $VERSION, so we don't
> +# need find-debuginfo(1) to recalculate them.
> +rm %{buildroot}%{_bindir}/pasta
> +objcopy --dump-section .note.gnu.build-id=%{buildroot}/build_id %{buildroot}%{_bindir}/passt
> +printf '\x'$(printf %02x $(( ( 0x$(xxd -ps -s 35 %{buildroot}/build_id) + 1 ) % 0xff )) ) | dd of=%{buildroot}/build_id seek=35 bs=1 count=1 conv=notrunc
> +objcopy --update-section .note.gnu.build-id=%{buildroot}/build_id %{buildroot}%{_bindir}/passt %{buildroot}%{_bindir}/pasta
> +rm %{buildroot}/build_id
> +
>  %ifarch x86_64
> -ln -f %{buildroot}%{_bindir}/passt.avx2 %{buildroot}%{_bindir}/pasta.avx2
> +rm %{buildroot}%{_bindir}/pasta.avx2
> +objcopy --dump-section .note.gnu.build-id=%{buildroot}/build_id %{buildroot}%{_bindir}/passt.avx2
> +printf '\x'$(printf %02x $(( ( 0x$(xxd -ps -s 35 %{buildroot}/build_id) + 1 ) % 0xff )) ) | dd of=%{buildroot}/build_id seek=35 bs=1 count=1 conv=notrunc
> +objcopy --update-section .note.gnu.build-id=%{buildroot}/build_id %{buildroot}%{_bindir}/passt.avx2 %{buildroot}%{_bindir}/pasta.avx2
> +rm %{buildroot}/build_id
>  
>  ln -sr %{buildroot}%{_mandir}/man1/passt.1 %{buildroot}%{_mandir}/man1/passt.avx2.1
>  ln -sr %{buildroot}%{_mandir}/man1/pasta.1 %{buildroot}%{_mandir}/man1/pasta.avx2.1
> -install -p -m 755 %{buildroot}%{_bindir}/passt.avx2 %{buildroot}%{_bindir}/pasta.avx2
>  %endif
>  
>  pushd contrib/selinux
> -- 
> 2.39.2

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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