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Date: Fri, 27 Mar 2020 16:19:18 +0100
From: Natanael Copa <ncopa@alpinelinux.org>
To: Henrik Holst <henrik.holst@omnimodular.com>
Cc: ~alpine/users@lists.alpinelinux.org
Subject: Re: tini-static dynamically linked
Message-ID: <20200327161918.4aedc0ca@ncopa-desktop.copa.dup.pw>
In-Reply-To: <CAHO+3xRtDT_kTLs3rpES2UZT0PPD+sS2H_Xi2NNj42BVEcFWgw@mail.gmail.com>
References: <CAHO+3xRtDT_kTLs3rpES2UZT0PPD+sS2H_Xi2NNj42BVEcFWgw@mail.gmail.com>
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On Fri, 27 Mar 2020 14:48:44 +0100
Henrik Holst <henrik.holst@omnimodular.com> wrote:

> Hi,
> 
> I installed the tini-static package and I was surprised that file
> report it as a dynamically linked binary?
> 
> /opt/certbot # file /sbin/tini-static
> /sbin/tini-static: ELF 64-bit LSB pie executable, x86-64, version 1
> (SYSV), dynamically linked, stripped
> 
> Is this a bug? Seems to me it would be a bug that a static package is
> dynamically linked even if just formally.
> 
> Thanks
> Henrik Holst

It is really statically linked, but it is linked as PIE:

$ readelf -d /sbin/tini-static 

Dynamic section at offset 0xae70 contains 16 entries:
  Tag        Type                         Name/Value
 0x000000000000000c (INIT)               0x1000
 0x000000000000000d (FINI)               0x7a2e
 0x000000006ffffef5 (GNU_HASH)           0x200
 0x0000000000000005 (STRTAB)             0x4b0
 0x0000000000000006 (SYMTAB)             0x2b8
 0x000000000000000a (STRSZ)              193 (bytes)
 0x000000000000000b (SYMENT)             24 (bytes)
 0x0000000000000015 (DEBUG)              0x0
 0x0000000000000003 (PLTGOT)             0xbfb0
 0x0000000000000007 (RELA)               0x578
 0x0000000000000008 (RELASZ)             1056 (bytes)
 0x0000000000000009 (RELAENT)            24 (bytes)
 0x0000000000000018 (BIND_NOW)           
 0x000000006ffffffb (FLAGS_1)            Flags: NOW PIE
 0x000000006ffffff9 (RELACOUNT)          44
 0x0000000000000000 (NULL)               0x0

As you see, it is not linked to anything (no (NEEDED)).

The benefit with linking it as PIE (position independent executable) is
that it give full address space layout randomization (ASLR), even if it
is linked statically.

Side effect is that is marked as ET_DYN in the elf header and looks
like a dynamically linked executable.

-nc