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Date: Sat, 27 Jan 2018 01:50:21 +0200
From: Stefan Fröberg <stefan.froberg@...roprogram.com>
To: Szabolcs Nagy <nsz@...t70.net>
Cc: musl@...ts.openwall.com
Subject: Re: BUG: $ORIGIN does not seem to work

Hello Szabolcs


My ldd is just symbolic link inside musl chroot environment, to
/lib/ld-musl-x86_64.so.1
and it's symbolic link to /lib/libc.so

Here is readelf output of that test program
readelf -d x

Dynamic section at offset 0xe10 contains 24 entries:
  Tag        Type                         Name/Value
 0x0000000000000001 (NEEDED)             Shared library: [libcrypto.so.1.1]
 0x0000000000000001 (NEEDED)             Shared library: [libc.so]
 0x000000000000000f (RPATH)              Library rpath: [$ORIGIN/lib]
 0x000000000000000c (INIT)               0x598
 0x000000000000000d (FINI)               0x812
 0x000000006ffffef5 (GNU_HASH)           0x220
 0x0000000000000005 (STRTAB)             0x390
 0x0000000000000006 (SYMTAB)             0x258
 0x000000000000000a (STRSZ)              241 (bytes)
 0x000000000000000b (SYMENT)             24 (bytes)
 0x0000000000000015 (DEBUG)              0x0
 0x0000000000000003 (PLTGOT)             0x201000
 0x0000000000000002 (PLTRELSZ)           48 (bytes)
 0x0000000000000014 (PLTREL)             RELA
 0x0000000000000017 (JMPREL)             0x568
 0x0000000000000007 (RELA)               0x4c0
 0x0000000000000008 (RELASZ)             168 (bytes)
 0x0000000000000009 (RELAENT)            24 (bytes)
 0x000000006ffffffb (FLAGS_1)            Flags: PIE
 0x000000006ffffffe (VERNEED)            0x4a0
 0x000000006fffffff (VERNEEDNUM)         1
 0x000000006ffffff0 (VERSYM)             0x482
 0x000000006ffffff9 (RELACOUNT)          2
 0x0000000000000000 (NULL)               0x0

So the $ORIGIN/lib is there but for some reason ldd won't show it???

Best Regards
Stefan Fröberg

Szabolcs Nagy kirjoitti 26.01.2018 klo 16:21:
> * Stefan Fröberg <stefan.froberg@...roprogram.com> [2018-01-26 15:39:23 +0200]:
>> On glibc the following:
>>
>> gcc  -o x -Wl,-rpath='$ORIGIN/lib' x.c -L ./lib -lcrypto
>>
>> or
>>
>> gcc  -o x -Wl,-rpath,'$ORIGIN/lib' x.c -L ./lib -lcrypto
>>
>> Gives me binary with relative library path
>>
>> ldd x
>>     linux-vdso.so.1 (0x00007ffcb6bee000)
>> *    libcrypto.so.1.0.0 => /home/wizard/kal-el/lib/libcrypto.so.1.0.0
>> (0x00007f0bc3593000)**
>> *    libc.so.6 => /lib64/libc.so.6 (0x00007f0bc31e2000)
>>     libdl.so.2 => /lib64/libdl.so.2 (0x00007f0bc2fde000)
>>     libz.so.1 => /lib64/libz.so.1 (0x00007f0bc2dc7000)
>>     /lib64/ld-linux-x86-64.so.2 (0x00007f0bc39d2000)
>>
>> cp -rap kal-el/* batman/
>> ldd x
>>     linux-vdso.so.1 (0x00007ffdbf0b6000)
>> *    libcrypto.so.1.0.0 => /home/wizard/batman/lib/libcrypto.so.1.0.0
>> (0x00007fb682149000)**
>> *    libc.so.6 => /lib64/libc.so.6 (0x00007fb681d98000)
>>     libdl.so.2 => /lib64/libdl.so.2 (0x00007fb681b94000)
>>     libz.so.1 => /lib64/libz.so.1 (0x00007fb68197d000)
>>     /lib64/ld-linux-x86-64.so.2 (0x00007fb682588000)
>>
>>
>> But trying the same with musl does not seem to work?
>> ldd x
>> /lib/ld-musl-x86_64.so.1 (0x7f07372e2000)
>>     libc.so => /lib/ld-musl-x86_64.so.1 (0x7f07372e2000)
>>
>> and if i remove the -L ./lib from the command it uses system library
>> gcc  -o x -Wl,-rpath,'$ORIGIN/lib'  x.c   -lcrypto
>> ldd xx
>>     /lib/ld-musl-x86_64.so.1 (0x7fdd8618d000)
>>     libcrypto.so.1.1 => /usr/lib/libcrypto.so.1.1 (0x7fdd85ed7000)
>>     libc.so => /lib/ld-musl-x86_64.so.1 (0x7fdd8618d000)
>>
>>
> $ORIGIN in rpath works fine in musl
>
> you are doing something wrong
>
> but it's hard to tell what: your ldd command is looking at
> the wrong binary, we don't know what ldd you are using (e.g.
> use ld-*-musl.so.1 --list foo to make this explicit), it's
> not clear if the binary has $ORIGIN set up correctly since
> you showed a gcc command line instead of readelf -d of the
> generated executable, we don't know what paths have the
> library and what paths the ldso tried (you can check this
> by strace).
>
> (there are some differences between musl and glibc:
> e.g. glibc expands $ORIGIN in dlopen too while musl does
> not, however in your case musl should work)

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