Linux ELF Implementation

Linux ELF Implementation

[dirty boy]

hey people :)

i would be greatful if one of you knowledgeable people could settle a bet 
for me...

im learning about the ELF specification with a friend of mine, were hoping 
to get a better understanding of how these things work, and a wild idea 
occurred to us - would it be possible to create a valid ELF executable from 
purely printable ASCII characters ?

by that i mean, you would be able to literally cat > a.out and enter your 
executable from the keyboard! it wouldnt have todo anything, just return 
0...

the file wouldnt have to be portable, only the fields that the kernel is 
going to notice would have to be present, so long as it executes!

im convinced the answer is no - but my friend says it is, he says hes seen 
it done in PE format ( although we cant find it on the web ) and therefore 
theres no reason why it couldnt be done in ELF.

Thanks  so much!!

[ please cc me if possible, im not a subscriber and will save me waiting for 
the responses to show up on google! ]

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Re: Linux ELF Implementation

[Ralf Baechle]

On Sun, Sep 01, 2002 at 10:26:10PM +0000, dirty boy wrote:

> im learning about the ELF specification with a friend of mine, were hoping 
> to get a better understanding of how these things work, and a wild idea 
> occurred to us - would it be possible to create a valid ELF executable from 
> purely printable ASCII characters ?
> 
> by that i mean, you would be able to literally cat > a.out and enter your 
> executable from the keyboard! it wouldnt have todo anything, just return 
> 0...
> 
> the file wouldnt have to be portable, only the fields that the kernel is 
> going to notice would have to be present, so long as it executes!
> 
> im convinced the answer is no - but my friend says it is, he says hes seen 
> it done in PE format ( although we cant find it on the web ) and therefore 
> theres no reason why it couldnt be done in ELF.

There answer is no; the ELF magic at the begin of an ELF file contains
a non-printable character.

  Ralf

Re: Linux ELF Implementation

[Thunder from the hill]

Hi,

On Mon, 2 Sep 2002, Ralf Baechle wrote:
> There answer is no; the ELF magic at the begin of an ELF file contains
> a non-printable character.

...and yes if you write a program which concatenates half-based characters 
to a full base, the only thing that hurts is that you have to write at 
least twice as much...

			Thunder
-- 
--./../...-/. -.--/---/..-/.-./..././.-../..-. .---/..-/.../- .-
--/../-./..-/-/./--..-- ../.----./.-../.-.. --./../...-/. -.--/---/..-
.- -/---/--/---/.-./.-./---/.--/.-.-.-
--./.-/-.../.-./.././.-../.-.-.-

Re: Linux ELF Implementation

[Chris Wedgwood]

On Sun, Sep 01, 2002 at 10:57:59PM -0600, Thunder from the hill wrote:

    ...and yes if you write a program which concatenates half-based
    characters to a full base, the only thing that hurts is that you
    have to write at least twice as much...

uudecode doesn't count

the answer is no


  --cw