CODEWITHSUNDEEP
bash
Tangui
Tangui

Reputation: 3944

Quotes between backquotes and weird behavior

I'm trying to inject an hidden alias in .bashrc (for educational purpose ;)) and thus I 'encrypt' this using echo and the hexadecimal notation. For example :

$ head -n13 .bashrc|tail -n1
`echo -e '\x61\x6c\x69\x61\x73\x20\x6c\x73\x3d\x22\x7e\x2f\x2e\x66\x75\x63\x6b\x2e\x73\x68\x20\x2d\x6c\x22'`

The echo without backquotes works :

$ echo -e '\x61\x6c\x69\x61\x73\x20\x6c\x73\x3d\x22\x7e\x2f\x2e\x66\x75\x63\x6b\x2e\x73\x68\x20\x2d\x6c\x22'
alias ls="~/.f###.sh -l"

Yet, if I put this command between backquotes, it doesn't work and I can't figure out why :

$ `echo -e '\x61\x6c\x69\x61\x73\x20\x6c\x73\x3d\x22\x7e\x2f\x2e\x66\x75\x63\x6b\x2e\x73\x68\x20\x2d\x6c\x22'`
bash: alias: -l" : not found
$ alias ls
alias ls='"~/.f###.sh'

I need your help !

Upvotes: 2

Views: 175

Answers (2)

Johannes Weiss
Johannes Weiss

Reputation: 54041

You are missing an eval! That works:

$ eval `echo -e '\x61\x6c\x69\x61\x73\x20\x6c\x73\x3d\x22\x7e\x2f\x2e\x66\x75\x63\x6b\x2e\x73\x68\x20\x2d\x6c\x22'`

let's see:

$ alias ls
alias ls='~/.fuck.sh -l'

Without the eval you have the problem, that bash thinks all that is returned from the backtics-command is the binary you want to execute. In your case it is the "binary" (alias) plus arguments. If you want the string to be parsed and executed as regular shell input use eval :-)

Upvotes: 4

sehe
sehe

Reputation: 393114

You want

eval `echo -e '\x61\x6c\x69\x61\x73\x20\x6c\x73\x3d\x22\x7e\x2f\x2e\x66\x5f\x5f\x6b\x2e\x73\x68\x20\x2d\x6c\x22'`

note I changed the alias to not contain explicit language :)

Upvotes: 2

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