It is also possible to decompress it using standard shell-script + gzip, if you don't have, or want to use openssl or other tools.
The trick is to prepend the gzip magic number and compress method to the actual data from zlib.compress:
printf "\x1f\x8b\x08\x00\x00\x00\x00\x00" |cat - /tmp/data |gzip -dc >/tmp/out
Edits:
@d0sboots commented: For RAW Deflate data, you need to add 2 more null bytes:
→ "\x1f\x8b\x08\x00\x00\x00\x00\x00\x00\x00"
This Q on SO gives more information about this approach. An answer there suggests that there is also an 8 byte footer.
Users @Vitali-Kushner and @mark-bessey reported success even with truncated files, so a gzip footer does not seem strictly required.
@tobias-kienzler suggested this function for the bashrc:
zlibd() (printf "\x1f\x8b\x08\x00\x00\x00\x00\x00" | cat - "$@" | gzip -dc)
It is also possible to decompress it using standard shell-script + gzip, if you don't have, or want to use openssl or other tools.
The trick is to prepend the gzip magic number and compress method to the actual data from zlib.compress:
printf "\x1f\x8b\x08\x00\x00\x00\x00\x00" |cat - /tmp/data |gzip -dc >/tmp/out
Edits:
@d0sboots commented: For RAW Deflate data, you need to add 2 more null bytes:
→ "\x1f\x8b\x08\x00\x00\x00\x00\x00\x00\x00"
This Q on SO gives more information about this approach. An answer there suggests that there is also an 8 byte footer.
Users @Vitali-Kushner and @mark-bessey reported success even with truncated files, so a gzip footer does not seem strictly required.
@tobias-kienzler suggested this function for the bashrc:
zlibd() (printf "\x1f\x8b\x08\x00\x00\x00\x00\x00" | cat - "$@" | gzip -dc)
zlib-flate -uncompress < IN_FILE > OUT_FILE
I tried this and it worked for me.
zlib-flate can be found in package qpdf (in Debian Squeeze, Fedora 23, and brew on MacOS according to comments in other answers)
(Thanks to user @tino who provided this as a comment below the OpenSSL answer. Made into propper answer for easy access.)
linux - How to run zlib from terminal on Ubuntu? - Unix & Linux Stack Exchange
red lang - How to decompress/deflate zlib data [rfc1951]? - Stack Overflow
Zlib uncompression for an noob
Looks like zlib compressed data, here's more info how to deflate it: https://unix.stackexchange.com/questions/22834/how-to-uncompress-zlib-data-in-unix
More on reddit.comblob - How can I DEFLATE with a command line tool to extract a Git object? - Stack Overflow
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i was playing ctf challenges and i stuck in this point can someone explain to me(this compression) and how i can uncompress this file .
$ file out.zlib out.zlib: zlib compressed data
Something like the following will print the raw content, including the "$type $length\0" header:
perl -MCompress::Zlib -e 'undef $/; print uncompress(<>)' \
< .git/objects/27/de0a1dd5a89a94990618632967a1c86a82d577
You can do this with the OpenSSL command line tool:
openssl zlib -d < $IN > $OUT
Unfortunately, at least on Ubuntu, the zlib subcommand is disabled in the default build configuration (--no-zlib --no-zlib-dynamic), so you would need to compile openssl from source to use it. But it is enabled by default on Arch, for example.
Edit: Seems like the zlib command is no longer supported on Arch either. This answer might not be useful anymore :(