[arch-general] adb backup broken named pipe

[Pascal]

when I looked a little closer at what adb backup was doing, I realized that
it was communicating with an adb server running in parallel and, by
mimicking the conversation with python, I managed to get what I wanted.
*(note that a small error was present in the question : the string to use
with printf is "\x1f\x8b\x08\x00\x00\x00\x00\x00").*

I still have a slight problem because the tar command ends with an error :
*(the same error is also present with adb, printf and tail).*

$ adb devices
List of devices attached
CB5A2B0M9R    device
$ python3 adbackup.py > /tmp/mybackup.tgz
$ tar tvzf /tmp/mybackup.tgz
... all my files are here :-)
gzip: stdin: unexpected end of file
tar: Child returned status 1
tar: Error is not recoverable: exiting now

adbackup.py :

#!/usr/bin/python3

# strace adb backup -all -f /tmp/backup.ab
#    ...
#    unlink("/tmp/backup.ab")                = 0
#    creat("/tmp/backup.ab", 0640)           = 3
#    ...
#    socket(AF_INET, SOCK_STREAM, IPPROTO_IP) = 4
#    bind(4, {sa_family=AF_INET, sin_port=htons(0),
sin_addr=inet_addr("127.0.0.1")}, 16) = 0
#    connect(4, {sa_family=AF_INET, sin_port=htons(5037),
sin_addr=inet_addr("127.0.0.1")}, 16) = 0
#    setsockopt(4, SOL_TCP, TCP_NODELAY, [1], 4) = 0
#    write(4, "0012host:transport-any", 22)  = 22
#    read(4, "OKAY", 4)                      = 4
#    write(4, "000ebackup: '-all'", 18)      = 18
#    read(4, "OKAY", 4)                      = 4
#    fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0x1), ...}) = 0
#    write(1, "Now unlock your device and confi"..., 59) = 59
#    read(4, "ANDROID BACKUP\n4\n1\nnone\n", 32768) = 24
#    write(3, "ANDROID BACKUP\n4\n1\nnone\n", 24) = 24
#    read(4, "x\332", 32768)                 = 2
#    write(3, "x\332", 2)                    = 2
#    read(4, "\344VY\256\35E\f}\337o\25\254
\361\\U\253A\256\301(\37$Q\22\366\317\251\233\274(\240"..., 32768) = 967

import socket, sys
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("localhost", 5037))
s.sendall(b"0012host:transport-any")
data = s.recv(4)        # b"OKAY"
s.sendall(b"000ebackup: '-all'")
data = s.recv(4)        # b"OKAY"
data = s.recv(32768)    # b"ANDROID BACKUP\n4\n1\nnone\n"
sys.stdout.buffer.write(b"\x1f\x8b\x08\x00\x00\x00\x00\x00")
data = s.recv(32768)
while data:
    sys.stdout.buffer.write(data)
    data = s.recv(32768)

regards, lacsaP.

Le jeu. 16 mai 2019 à 10:57, Pascal <patatetom at gmail.com> a écrit :

> hello,
>
> I'm looking for a solution for the problem below : all leads are welcome !
>
> the adb tool is able to make a backup of a smartphone in a file:
> adb backup -all -f mybackup.ab
>
> however, the file mybackup.ab has a particular format that prevents it
> from being used "simply".
> to convert it into a tgz archive, it is possible to do this:
> ( printf "\x1f\x8b\x08\x08\x00\x00\x00\x00\x00\x00\x00"; tail -c +25
> mybackup.ab ) > mybackup.tgz
>
> but in this case, I can easily end up with two files of 16Gb or more...
> to avoid this volume problem, I tried to do this:
> mkfifo backup.fifo
> adb backup -all -f backup.fifo &
> ( printf "\x1f\x8b\x08\x08\x00\x00\x00\x00\x00\x00" ; tail -c +25
> backup.fifo) > mybackup.tgz
>
> but adb systematically breaks my named pipe and my code doesn't work as
> expected.
> how to prevent adb from breaking the named pipe ?
> I'm considering using fuse but there may be a simpler way...
>
> regards, lacsaP.
>