On 9/22/18 7:30 AM, Bob Proulx wrote:
> dirk+b...@testssl.sh wrote:
>> we discovered a strange phenomenon in the project testssl.sh:
>
> You are doing something that is quite unusual. You are using a shell
> script direction on a TCP socket. That isn't very common.
Do you think there should be a paragraph NOT COMMON where bash sockets
should rather belong to?
> More
> typically one would use a C program instead. So it isn't surprising
> that you are finding interactions that are not well known.
Bob, my intention was not to discuss program languages and what is typical
with you or anybody else here.
>> printf -- "$data" >&5 2>/dev/null
>
> Why is stderr discarded? That is almost always bad because it
> discards any errors that might occur. You probably shouldn't do this.>
> What happens if $data contains % format strings? What happens if the
> format contains a sequence such as \c? This looks problematic. This
> is not a safe programming proctice.
I doubt you can judge on this by just looking at a single line
of code -- the project has > 18k LoC in bash.
Github is the place to discuss and do PRs for our project.
>> If there's a workaround, please let me know. (tried to add "%b" with no
>> effect). Otherwise I believe it's a bug.
>
> You can re-block the output stream using other tools such as 'cat' or
> 'dd'. Since you are concerned about block size then perhaps dd is the
> better of the two.
>
> | cat
cat has a problem with binary chars, right? And: see below.
> Or probably better:
>
> | dd status=none bs=1M
>
> Or use whatever block size you wish. The 'dd' program will read the
> input into its buffer and then output that block of data all in one
> write(2). That seems to be what you are wanting.
We actually use dd to read from the socket. Of course we could use
writing to it as well -- at a certain point of time.
Still, a prerequisite would be that printf is the culprit and not
how bash + libs do sockets.
> P.S. You can possibly use the 'stdbuf' command to control the output
> buffering depending upon the program.
>
> info stdbuf
That could be an option, thanks. Need to check though whether
a) it doesn't fragment then -- not sure while reading it
b) it's per default available on every platform supported by testssl.sh.
Cheers, Dirk
