threads / discuss / 52258

Protocol v2: The wrong --shallow-since time format causes git to wait indefinitely

Subject: Protocol v2: The wrong --shallow-since time format causes git to wait indefinitely

## tl;dr

4 messages between Nov 13, 2019 and Nov 19, 2019.

replies: 3people: 3as markdown or json

Force.Charlie· Nov 13, 2019, 01:00 UTC · lore
Recently, when I tested my Git Over HTTP server, I found a bug in Git. When we used git -c protocol.version=2 clone --shallow-since , if the time format is wrong, it will cause git to wait indefinitely.
Github supports Wire Protocol to reproduce, Gitlab does not support it and does not reproduce it.
The commands that can be retried are as follows:

```shell # time format wrong git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=20151012 # trace GIT_TRACE=1 GIT_CURL_VERBOSE=1 GIT_TRACE_PACKET=2 git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=20151012 ``` We can see that the server closes the HTTP connection after sending the `shallow-info\n` message, and git-remote-http(s) is still waiting.

``` $ git --version --build-options git version 2.24.0 cpu: x86_64 no commit associated with this build sizeof-long: 8 sizeof-size_t: 8

```
When the time format is correct, the clone is successful, so this is followed by the shallow-list：

```shell GIT_TRACE=1 GIT_CURL_VERBOSE=1 GIT_TRACE_PACKET=2 git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=2015-10-12 ```

Github Issues: https://github.com/gitgitgadget/git/issues/457
Junio C Hamano· Nov 13, 2019, 03:42 UTC · re: Force.Charlie · lore

Re: Protocol v2: The wrong --shallow-since time format causes git to wait indefinitely

"Force.Charlie" <force@forcemz.net> writes:
> # time format wrong
> git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=20151012

That's the valid/right way to specify the timestamp that is 20,151,012 seconds after the epoch (i.e. 1970-01-01), isn't it?

Denton Liu· Nov 19, 2019, 23:36 UTC · re: Junio C Hamano · lore

Re: Protocol v2: The wrong --shallow-since time format causes git to wait indefinitely

Hi Junio,
On Wed, Nov 13, 2019 at 12:42:28PM +0900, Junio C Hamano wrote:
Show 7 quoted lines
> "Force.Charlie" <force@forcemz.net> writes:
> 
> > # time format wrong
> > git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=20151012
> 
> That's the valid/right way to specify the timestamp that is
> 20,151,012 seconds after the epoch (i.e. 1970-01-01), isn't it?

I don't think so. When we run the same thing under protocol v1, we get the following:

	$ git -c protocol.version=1 clone https://github.com/git/git.git --shallow-since=20151012
	Cloning into 'git'...
	fatal: the remote end hung up unexpectedly
even though the following does work:
	$ git -c protocol.version=1 clone https://github.com/git/git.git --shallow-since=2015-10-12
	Cloning into 'git'...
	remote: Enumerating objects: 93982, done.
	...
which suggests to me that the non-dashed form is invalid.
Thanks,
Denton
Denton Liu· Nov 19, 2019, 23:46 UTC · re: Force.Charlie · lore

Re: Protocol v2: The wrong --shallow-since time format causes git to wait indefinitely

On Wed, Nov 13, 2019 at 09:00:52AM +0800, Force.Charlie wrote:
Show 31 quoted lines
> Recently, when I tested my Git Over HTTP server, I found a bug in Git. When we used git -c protocol.version=2 clone --shallow-since , if the time format is wrong, it will cause git to wait indefinitely.
> 
> Github supports Wire Protocol to reproduce, Gitlab does not support it and does not reproduce it.
> 
> The commands that can be retried are as follows:
> 
> ```shell
> # time format wrong
> git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=20151012
> # trace
> GIT_TRACE=1 GIT_CURL_VERBOSE=1 GIT_TRACE_PACKET=2 git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=20151012
> ```
> We can see that the server closes the HTTP connection after sending the `shallow-info\n` message, and git-remote-http(s) is still waiting.
> 
> ```
> $ git --version --build-options
> git version 2.24.0
> cpu: x86_64
> no commit associated with this build
> sizeof-long: 8
> sizeof-size_t: 8
> 
> ```
> 
> When the time format is correct, the clone is successful, so this is followed by the shallow-list：
> 
> ```shell
> GIT_TRACE=1 GIT_CURL_VERBOSE=1 GIT_TRACE_PACKET=2 git -c protocol.version=2 clone https://github.com/git/git.git --shallow-since=2015-10-12
> ```
> 
> Github Issues: https://github.com/gitgitgadget/git/issues/457

FWIW, I can reproduce this issue as well. From what I can tell (without actually looking at any code), it seems like when an invalid `--shallow-since` is given to the server, it'll hang up on the client.

With protocol v1, the client quits as expected:
	$ git -c protocol.version=1 clone https://github.com/git/git.git --shallow-since=20151012
	Cloning into 'git'...
	fatal: the remote end hung up unexpectedly

However, with v2, I believe that the client doesn't detect the hang up and just waits forever.

Unfortunately, I don't know the networking code at all and I don't have time to actually dig into the code. Hopefully this helps a little bit, though.

Thanks,
Denton

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