Re: [PATCH] gpg-interface: trim CR from ssh-keygen -Y find-principals

From: Fabian Stelzer <fs@gigacodes.de>
Date: Dec 3, 2021, 14:18 UTC
Message-ID: <20211203141822.w3d2poeiylm6zpf6@fs>
In-Reply-To: <pull.1090.git.1638538276608.gitgitgadget@gmail.com>

On 03.12.2021 13:31, Johannes Schindelin via GitGitGadget wrote:

Show 6 quoted lines

>From: pedro martelletto <pedro@yubico.com>
>
>We need to trim \r from the output of 'ssh-keygen -Y find-principals' on
>Windows, or we end up calling 'ssh-keygen -Y verify' with a bogus signer
>identity. ssh-keygen.c:2841 contains a call to puts(3), which confirms this
>hypothesis. Signature verification passes with the fix.

This fix is obviously fine. But I'm a unsure if this is the only place where we would need to account for windows line endings. There are at least two similar uses in gpg-interface.c. parse_ssh_output() might include a trailing \r in the fingerprint. So I think we should do the same thing here:

diff --git a/gpg-interface.c b/gpg-interface.c
index 330cfc5845..92cd0f0ebd 100644
--- a/gpg-interface.c
+++ b/gpg-interface.c
@@ -383,7 +383,7 @@ static void parse_ssh_output(struct signature_check *sigc)
  	sigc->result = 'B';
  	sigc->trust_level = TRUST_NEVER;
  
-	line = to_free = xmemdupz(sigc->output, strcspn(sigc->output, "\n"));
+	line = to_free = xmemdupz(sigc->output, strcspn(sigc->output, "\r\n"));
  
  	if (skip_prefix(line, "Good \"git\" signature for ", &line)) {
  		/* Search for the last "with" to get the full principal */

get_default_ssh_signing_key() also splits the defaultKeyCommand output by \n 
but only puts the result into a file for ssh to use which should be able to 
deal with it.

However the whole parse_gpg_output() also assumes "\n" everywhere. So either 
GPG behaves differently under windows than ssh or a similar bug could be in 
there (and if, then probably is for a long time).
I'm not familiar with the windows details (like what MSYS2 is / whats 
different here) and don't really have the means to test it.


>
>Signed-off-by: pedro martelletto <pedro@yubico.com>
>Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
>---
>    Allow for CR in the output of ssh-keygen
>
>    This came in via https://github.com/git-for-windows/git/pull/3561. It
>    affects current Windows versions of OpenSSH (but apparently not the
>    MSYS2 version included in Git for Windows).
>
>Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1090%2Fdscho%2Fallow-cr-from-ssh-keygen-v1
>Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1090/dscho/allow-cr-from-ssh-keygen-v1
>Pull-Request: https://github.com/gitgitgadget/git/pull/1090
>
> gpg-interface.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>diff --git a/gpg-interface.c b/gpg-interface.c
>index 3e7255a2a91..85e26882782 100644
>--- a/gpg-interface.c
>+++ b/gpg-interface.c
>@@ -497,7 +497,7 @@ static int verify_ssh_signed_buffer(struct signature_check *sigc,
> 			if (!*line)
> 				break;
>
>-			trust_size = strcspn(line, "\n");
>+			trust_size = strcspn(line, "\r\n");
> 			principal = xmemdupz(line, trust_size);
>
> 			child_process_init(&ssh_keygen);
>
>base-commit: abe6bb3905392d5eb6b01fa6e54d7e784e0522aa
>-- 
>gitgitgadget