ssh signing: don't detach the filename strbuf from key_file tempfile

Detaching the filename string from the tempfile structure used to cause
delete_tempfile() to fail and the temporary file was not cleaned up.

While it's possible to get rid of the allocation and copy from
xstrdup(), it keeps the code symetric with the other branch since
interpolate_path() also allocates and ssh_signing_key_file is freed
in both cases.

The exisiting test was updated to check if the temporary files are
properly deleted. To prevent TMPDIR from leaking into the other tests, a
new subshell is created, however this prevents test_config from working.
The cleanup of the config changed in the subshell is done by
test_unconfig in a call to test_when_finished outside of it.

Helped-by: brian m. carlson <[email protected]>
Helped-by: Patrick Steinhardt <[email protected]>
Helped-by: Phillip Wood <[email protected]>
Signed-off-by: redoste <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: redoste

gpg-interface.c

@@ -1048,7 +1048,7 @@ static int sign_buffer_ssh(struct strbuf *buffer, struct strbuf *signature,
 				    key_file->filename.buf);
 			goto out;
 		}
-		ssh_signing_key_file = strbuf_detach(&key_file->filename, NULL);
+		ssh_signing_key_file = xstrdup(key_file->filename.buf);
 	} else {
 		/* We assume a file */
 		ssh_signing_key_file = interpolate_path(signing_key, 1);

t/t7528-signed-commit-ssh.sh

@@ -84,18 +84,26 @@ test_expect_success GPGSSH 'sign commits using literal public keys with ssh-agen
 	test_config gpg.format ssh &&
 	eval $(ssh-agent) &&
 	test_when_finished "kill ${SSH_AGENT_PID}" &&
-	ssh-add "${GPGSSH_KEY_PRIMARY}" &&
-	echo 1 >file && git add file &&
-	git commit -a -m rsa-inline -S"$(cat "${GPGSSH_KEY_PRIMARY}.pub")" &&
-	echo 2 >file &&
-	test_config user.signingkey "$(cat "${GPGSSH_KEY_PRIMARY}.pub")" &&
-	git commit -a -m rsa-config -S &&
-	ssh-add "${GPGSSH_KEY_ECDSA}" &&
-	echo 3 >file &&
-	git commit -a -m ecdsa-inline -S"key::$(cat "${GPGSSH_KEY_ECDSA}.pub")" &&
-	echo 4 >file &&
-	test_config user.signingkey "key::$(cat "${GPGSSH_KEY_ECDSA}.pub")" &&
-	git commit -a -m ecdsa-config -S
+	test_when_finished "test_unconfig user.signingkey" &&
+	mkdir tmpdir &&
+	TMPDIR="$(pwd)/tmpdir" &&
+	(
+		export TMPDIR &&
+		ssh-add "${GPGSSH_KEY_PRIMARY}" &&
+		echo 1 >file && git add file &&
+		git commit -a -m rsa-inline -S"$(cat "${GPGSSH_KEY_PRIMARY}.pub")" &&
+		echo 2 >file &&
+		git config user.signingkey "$(cat "${GPGSSH_KEY_PRIMARY}.pub")" &&
+		git commit -a -m rsa-config -S &&
+		ssh-add "${GPGSSH_KEY_ECDSA}" &&
+		echo 3 >file &&
+		git commit -a -m ecdsa-inline -S"key::$(cat "${GPGSSH_KEY_ECDSA}.pub")" &&
+		echo 4 >file &&
+		git config user.signingkey "key::$(cat "${GPGSSH_KEY_ECDSA}.pub")" &&
+		git commit -a -m ecdsa-config -S
+	) &&
+	find tmpdir -type f >tmpfiles &&
+	test_must_be_empty tmpfiles
 '
 
 test_expect_success GPGSSH,GPGSSH_VERIFYTIME 'create signed commits with keys having defined lifetimes' '