ci: use ecdsa keys for ssh

Using modern rsa (sha2-256 or sha2-512) with libssh2 is complicated and
depends on numerous factors for support. Just use ecdsa, which is
supported by both libssh2 v1.11.0 and modern OpenSSH (which we use for
our server in CI).

ci/test.sh

@@ -25,6 +25,8 @@ CTEST=$(which ctest)
 TMPDIR=${TMPDIR:-/tmp}
 USER=${USER:-$(whoami)}
 
+GITTEST_SSH_KEYTYPE=${GITTEST_SSH_KEYTYPE:="ecdsa"}
+
 HOME=`mktemp -d ${TMPDIR}/home.XXXXXXXX`
 export CLAR_HOMEDIR=${HOME}
 
@@ -207,7 +209,7 @@ if should_run "SSH_TESTS"; then
 	Port 2222
 	ListenAddress 0.0.0.0
 	Protocol 2
-	HostKey ${SSHD_DIR}/id_rsa
+	HostKey ${SSHD_DIR}/id_${GITTEST_SSH_KEYTYPE}
 	PidFile ${SSHD_DIR}/pid
 	AuthorizedKeysFile ${HOME}/.ssh/authorized_keys
 	LogLevel DEBUG
@@ -216,21 +218,21 @@ if should_run "SSH_TESTS"; then
 	PubkeyAuthentication yes
 	ChallengeResponseAuthentication no
 	StrictModes no
-	HostCertificate ${SSHD_DIR}/id_rsa.pub
-	HostKey ${SSHD_DIR}/id_rsa
+	HostCertificate ${SSHD_DIR}/id_${GITTEST_SSH_KEYTYPE}.pub
+	HostKey ${SSHD_DIR}/id_${GITTEST_SSH_KEYTYPE}
 	# Required here as sshd will simply close connection otherwise
 	UsePAM no
 	EOF
-	ssh-keygen -t rsa -f "${SSHD_DIR}/id_rsa" -N "" -q
+	ssh-keygen -t "${GITTEST_SSH_KEYTYPE}" -f "${SSHD_DIR}/id_${GITTEST_SSH_KEYTYPE}" -N "" -q
 	/usr/sbin/sshd -f "${SSHD_DIR}/sshd_config" -E "${SSHD_DIR}/log"
 
 	# Set up keys
 	mkdir "${HOME}/.ssh"
-	ssh-keygen -t rsa -f "${HOME}/.ssh/id_rsa" -N "" -q
-	cat "${HOME}/.ssh/id_rsa.pub" >>"${HOME}/.ssh/authorized_keys"
+	ssh-keygen -t "${GITTEST_SSH_KEYTYPE}" -f "${HOME}/.ssh/id_${GITTEST_SSH_KEYTYPE}" -N "" -q
+	cat "${HOME}/.ssh/id_${GITTEST_SSH_KEYTYPE}.pub" >>"${HOME}/.ssh/authorized_keys"
 	while read algorithm key comment; do
 		echo "[localhost]:2222 $algorithm $key" >>"${HOME}/.ssh/known_hosts"
-	done <"${SSHD_DIR}/id_rsa.pub"
+	done <"${SSHD_DIR}/id_${GITTEST_SSH_KEYTYPE}.pub"
 
 	# Append the github.com keys for the tests that don't override checks.
 	# We ask for ssh-rsa to test that the selection based off of known_hosts
@@ -428,12 +430,12 @@ fi
 
 if should_run "SSH_TESTS"; then
 	export GITTEST_REMOTE_USER=$USER
-	export GITTEST_REMOTE_SSH_KEY="${HOME}/.ssh/id_rsa"
-	export GITTEST_REMOTE_SSH_PUBKEY="${HOME}/.ssh/id_rsa.pub"
+	export GITTEST_REMOTE_SSH_KEY="${HOME}/.ssh/id_${GITTEST_SSH_KEYTYPE}"
+	export GITTEST_REMOTE_SSH_PUBKEY="${HOME}/.ssh/id_${GITTEST_SSH_KEYTYPE}.pub"
 	export GITTEST_REMOTE_SSH_PASSPHRASE=""
 	export GITTEST_REMOTE_SSH_FINGERPRINT="${SSH_FINGERPRINT}"
 
-	export GITTEST_SSH_CMD="ssh -i ${HOME}/.ssh/id_rsa -o UserKnownHostsFile=${HOME}/.ssh/known_hosts"
+	export GITTEST_SSH_CMD="ssh -i ${HOME}/.ssh/id_${GITTEST_SSH_KEYTYPE} -o UserKnownHostsFile=${HOME}/.ssh/known_hosts"
 
 	echo ""
 	echo "Running ssh tests"