ssh signing: support non ssh-* keytypes
The user.signingKey config for ssh signing supports either a path to a file containing the key or for the sake of convenience a literal string with the ssh public key. To differentiate between those two cases we check if the first few characters contain "ssh-" which is unlikely to be the start of a path. ssh supports other key types which are not prefixed with "ssh-" and will currently be treated as a file path and therefore fail to load. To remedy this we move the prefix check into its own function and introduce the prefix `key::` for literal ssh keys. This way we don't need to add new key types when they become available. The existing `ssh-` prefix is retained for compatibility with current user configs but removed from the official documentation to discourage its use. Signed-off-by: Fabian Stelzer <fs@gigacodes.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Fabian Stelzer committed
Nov 19, 2021 at 16:07 UTC
350a2518c8ea4f42934b4d6f3466d2815efff97f
4 files changed
+65
-15
Documentation/config/user.txt
+10
-7
@@ -36,10 +36,13 @@ user.signingKey::
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commit, you can override the default selection with this variable.
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This option is passed unchanged to gpg's --local-user parameter,
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so you may specify a key using any method that gpg supports.
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- If gpg.format is set to "ssh" this can contain the literal ssh public
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- key (e.g.: "ssh-rsa XXXXXX identifier") or a file which contains it and
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- corresponds to the private key used for signing. The private key
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- needs to be available via ssh-agent. Alternatively it can be set to
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- a file containing a private key directly. If not set git will call
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- gpg.ssh.defaultKeyCommand (e.g.: "ssh-add -L") and try to use the first
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- key available.
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+ If gpg.format is set to `ssh` this can contain the path to either
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+ your private ssh key or the public key when ssh-agent is used.
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+ Alternatively it can contain a public key prefixed with `key::`
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+ directly (e.g.: "key::ssh-rsa XXXXXX identifier"). The private key
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+ needs to be available via ssh-agent. If not set git will call
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+ gpg.ssh.defaultKeyCommand (e.g.: "ssh-add -L") and try to use the
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+ first key available. For backward compatibility, a raw key which
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+ begins with "ssh-", such as "ssh-rsa XXXXXX identifier", is treated
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+ as "key::ssh-rsa XXXXXX identifier", but this form is deprecated;
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+ use the `key::` form instead.
gpg-interface.c
+29
-7
@@ -707,6 +707,21 @@ int git_gpg_config(const char *var, const char *value, void *cb)
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return 0;
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}
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+/*
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+ * Returns 1 if `string` contains a literal ssh key, 0 otherwise
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+ * `key` will be set to the start of the actual key if a prefix is present.
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+ */
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+static int is_literal_ssh_key(const char *string, const char **key)
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+{
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+ if (skip_prefix(string, "key::", key))
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+ return 1;
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+ if (starts_with(string, "ssh-")) {
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+ *key = string;
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+ return 1;
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+ }
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+ return 0;
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+}
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+
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static char *get_ssh_key_fingerprint(const char *signing_key)
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{
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struct child_process ssh_keygen = CHILD_PROCESS_INIT;
@@ -714,15 +729,16 @@ static char *get_ssh_key_fingerprint(const char *signing_key)
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struct strbuf fingerprint_stdout = STRBUF_INIT;
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struct strbuf **fingerprint;
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char *fingerprint_ret;
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+ const char *literal_key = NULL;
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/*
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* With SSH Signing this can contain a filename or a public key
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* For textual representation we usually want a fingerprint
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*/
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- if (starts_with(signing_key, "ssh-")) {
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+ if (is_literal_ssh_key(signing_key, &literal_key)) {
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strvec_pushl(&ssh_keygen.args, "ssh-keygen", "-lf", "-", NULL);
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- ret = pipe_command(&ssh_keygen, signing_key,
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- strlen(signing_key), &fingerprint_stdout, 0,
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+ ret = pipe_command(&ssh_keygen, literal_key,
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+ strlen(literal_key), &fingerprint_stdout, 0,
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NULL, 0);
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} else {
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strvec_pushl(&ssh_keygen.args, "ssh-keygen", "-lf",
@@ -757,6 +773,7 @@ static const char *get_default_ssh_signing_key(void)
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const char **argv;
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int n;
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char *default_key = NULL;
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+ const char *literal_key = NULL;
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if (!ssh_default_key_command)
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die(_("either user.signingkey or gpg.ssh.defaultKeyCommand needs to be configured"));
@@ -774,7 +791,11 @@ static const char *get_default_ssh_signing_key(void)
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if (!ret) {
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keys = strbuf_split_max(&key_stdout, '\n', 2);
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- if (keys[0] && starts_with(keys[0]->buf, "ssh-")) {
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+ if (keys[0] && is_literal_ssh_key(keys[0]->buf, &literal_key)) {
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+ /*
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+ * We only use `is_literal_ssh_key` here to check validity
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+ * The prefix will be stripped when the key is used.
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+ */
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default_key = strbuf_detach(keys[0], NULL);
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} else {
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warning(_("gpg.ssh.defaultKeyCommand succeeded but returned no keys: %s %s"),
@@ -889,19 +910,20 @@ static int sign_buffer_ssh(struct strbuf *buffer, struct strbuf *signature,
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struct tempfile *key_file = NULL, *buffer_file = NULL;
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char *ssh_signing_key_file = NULL;
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struct strbuf ssh_signature_filename = STRBUF_INIT;
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+ const char *literal_key = NULL;
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if (!signing_key || signing_key[0] == '\0')
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return error(
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_("user.signingkey needs to be set for ssh signing"));
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- if (starts_with(signing_key, "ssh-")) {
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+ if (is_literal_ssh_key(signing_key, &literal_key)) {
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/* A literal ssh key */
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key_file = mks_tempfile_t(".git_signing_key_tmpXXXXXX");
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if (!key_file)
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return error_errno(
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_("could not create temporary file"));
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- keylen = strlen(signing_key);
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- if (write_in_full(key_file->fd, signing_key, keylen) < 0 ||
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+ keylen = strlen(literal_key);
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+ if (write_in_full(key_file->fd, literal_key, keylen) < 0 ||
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close_tempfile_gently(key_file) < 0) {
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error_errno(_("failed writing ssh signing key to '%s'"),
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key_file->filename.buf);
t/lib-gpg.sh
+3
@@ -91,6 +91,7 @@ GPGSSH_KEY_PRIMARY="${GNUPGHOME}/ed25519_ssh_signing_key"
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GPGSSH_KEY_SECONDARY="${GNUPGHOME}/rsa_2048_ssh_signing_key"
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GPGSSH_KEY_UNTRUSTED="${GNUPGHOME}/untrusted_ssh_signing_key"
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GPGSSH_KEY_WITH_PASSPHRASE="${GNUPGHOME}/protected_ssh_signing_key"
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+GPGSSH_KEY_ECDSA="${GNUPGHOME}/ecdsa_ssh_signing_key"
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GPGSSH_KEY_PASSPHRASE="super_secret"
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GPGSSH_ALLOWED_SIGNERS="${GNUPGHOME}/ssh.all_valid.allowedSignersFile"
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@@ -119,6 +120,8 @@ test_lazy_prereq GPGSSH '
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echo "\"principal with number 2\" $(cat "${GPGSSH_KEY_SECONDARY}.pub")" >> "${GPGSSH_ALLOWED_SIGNERS}" &&
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ssh-keygen -t ed25519 -N "${GPGSSH_KEY_PASSPHRASE}" -C "git ed25519 encrypted key" -f "${GPGSSH_KEY_WITH_PASSPHRASE}" >/dev/null &&
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echo "\"principal with number 3\" $(cat "${GPGSSH_KEY_WITH_PASSPHRASE}.pub")" >> "${GPGSSH_ALLOWED_SIGNERS}" &&
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+ ssh-keygen -t ecdsa -N "" -f "${GPGSSH_KEY_ECDSA}" >/dev/null
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+ echo "\"principal with number 4\" $(cat "${GPGSSH_KEY_ECDSA}.pub")" >> "${GPGSSH_ALLOWED_SIGNERS}" &&
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ssh-keygen -t ed25519 -N "" -f "${GPGSSH_KEY_UNTRUSTED}" >/dev/null
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'
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t/t7528-signed-commit-ssh.sh
+23
-1
@@ -73,7 +73,29 @@ test_expect_success GPGSSH 'create signed commits' '
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git tag eleventh-signed $(cat oid) &&
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echo 12 | git commit-tree --gpg-sign="${GPGSSH_KEY_UNTRUSTED}" HEAD^{tree} >oid &&
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test_line_count = 1 oid &&
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- git tag twelfth-signed-alt $(cat oid)
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+ git tag twelfth-signed-alt $(cat oid) &&
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+
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+ echo 13>file && test_tick && git commit -a -m thirteenth -S"${GPGSSH_KEY_ECDSA}" &&
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+ git tag thirteenth-signed-ecdsa
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+'
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+
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+test_expect_success GPGSSH 'sign commits using literal public keys with ssh-agent' '
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+ test_when_finished "test_unconfig commit.gpgsign" &&
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+ test_config gpg.format ssh &&
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+ eval $(ssh-agent) &&
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+ test_when_finished "kill ${SSH_AGENT_PID}" &&
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+ ssh-add "${GPGSSH_KEY_PRIMARY}" &&
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+ echo 1 >file && git add file &&
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+ git commit -a -m rsa-inline -S"$(cat "${GPGSSH_KEY_PRIMARY}.pub")" &&
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+ echo 2 >file &&
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+ test_config user.signingkey "$(cat "${GPGSSH_KEY_PRIMARY}.pub")" &&
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+ git commit -a -m rsa-config -S &&
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+ ssh-add "${GPGSSH_KEY_ECDSA}" &&
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+ echo 3 >file &&
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+ git commit -a -m ecdsa-inline -S"key::$(cat "${GPGSSH_KEY_ECDSA}.pub")" &&
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+ echo 4 >file &&
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+ test_config user.signingkey "key::$(cat "${GPGSSH_KEY_ECDSA}.pub")" &&
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+ git commit -a -m ecdsa-config -S
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'
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test_expect_success GPGSSH 'verify and show signatures' '