This is implements --peer-fingerprint command to support OpenVPN authentication
without involving a PKI.
The current implementation in OpenVPN for peer fingerprint has been already
extensively rewritten from the original submission from Jason. The commit
preserved the original author since it was based on Jason code/idea.
The code uses two commits to prepare the --peer-fingerprint solution as
which choose to use a simple to use --peer-fingerprint directive instead
of using using a --tls-verify script like the v1 of the patch proposed.
The two commit preparing this are:
- Extend verify-hash to allow multiple hashes
- Implement peer-fingerprint to check fingerprint of peer certificate
This perparing patches make this actual patch quite short. There are some
lines in this patch that bear some similarity to the ones like
if (!preverify_ok && !session->opt->verify_hash_no_ca)
vs
if (!preverify_ok && !session->opt->ca_file_none)
But these similarities are one line fragments and dictated by the
surrounding style and program flow, so even a complete black box
implementation will likely end up with the same lines.
Patch V2: Changes in V2 (by Arne Schwabe):
- Only check peer certificates, not all cert levels, if you need
multiple levels of certificate you should use a real CA
- Use peer-fingerprint instead tls-verify on server side in example.
- rename variable ca_file_none to verify_hash_no_ca
- do no require --ca none but allow --ca simply
to be absent when --peer-fingprint is present
- adjust warnings/errors messages to also point to
peer-fingerprint as valid verification method.
- Fix mbed TLS version of not requiring CA
not working
Patch v3: Fix minor style. Remove unessary check of verify_hash_no_ca in
ssl.c.
Patch v4: remove the last parts of Jason's original patch.
Change-Id: Ie74c3d606c5429455c293c367462244566a936e3
Signed-off-by: Arne Schwabe <a...@rfc2549.org>
---
src/openvpn/init.c | 1 +
src/openvpn/options.c | 26 +++++++++++++-------------
src/openvpn/options.h | 1 +
src/openvpn/ssl_common.h | 1 +
src/openvpn/ssl_verify_mbedtls.c | 16 ++++++++++++++++
src/openvpn/ssl_verify_openssl.c | 2 +-
6 files changed, 33 insertions(+), 14 deletions(-)
diff --git a/src/openvpn/init.c b/src/openvpn/init.c
index c023b33c6..d358ad003 100644
--- a/src/openvpn/init.c
+++ b/src/openvpn/init.c
@@ -3347,6 +3347,7 @@ do_init_crypto_tls(struct context *c, const unsigned int
flags)
to.verify_hash = options->verify_hash;
to.verify_hash_algo = options->verify_hash_algo;
to.verify_hash_depth = options->verify_hash_depth;
+ to.verify_hash_no_ca = options->verify_hash_no_ca;
#ifdef ENABLE_X509ALTUSERNAME
memcpy(to.x509_username_field, options->x509_username_field,
sizeof(to.x509_username_field));
#else
diff --git a/src/openvpn/options.c b/src/openvpn/options.c
index fe9285384..e4c596b89 100644
--- a/src/openvpn/options.c
+++ b/src/openvpn/options.c
@@ -2991,21 +2991,11 @@ options_postprocess_verify_ce(const struct options
*options,
else
{
#ifdef ENABLE_CRYPTO_MBEDTLS
- if (!(options->ca_file))
- {
- msg(M_USAGE, "You must define CA file (--ca)");
- }
-
if (options->ca_path)
{
msg(M_USAGE, "Parameter --capath cannot be used with the mbed
TLS version version of OpenVPN.");
}
-#else /* ifdef ENABLE_CRYPTO_MBEDTLS */
- if ((!(options->ca_file)) && (!(options->ca_path)))
- {
- msg(M_USAGE, "You must define CA file (--ca) or CA path
(--capath)");
- }
-#endif
+#endif /* ifdef ENABLE_CRYPTO_MBEDTLS */
if (pull)
{
@@ -3737,6 +3727,13 @@ options_postprocess_mutate(struct options *o, struct
env_set *es)
options_postprocess_http_proxy_override(o);
}
#endif
+ if (!o->ca_file && !o->ca_path && o->verify_hash
+ && o->verify_hash_depth == 0)
+ {
+ msg(M_INFO, "Using certificate fingerprint to verify peer (no CA "
+ "option set). ");
+ o->verify_hash_no_ca = true;
+ }
if (o->config && streq(o->config, "stdin") && o->remap_sigusr1 == SIGHUP)
{
@@ -4032,8 +4029,11 @@ options_postprocess_filechecks(struct options *options)
errs |= check_file_access_inline(options->dh_file_inline, CHKACC_FILE,
options->dh_file, R_OK, "--dh");
- errs |= check_file_access_inline(options->ca_file_inline, CHKACC_FILE,
- options->ca_file, R_OK, "--ca");
+ if (!options->verify_hash_no_ca)
+ {
+ errs |= check_file_access_inline(options->ca_file_inline, CHKACC_FILE,
+ options->ca_file, R_OK, "--ca");
+ }
errs |= check_file_access_chroot(options->chroot_dir, CHKACC_FILE,
options->ca_path, R_OK, "--capath");
diff --git a/src/openvpn/options.h b/src/openvpn/options.h
index 95f1158a4..f5890b90f 100644
--- a/src/openvpn/options.h
+++ b/src/openvpn/options.h
@@ -604,6 +604,7 @@ struct options
struct verify_hash_list *verify_hash;
hash_algo_type verify_hash_algo;
int verify_hash_depth;
+ bool verify_hash_no_ca;
unsigned int ssl_flags; /* set to SSLF_x flags from ssl.h */
#ifdef ENABLE_PKCS11
diff --git a/src/openvpn/ssl_common.h b/src/openvpn/ssl_common.h
index c0b3caa71..27b029479 100644
--- a/src/openvpn/ssl_common.h
+++ b/src/openvpn/ssl_common.h
@@ -345,6 +345,7 @@ struct tls_options
const char *remote_cert_eku;
struct verify_hash_list *verify_hash;
int verify_hash_depth;
+ bool verify_hash_no_ca;
hash_algo_type verify_hash_algo;
#ifdef ENABLE_X509ALTUSERNAME
char *x509_username_field[MAX_PARMS];
diff --git a/src/openvpn/ssl_verify_mbedtls.c b/src/openvpn/ssl_verify_mbedtls.c
index c9ef7a171..e3437f740 100644
--- a/src/openvpn/ssl_verify_mbedtls.c
+++ b/src/openvpn/ssl_verify_mbedtls.c
@@ -62,6 +62,22 @@ verify_callback(void *session_obj, mbedtls_x509_crt *cert,
int cert_depth,
struct buffer cert_fingerprint = x509_get_sha256_fingerprint(cert, &gc);
cert_hash_remember(session, cert_depth, &cert_fingerprint);
+ if (session->opt->verify_hash_no_ca)
+ {
+ /*
+ * If we decide to verify the peer certificate based on the fingerprint
+ * we ignore wrong dates and the certificate not being trusted.
+ * Any other problem with the certificate (wrong key, bad cert,...)
+ * will still trigger an error.
+ * Clearing these flags relies on verify_cert will later rejecting a
+ * certificate that has no matching fingerprint.
+ */
+ uint32_t flags_ignore = MBEDTLS_X509_BADCERT_NOT_TRUSTED
+ | MBEDTLS_X509_BADCERT_EXPIRED
+ | MBEDTLS_X509_BADCERT_FUTURE;
+ *flags = *flags & ~flags_ignore;
+ }
+
/* did peer present cert which was signed by our root cert? */
if (*flags != 0)
{
diff --git a/src/openvpn/ssl_verify_openssl.c b/src/openvpn/ssl_verify_openssl.c
index ac36f09db..e24ce4e4a 100644
--- a/src/openvpn/ssl_verify_openssl.c
+++ b/src/openvpn/ssl_verify_openssl.c
@@ -67,7 +67,7 @@ verify_callback(int preverify_ok, X509_STORE_CTX *ctx)
cert_hash_remember(session, X509_STORE_CTX_get_error_depth(ctx),
&cert_hash);
/* did peer present cert which was signed by our root cert? */
- if (!preverify_ok)
+ if (!preverify_ok && !session->opt->verify_hash_no_ca)
{
/* get the X509 name */
char *subject = x509_get_subject(current_cert, &gc);
--
2.39.2 (Apple Git-143)
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