[Openvpn-devel,v2] Fix OpenSSL error stack handling of tls_ctx_add_extra_certs

Message ID 20200402081829.28362-1-arne@rfc2549.org
State Superseded
Headers show
Series
  • [Openvpn-devel,v2] Fix OpenSSL error stack handling of tls_ctx_add_extra_certs
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Commit Message

Arne Schwabe April 2, 2020, 8:18 a.m.
Commit f67efa94 exposed that tls_ctx_add_extra_certs will always leave
an error of PEM_R_NO_START_LINE on the stack that will printed the next
time that the error is printed.

Fix this by discarding this error. Also clean up the logic to report
real error on other errors and also the no start line error if no
certificate can be found at all and it is required (--extra-certs
config option)

Patch V2: fix optional flag was flipped betwen --cert and --extra-certs

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
---
 src/openvpn/ssl_openssl.c | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

Patch

diff --git a/src/openvpn/ssl_openssl.c b/src/openvpn/ssl_openssl.c
index 3f0031ff..ef5dfc52 100644
--- a/src/openvpn/ssl_openssl.c
+++ b/src/openvpn/ssl_openssl.c
@@ -881,24 +881,36 @@  tls_ctx_load_cryptoapi(struct tls_root_ctx *ctx, const char *cryptoapi_cert)
 #endif /* ENABLE_CRYPTOAPI */
 
 static void
-tls_ctx_add_extra_certs(struct tls_root_ctx *ctx, BIO *bio)
+tls_ctx_add_extra_certs(struct tls_root_ctx *ctx, BIO *bio, bool optional)
 {
     X509 *cert;
-    for (;; )
+    for (;;)
     {
         cert = NULL;
-        if (!PEM_read_bio_X509(bio, &cert, NULL, NULL)) /* takes ownership of cert */
+        if (!PEM_read_bio_X509(bio, &cert, NULL, NULL))
         {
-            break;
+            /* Error indicates that no more certificates is found in buffer
+               and loading more certificates is optional, break without
+               error */
+            if (optional &&
+                ERR_GET_REASON(ERR_peek_error()) == PEM_R_NO_START_LINE)
+            {
+                /* remove that error from error stack */
+                (void)ERR_get_error();
+                break;
+            }
         }
         if (!cert)
         {
             crypto_msg(M_FATAL, "Error reading extra certificate");
         }
+        /* takes ownership of cert like a set1 method */
         if (SSL_CTX_add_extra_chain_cert(ctx->ctx, cert) != 1)
         {
             crypto_msg(M_FATAL, "Error adding extra certificate");
         }
+        /* We loaded at least one certificate, so loading more is optional */
+        optional = true;
     }
 }
 
@@ -942,7 +954,7 @@  tls_ctx_load_cert_file(struct tls_root_ctx *ctx, const char *cert_file,
     ret = SSL_CTX_use_certificate(ctx->ctx, x);
     if (ret)
     {
-        tls_ctx_add_extra_certs(ctx, in);
+        tls_ctx_add_extra_certs(ctx, in, true);
     }
 
 end:
@@ -1663,7 +1675,7 @@  tls_ctx_load_extra_certs(struct tls_root_ctx *ctx, const char *extra_certs_file,
     }
     else
     {
-        tls_ctx_add_extra_certs(ctx, in);
+        tls_ctx_add_extra_certs(ctx, in, false);
     }
 
     BIO_free(in);