HTTP: Implement persistent connections (keep-alive)

Both at API and at CLI level (for the CMP app only, so far)
there is a new parameter/option: keep_alive.
* 0 means HTTP connections are not kept open after
receiving a response, which is the default behavior for HTTP 1.0.
* 1 means that persistent connections are requested.
* 2 means that persistent connections are required, i.e.,
in case the server does not grant them an error occurs.

For the CMP app the default value is 1, which means preferring to keep
the connection open. For all other internal uses of the HTTP client
(fetching an OCSP response, a cert, or a CRL) it does not matter
because these operations just take one round trip.

If the client application requested or required a persistent connection
and this was granted by the server, it can keep the OSSL_HTTP_REQ_CTX *
as long as it wants to send further requests and OSSL_HTTP_is_alive()
returns nonzero,
else it should call OSSL_HTTP_REQ_CTX_free() or OSSL_HTTP_close().
In case the client application keeps the OSSL_HTTP_REQ_CTX *
but the connection then dies for any reason at the server side, it will
notice this obtaining an I/O error when trying to send the next request.

This requires extending the HTTP header parsing and
rearranging the high-level HTTP client API. In particular:
* Split the monolithic OSSL_HTTP_transfer() into OSSL_HTTP_open(),
  OSSL_HTTP_set_request(), a lean OSSL_HTTP_transfer(), and OSSL_HTTP_close().
* Split the timeout functionality accordingly and improve default behavior.
* Extract part of OSSL_HTTP_REQ_CTX_new() to OSSL_HTTP_REQ_CTX_set_expected().
* Extend struct ossl_http_req_ctx_st accordingly.

Use the new feature for the CMP client, which requires extending
related transaction management of CMP client and test server.

Update the documentation and extend the tests accordingly.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/15053)

1 files changed, 33 insertions, 7 deletions

diff --git a/apps/cmp.c b/apps/cmp.c
index d0d18c69ca..303eff10c0 100644
--- a/apps/cmp.c
+++ b/apps/cmp.c
@@ -72,6 +72,7 @@ static char *opt_path = NULL;
 static char *opt_proxy = NULL;
 static char *opt_no_proxy = NULL;
 static char *opt_recipient = NULL;
+static int opt_keep_alive = 1;
 static int opt_msg_timeout = -1;
 static int opt_total_timeout = -1;
 
@@ -205,7 +206,7 @@ typedef enum OPTION_choice {
 
     OPT_SERVER, OPT_PATH, OPT_PROXY, OPT_NO_PROXY,
     OPT_RECIPIENT,
-    OPT_MSG_TIMEOUT, OPT_TOTAL_TIMEOUT,
+    OPT_KEEP_ALIVE, OPT_MSG_TIMEOUT, OPT_TOTAL_TIMEOUT,
 
     OPT_TRUSTED, OPT_UNTRUSTED, OPT_SRVCERT,
     OPT_EXPECT_SENDER,
@@ -344,8 +345,10 @@ const OPTIONS cmp_options[] = {
      "Default from environment variable 'no_proxy', else 'NO_PROXY', else none"},
     {"recipient", OPT_RECIPIENT, 's',
      "DN of CA. Default: subject of -srvcert, -issuer, issuer of -oldcert or -cert"},
+    {"keep_alive", OPT_KEEP_ALIVE, 'N',
+     "Persistent HTTP connections. 0: no, 1 (the default): request, 2: require"},
     {"msg_timeout", OPT_MSG_TIMEOUT, 'N',
-     "Timeout per CMP message round trip (or 0 for none). Default 120 seconds"},
+     "Number of seconds allowed per CMP message round trip, or 0 for infinite"},
     {"total_timeout", OPT_TOTAL_TIMEOUT, 'N',
      "Overall time an enrollment incl. polling may take. Default 0 = infinite"},
 
@@ -530,7 +533,7 @@ static varref cmp_vars[] = { /* must be in same order as enumerated above! */
     {&opt_oldcert}, {(char **)&opt_revreason},
 
     {&opt_server}, {&opt_path}, {&opt_proxy}, {&opt_no_proxy},
-    {&opt_recipient},
+    {&opt_recipient}, {(char **)&opt_keep_alive},
     {(char **)&opt_msg_timeout}, {(char **)&opt_total_timeout},
 
     {&opt_trusted}, {&opt_untrusted}, {&opt_srvcert},
@@ -1817,6 +1820,15 @@ static int setup_client_ctx(OSSL_CMP_CTX *ctx, ENGINE *engine)
     if (!setup_verification_ctx(ctx))
         goto err;
 
+    if (opt_keep_alive != 1)
+        (void)OSSL_CMP_CTX_set_option(ctx, OSSL_CMP_OPT_KEEP_ALIVE,
+                                      opt_keep_alive);
+    if (opt_total_timeout > 0 && opt_msg_timeout > 0
+            && opt_total_timeout < opt_msg_timeout) {
+        CMP_err2("-total_timeout argument = %d must not be < %d (-msg_timeout)",
+                 opt_total_timeout, opt_msg_timeout);
+        goto err;
+    }
     if (opt_msg_timeout >= 0) /* must do this before setup_ssl_ctx() */
         (void)OSSL_CMP_CTX_set_option(ctx, OSSL_CMP_OPT_MSG_TIMEOUT,
                                       opt_msg_timeout);
@@ -2232,6 +2244,13 @@ static int get_opts(int argc, char **argv)
         case OPT_RECIPIENT:
             opt_recipient = opt_str();
             break;
+        case OPT_KEEP_ALIVE:
+            opt_keep_alive = opt_int_arg();
+            if (opt_keep_alive > 2) {
+                CMP_err("-keep_alive argument must be 0, 1, or 2");
+                goto opthelp;
+            }
+            break;
         case OPT_MSG_TIMEOUT:
             opt_msg_timeout = opt_int_arg();
             break;
@@ -2668,6 +2687,7 @@ int cmp_main(int argc, char **argv)
 #else
         BIO *acbio;
         BIO *cbio = NULL;
+        int keep_alive = 0;
         int msgs = 0;
         int retry = 1;
 
@@ -2680,7 +2700,8 @@ int cmp_main(int argc, char **argv)
 
             ret = http_server_get_asn1_req(ASN1_ITEM_rptr(OSSL_CMP_MSG),
                                            (ASN1_VALUE **)&req, &path,
-                                           &cbio, acbio, prog, 0, 0);
+                                           &cbio, acbio, &keep_alive,
+                                           prog, opt_port, 0, 0);
             if (ret == 0) { /* no request yet */
                 if (retry) {
                     sleep(1);
@@ -2712,7 +2733,8 @@ int cmp_main(int argc, char **argv)
                                                   500, "Internal Server Error");
                     break; /* treated as fatal error */
                 }
-                ret = http_server_send_asn1_resp(cbio, "application/pkixcmp",
+                ret = http_server_send_asn1_resp(cbio, keep_alive,
+                                                 "application/pkixcmp",
                                                  ASN1_ITEM_rptr(OSSL_CMP_MSG),
                                                  (const ASN1_VALUE *)resp);
                 OSSL_CMP_MSG_free(resp);
@@ -2724,8 +2746,12 @@ int cmp_main(int argc, char **argv)
                 (void)OSSL_CMP_CTX_set1_transactionID(srv_cmp_ctx, NULL);
                 (void)OSSL_CMP_CTX_set1_senderNonce(srv_cmp_ctx, NULL);
             }
-            BIO_free_all(cbio);
-            cbio = NULL;
+            if (!ret || !keep_alive
+                || OSSL_CMP_CTX_get_status(srv_cmp_ctx) == -1
+                 /* transaction closed by OSSL_CMP_CTX_server_perform() */) {
+                BIO_free_all(cbio);
+                cbio = NULL;
+            }
         }
         BIO_free_all(cbio);
         BIO_free_all(acbio);