From bf535969ac23962b65b72ea3893c6b384e1d3218 Mon Sep 17 00:00:00 2001
From: Julian Brost <julian.brost@icinga.com>
Date: Thu, 12 Aug 2021 16:42:23 +0200
Subject: [PATCH] ElasticsearchWriter: actually verify TLS server certificates

And add a new option insecure_noverify to explicitly disable it if desired.
---
 doc/09-object-types.md               |  1 +
 lib/perfdata/elasticsearchwriter.cpp | 12 ++++++++++++
 lib/perfdata/elasticsearchwriter.ti  |  3 +++
 3 files changed, 16 insertions(+)

diff --git a/doc/09-object-types.md b/doc/09-object-types.md
index b2c8417f2..746ed7c14 100644
--- a/doc/09-object-types.md
+++ b/doc/09-object-types.md
@@ -1232,6 +1232,7 @@ Configuration Attributes:
   username                  | String                | **Optional.** Basic auth username if Elasticsearch is hidden behind an HTTP proxy.
   password                  | String                | **Optional.** Basic auth password if Elasticsearch is hidden behind an HTTP proxy.
   enable\_tls               | Boolean               | **Optional.** Whether to use a TLS stream. Defaults to `false`. Requires an HTTP proxy.
+  insecure\_noverify        | Boolean               | **Optional.** Disable TLS peer verification.
   ca\_path                  | String                | **Optional.** Path to CA certificate to validate the remote host. Requires `enable_tls` set to `true`.
   cert\_path                | String                | **Optional.** Path to host certificate to present to the remote host for mutual verification. Requires `enable_tls` set to `true`.
   key\_path                 | String                | **Optional.** Path to host key to accompany the cert\_path. Requires `enable_tls` set to `true`.
diff --git a/lib/perfdata/elasticsearchwriter.cpp b/lib/perfdata/elasticsearchwriter.cpp
index 9ab277f20..97f906535 100644
--- a/lib/perfdata/elasticsearchwriter.cpp
+++ b/lib/perfdata/elasticsearchwriter.cpp
@@ -622,6 +622,18 @@ OptionalTlsStream ElasticsearchWriter::Connect()
 				<< "TLS handshake with host '" << GetHost() << "' on port " << GetPort() << " failed.";
 			throw;
 		}
+
+		if (!GetInsecureNoverify()) {
+			if (!tlsStream.GetPeerCertificate()) {
+				BOOST_THROW_EXCEPTION(std::runtime_error("Elasticsearch didn't present any TLS certificate."));
+			}
+
+			if (!tlsStream.IsVerifyOK()) {
+				BOOST_THROW_EXCEPTION(std::runtime_error(
+					"TLS certificate validation failed: " + std::string(tlsStream.GetVerifyError())
+				));
+			}
+		}
 	}
 
 	return std::move(stream);
diff --git a/lib/perfdata/elasticsearchwriter.ti b/lib/perfdata/elasticsearchwriter.ti
index a072220de..e3b8e27f5 100644
--- a/lib/perfdata/elasticsearchwriter.ti
+++ b/lib/perfdata/elasticsearchwriter.ti
@@ -29,6 +29,9 @@ class ElasticsearchWriter : ConfigObject
 	[config] bool enable_tls {
 		default {{{ return false; }}}
 	};
+	[config] bool insecure_noverify {
+		default {{{ return false; }}}
+	};
 	[config] String ca_path;
 	[config] String cert_path;
 	[config] String key_path;