From 2fcaec4b21ebb85183310c58c4c2a731be81f4aa Mon Sep 17 00:00:00 2001
From: Alexander Scheel <alex.scheel@hashicorp.com>
Date: Tue, 21 Mar 2023 18:37:17 -0400
Subject: [PATCH] Add support for HEAD operations (#19520)

* Add header operation to sdk/logical

Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com>

* Add support for routing HEAD operations

Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com>

* Add changelog entry

Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com>

---------

Signed-off-by: Alexander Scheel <alex.scheel@hashicorp.com>
---
 changelog/19520.txt               | 3 +++
 http/logical.go                   | 6 ++++--
 sdk/logical/request.go            | 1 +
 sdk/logical/response_util.go      | 2 +-
 sdk/logical/response_util_test.go | 8 ++++++++
 5 files changed, 17 insertions(+), 3 deletions(-)
 create mode 100644 changelog/19520.txt

diff --git a/changelog/19520.txt b/changelog/19520.txt
new file mode 100644
index 000000000..726be2c13
--- /dev/null
+++ b/changelog/19520.txt
@@ -0,0 +1,3 @@
+```release-note:improvement
+http: Support responding to HEAD operation from plugins
+```
diff --git a/http/logical.go b/http/logical.go
index 6da2e7dc7..8a681d910 100644
--- a/http/logical.go
+++ b/http/logical.go
@@ -183,8 +183,10 @@ func buildLogicalRequestNoAuth(perfStandby bool, w http.ResponseWriter, r *http.
 		}
 
 		data = parseQuery(r.URL.Query())
-
-	case "OPTIONS", "HEAD":
+	case "HEAD":
+		op = logical.HeaderOperation
+		data = parseQuery(r.URL.Query())
+	case "OPTIONS":
 	default:
 		return nil, nil, http.StatusMethodNotAllowed, nil
 	}
diff --git a/sdk/logical/request.go b/sdk/logical/request.go
index c50b7a031..2e54af1c0 100644
--- a/sdk/logical/request.go
+++ b/sdk/logical/request.go
@@ -369,6 +369,7 @@ const (
 	HelpOperation                     = "help"
 	AliasLookaheadOperation           = "alias-lookahead"
 	ResolveRoleOperation              = "resolve-role"
+	HeaderOperation                   = "header"
 
 	// The operations below are called globally, the path is less relevant.
 	RevokeOperation   Operation = "revoke"
diff --git a/sdk/logical/response_util.go b/sdk/logical/response_util.go
index 42529eb78..6708871f4 100644
--- a/sdk/logical/response_util.go
+++ b/sdk/logical/response_util.go
@@ -20,7 +20,7 @@ import (
 func RespondErrorCommon(req *Request, resp *Response, err error) (int, error) {
 	if err == nil && (resp == nil || !resp.IsError()) {
 		switch {
-		case req.Operation == ReadOperation:
+		case req.Operation == ReadOperation || req.Operation == HeaderOperation:
 			if resp == nil {
 				return http.StatusNotFound, nil
 			}
diff --git a/sdk/logical/response_util_test.go b/sdk/logical/response_util_test.go
index d430b961e..eafaa2fc7 100644
--- a/sdk/logical/response_util_test.go
+++ b/sdk/logical/response_util_test.go
@@ -42,6 +42,14 @@ func TestResponseUtil_RespondErrorCommon_basic(t *testing.T) {
 			respErr:        nil,
 			expectedStatus: 404,
 		},
+		{
+			title: "Header not found",
+			req: &Request{
+				Operation: HeaderOperation,
+			},
+			respErr:        nil,
+			expectedStatus: 404,
+		},
 		{
 			title: "List with response and no keys",
 			req: &Request{