From 36662c38604c80e27f2528dfc3973abf7127f201 Mon Sep 17 00:00:00 2001
From: Michael Kaufmann <mail@michael-kaufmann.ch>
Date: Mon, 6 Nov 2023 17:15:59 +0100
Subject: [PATCH] vtls: use ALPN "http/1.1" for HTTP/1.x, including HTTP/1.0

Some servers don't support the ALPN protocol "http/1.0" (e.g. IIS 10),
avoid it and use "http/1.1" instead.

This reverts commit df856cb5c9 (#10183).

Fixes #12259
Closes #12285
---
 lib/cf-https-connect.c |  3 ---
 lib/http.c             |  2 +-
 lib/vtls/vtls.c        | 13 ++++---------
 lib/vtls/vtls_int.h    |  2 --
 4 files changed, 5 insertions(+), 15 deletions(-)

diff --git a/lib/cf-https-connect.c b/lib/cf-https-connect.c
index 99a16a01e7..9aedf07f6f 100644
--- a/lib/cf-https-connect.c
+++ b/lib/cf-https-connect.c
@@ -188,9 +188,6 @@ static CURLcode baller_connected(struct Curl_cfilter *cf,
 #endif
     infof(data, "using HTTP/2");
     break;
-  case CURL_HTTP_VERSION_1_1:
-    infof(data, "using HTTP/1.1");
-    break;
   default:
     infof(data, "using HTTP/1.x");
     break;
diff --git a/lib/http.c b/lib/http.c
index 4c7059cd2a..0f685035db 100644
--- a/lib/http.c
+++ b/lib/http.c
@@ -3182,7 +3182,7 @@ CURLcode Curl_http(struct Curl_easy *data, bool *done)
       DEBUGASSERT(Curl_conn_is_http2(data, conn, FIRSTSOCKET));
     break;
   case CURL_HTTP_VERSION_1_1:
-    /* continue with HTTP/1.1 when explicitly requested */
+    /* continue with HTTP/1.x when explicitly requested */
     break;
   default:
     /* Check if user wants to use HTTP/2 with clear TCP */
diff --git a/lib/vtls/vtls.c b/lib/vtls/vtls.c
index 7104995ac1..c129b121fe 100644
--- a/lib/vtls/vtls.c
+++ b/lib/vtls/vtls.c
@@ -131,9 +131,6 @@ static bool blobcmp(struct curl_blob *first, struct curl_blob *second)
 }
 
 #ifdef USE_SSL
-static const struct alpn_spec ALPN_SPEC_H10 = {
-  { ALPN_HTTP_1_0 }, 1
-};
 static const struct alpn_spec ALPN_SPEC_H11 = {
   { ALPN_HTTP_1_1 }, 1
 };
@@ -147,12 +144,14 @@ static const struct alpn_spec *alpn_get_spec(int httpwant, bool use_alpn)
 {
   if(!use_alpn)
     return NULL;
-  if(httpwant == CURL_HTTP_VERSION_1_0)
-    return &ALPN_SPEC_H10;
 #ifdef USE_HTTP2
   if(httpwant >= CURL_HTTP_VERSION_2)
     return &ALPN_SPEC_H2_H11;
+#else
+  (void)httpwant;
 #endif
+  /* Use the ALPN protocol "http/1.1" for HTTP/1.x.
+     Avoid "http/1.0" because some servers don't support it. */
   return &ALPN_SPEC_H11;
 }
 #endif /* USE_SSL */
@@ -2107,10 +2106,6 @@ CURLcode Curl_alpn_set_negotiated(struct Curl_cfilter *cf,
        !memcmp(ALPN_HTTP_1_1, proto, ALPN_HTTP_1_1_LENGTH)) {
       *palpn = CURL_HTTP_VERSION_1_1;
     }
-    else if(proto_len == ALPN_HTTP_1_0_LENGTH &&
-            !memcmp(ALPN_HTTP_1_0, proto, ALPN_HTTP_1_0_LENGTH)) {
-      *palpn = CURL_HTTP_VERSION_1_0;
-    }
 #ifdef USE_HTTP2
     else if(proto_len == ALPN_H2_LENGTH &&
             !memcmp(ALPN_H2, proto, ALPN_H2_LENGTH)) {
diff --git a/lib/vtls/vtls_int.h b/lib/vtls/vtls_int.h
index 2e65e6303c..3729fedac4 100644
--- a/lib/vtls/vtls_int.h
+++ b/lib/vtls/vtls_int.h
@@ -32,8 +32,6 @@
 /* see https://www.iana.org/assignments/tls-extensiontype-values/ */
 #define ALPN_HTTP_1_1_LENGTH 8
 #define ALPN_HTTP_1_1 "http/1.1"
-#define ALPN_HTTP_1_0_LENGTH 8
-#define ALPN_HTTP_1_0 "http/1.0"
 #define ALPN_H2_LENGTH 2
 #define ALPN_H2 "h2"
 #define ALPN_H3_LENGTH 2