ECH: renamed from ESNI in docs and configure

Encrypted Client Hello (ECH) is the current name.

Closes #6022

configure.ac

@@ -49,7 +49,7 @@ CURL_CHECK_OPTION_CURLDEBUG
 CURL_CHECK_OPTION_SYMBOL_HIDING
 CURL_CHECK_OPTION_ARES
 CURL_CHECK_OPTION_RT
-CURL_CHECK_OPTION_ESNI
+CURL_CHECK_OPTION_ECH
 
 XC_CHECK_PATH_SEPARATOR
 
@@ -4873,32 +4873,32 @@ if test "$enable_altsvc" = "yes"; then
 fi
 
 dnl *************************************************************
-dnl check whether ESNI support, if desired, is actually available
+dnl check whether ECH support, if desired, is actually available
 dnl
-if test "x$want_esni" != "xno"; then
+if test "x$want_ech" != "xno"; then
-  AC_MSG_CHECKING([whether ESNI support is available])
+  AC_MSG_CHECKING([whether ECH support is available])
 
   dnl assume NOT and look for sufficient condition
-  ESNI_ENABLED=0
+  ECH_ENABLED=0
-  ESNI_SUPPORT=''
+  ECH_SUPPORT=''
 
-  dnl OpenSSL with a chosen ESNI function should be enough
+  dnl OpenSSL with a chosen ECH function should be enough
   dnl so more exhaustive checking seems unnecessary for now
   if test "x$OPENSSL_ENABLED" = "x1"; then
-    AC_CHECK_FUNCS(SSL_get_esni_status,
+    AC_CHECK_FUNCS(SSL_get_ech_status,
-      ESNI_SUPPORT="ESNI support available (OpenSSL with SSL_get_esni_status)"
+      ECH_SUPPORT="ECH support available (OpenSSL with SSL_get_ech_status)"
-      ESNI_ENABLED=1)
+      ECH_ENABLED=1)
 
   dnl add 'elif' chain here for additional implementations
   fi
 
   dnl now deal with whatever we found
-  if test "x$ESNI_ENABLED" = "x1"; then
+  if test "x$ECH_ENABLED" = "x1"; then
-    AC_DEFINE(USE_ESNI, 1, [if ESNI support is available])
+    AC_DEFINE(USE_ECH, 1, [if ECH support is available])
-    AC_MSG_RESULT($ESNI_SUPPORT)
+    AC_MSG_RESULT($ECH_SUPPORT)
-    experimental="$experimental ESNI"
+    experimental="$experimental ECH"
   else
-    AC_MSG_ERROR([--enable-esni ignored: No ESNI support found])
+    AC_MSG_ERROR([--enable-ech ignored: No ECH support found])
   fi
 fi
 
@@ -5034,8 +5034,8 @@ if test "x$OPENSSL_ENABLED" = "x1" -o "x$GNUTLS_ENABLED" = "x1" \
   SUPPORT_FEATURES="$SUPPORT_FEATURES HTTPS-proxy"
 fi
 
-if test "x$ESNI_ENABLED" = "x1"; then
+if test "x$ECH_ENABLED" = "x1"; then
-  SUPPORT_FEATURES="$SUPPORT_FEATURES ESNI"
+  SUPPORT_FEATURES="$SUPPORT_FEATURES ECH"
 fi
 
 dnl replace spaces with newlines
@@ -5233,7 +5233,7 @@ AC_MSG_NOTICE([Configured to build curl/libcurl:
   Alt-svc:          ${curl_altsvc_msg}
   HTTP2:            ${curl_h2_msg}
   HTTP3:            ${curl_h3_msg}
-  ESNI:             ${curl_esni_msg}
+  ECH:              ${curl_ech_msg}
   Protocols:        ${SUPPORT_PROTOCOLS}
   Features:         ${SUPPORT_FEATURES}
 ])

docs/ECH.md

@@ -1,24 +1,23 @@
-# TLS: ESNI support in curl and libcurl
+# TLS: ECH support in curl and libcurl
 
 ## Summary
 
-**ESNI** means **Encrypted Server Name Indication**, a TLS 1.3
+**ECH** means **Encrypted Client Hello**, a TLS 1.3 extension which is
-extension which is currently the subject of an
+currently the subject of an [IETF Draft][tlsesni]. (ECH was formerly known as
-[IETF Draft][tlsesni].
+ESNI).
 
-This file is intended to show the latest current state of ESNI support
+This file is intended to show the latest current state of ECH support
 in **curl** and **libcurl**.
 
-At end of August 2019, an [experimental fork of curl][niallorcurl],
+At end of August 2019, an [experimental fork of curl][niallorcurl], built
-built using an [experimental fork of OpenSSL][sftcdopenssl], which in
+using an [experimental fork of OpenSSL][sftcdopenssl], which in turn provided
-turn provided an implementation of ESNI, was demonstrated
+an implementation of ECH, was demonstrated interoperating with a server
-interoperating with a server belonging to the [DEfO
+belonging to the [DEfO Project][defoproj].
-Project][defoproj].
 
 Further sections here describe
 
 -   resources needed for building and demonstrating **curl** support
-    for ESNI,
+    for ECH,
 
 -   progress to date,
 
@@ -28,18 +27,18 @@ Further sections here describe
 
 ## Resources needed
 
-To build and demonstrate ESNI support in **curl** and/or **libcurl**,
+To build and demonstrate ECH support in **curl** and/or **libcurl**,
 you will need
 
--   a TLS library, supported by **libcurl**, which implements ESNI;
+-   a TLS library, supported by **libcurl**, which implements ECH;
 
--   an edition of **curl** and/or **libcurl** which supports the ESNI
+-   an edition of **curl** and/or **libcurl** which supports the ECH
     implementation of the chosen TLS library;
 
 -   an environment for building and running **curl**, and at least
     building **OpenSSL**;
 
--   a server, supporting ESNI, against which to run a demonstration
+-   a server, supporting ECH, against which to run a demonstration
     and perhaps a specific target URL;
 
 -   some instructions.
@@ -58,52 +57,49 @@ The following set of resources is currently known to be available.
 
 -   Details [below](#pr4011);
 
--   New **curl** feature: `CURL_VERSION_ESNI`;
+-   New configuration option: `--enable-ech`;
 
--   New configuration option: `--enable-esni`;
+-   Build-time check for availability of resources needed for ECH
-
--   Build-time check for availability of resources needed for ESNI
     support;
 
--   Pre-processor symbol `USE_ESNI` for conditional compilation of
+-   Pre-processor symbol `USE_ECH` for conditional compilation of
-    ESNI support code, subject to configuration option and
+    ECH support code, subject to configuration option and
     availability of needed resources.
 
 ## TODO
 
--   (next PR) Add libcurl options to set ESNI parameters.
+-   (next PR) Add libcurl options to set ECH parameters.
 
--   (next PR) Add curl tool command line options to set ESNI parameters.
+-   (next PR) Add curl tool command line options to set ECH parameters.
 
--   (WIP) Extend DoH functions so that published ESNI parameters can be
+-   (WIP) Extend DoH functions so that published ECH parameters can be
     retrieved from DNS instead of being required as options.
 
--   (WIP) Work with OpenSSL community to finalize ESNI API.
+-   (WIP) Work with OpenSSL community to finalize ECH API.
 
--   Track OpenSSL ESNI API in libcurl
+-   Track OpenSSL ECH API in libcurl
 
 -   Identify and implement any changes needed for CMake.
 
 -   Optimize build-time checking of available resources.
 
--   Encourage ESNI support work on other TLS/SSL backends.
+-   Encourage ECH support work on other TLS/SSL backends.
 
 ## Additional detail
 
 ### PR 4011
 
-**TLS: Provide ESNI support framework for curl and libcurl**
+**TLS: Provide ECH support framework for curl and libcurl**
 
-The proposed change provides a framework to facilitate work to
+The proposed change provides a framework to facilitate work to implement ECH
-implement ESNI support in curl and libcurl. It is not intended
+support in curl and libcurl. It is not intended either to provide ECH
-either to provide ESNI functionality or to favour any particular
+functionality or to favour any particular TLS-providing backend. Specifically,
-TLS-providing backend. Specifically, the change reserves a
+the change reserves a feature bit for ECH support (symbol
-feature bit for ESNI support (symbol `CURL_VERSION_ESNI`),
+`CURL_VERSION_ECH`), implements setting and reporting of this bit, includes
-implements setting and reporting of this bit, includes dummy
+dummy book-keeping for the symbol, adds a build-time configuration option
-book-keeping for the symbol, adds a build-time configuration
+(`--enable-ech`), provides an extensible check for resources available to
-option (`--enable-esni`), provides an extensible check for
+provide ECH support, and defines a compiler pre-processor symbol (`USE_ECH`)
-resources available to provide ESNI support, and defines a
+accordingly.
-compiler pre-processor symbol (`USE_ESNI`) accordingly.
 
 Proposed-by: @niallor (Niall O'Reilly)\
 Encouraged-by: @sftcd (Stephen Farrell)\
@@ -117,7 +113,7 @@ Limitations:
 -   Check for available resources, although extensible, refers only to
     specific work in progress ([described
     here](https://github.com/sftcd/openssl/tree/master/esnistuff)) to
-    implement ESNI for OpenSSL, as this is the immediate motivation
+    implement ECH for OpenSSL, as this is the immediate motivation
     for the proposed change.
 
 ## References

docs/Makefile.am

@@ -56,7 +56,7 @@ EXTRA_DIST =                                    \
  CURL-DISABLE.md                                \
  DEPRECATE.md                                   \
  DYNBUF.md                                      \
- ESNI.md                                        \
+ ECH.md                                         \
  EXPERIMENTAL.md                                \
  FAQ                                            \
  FEATURES                                       \

m4/curl-confopts.m4

@@ -649,37 +649,37 @@ AC_DEFUN([CURL_CHECK_NTLM_WB], [
   fi
 ])
 
-dnl CURL_CHECK_OPTION_ESNI
+dnl CURL_CHECK_OPTION_ECH
 dnl -----------------------------------------------------
 dnl Verify whether configure has been invoked with option
-dnl --enable-esni or --disable-esni, and set
+dnl --enable-ech or --disable-ech, and set
-dnl shell variable want_esni as appropriate.
+dnl shell variable want_ech as appropriate.
 
-AC_DEFUN([CURL_CHECK_OPTION_ESNI], [
+AC_DEFUN([CURL_CHECK_OPTION_ECH], [
-  AC_MSG_CHECKING([whether to enable ESNI support])
+  AC_MSG_CHECKING([whether to enable ECH support])
-  OPT_ESNI="default"
+  OPT_ECH="default"
-  AC_ARG_ENABLE(esni,
+  AC_ARG_ENABLE(ech,
-AC_HELP_STRING([--enable-esni],[Enable ESNI support])
+AC_HELP_STRING([--enable-ech],[Enable ECH support])
-AC_HELP_STRING([--disable-esni],[Disable ESNI support]),
+AC_HELP_STRING([--disable-ech],[Disable ECH support]),
-  OPT_ESNI=$enableval)
+  OPT_ECH=$enableval)
-  case "$OPT_ESNI" in
+  case "$OPT_ECH" in
     no)
-      dnl --disable-esni option used
+      dnl --disable-ech option used
-      want_esni="no"
+      want_ech="no"
-      curl_esni_msg="no      (--enable-esni)"
+      curl_ech_msg="no      (--enable-ech)"
       AC_MSG_RESULT([no])
       ;;
     default)
       dnl configure option not specified
-      want_esni="no"
+      want_ech="no"
-      curl_esni_msg="no      (--enable-esni)"
+      curl_ech_msg="no      (--enable-ech)"
       AC_MSG_RESULT([no])
       ;;
     *)
-      dnl --enable-esni option used
+      dnl --enable-ech option used
-      want_esni="yes"
+      want_ech="yes"
-      curl_esni_msg="enabled (--disable-esni)"
+      curl_ech_msg="enabled (--disable-ech)"
-      experimental="esni"
+      experimental="ech"
       AC_MSG_RESULT([yes])
       ;;
   esac