[PATCH 4/5] http: centralize the accounting of libcurl dependencies

From: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Date: Sep 8, 2021, 15:31 UTC
Message-ID: <patch-4.5-47b513a261b-20210908T152807Z-avarab@gmail.com>
In-Reply-To: <cover-0.5-00000000000-20210908T152807Z-avarab@gmail.com>

As discussed in 644de29e220 (http: drop support for curl < 7.19.4, 2021-07-30) checking against LIBCURL_VERSION_NUM isn't as reliable as checking specific defines in curl, as some distros have been known to backport features. Furthermore as shown in the preceding commit doing these version checks makes for hard to read and possibly buggy code, as shown by the bug fixed there where we were conflating base 10 for base 16 when comparing the version.

Let's instead add a new git-curl-compat.h header that'll keep track of these dependencies. Following this pattern will also make it much easier to track when we should deprecate curl versions in the future, as we just did post-v2.33 e48a623dea0 (Merge branch 'ab/http-drop-old-curl', 2021-08-24).

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 git-curl-compat.h | 112 ++++++++++++++++++++++++++++++++++++++++++++++
 http.c            |  31 +++++++------
 imap-send.c       |   2 +-
 3 files changed, 128 insertions(+), 17 deletions(-)
 create mode 100644 git-curl-compat.h

diff --git a/git-curl-compat.h b/git-curl-compat.h
new file mode 100644
index 00000000000..2bba7adefa6
--- /dev/null
+++ b/git-curl-compat.h
@@ -0,0 +1,112 @@
+#ifndef GIT_CURL_COMPAT_H
+#define GIT_CURL_COMPAT_H
+
+/**
+ * This header centralizes the declaration of our libcurl dependencies
+ * to make it easy to discover the oldest versions we support, and to
+ * inform decisions about removing support for older libcurl in the
+ * future.
+ *
+ * The source of truth for what versions have which symbols is
+ * https://github.com/curl/curl/blob/master/docs/libcurl/symbols-in-versions;
+ * the release dates are taken from curl.git (at
+ * https://github.com/curl/curl/).
+ *
+ * For each X symbol we need from curl we check if it exists and
+ * declare our own GIT_CURL_HAVE_X, or if it's for both X and Y
+ * GIT_CURL_HAVE_X_and_Y, where the "Y" in "X_and_Y" is only the part
+ * of the symbol name that "X" and "Y" don't have in common.
+ *
+ * We avoid comparisons against LIBCURL_VERSION_NUM, enterprise
+ * distros have been known to backport symbols to their older curl
+ * versions.
+ *
+ * Keep any symbols in date order of when their support was
+ * introduced, oldest first, in the official version of cURL library.
+ */
+
+/**
+ * CURLOPT_TCP_KEEPALIVE was added in 7.25.0, released in March 2012.
+ */
+#ifdef CURLOPT_TCP_KEEPALIVE
+#define GITCURL_HAVE_CURLOPT_TCP_KEEPALIVE 1
+#endif
+
+
+/**
+ * CURLOPT_LOGIN_OPTIONS was added in 7.34.0, released in December
+ * 2013.
+ */
+#ifdef CURLOPT_LOGIN_OPTIONS
+#define GIT_CURL_HAVE_CURLOPT_LOGIN_OPTIONS 1
+#endif
+
+/**
+ * CURL_SSLVERSION_TLSv1_[012] was added in 7.34.0, released in
+ * December 2013.
+ */
+#if defined(CURL_SSLVERSION_TLSv1_0) && \
+    defined(CURL_SSLVERSION_TLSv1_1) && \
+    defined(CURL_SSLVERSION_TLSv1_2)
+#define GIT_CURL_HAVE_CURL_SSLVERSION_TLSv1_0_and_1_and_2
+#endif
+
+/**
+ * CURLOPT_PINNEDPUBLICKEY was added in 7.39.0, released in November
+ * 2014.
+ */
+#ifdef CURLOPT_PINNEDPUBLICKEY
+#define GIT_CURL_HAVE_CURLOPT_PINNEDPUBLICKEY 1
+#endif
+
+/**
+ * CURL_HTTP_VERSION_2 was added in 7.43.0, released in June 2015.
+ */
+#ifdef CURL_HTTP_VERSION_2
+#define GIT_CURL_HAVE_CURL_HTTP_VERSION_2 1
+#endif
+
+/**
+ * CURLSSLOPT_NO_REVOKE was added in 7.44.0, released in August 2015.
+ */
+#ifdef CURLSSLOPT_NO_REVOKE
+#define GIT_CURL_HAVE_CURLSSLOPT_NO_REVOKE 1
+#endif
+
+/**
+ * CURLOPT_PROXY_CAINFO was added in 7.52.0, released in August 2017.
+ */
+#ifdef CURLOPT_PROXY_CAINFO
+#define GIT_CURL_HAVE_CURLOPT_PROXY_CAINFO 1
+#endif
+
+/**
+ * CURLOPT_PROXY_{KEYPASSWD,SSLCERT,SSLKEY} was added in 7.52.0,
+ * released in August 2017.
+ */
+#if defined(CURLOPT_PROXY_KEYPASSWD) && \
+    defined(CURLOPT_PROXY_SSLCERT) && \
+    defined(CURLOPT_PROXY_SSLKEY)
+#define GIT_CURL_HAVE_CURLOPT_PROXY_KEYPASSWD_and_SSLCERT_and_SSLKEY 1
+#endif
+
+/**
+ * CURL_SSLVERSION_TLSv1_3 was added in 7.53.0, released in February
+ * 2017.
+ */
+#ifdef CURL_SSLVERSION_TLSv1_3
+#define GIT_CURL_HAVE_CURL_SSLVERSION_TLSv1_3 1
+#endif
+
+/**
+ * CURLSSLSET_{NO_BACKENDS,OK,TOO_LATE,UNKNOWN_BACKEND} were added in
+ * 7.56.0, released in September 2017.
+ */
+#if defined(CURLSSLSET_NO_BACKENDS) && \
+    defined(CURLSSLSET_OK) && \
+    defined(CURLSSLSET_TOO_LATE) && \
+    defined(CURLSSLSET_UNKNOWN_BACKEND)
+#define GIT_CURL_HAVE_CURLSSLSET_NO_BACKENDS_and_OK_and_TOO_LATE_and_UNKNOWN_BACKEND 1
+#endif
+
+#endif
diff --git a/http.c b/http.c
index b19d0a697d8..e38fcc34d64 100644
--- a/http.c
+++ b/http.c
@@ -1,4 +1,5 @@
 #include "git-compat-util.h"
+#include "git-curl-compat.h"
 #include "http.h"
 #include "config.h"
 #include "pack.h"
@@ -47,12 +48,12 @@ static struct {
 	{ "sslv2", CURL_SSLVERSION_SSLv2 },
 	{ "sslv3", CURL_SSLVERSION_SSLv3 },
 	{ "tlsv1", CURL_SSLVERSION_TLSv1 },
-#if LIBCURL_VERSION_NUM >= 0x072200
+#if GIT_CURL_HAVE_CURL_SSLVERSION_TLSv1_0_AND_1_AND_2
 	{ "tlsv1.0", CURL_SSLVERSION_TLSv1_0 },
 	{ "tlsv1.1", CURL_SSLVERSION_TLSv1_1 },
 	{ "tlsv1.2", CURL_SSLVERSION_TLSv1_2 },
 #endif
-#if LIBCURL_VERSION_NUM >= 0x073400
+#if GIT_CURL_HAVE_CURL_SSLVERSION_TLSv1_3
 	{ "tlsv1.3", CURL_SSLVERSION_TLSv1_3 },
 #endif
 };
@@ -371,12 +372,10 @@ static int http_options(const char *var, const char *value, void *cb)
 	}
 
 	if (!strcmp("http.pinnedpubkey", var)) {
-#if LIBCURL_VERSION_NUM >= 0x072700
-		return git_config_pathname(&ssl_pinnedkey, var, value);
-#else
+#ifndef GIT_CURL_HAVE_CURLOPT_PINNEDPUBLICKEY
 		warning(_("Public key pinning not supported with cURL < 7.39.0"));
-		return 0;
 #endif
+		return git_config_pathname(&ssl_pinnedkey, var, value);
 	}
 
 	if (!strcmp("http.extraheader", var)) {
@@ -498,7 +497,7 @@ static int has_cert_password(void)
 	return 1;
 }
 
-#if LIBCURL_VERSION_NUM >= 0x073400
+#ifdef GIT_CURL_HAVE_CURLOPT_PROXY_KEYPASSWD_and_SSLCERT_and_SSLKEY
 static int has_proxy_cert_password(void)
 {
 	if (http_proxy_ssl_cert == NULL || proxy_ssl_cert_password_required != 1)
@@ -514,7 +513,7 @@ static int has_proxy_cert_password(void)
 }
 #endif
 
-#if LIBCURL_VERSION_NUM >= 0x071900
+#ifdef GITCURL_HAVE_CURLOPT_TCP_KEEPALIVE
 static void set_curl_keepalive(CURL *c)
 {
 	curl_easy_setopt(c, CURLOPT_TCP_KEEPALIVE, 1);
@@ -730,7 +729,7 @@ static long get_curl_allowed_protocols(int from_user)
 	return allowed_protocols;
 }
 
-#if LIBCURL_VERSION_NUM >=0x072b00
+#ifdef GIT_CURL_HAVE_CURL_HTTP_VERSION_2
 static int get_curl_http_version_opt(const char *version_string, long *opt)
 {
 	int i;
@@ -772,7 +771,7 @@ static CURL *get_curl_handle(void)
 		curl_easy_setopt(result, CURLOPT_SSL_VERIFYHOST, 2);
 	}
 
-#if LIBCURL_VERSION_NUM >= 0x072b00
+#ifdef GIT_CURL_HAVE_CURL_HTTP_VERSION_2
     if (curl_http_version) {
 		long opt;
 		if (!get_curl_http_version_opt(curl_http_version, &opt)) {
@@ -803,7 +802,7 @@ static CURL *get_curl_handle(void)
 
 	if (http_ssl_backend && !strcmp("schannel", http_ssl_backend) &&
 	    !http_schannel_check_revoke) {
-#if LIBCURL_VERSION_NUM >= 0x072c00
+#ifdef GIT_CURL_HAVE_CURLSSLOPT_NO_REVOKE
 		curl_easy_setopt(result, CURLOPT_SSL_OPTIONS, CURLSSLOPT_NO_REVOKE);
 #else
 		warning(_("CURLSSLOPT_NO_REVOKE not supported with cURL < 7.44.0"));
@@ -843,20 +842,20 @@ static CURL *get_curl_handle(void)
 		curl_easy_setopt(result, CURLOPT_SSLKEY, ssl_key);
 	if (ssl_capath != NULL)
 		curl_easy_setopt(result, CURLOPT_CAPATH, ssl_capath);
-#if LIBCURL_VERSION_NUM >= 0x072700
+#ifdef GIT_CURL_HAVE_CURLOPT_PINNEDPUBLICKEY
 	if (ssl_pinnedkey != NULL)
 		curl_easy_setopt(result, CURLOPT_PINNEDPUBLICKEY, ssl_pinnedkey);
 #endif
 	if (http_ssl_backend && !strcmp("schannel", http_ssl_backend) &&
 	    !http_schannel_use_ssl_cainfo) {
 		curl_easy_setopt(result, CURLOPT_CAINFO, NULL);
-#if LIBCURL_VERSION_NUM >= 0x073400
+#ifdef GIT_CURL_HAVE_CURLOPT_PROXY_CAINFO
 		curl_easy_setopt(result, CURLOPT_PROXY_CAINFO, NULL);
 #endif
 	} else if (ssl_cainfo != NULL || http_proxy_ssl_ca_info != NULL) {
 		if (ssl_cainfo != NULL)
 			curl_easy_setopt(result, CURLOPT_CAINFO, ssl_cainfo);
-#if LIBCURL_VERSION_NUM >= 0x073400
+#ifdef GIT_CURL_HAVE_CURLOPT_PROXY_CAINFO
 		if (http_proxy_ssl_ca_info != NULL)
 			curl_easy_setopt(result, CURLOPT_PROXY_CAINFO, http_proxy_ssl_ca_info);
 #endif
@@ -937,7 +936,7 @@ static CURL *get_curl_handle(void)
 		else if (starts_with(curl_http_proxy, "socks"))
 			curl_easy_setopt(result,
 				CURLOPT_PROXYTYPE, CURLPROXY_SOCKS4);
-#if LIBCURL_VERSION_NUM >= 0x073400
+#ifdef GIT_CURL_HAVE_CURLOPT_PROXY_KEYPASSWD_and_SSLCERT_and_SSLKEY
 		else if (starts_with(curl_http_proxy, "https")) {
 			curl_easy_setopt(result, CURLOPT_PROXYTYPE, CURLPROXY_HTTPS);
 
@@ -1002,7 +1001,7 @@ void http_init(struct remote *remote, const char *url, int proactive_auth)
 	free(normalized_url);
 	string_list_clear(&config.vars, 1);
 
-#if LIBCURL_VERSION_NUM >= 0x073800
+#ifdef GIT_CURL_HAVE_CURLSSLSET_NO_BACKENDS_and_OK_and_TOO_LATE_and_UNKNOWN_BACKEND
 	if (http_ssl_backend) {
 		const curl_ssl_backend **backends;
 		struct strbuf buf = STRBUF_INIT;
diff --git a/imap-send.c b/imap-send.c
index 49a5f8aa597..e6090a0346a 100644
--- a/imap-send.c
+++ b/imap-send.c
@@ -1441,7 +1441,7 @@ static CURL *setup_curl(struct imap_server_conf *srvc, struct credential *cred)
 	curl_easy_setopt(curl, CURLOPT_PORT, server.port);
 
 	if (server.auth_method) {
-#if LIBCURL_VERSION_NUM < 0x072200
+#ifndef GIT_CURL_HAVE_CURLOPT_LOGIN_OPTIONS
 		warning("No LOGIN_OPTIONS support in this cURL version");
 #else
 		struct strbuf auth = STRBUF_INIT;

-- 
2.33.0.825.g2bf60429931