Auto-detect OpenSSL version

This script was originally written for vibe-d:tls module.
However, it makes more sense to have the detection done in bindings.
Before this commit, the OpenSSL version was just assumed to be 1.1.0h.

Author: Geod24

.gitignore

@@ -0,0 +1,7 @@
+# Generated version file
+/source/deimos/openssl/version_.d
+
+# DUB artifacts
+/.dub/
+/openssl
+/*-test-library

dub.sdl

@@ -4,7 +4,14 @@ homepage "http://www.openssl.org/"
 license "OpenSSL or SSLeay"
 libs "ssl" "crypto" platform="posix"
 
-configuration "library" {
+configuration "library-autodetect" {
+	targetType "sourceLibrary"
+	excludedSourceFiles "source/deimos/openssl/applink.d"
+	preGenerateCommands `${DUB} scripts/generate_version.d` platform="posix"
+	versions `DeimosOpenSSLAutoDetect`
+}
+
+configuration "library-manual-version" {
 	targetType "sourceLibrary"
 	excludedSourceFiles "source/deimos/openssl/applink.d"
 }
@@ -19,4 +26,6 @@ configuration "unittest" {
 	targetType "executable"
 	dflags "-main"
 	excludedSourceFiles "source/deimos/openssl/applink.d"
+	preGenerateCommands `${DUB} scripts/generate_version.d` platform="posix"
+	versions `DeimosOpenSSLAutoDetect`
 }

scripts/generate_version.d

@@ -0,0 +1,112 @@
+/+ dub.sdl:
+ name "script"
+ +/
+
+/**
+ * This program will attempt to detect which version of openssl is installed
+ *
+ * End-users might have different versions of OpenSSL installed.
+ * The version might ever differ among members of a development team.
+ *
+ * This script attempts to first calls `pkg-config` to find out the version,
+ * then reverts to calling the `openssl` binary if `pkg-config` didn't work.
+ *
+ * It is called directly as a `preGenerateCommand` (see dub.sdl).
+ * To use it with another build system, pass the directory in which to write
+ * the `version_.d` file as first and only argument. The directory
+ * must exist, this script will not create it.
+ */
+module generate_version;
+
+import std.algorithm;
+import std.conv;
+import std.file;
+import std.functional;
+import std.path;
+import std.process;
+import std.range;
+import std.stdio;
+import std.string;
+import std.uni;
+
+// file full path is: $SOME_PATH/openssl/scripts/generate_version.d
+// We want: $SOME_PATH/openssl/deimos/openssl/
+immutable TARGET_DIR_PATH = __FILE_FULL_PATH__
+    .dirName.dirName.buildPath("source", "deimos", "openssl");
+
+void main(string[] args)
+{
+    string target;
+
+    if (args.length == 2)
+    {
+        assert(args[1].isDir(),
+               "OpenSSL version detection: Argument '" ~ args[1] ~ "' is not a directory");
+        target = args[1].buildPath("version_.d");
+    }
+    else
+    {
+        assert(args.length == 1,
+               "OpenSSL version detection expects only one argument, " ~
+               "a directory path where to write `version_.d`");
+        target = TARGET_DIR_PATH.buildPath("version_.d");
+    }
+
+    string opensslVersion;
+    try
+    {
+        const res = execute(["pkg-config", "openssl", "--modversion"]);
+        if (res.status == 0)
+            opensslVersion = res.output.strip();
+    }
+    catch (Exception e) {}
+
+    if (!opensslVersion.length) try
+    {
+        const res = execute(["openssl", "version"]).output;
+        if (res.canFind("OpenSSL "))
+        {
+            opensslVersion = res.splitter(" ").dropOne.front.filter!(not!(std.uni.isAlpha)).text;
+        }
+        else if (res.canFind("LibreSSL "))
+        {
+            writeln("\tWarning: Your default openssl binary points to LibreSSL, which is not supported.");
+            version (OSX)
+            {
+                writeln("\tOn Mac OSX, this is the default behavior.");
+                writeln("\tIf you installed openssl via a package manager, you need to tell DUB how to find it.");
+                writeln("\tAssuming brew, run [brew link openssl] and follow the instructions for pkg-config.\n");
+            }
+        }
+    }
+    catch (Exception e) {}
+
+    if (!opensslVersion.length)
+    {
+         writeln("\tWarning: Could not find OpenSSL version via pkg-config nor by calling the openssl binary.");
+         writeln("\tAssuming version 1.1.0.");
+         writeln("\tYou might need to export PKG_CONFIG_PATH or install the openssl package if you have a library-only package.");
+         opensslVersion = "1.1.0h";
+    }
+    auto data = format(q{/**
+ * Provide the version of the libssl being linked to at compile time
+ *
+ * This module was auto-generated by deimos/openssl's script/generate_version.d
+ * Manual edit might get overwritten by later build.
+ *
+ * This module should not be directly dependend upon.
+ * Instead, use `deimos.openssl.opensslv`, which handles explicit overrides
+ * provides a uniform interface, and a few utilities.
+ */
+module deimos.openssl.version_;
+
+/// Ditto
+package enum OpenSSLTextVersion = "%s";
+}, opensslVersion);
+
+    // Only write the file iff it has changed or didn't exist before.
+    // This way timestamp-based build system will not rebuild,
+    // and changes on the installed OpenSSL will be correctly detected.
+    if (!target.exists || target.readText.strip != data.strip)
+        data.toFile(target);
+}

source/deimos/openssl/opensslv.d

@@ -1,7 +1,93 @@
+/**
+ * Module to deal with the library version being used
+ *
+ * This library provide bindings for a wide range of OpenSSL versions,
+ * ranging from v0.9.x to v3.0.x. Some versions are not compatible with
+ * one another, either due to different ABI or different behavior,
+ * for example OpenSSL 1.0 requires initialization but later versions do not.
+ *
+ * While things tend to mostly work or error out while linking when the version
+ * the bindings assume and the actually C library version are too different,
+ * we prefer to try detecting the currently used version, and allow users
+ * to specify the version explicitly, before falling back to the latest bindings
+ */
 module deimos.openssl.opensslv;
 
 import deimos.openssl._d_util;
 
+version (DeimosOpenSSL_1_0_0)
+{
+    // https://www.openssl.org/news/changelog.html#openssl-100
+    // OpenSSL 1.0.0t was released 2015-12-03
+    public alias OpenSSLVersion = OpenSSLVersionTemplate!"1.0.0t";
+}
+else version (DeimosOpenSSL_1_0_1)
+{
+    // https://www.openssl.org/news/changelog.html#openssl-101
+    // OpenSSL 1.0.1u was released 2016-09-22
+    public alias OpenSSLVersion = OpenSSLVersionTemplate!"1.0.1u";
+}
+else version (DeimosOpenSSL_1_0_2)
+{
+    // https://www.openssl.org/news/changelog.html#openssl-102
+    // OpenSSL 1.0.2t was released 2019-09-10
+    public alias OpenSSLVersion = OpenSSLVersionTemplate!"1.0.2t";
+}
+else version (DeimosOpenSSL_1_1_0)
+{
+    // https://www.openssl.org/news/changelog.html#openssl-110
+    // OpenSSL 1.1.0l was released 2019-09-10
+    public alias OpenSSLVersion = OpenSSLVersionTemplate!"1.1.0l";
+}
+else version (DeimosOpenSSL_1_1_1)
+{
+    // https://www.openssl.org/news/changelog.html#openssl-111
+    // OpenSSL 1.1.1m was released 2021-12-14
+    public alias OpenSSLVersion = OpenSSLVersionTemplate!"1.1.1m";
+}
+else version (DeimosOpenSSL_3_0)
+{
+    // https://www.openssl.org/news/changelog.html#openssl-30
+    // OpenSSL 3.0.3 was released 2022-05-03
+    public alias OpenSSLVersion = OpenSSLVersionTemplate!"3.0.3";
+}
+else version (DeimosOpenSSLAutoDetect)
+{
+    import deimos.openssl.version_;
+
+    public alias OpenSSLVersion = OpenSSLVersionTemplate!OpenSSLTextVersion;
+}
+else
+{
+    // It was decided in https://github.com/D-Programming-Deimos/openssl/pull/66
+    // that we should fall back to the latest supported version of the bindings,
+    // should the user provide neither explicit version nor `DeimosOpenSSLAutoDetect`
+    public alias OpenSSLVersion = OpenSSLVersionTemplate!"1.1.0h";
+}
+
+// Publicly aliased above
+private struct OpenSSLVersionTemplate (string textVersion)
+{
+    enum text = textVersion;
+
+    enum int major = (text[0] - '0');
+    static assert (major >= 0);
+
+    enum int minor = (text[2] - '0');
+    static assert (minor >= 0);
+
+    enum int patch = (text[4] - '0');
+    static assert (patch >= 0);
+
+    static if (text.length == "1.1.0h".length)
+    {
+        enum int build = (text[5] - '`');
+        static assert (build >= 0);
+    }
+    else
+        enum int build = 0;
+}
+
 /* Numeric release version identifier:
  * MNNFFPPS: major minor fix patch status
  * The status nibble has one of the values 0 for development, 1 to e for betas
@@ -28,21 +114,22 @@ import deimos.openssl._d_util;
  */
 
 /* Version macros for compile-time API version detection */
-enum
-{
-    OPENSSL_VERSION_MAJOR   = 1,
-    OPENSSL_VERSION_MINOR   = 1,
-    OPENSSL_VERSION_PATCH   = 0,
-    OPENSSL_VERSION_BUILD   = 'h' - '`'
-}
+enum OPENSSL_VERSION_MAJOR   = OpenSSLVersion.major;
+
+enum OPENSSL_VERSION_MINOR   = OpenSSLVersion.minor;
+
+enum OPENSSL_VERSION_PATCH   = OpenSSLVersion.patch;
+
+enum OPENSSL_VERSION_BUILD   = OpenSSLVersion.build;
 
 int OPENSSL_MAKE_VERSION(int major, int minor, int patch, int build)
 {
     return (major << 28) | (minor << 20) | (patch << 12) | (build << 4) | 0xf;
 }
 
 enum OPENSSL_VERSION_NUMBER =
-    OPENSSL_MAKE_VERSION(OPENSSL_VERSION_MAJOR, OPENSSL_VERSION_MINOR, OPENSSL_VERSION_PATCH, OPENSSL_VERSION_BUILD);
+    OPENSSL_MAKE_VERSION(OpenSSLVersion.major, OpenSSLVersion.minor,
+                         OpenSSLVersion.patch, OpenSSLVersion.build);
 
 bool OPENSSL_VERSION_AT_LEAST(int major, int minor, int patch = 0, int build = 0)
 {
@@ -54,13 +141,6 @@ bool OPENSSL_VERSION_BEFORE(int major, int minor, int patch = 0, int build = 0)
     return OPENSSL_VERSION_NUMBER < OPENSSL_MAKE_VERSION(major, minor, patch, build);
 }
 
-version (OPENSSL_FIPS) {
-enum OPENSSL_VERSION_TEXT = "OpenSSL 1.1.0h-fips 27 Mar 2018";
-} else {
-enum OPENSSL_VERSION_TEXT = "OpenSSL 1.1.0h 27 Mar 2018";
-}
-enum OPENSSL_VERSION_PTEXT = " part of " ~ OPENSSL_VERSION_TEXT;
-
 /* The macros below are to be used for shared library (.so, .dll, ...)
  * versioning.  That kind of versioning works a bit differently between
  * operating systems.  The most usual scheme is to set a major and a minor