OpenSSL: guard X509_check_host against LibreSSL

LibreSSL's fork does not have this new function; as well as adding a
`LIBRESSL_VERSION_NUMBER` value, that project bumped the OpenSSL version
number in such a way as to conflict with our existing version checks.

* Add a guard.
* Add commentary, suggesting how to avoid getting into twistier knots
  with API divergence.

Reported by Jasper Wallace, who provided a slightly different patch.

Fixes bug 1635

diff --git a/src/ACKNOWLEDGMENTS b/src/ACKNOWLEDGMENTS
index 1c4a93445a415e657c9bb3eae68db3f7498c7ccd..ca88603e0ab2749bca52151740ec988c2e8e4972 100644 (file)
--- a/src/ACKNOWLEDGMENTS
+++ b/src/ACKNOWLEDGMENTS
@@ -449,6 +449,7 @@ Jan Srzednicki            Patch improving Dovecot authenticator
 Samuel Thibault           Patch fixing IPv6 interface address detection on Hurd
 Martin Tscholak           Reported issue with TLS anonymous ciphersuites
 Stephen Usher             Patch fixing use of Oracle's LDAP libraries on Solaris
+Jasper Wallace            Patch for LibreSSL compatibility
 Holger Weiß               Patch leting ${run} return more data than OS pipe
                             buffer size
 Moritz Wilhelmy           Pointed out PCRE_PRERELEASE glitch

diff --git a/src/src/tls-openssl.c b/src/src/tls-openssl.c
index f183e8b452066e33ae368c8f28a4859dc150b68f..456ca8142d36b0ce56e18651109a0ed30ff8c403 100644 (file)
--- a/src/src/tls-openssl.c
+++ b/src/src/tls-openssl.c
@@ -38,12 +38,27 @@ functions from the OpenSSL library. */
 #if OPENSSL_VERSION_NUMBER >= 0x0090806fL && !defined(OPENSSL_NO_TLSEXT)
 # define EXIM_HAVE_OPENSSL_TLSEXT
 #endif
-#if OPENSSL_VERSION_NUMBER >= 0x010100000L
-# define EXIM_HAVE_OPENSSL_CHECKHOST
-#endif
-#if OPENSSL_VERSION_NUMBER >= 0x010000000L \
+
+/*
+ * X509_check_host provides sane certificate hostname checking, but was added
+ * to OpenSSL late, after other projects forked off the code-base.  So in
+ * addition to guarding against the base version number, beware that LibreSSL
+ * does not (at this time) support this function.
+ *
+ * If LibreSSL gains a different API, perhaps via libtls, then we'll probably
+ * opt to disentangle and ask a LibreSSL user to provide glue for a third
+ * crypto provider for libtls instead of continuing to tie the OpenSSL glue
+ * into even twistier knots.  If LibreSSL gains the same API, we can just
+ * change this guard and punt the issue for a while longer.
+ */
+#ifndef LIBRESSL_VERSION_NUMBER
+# if OPENSSL_VERSION_NUMBER >= 0x010100000L
+#  define EXIM_HAVE_OPENSSL_CHECKHOST
+# endif
+# if OPENSSL_VERSION_NUMBER >= 0x010000000L \
     && (OPENSSL_VERSION_NUMBER & 0x0000ff000L) >= 0x000002000L
-# define EXIM_HAVE_OPENSSL_CHECKHOST
+#  define EXIM_HAVE_OPENSSL_CHECKHOST
+# endif
 #endif
 
 #if !defined(EXIM_HAVE_OPENSSL_TLSEXT) && !defined(DISABLE_OCSP)