build: avoid -lgcrypt with newer gnutls

https://bugzilla.redhat.com/show_bug.cgi?id=951637

Newer gnutls uses nettle, rather than gcrypt, which is a lot nicer
regarding initialization.  Yet we were unconditionally initializing
gcrypt even when gnutls wouldn't be using it, and having two crypto
libraries linked into libvirt.so is pointless, but mostly harmless
(it doesn't crash, but does interfere with certification efforts).

There are three distinct version ranges to worry about when
determining which crypto lib gnutls uses, per these gnutls mails:
2.12: http://lists.gnu.org/archive/html/gnutls-devel/2011-03/msg00034.html
3.0: http://lists.gnu.org/archive/html/gnutls-devel/2011-07/msg00035.html

If pkg-config can prove version numbers and/or list the crypto
library used for static linking, we have our proof; if not, it
is safer (even if pointless) to continue to use gcrypt ourselves.

* configure.ac (WITH_GNUTLS): Probe whether to add -lgcrypt, and
define a witness WITH_GNUTLS_GCRYPT.
* src/libvirt.c (virTLSMutexInit, virTLSMutexDestroy)
(virTLSMutexLock, virTLSMutexUnlock, virTLSThreadImpl)
(virGlobalInit): Honor the witness.
* libvirt.spec.in (BuildRequires): Make gcrypt usage conditional,
no longer needed in Fedora 19.

Signed-off-by: Eric Blake <eblake@redhat.com>
(cherry picked from commit 6094b1ff1992e6c7c7b17a2e1a3ddbf29f7f6591)

diff --git a/configure.ac b/configure.ac
index 6538ef48cedb770caf30b456eb8bbdd2f4b5e271..095d1cf57c434a7952e87ba9dc1285c7cb1ac0ee 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -1075,12 +1075,26 @@ if test "x$with_gnutls" != "xno"; then
   LIBS="$LIBS $GNUTLS_LIBS"
 
   GNUTLS_FOUND=no
+  GNUTLS_GCRYPT=unknown
   if test -x "$PKG_CONFIG" ; then
+    dnl Triple probe: gnutls < 2.12 only used gcrypt, gnutls >= 3.0 uses
+    dnl only nettle, and versions in between had a configure option.
+    dnl Our goal is to avoid gcrypt if we can prove gnutls uses nettle,
+    dnl but it is a safe fallback to use gcrypt if we can't prove anything.
+    if $PKG_CONFIG --exists 'gnutls >= 3.0'; then
+      GNUTLS_GCRYPT=no
+    elif $PKG_CONFIG --exists 'gnutls >= 2.12'; then
+      GNUTLS_GCRYPT=probe
+    else
+      GNUTLS_GCRYPT=yes
+    fi
     PKG_CHECK_MODULES(GNUTLS, gnutls >= $GNUTLS_REQUIRED,
       [GNUTLS_FOUND=yes], [GNUTLS_FOUND=no])
   fi
   if test "$GNUTLS_FOUND" = "no"; then
+    dnl pkg-config couldn't help us, assume gcrypt is necessary
     fail=0
+    GNUTLS_GCRYPT=yes
     AC_CHECK_HEADER([gnutls/gnutls.h], [], [fail=1])
     AC_CHECK_LIB([gnutls], [gnutls_handshake],[], [fail=1], [-lgcrypt])
 
@@ -1097,13 +1111,22 @@ if test "x$with_gnutls" != "xno"; then
       AC_MSG_ERROR([You must install the GnuTLS library in order to compile and run libvirt])
     fi
   else
-    dnl Not all versions of gnutls include -lgcrypt, and so we add
-    dnl it explicitly for the calls to gcry_control/check_version
-    GNUTLS_LIBS="$GNUTLS_LIBS -lgcrypt"
-
-    dnl We're not using gcrypt deprecated features so define
-    dnl GCRYPT_NO_DEPRECATED to avoid deprecated warnings
-    GNUTLS_CFLAGS="$GNUTLS_CFLAGS -DGCRYPT_NO_DEPRECATED"
+    dnl See comments above about when to use gcrypt.
+    if test "$GNUTLS_GCRYPT" = probe; then
+      case `$PKG_CONFIG --libs --static gnutls` in
+        *gcrypt*) GNUTLS_GCRYPT=yes     ;;
+        *nettle*) GNUTLS_GCRYPT=no      ;;
+        *)        GNUTLS_GCRYPT=unknown ;;
+      esac
+    fi
+    if test "$GNUTLS_GCRYPT" = yes || test "$GNUTLS_GCRYPT" = unknown; then
+      GNUTLS_LIBS="$GNUTLS_LIBS -lgcrypt"
+      dnl We're not using gcrypt deprecated features so define
+      dnl GCRYPT_NO_DEPRECATED to avoid deprecated warnings
+      GNUTLS_CFLAGS="$GNUTLS_CFLAGS -DGCRYPT_NO_DEPRECATED"
+      AC_DEFINE_UNQUOTED([WITH_GNUTLS_GCRYPT], 1,
+        [set to 1 if it is known or assumed that GNUTLS uses gcrypt])
+    fi
 
     dnl gnutls 3.x moved some declarations to a new header
     AC_CHECK_HEADERS([gnutls/crypto.h], [], [], [[

diff --git a/libvirt.spec.in b/libvirt.spec.in
index e5952225c6158d1980a8fc26442b6ebc1d60609e..9f91517df96128010964909dd9823f75dd56d997 100644 (file)
--- a/libvirt.spec.in
+++ b/libvirt.spec.in
@@ -422,7 +422,9 @@ BuildRequires: readline-devel
 BuildRequires: ncurses-devel
 BuildRequires: gettext
 BuildRequires: libtasn1-devel
+%if (0%{?rhel} && 0%{?rhel} < 7) || (0%{?fedora} && 0%{?fedora} < 19)
 BuildRequires: libgcrypt-devel
+%endif
 BuildRequires: gnutls-devel
 BuildRequires: libattr-devel
 %if %{with_libvirtd}

diff --git a/src/libvirt.c b/src/libvirt.c
index a9d0e04f02b3dc21e4220470f59cba404db35b2f..e515ea6c53877225e8e915ac0fc980a6c59c8b41 100644 (file)
--- a/src/libvirt.c
+++ b/src/libvirt.c
@@ -55,7 +55,9 @@
 #include "intprops.h"
 #include "virconf.h"
 #if WITH_GNUTLS
-# include <gcrypt.h>
+# if WITH_GNUTLS_GCRYPT
+#  include <gcrypt.h>
+# endif
 # include "rpc/virnettlscontext.h"
 #endif
 #include "vircommand.h"
@@ -270,7 +272,7 @@ winsock_init(void)
 #endif
 
 
-#ifdef WITH_GNUTLS
+#ifdef WITH_GNUTLS_GCRYPT
 static int virTLSMutexInit(void **priv)
 {
     virMutexPtr lock = NULL;
@@ -323,7 +325,7 @@ static struct gcry_thread_cbs virTLSThreadImpl = {
     virTLSMutexUnlock,
     NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL
 };
-#endif
+#endif /* WITH_GNUTLS_GCRYPT */
 
 /* Helper macros to implement VIR_DOMAIN_DEBUG using just C99.  This
  * assumes you pass fewer than 15 arguments to VIR_DOMAIN_DEBUG, but
@@ -407,7 +409,7 @@ virGlobalInit(void)
         virErrorInitialize() < 0)
         goto error;
 
-#ifdef WITH_GNUTLS
+#ifdef WITH_GNUTLS_GCRYPT
     /*
      * This sequence of API calls it copied exactly from
      * gnutls 2.12.23 source lib/gcrypt/init.c, with