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Re: [libvirt] [PATCHv3] build: avoid -lgcrypt with newer gnutls



ping

On 07/30/2013 02:45 PM, Eric Blake wrote:
> 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>
> ---
> 
> v3: configure logic is enhanced to try harder to get the
> right answer for gentoo.  I tested with Fedora 19 and RHEL 6,
> but need feedback from a gentoo tester before this can go in.
> 
>  configure.ac    |   37 ++++++++++++++++++++++++++++++-------
>  libvirt.spec.in |    2 ++
>  src/libvirt.c   |   10 ++++++----
>  3 files changed, 38 insertions(+), 11 deletions(-)
> 
> diff --git a/configure.ac b/configure.ac
> index 1817126..e3d148c 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -1076,12 +1076,26 @@ 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])
> 
> @@ -1098,13 +1112,22 @@ 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 fce7f91..7fd3c85 100644
> --- a/libvirt.spec.in
> +++ b/libvirt.spec.in
> @@ -438,7 +438,9 @@ 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 8157488..66e8248 100644
> --- 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
> 

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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