From: Daiki Ueno <ueno@gnu.org>
Date: Fri, 19 Aug 2022 12:32:27 +0900
Subject: [PATCH] build: allow GMP to be statically linked

Even though we set the custom allocator[1] to zeroize sensitive data,
it can be easily invalidated if the application sets its own custom
allocator.  An approach to prevent that is to link against a static
library of GMP, so the use of GMP is privatized and the custom
allocator configuration is not shared with other applications.

This patch allows libgnutls to be linked with the static library of
GMP.  Note that, to this work libgmp.a needs to be compiled with -fPIC
and libhogweed in Nettle is also linked to the static library of GMP.

1. https://gitlab.com/gnutls/gnutls/-/merge_requests/1554

Signed-off-by: Daiki Ueno <ueno@gnu.org>
---
diff --color -ruNp a/configure.ac b/configure.ac
--- a/configure.ac	2022-12-15 11:06:16.782726043 +0100
+++ b/configure.ac	2022-12-15 11:08:35.603451427 +0100
@@ -744,6 +744,8 @@ AC_CHECK_FUNCS(nettle_cmac_kuznyechik_up
 LIBS=$save_LIBS
 
 # Check sonames of the linked libraries needed for FIPS selftests.
+save_CFLAGS=$CFLAGS
+CFLAGS="$CFLAGS $GMP_CFLAGS"
 save_LIBS=$LIBS
 LIBS="$LIBS $GMP_LIBS"
 AC_MSG_CHECKING([gmp soname])
@@ -757,9 +759,14 @@ if test -z "$gmp_so"; then
 	gmp_so=none
 fi
 AC_MSG_RESULT($gmp_so)
-AC_DEFINE_UNQUOTED([GMP_LIBRARY_SONAME], ["$gmp_so"], [The soname of gmp library])
+if test "$gmp_so" != none; then
+	AC_DEFINE_UNQUOTED([GMP_LIBRARY_SONAME], ["$gmp_so"], [The soname of gmp library])
+fi
 LIBS=$save_LIBS
+CFLAGS=$save_CFLAGS
 
+save_CFLAGS=$CFLAGS
+CFLAGS="$CFLAGS $NETTLE_CFLAGS"
 save_LIBS=$LIBS
 LIBS="$LIBS $NETTLE_LIBS"
 AC_MSG_CHECKING([nettle soname])
@@ -775,7 +782,11 @@ fi
 AC_MSG_RESULT($nettle_so)
 AC_DEFINE_UNQUOTED([NETTLE_LIBRARY_SONAME], ["$nettle_so"], [The soname of nettle library])
 LIBS=$save_LIBS
+CFLAGS=$save_CFLAGS
 
+save_CFLAGS=$CFLAGS
+# <nettle/bignum.h> includes <gmp.h>
+CFLAGS="$CFLAGS $HOGWEED_CFLAGS $GMP_CFLAGS"
 save_LIBS=$LIBS
 LIBS="$LIBS $HOGWEED_LIBS"
 AC_MSG_CHECKING([hogweed soname])
@@ -791,6 +802,7 @@ fi
 AC_MSG_RESULT($hogweed_so)
 AC_DEFINE_UNQUOTED([HOGWEED_LIBRARY_SONAME], ["$hogweed_so"], [The soname of hogweed library])
 LIBS=$save_LIBS
+CFLAGS=$save_CFLAGS
 
 gnutls_so=libgnutls.so.`expr "$LT_CURRENT" - "$LT_AGE"`
 AC_DEFINE_UNQUOTED([GNUTLS_LIBRARY_SONAME], ["$gnutls_so"], [The soname of gnutls library])
diff --color -ruNp a/lib/fips.c b/lib/fips.c
--- a/lib/fips.c	2022-12-15 11:06:16.868727731 +0100
+++ b/lib/fips.c	2022-12-15 11:12:42.744303409 +0100
@@ -155,7 +155,11 @@ void _gnutls_fips_mode_reset_zombie(void
 #define GNUTLS_LIBRARY_NAME GNUTLS_LIBRARY_SONAME
 #define NETTLE_LIBRARY_NAME NETTLE_LIBRARY_SONAME
 #define HOGWEED_LIBRARY_NAME HOGWEED_LIBRARY_SONAME
+
+/* GMP can be statically linked */
+#ifdef GMP_LIBRARY_SONAME
 #define GMP_LIBRARY_NAME GMP_LIBRARY_SONAME
+#endif
 
 #define HMAC_SIZE 32
 #define HMAC_ALGO GNUTLS_MAC_SHA256
@@ -173,7 +177,9 @@ struct hmac_file
 	struct hmac_entry gnutls;
 	struct hmac_entry nettle;
 	struct hmac_entry hogweed;
+#ifdef GMP_LIBRARY_SONAME
 	struct hmac_entry gmp;
+#endif
 };
 
 struct lib_paths
@@ -181,7 +187,9 @@ struct lib_paths
 	char gnutls[GNUTLS_PATH_MAX];
 	char nettle[GNUTLS_PATH_MAX];
 	char hogweed[GNUTLS_PATH_MAX];
+#ifdef GMP_LIBRARY_SONAME
 	char gmp[GNUTLS_PATH_MAX];
+#endif
 };
 
 /*
@@ -245,8 +253,10 @@ static int handler(void *user, const cha
 		return lib_handler(&p->nettle, section, name, value);
 	} else if (!strcmp(section, HOGWEED_LIBRARY_NAME)) {
 		return lib_handler(&p->hogweed, section, name, value);
+#ifdef GMP_LIBRARY_SONAME
 	} else if (!strcmp(section, GMP_LIBRARY_NAME)) {
 		return lib_handler(&p->gmp, section, name, value);
+#endif
 	} else {
 		return 0;
 	}
@@ -389,8 +399,10 @@ static int callback(struct dl_phdr_info
 		_gnutls_str_cpy(paths->nettle, GNUTLS_PATH_MAX, path);
 	else if (!strcmp(soname, HOGWEED_LIBRARY_SONAME))
 		_gnutls_str_cpy(paths->hogweed, GNUTLS_PATH_MAX, path);
+#ifdef GMP_LIBRARY_SONAME
 	else if (!strcmp(soname, GMP_LIBRARY_SONAME))
 		_gnutls_str_cpy(paths->gmp, GNUTLS_PATH_MAX, path);
+#endif
 	return 0;
 }
 
@@ -411,10 +423,12 @@ static int load_lib_paths(struct lib_pat
 		_gnutls_debug_log("Hogweed library path was not found\n");
 		return gnutls_assert_val(GNUTLS_E_FILE_ERROR);
 	}
+#ifdef GMP_LIBRARY_SONAME
 	if (paths->gmp[0] == '\0') {
 		_gnutls_debug_log("Gmp library path was not found\n");
 		return gnutls_assert_val(GNUTLS_E_FILE_ERROR);
 	}
+#endif
 
 	return GNUTLS_E_SUCCESS;
 }
@@ -467,9 +481,11 @@ static int check_binary_integrity(void)
 	ret = check_lib_hmac(&hmac.hogweed, paths.hogweed);
 	if (ret < 0)
 		return ret;
+#ifdef GMP_LIBRARY_SONAME
 	ret = check_lib_hmac(&hmac.gmp, paths.gmp);
 	if (ret < 0)
 		return ret;
+#endif
 
 	return 0;
 }
diff --color -ruNp a/lib/fipshmac.c b/lib/fipshmac.c
--- a/lib/fipshmac.c	2022-12-15 11:06:16.785726102 +0100
+++ b/lib/fipshmac.c	2022-12-15 11:13:34.533320156 +0100
@@ -107,8 +107,10 @@ static int callback(struct dl_phdr_info
 		return print_lib(path, soname);
 	if (!strcmp(soname, HOGWEED_LIBRARY_SONAME))
 		return print_lib(path, soname);
+#ifdef GMP_LIBRARY_SONAME
 	if (!strcmp(soname, GMP_LIBRARY_SONAME))
 		return print_lib(path, soname);
+#endif
         return 0;
 }
 
diff --color -ruNp a/lib/global.c b/lib/global.c
--- a/lib/global.c	2022-12-15 11:06:16.061711888 +0100
+++ b/lib/global.c	2022-12-15 11:08:35.604451446 +0100
@@ -540,7 +540,9 @@ static const struct gnutls_library_confi
 	{ "libgnutls-soname", GNUTLS_LIBRARY_SONAME },
 	{ "libnettle-soname", NETTLE_LIBRARY_SONAME },
 	{ "libhogweed-soname", HOGWEED_LIBRARY_SONAME },
+#ifdef GMP_LIBRARY_SONAME
 	{ "libgmp-soname", GMP_LIBRARY_SONAME },
+#endif
 	{ "hardware-features", HW_FEATURES },
 	{ "tls-features", TLS_FEATURES },
 	{ NULL, NULL }