SUNRPC: Enable rpcsec_gss_krb5.ko to be built without CRYPTO_DES

Because the DES block cipher has been deprecated by Internet
standard, highly secure configurations might require that DES
support be blacklisted or not installed. NFS Kerberos should still
be able to work correctly with only the AES-based enctypes in that
situation.

Also note that MIT Kerberos has begun a deprecation process for DES
encryption types. Their README for 1.19.3 states:

> Beginning with the krb5-1.19 release, a warning will be issued
> if initial credentials are acquired using the des3-cbc-sha1
> encryption type.  In future releases, this encryption type will
> be disabled by default and eventually removed.
>
> Beginning with the krb5-1.18 release, single-DES encryption
> types have been removed.

Aside from the CONFIG option name change, there are two important
policy changes:

1. The 'insecure enctype' group is now disabled by default.
   Distributors have to take action to enable support for deprecated
   enctypes. Implementation of these enctypes will be removed in a
   future kernel release.

2. des3-cbc-sha1 is now considered part of the 'insecure enctype'
   group, having been deprecated by RFC 8429, and is thus disabled
   by default

After this patch is applied, SunRPC support can be built with
Kerberos 5 support but without CRYPTO_DES enabled in the kernel.
And, when these enctypes are disabled, the Linux kernel's SunRPC
RPCSEC GSS implementation fully complies with BCP 179 / RFC 6649
and BCP 218 / RFC 8429.

Tested-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

1 files changed, 21 insertions, 6 deletions

diff --git a/net/sunrpc/auth_gss/gss_krb5_mech.c b/net/sunrpc/auth_gss/gss_krb5_mech.c
index 2553d18fd2881b..9ddc6fc7077fdb 100644
--- a/net/sunrpc/auth_gss/gss_krb5_mech.c
+++ b/net/sunrpc/auth_gss/gss_krb5_mech.c
@@ -29,12 +29,16 @@
 
 static struct gss_api_mech gss_kerberos_mech;
 
+#if defined(CONFIG_RPCSEC_GSS_KRB5_SIMPLIFIED)
 static int gss_krb5_import_ctx_des(struct krb5_ctx *ctx, gfp_t gfp_mask);
 static int gss_krb5_import_ctx_v1(struct krb5_ctx *ctx, gfp_t gfp_mask);
+#endif
+#if defined(CONFIG_RPCSEC_GSS_KRB5_CRYPTOSYSTEM)
 static int gss_krb5_import_ctx_v2(struct krb5_ctx *ctx, gfp_t gfp_mask);
+#endif
 
 static const struct gss_krb5_enctype supported_gss_krb5_enctypes[] = {
-#ifndef CONFIG_SUNRPC_DISABLE_INSECURE_ENCTYPES
+#if defined(CONFIG_RPCSEC_GSS_KRB5_ENCTYPES_DES)
 	/*
 	 * DES (All DES enctypes are mapped to the same gss functionality)
 	 */
@@ -59,7 +63,6 @@ static const struct gss_krb5_enctype supported_gss_krb5_enctypes[] = {
 	  .cksumlength = 8,
 	  .keyed_cksum = 0,
 	},
-#endif	/* CONFIG_SUNRPC_DISABLE_INSECURE_ENCTYPES */
 	/*
 	 * 3DES
 	 */
@@ -84,8 +87,11 @@ static const struct gss_krb5_enctype supported_gss_krb5_enctypes[] = {
 	  .cksumlength = 20,
 	  .keyed_cksum = 1,
 	},
+#endif
+
+#if defined(CONFIG_RPCSEC_GSS_KRB5_ENCTYPES_AES_SHA1)
 	/*
-	 * AES128
+	 * AES-128 with SHA-1 (RFC 3962)
 	 */
 	{
 	  .etype = ENCTYPE_AES128_CTS_HMAC_SHA1_96,
@@ -114,7 +120,7 @@ static const struct gss_krb5_enctype supported_gss_krb5_enctypes[] = {
 	  .keyed_cksum = 1,
 	},
 	/*
-	 * AES256
+	 * AES-256 with SHA-1 (RFC 3962)
 	 */
 	{
 	  .etype = ENCTYPE_AES256_CTS_HMAC_SHA1_96,
@@ -142,6 +148,7 @@ static const struct gss_krb5_enctype supported_gss_krb5_enctypes[] = {
 	  .cksumlength = 12,
 	  .keyed_cksum = 1,
 	},
+#endif
 };
 
 /*
@@ -153,10 +160,12 @@ static char gss_krb5_enctype_priority_list[64];
 static void gss_krb5_prepare_enctype_priority_list(void)
 {
 	static const u32 gss_krb5_enctypes[] = {
+#if defined(CONFIG_RPCSEC_GSS_KRB5_ENCTYPES_AES_SHA1)
 		ENCTYPE_AES256_CTS_HMAC_SHA1_96,
 		ENCTYPE_AES128_CTS_HMAC_SHA1_96,
+#endif
+#if defined(CONFIG_RPCSEC_GSS_KRB5_ENCTYPES_DES)
 		ENCTYPE_DES3_CBC_SHA1,
-#ifndef CONFIG_SUNRPC_DISABLE_INSECURE_ENCTYPES
 		ENCTYPE_DES_CBC_MD5,
 		ENCTYPE_DES_CBC_CRC,
 		ENCTYPE_DES_CBC_MD4,
@@ -337,7 +346,7 @@ out_err:
 	return PTR_ERR(p);
 }
 
-static struct crypto_sync_skcipher *
+static inline struct crypto_sync_skcipher *
 context_v2_alloc_cipher(struct krb5_ctx *ctx, const char *cname, u8 *key)
 {
 	struct crypto_sync_skcipher *cp;
@@ -367,6 +376,7 @@ set_cdata(u8 cdata[GSS_KRB5_K5CLENGTH], u32 usage, u8 seed)
 	cdata[4] = seed;
 }
 
+#if defined(CONFIG_RPCSEC_GSS_KRB5_SIMPLIFIED)
 static int
 gss_krb5_import_ctx_des(struct krb5_ctx *ctx, gfp_t gfp_mask)
 {
@@ -417,6 +427,9 @@ out_free_seq:
 out_err:
 	return -EINVAL;
 }
+#endif
+
+#if defined(CONFIG_RPCSEC_GSS_KRB5_CRYPTOSYSTEM)
 
 static struct crypto_ahash *
 gss_krb5_alloc_hash_v2(struct krb5_ctx *kctx, const struct xdr_netobj *key)
@@ -551,6 +564,8 @@ out_free:
 	goto out;
 }
 
+#endif
+
 static int
 gss_import_v2_context(const void *p, const void *end, struct krb5_ctx *ctx,
 		gfp_t gfp_mask)