From a3408731e3d73f99028f20c3f33caa5a411b430c Mon Sep 17 00:00:00 2001

From: Simo Sorce <simo@redhat.com>

Date: Thu, 30 Mar 2017 11:27:09 -0400

Subject: [PATCH] Add support to query the SSF of a GSS context

Cyrus SASL provides a Security Strength Factor number to assess the

relative "strength" of the negotiated mechanism, and applications

sometimes make access control decisions based on it.

Add a call that allows us to query the mechanism that established the

GSS security context to ask what is the current SSF, based on the

enctype of the session key.

ticket: 8569 (new)

(cherry picked from commit 7feb7da54c0321b5a3eeb6c3797846a3cf7eda28)

[rharwood@redhat.com: hide GSS_KRB5_GET_CRED_IMPERSONATOR symbol]

---

 src/include/k5-int.h                    |  1 +

 src/lib/crypto/krb/crypto_int.h         |  1 +

 src/lib/crypto/krb/enctype_util.c       | 16 ++++++++++++++++

 src/lib/crypto/krb/etypes.c             | 33 ++++++++++++++++++---------------

 src/lib/crypto/libk5crypto.exports      |  1 +

 src/lib/gssapi/generic/gssapi_ext.h     | 11 +++++++++++

 src/lib/gssapi/generic/gssapi_generic.c |  9 +++++++++

 src/lib/gssapi/krb5/gssapiP_krb5.h      |  6 ++++++

 src/lib/gssapi/krb5/gssapi_krb5.c       |  4 ++++

 src/lib/gssapi/krb5/inq_context.c       | 27 +++++++++++++++++++++++++++

 src/lib/gssapi/libgssapi_krb5.exports   |  1 +

 src/lib/gssapi32.def                    |  3 +++

 src/lib/krb5_32.def                     |  3 +++

 src/tests/gssapi/t_enctypes.c           | 14 ++++++++++++++

 14 files changed, 115 insertions(+), 15 deletions(-)

diff --git a/src/include/k5-int.h b/src/include/k5-int.h

index cea644d0a..06ca2b66d 100644

--- a/src/include/k5-int.h

+++ b/src/include/k5-int.h

@@ -2114,6 +2114,7 @@ krb5_get_tgs_ktypes(krb5_context, krb5_const_principal, krb5_enctype **);

 krb5_boolean krb5_is_permitted_enctype(krb5_context, krb5_enctype);

 krb5_boolean KRB5_CALLCONV krb5int_c_weak_enctype(krb5_enctype);

+krb5_error_code k5_enctype_to_ssf(krb5_enctype enctype, unsigned int *ssf_out);

 krb5_error_code krb5_kdc_rep_decrypt_proc(krb5_context, const krb5_keyblock *,

                                           krb5_const_pointer, krb5_kdc_rep *);

diff --git a/src/lib/crypto/krb/crypto_int.h b/src/lib/crypto/krb/crypto_int.h

index d75b49c69..e5099291e 100644

--- a/src/lib/crypto/krb/crypto_int.h

+++ b/src/lib/crypto/krb/crypto_int.h

@@ -111,6 +111,7 @@ struct krb5_keytypes {

     prf_func prf;

     krb5_cksumtype required_ctype;

     krb5_flags flags;

+    unsigned int ssf;

 };

 #define ETYPE_WEAK 1

diff --git a/src/lib/crypto/krb/enctype_util.c b/src/lib/crypto/krb/enctype_util.c

index 0ed74bd6e..b1b40e7ec 100644

--- a/src/lib/crypto/krb/enctype_util.c

+++ b/src/lib/crypto/krb/enctype_util.c

@@ -131,3 +131,19 @@ krb5_enctype_to_name(krb5_enctype enctype, krb5_boolean shortest,

         return ENOMEM;

     return 0;

 }

+

+/* The security of a mechanism cannot be summarized with a simple integer

+ * value, but we provide a per-enctype value for Cyrus SASL's SSF. */

+krb5_error_code

+k5_enctype_to_ssf(krb5_enctype enctype, unsigned int *ssf_out)

+{

+    const struct krb5_keytypes *ktp;

+

+    *ssf_out = 0;

+

+    ktp = find_enctype(enctype);

+    if (ktp == NULL)

+        return EINVAL;

+    *ssf_out = ktp->ssf;

+    return 0;

+}

diff --git a/src/lib/crypto/krb/etypes.c b/src/lib/crypto/krb/etypes.c

index 0e5e977d4..53d4a5c79 100644

--- a/src/lib/crypto/krb/etypes.c

+++ b/src/lib/crypto/krb/etypes.c

@@ -42,7 +42,7 @@ const struct krb5_keytypes krb5int_enctypes_list[] = {

       krb5int_des_string_to_key, k5_rand2key_des,

       krb5int_des_prf,

       CKSUMTYPE_RSA_MD5_DES,

-      ETYPE_WEAK },

+      ETYPE_WEAK, 56 },

     { ENCTYPE_DES_CBC_MD4,

       "des-cbc-md4", { 0 }, "DES cbc mode with RSA-MD4",

       &krb5int_enc_des, &krb5int_hash_md4,

@@ -51,7 +51,7 @@ const struct krb5_keytypes krb5int_enctypes_list[] = {

       krb5int_des_string_to_key, k5_rand2key_des,

       krb5int_des_prf,

       CKSUMTYPE_RSA_MD4_DES,

-      ETYPE_WEAK },

+      ETYPE_WEAK, 56 },

     { ENCTYPE_DES_CBC_MD5,

       "des-cbc-md5", { "des" }, "DES cbc mode with RSA-MD5",

       &krb5int_enc_des, &krb5int_hash_md5,

@@ -60,7 +60,7 @@ const struct krb5_keytypes krb5int_enctypes_list[] = {

       krb5int_des_string_to_key, k5_rand2key_des,

       krb5int_des_prf,

       CKSUMTYPE_RSA_MD5_DES,

-      ETYPE_WEAK },

+      ETYPE_WEAK, 56 },

     { ENCTYPE_DES_CBC_RAW,

       "des-cbc-raw", { 0 }, "DES cbc mode raw",

       &krb5int_enc_des, NULL,

@@ -69,7 +69,7 @@ const struct krb5_keytypes krb5int_enctypes_list[] = {

       krb5int_des_string_to_key, k5_rand2key_des,

       krb5int_des_prf,

       0,

-      ETYPE_WEAK },

+      ETYPE_WEAK, 56 },

     { ENCTYPE_DES3_CBC_RAW,

       "des3-cbc-raw", { 0 }, "Triple DES cbc mode raw",

       &krb5int_enc_des3, NULL,

@@ -78,7 +78,7 @@ const struct krb5_keytypes krb5int_enctypes_list[] = {

       krb5int_dk_string_to_key, k5_rand2key_des3,

       NULL, /*PRF*/

       0,

-      ETYPE_WEAK },

+      ETYPE_WEAK, 112 },

     { ENCTYPE_DES3_CBC_SHA1,

       "des3-cbc-sha1", { "des3-hmac-sha1", "des3-cbc-sha1-kd" },

@@ -89,7 +89,7 @@ const struct krb5_keytypes krb5int_enctypes_list[] = {

       krb5int_dk_string_to_key, k5_rand2key_des3,

       krb5int_dk_prf,

       CKSUMTYPE_HMAC_SHA1_DES3,

-      0 /*flags*/ },

+      0 /*flags*/, 112 },

     { ENCTYPE_DES_HMAC_SHA1,

       "des-hmac-sha1", { 0 }, "DES with HMAC/sha1",

@@ -99,7 +99,10 @@ const struct krb5_keytypes krb5int_enctypes_list[] = {

       krb5int_dk_string_to_key, k5_rand2key_des,

       NULL, /*PRF*/

       0,

-      ETYPE_WEAK },

+      ETYPE_WEAK, 56 },

+

+    /* rc4-hmac uses a 128-bit key, but due to weaknesses in the RC4 cipher, we

+     * consider its strength degraded and assign it an SSF value of 64. */

     { ENCTYPE_ARCFOUR_HMAC,

       "arcfour-hmac", { "rc4-hmac", "arcfour-hmac-md5" },

       "ArcFour with HMAC/md5",

@@ -110,7 +113,7 @@ const struct krb5_keytypes krb5int_enctypes_list[] = {

       krb5int_arcfour_decrypt, krb5int_arcfour_string_to_key,

       k5_rand2key_direct, krb5int_arcfour_prf,

       CKSUMTYPE_HMAC_MD5_ARCFOUR,

-      0 /*flags*/ },

+      0 /*flags*/, 64 },

     { ENCTYPE_ARCFOUR_HMAC_EXP,

       "arcfour-hmac-exp", { "rc4-hmac-exp", "arcfour-hmac-md5-exp" },

       "Exportable ArcFour with HMAC/md5",

@@ -121,7 +124,7 @@ const struct krb5_keytypes krb5int_enctypes_list[] = {

       krb5int_arcfour_decrypt, krb5int_arcfour_string_to_key,

       k5_rand2key_direct, krb5int_arcfour_prf,

       CKSUMTYPE_HMAC_MD5_ARCFOUR,

-      ETYPE_WEAK

+      ETYPE_WEAK, 40

     },

     { ENCTYPE_AES128_CTS_HMAC_SHA1_96,

@@ -133,7 +136,7 @@ const struct krb5_keytypes krb5int_enctypes_list[] = {

       krb5int_aes_string_to_key, k5_rand2key_direct,

       krb5int_dk_prf,

       CKSUMTYPE_HMAC_SHA1_96_AES128,

-      0 /*flags*/ },

+      0 /*flags*/, 128 },

     { ENCTYPE_AES256_CTS_HMAC_SHA1_96,

       "aes256-cts-hmac-sha1-96", { "aes256-cts", "aes256-sha1" },

       "AES-256 CTS mode with 96-bit SHA-1 HMAC",

@@ -143,7 +146,7 @@ const struct krb5_keytypes krb5int_enctypes_list[] = {

       krb5int_aes_string_to_key, k5_rand2key_direct,

       krb5int_dk_prf,

       CKSUMTYPE_HMAC_SHA1_96_AES256,

-      0 /*flags*/ },

+      0 /*flags*/, 256 },

     { ENCTYPE_CAMELLIA128_CTS_CMAC,

       "camellia128-cts-cmac", { "camellia128-cts" },

@@ -155,7 +158,7 @@ const struct krb5_keytypes krb5int_enctypes_list[] = {

       krb5int_camellia_string_to_key, k5_rand2key_direct,

       krb5int_dk_cmac_prf,

       CKSUMTYPE_CMAC_CAMELLIA128,

-      0 /*flags*/ },

+      0 /*flags*/, 128 },

     { ENCTYPE_CAMELLIA256_CTS_CMAC,

       "camellia256-cts-cmac", { "camellia256-cts" },

       "Camellia-256 CTS mode with CMAC",

@@ -166,7 +169,7 @@ const struct krb5_keytypes krb5int_enctypes_list[] = {

       krb5int_camellia_string_to_key, k5_rand2key_direct,

       krb5int_dk_cmac_prf,

       CKSUMTYPE_CMAC_CAMELLIA256,

-      0 /*flags */ },

+      0 /*flags */, 256 },

     { ENCTYPE_AES128_CTS_HMAC_SHA256_128,

       "aes128-cts-hmac-sha256-128", { "aes128-sha2" },

@@ -177,7 +180,7 @@ const struct krb5_keytypes krb5int_enctypes_list[] = {

       krb5int_aes2_string_to_key, k5_rand2key_direct,

       krb5int_aes2_prf,

       CKSUMTYPE_HMAC_SHA256_128_AES128,

-      0 /*flags*/ },

+      0 /*flags*/, 128 },

     { ENCTYPE_AES256_CTS_HMAC_SHA384_192,

       "aes256-cts-hmac-sha384-192", { "aes256-sha2" },

       "AES-256 CTS mode with 192-bit SHA-384 HMAC",

@@ -187,7 +190,7 @@ const struct krb5_keytypes krb5int_enctypes_list[] = {

       krb5int_aes2_string_to_key, k5_rand2key_direct,

       krb5int_aes2_prf,

       CKSUMTYPE_HMAC_SHA384_192_AES256,

-      0 /*flags*/ },

+      0 /*flags*/, 256 },

 };

 const int krb5int_enctypes_length =

diff --git a/src/lib/crypto/libk5crypto.exports b/src/lib/crypto/libk5crypto.exports

index 447e45644..82eb5f30c 100644

--- a/src/lib/crypto/libk5crypto.exports

+++ b/src/lib/crypto/libk5crypto.exports

@@ -108,3 +108,4 @@ krb5int_nfold

 k5_allow_weak_pbkdf2iter

 krb5_c_prfplus

 krb5_c_derive_prfplus

+k5_enctype_to_ssf

diff --git a/src/lib/gssapi/generic/gssapi_ext.h b/src/lib/gssapi/generic/gssapi_ext.h

index 9ad44216d..9d3a7e736 100644

--- a/src/lib/gssapi/generic/gssapi_ext.h

+++ b/src/lib/gssapi/generic/gssapi_ext.h

@@ -575,4 +575,15 @@ gss_import_cred(

 }

 #endif

+/*

+ * When used with gss_inquire_sec_context_by_oid(), return a buffer set with

+ * the first member containing an unsigned 32-bit integer in network byte

+ * order.  This is the Security Strength Factor (SSF) associated with the

+ * secure channel established by the security context.  NOTE: This value is

+ * made available solely as an indication for use by APIs like Cyrus SASL that

+ * classify the strength of a secure channel via this number.  The strength of

+ * a channel cannot necessarily be represented by a simple number.

+ */

+GSS_DLLIMP extern gss_OID GSS_C_SEC_CONTEXT_SASL_SSF;

+

 #endif /* GSSAPI_EXT_H_ */

diff --git a/src/lib/gssapi/generic/gssapi_generic.c b/src/lib/gssapi/generic/gssapi_generic.c

index 5496aa335..fa144c2bf 100644

--- a/src/lib/gssapi/generic/gssapi_generic.c

+++ b/src/lib/gssapi/generic/gssapi_generic.c

@@ -157,6 +157,13 @@ static const gss_OID_desc const_oids[] = {

     {7, (void *)"\x2b\x06\x01\x05\x05\x0d\x19"},

     {7, (void *)"\x2b\x06\x01\x05\x05\x0d\x1a"},

     {7, (void *)"\x2b\x06\x01\x05\x05\x0d\x1b"},

+

+    /*

+     * GSS_SEC_CONTEXT_SASL_SSF_OID 1.2.840.113554.1.2.2.5.15

+     * iso(1) member-body(2) United States(840) mit(113554)

+     * infosys(1) gssapi(2) krb5(2) krb5-gssapi-ext(5) sasl-ssf(15)

+     */

+    {11, (void *)"\x2a\x86\x48\x86\xf7\x12\x01\x02\x02\x05\x0f"},

 };

 /* Here are the constants which point to the static structure above.

@@ -218,6 +225,8 @@ GSS_DLLIMP gss_const_OID GSS_C_MA_PFS               = oids+33;

 GSS_DLLIMP gss_const_OID GSS_C_MA_COMPRESS          = oids+34;

 GSS_DLLIMP gss_const_OID GSS_C_MA_CTX_TRANS         = oids+35;

+GSS_DLLIMP gss_OID GSS_C_SEC_CONTEXT_SASL_SSF = oids+36;

+

 static gss_OID_set_desc gss_ma_known_attrs_desc = { 27, oids+9 };

 gss_OID_set gss_ma_known_attrs = &gss_ma_known_attrs_desc;

diff --git a/src/lib/gssapi/krb5/gssapiP_krb5.h b/src/lib/gssapi/krb5/gssapiP_krb5.h

index d7bdef7e2..ef030707e 100644

--- a/src/lib/gssapi/krb5/gssapiP_krb5.h

+++ b/src/lib/gssapi/krb5/gssapiP_krb5.h

@@ -1144,6 +1144,12 @@ gss_krb5int_extract_authtime_from_sec_context(OM_uint32 *,

                                               const gss_OID,

                                               gss_buffer_set_t *);

+#define GET_SEC_CONTEXT_SASL_SSF_OID_LENGTH 11

+#define GET_SEC_CONTEXT_SASL_SSF_OID "\x2a\x86\x48\x86\xf7\x12\x01\x02\x02\x05\x0f"

+OM_uint32

+gss_krb5int_sec_context_sasl_ssf(OM_uint32 *, const gss_ctx_id_t,

+                                 const gss_OID, gss_buffer_set_t *);

+

 #define GSS_KRB5_IMPORT_CRED_OID_LENGTH 11

 #define GSS_KRB5_IMPORT_CRED_OID "\x2a\x86\x48\x86\xf7\x12\x01\x02\x02\x05\x0d"

diff --git a/src/lib/gssapi/krb5/gssapi_krb5.c b/src/lib/gssapi/krb5/gssapi_krb5.c

index 99092ccab..de4131980 100644

--- a/src/lib/gssapi/krb5/gssapi_krb5.c

+++ b/src/lib/gssapi/krb5/gssapi_krb5.c

@@ -352,6 +352,10 @@ static struct {

     {

         {GSS_KRB5_EXTRACT_AUTHTIME_FROM_SEC_CONTEXT_OID_LENGTH, GSS_KRB5_EXTRACT_AUTHTIME_FROM_SEC_CONTEXT_OID},

         gss_krb5int_extract_authtime_from_sec_context

+    },

+    {

+        {GET_SEC_CONTEXT_SASL_SSF_OID_LENGTH, GET_SEC_CONTEXT_SASL_SSF_OID},

+        gss_krb5int_sec_context_sasl_ssf

     }

 };

diff --git a/src/lib/gssapi/krb5/inq_context.c b/src/lib/gssapi/krb5/inq_context.c

index 9024b3c7e..d2e466e60 100644

--- a/src/lib/gssapi/krb5/inq_context.c

+++ b/src/lib/gssapi/krb5/inq_context.c

@@ -310,3 +310,30 @@ gss_krb5int_extract_authtime_from_sec_context(OM_uint32 *minor_status,

     return generic_gss_add_buffer_set_member(minor_status, &rep, data_set);

 }

+

+OM_uint32

+gss_krb5int_sec_context_sasl_ssf(OM_uint32 *minor_status,

+                                 const gss_ctx_id_t context_handle,

+                                 const gss_OID desired_object,

+                                 gss_buffer_set_t *data_set)

+{

+    krb5_gss_ctx_id_rec *ctx;

+    krb5_key key;

+    krb5_error_code code;

+    gss_buffer_desc ssfbuf;

+    unsigned int ssf;

+    uint8_t buf[4];

+

+    ctx = (krb5_gss_ctx_id_rec *)context_handle;

+    key = ctx->have_acceptor_subkey ? ctx->acceptor_subkey : ctx->subkey;

+

+    code = k5_enctype_to_ssf(key->keyblock.enctype, &ssf;;

+    if (code)

+        return GSS_S_FAILURE;

+

+    store_32_be(ssf, buf);

+    ssfbuf.value = buf;

+    ssfbuf.length = sizeof(buf);

+

+    return generic_gss_add_buffer_set_member(minor_status, &ssfbuf, data_set);

+}

diff --git a/src/lib/gssapi/libgssapi_krb5.exports b/src/lib/gssapi/libgssapi_krb5.exports

index 9facb3f42..936540e41 100644

--- a/src/lib/gssapi/libgssapi_krb5.exports

+++ b/src/lib/gssapi/libgssapi_krb5.exports

@@ -37,6 +37,7 @@ GSS_C_MA_CBINDINGS

 GSS_C_MA_PFS

 GSS_C_MA_COMPRESS

 GSS_C_MA_CTX_TRANS

+GSS_C_SEC_CONTEXT_SASL_SSF

 gss_accept_sec_context

 gss_acquire_cred

 gss_acquire_cred_with_password

diff --git a/src/lib/gssapi32.def b/src/lib/gssapi32.def

index 362b9bce8..dff057754 100644

--- a/src/lib/gssapi32.def

+++ b/src/lib/gssapi32.def

@@ -182,3 +182,6 @@ EXPORTS

 	gss_verify_mic_iov				@146

 ; Added in 1.14

 	GSS_KRB5_CRED_NO_CI_FLAGS_X			@147	DATA

+; Added in 1.16

+;	GSS_KRB5_GET_CRED_IMPERSONATOR			@148	DATA

+	GSS_C_SEC_CONTEXT_SASL_SSF			@149	DATA

diff --git a/src/lib/krb5_32.def b/src/lib/krb5_32.def

index e5b560dfc..f7b428e16 100644

--- a/src/lib/krb5_32.def

+++ b/src/lib/krb5_32.def

@@ -470,3 +470,6 @@ EXPORTS

 	krb5_get_init_creds_opt_set_pac_request		@435

 	krb5int_trace					@436 ; PRIVATE GSSAPI

 	krb5_expand_hostname				@437

+

+; new in 1.16

+	k5_enctype_to_ssf				@438 ; PRIVATE GSSAPI

diff --git a/src/tests/gssapi/t_enctypes.c b/src/tests/gssapi/t_enctypes.c

index a2ad18f47..3fd31e2f8 100644

--- a/src/tests/gssapi/t_enctypes.c

+++ b/src/tests/gssapi/t_enctypes.c

@@ -32,6 +32,7 @@

 #include "k5-int.h"

 #include "common.h"

+#include "gssapi_ext.h"

 /*

  * This test program establishes contexts with the krb5 mech, the default

@@ -86,6 +87,9 @@ main(int argc, char *argv[])

     gss_krb5_lucid_context_v1_t *ilucid, *alucid;

     gss_krb5_rfc1964_keydata_t *i1964, *a1964;

     gss_krb5_cfx_keydata_t *icfx, *acfx;

+    gss_buffer_set_t bufset = GSS_C_NO_BUFFER_SET;

+    gss_OID ssf_oid = GSS_C_SEC_CONTEXT_SASL_SSF;

+    unsigned int ssf;

     size_t count;

     void *lptr;

     int c;

@@ -139,6 +143,16 @@ main(int argc, char *argv[])

     establish_contexts(&mech_krb5, icred, acred, tname, flags, &ictx, &actx,

                        NULL, NULL, NULL);

+    /* Query the SSF value and range-check the result. */

+    major = gss_inquire_sec_context_by_oid(&minor, ictx, ssf_oid, &bufset);

+    check_gsserr("gss_inquire_sec_context_by_oid(ssf)", major, minor);

+    if (bufset->elements[0].length != 4)

+        errout("SSF buffer has unexpected length");

+    ssf = load_32_be(bufset->elements[0].value);

+    if (ssf < 56 || ssf > 256)

+        errout("SSF value not within acceptable range (56-256)");

+    (void)gss_release_buffer_set(&minor, &bufset);

+

     /* Export to lucid contexts. */

     major = gss_krb5_export_lucid_sec_context(&minor, &ictx, 1, &lptr);

     check_gsserr("gss_export_lucid_sec_context(initiator)", major, minor);