From 2a7ea306e35a35296314484eec9eff5d8e38f02a 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);