From 0e04be2c1398dac40c50910a59157eed0ad5a7e4 Mon Sep 17 00:00:00 2001

From: Simo Sorce <simo@redhat.com>

Date: Tue, 14 Mar 2017 10:43:17 -0400

Subject: [PATCH] Allow connection to self when impersonator set

If the target of a context establishment is the impersonator itself,

then allow it. This kind of context establishment is used by tools like

mod_auth_gssapi to be able to inspect the ticket just obtained via

impersonation and it is basically a noop as the acceptor and the

impersonator are the same entitiy.

Signed-off-by: Simo Sorce <simo@redhat.com>

Reviewed-by: Robbie Harwood <rharwood@redhat.com>

Merges: #172

(cherry picked from commit eada55e831d12b42d3be3a555ff4e133bed7f594)

---

 proxy/src/gp_creds.c                | 57 ++++++++++++++++++++++++++++++++-----

 proxy/src/gp_rpc_creds.h            |  3 +-

 proxy/src/gp_rpc_init_sec_context.c |  2 +-

 proxy/tests/t_impersonate.py        | 35 ++++++++++++++++-------

 4 files changed, 78 insertions(+), 19 deletions(-)

diff --git a/proxy/src/gp_creds.c b/proxy/src/gp_creds.c

index 95a1c48..7d89b06 100644

--- a/proxy/src/gp_creds.c

+++ b/proxy/src/gp_creds.c

@@ -883,7 +883,8 @@ static uint32_t get_impersonator_name(uint32_t *min, gss_cred_id_t cred,

         }

     } else if (ret_maj == GSS_S_UNAVAILABLE) {

         /* Not supported by krb5 library yet, fallback to raw krb5 calls */

-        /* TODO: Remove once we set a required dependency on MIT 1.15+ */

+        /* TODO: Remove once we set a minimum required dependency on a

+         * release that supports this call */

         ret_maj = get_impersonator_fallback(&ret_min, cred, impersonator);

         if (ret_maj == GSS_S_FAILURE) {

             if (ret_min == KRB5_CC_NOTFOUND) {

@@ -899,9 +900,47 @@ done:

     return ret_maj;

 }

+static uint32_t check_impersonator_name(uint32_t *min,

+                                        gss_name_t target_name,

+                                        const char *impersonator)

+{

+    gss_name_t canon_name = NULL;

+    gss_buffer_desc buf;

+    uint32_t ret_maj = 0;

+    uint32_t ret_min = 0;

+    uint32_t discard;

+    bool match;

+

+    ret_maj = gss_canonicalize_name(&discard, target_name, &gp_mech_krb5,

+                                    &canon_name);

+    if (ret_maj != GSS_S_COMPLETE) {

+        *min = ret_min;

+        return ret_maj;

+    }

+

+    ret_maj = gss_display_name(&discard, canon_name, &buf, NULL);

+    gss_release_name(&discard, &canon_name);

+    if (ret_maj != GSS_S_COMPLETE) {

+        *min = ret_min;

+        return ret_maj;

+    }

+

+    match = (strncmp(impersonator, buf.value, buf.length) == 0) &&

+            (strlen(impersonator) == buf.length);

+    gss_release_buffer(&discard, &buf;;

+

+    *min = 0;

+    if (match) {

+        return GSS_S_COMPLETE;

+    } else {

+        return GSS_S_UNAUTHORIZED;

+    }

+}

+

 uint32_t gp_cred_allowed(uint32_t *min,

                          struct gp_call_ctx *gpcall,

-                         gss_cred_id_t cred)

+                         gss_cred_id_t cred,

+                         gss_name_t target_name)

 {

     char *impersonator = NULL;

     uint32_t ret_maj = 0;

@@ -924,11 +963,11 @@ uint32_t gp_cred_allowed(uint32_t *min,

     if (ret_maj) goto done;

     /* if we find an impersonator entry we bail as that is not authorized,

-     * if it were then gpcall->service->allow_const_deleg would have caused

-     * the ealier check to return GSS_S_COMPLETE already */

+     * *unless* the target is the impersonator itself! If the operation

+     * were authorized then gpcall->service->allow_const_deleg would have

+     * caused the ealier check to return GSS_S_COMPLETE already */

     if (impersonator != NULL) {

-        ret_min = 0;

-        ret_maj = GSS_S_UNAUTHORIZED;

+        ret_maj = check_impersonator_name(&ret_min, target_name, impersonator);

     }

 done:

@@ -937,7 +976,11 @@ done:

         GPDEBUGN(2, "Unauthorized impersonator credentials detected\n");

         break;

     case GSS_S_COMPLETE:

-        GPDEBUGN(2, "No impersonator credentials detected\n");

+        if (impersonator) {

+            GPDEBUGN(2, "Credentials allowed for 'self'\n");

+        } else {

+            GPDEBUGN(2, "No impersonator credentials detected\n");

+        }

         break;

     default:

         GPDEBUG("Failure while checking credentials\n");

diff --git a/proxy/src/gp_rpc_creds.h b/proxy/src/gp_rpc_creds.h

index 54fe482..c116e53 100644

--- a/proxy/src/gp_rpc_creds.h

+++ b/proxy/src/gp_rpc_creds.h

@@ -34,7 +34,8 @@ uint32_t gp_add_krb5_creds(uint32_t *min,

 uint32_t gp_cred_allowed(uint32_t *min,

                          struct gp_call_ctx *gpcall,

-                         gss_cred_id_t cred);

+                         gss_cred_id_t cred,

+                         gss_name_t target_name);

 void gp_filter_flags(struct gp_call_ctx *gpcall, uint32_t *flags);

diff --git a/proxy/src/gp_rpc_init_sec_context.c b/proxy/src/gp_rpc_init_sec_context.c

index 767a3ff..413e2ec 100644

--- a/proxy/src/gp_rpc_init_sec_context.c

+++ b/proxy/src/gp_rpc_init_sec_context.c

@@ -108,7 +108,7 @@ int gp_init_sec_context(struct gp_call_ctx *gpcall,

         }

     }

-    ret_maj = gp_cred_allowed(&ret_min, gpcall, ich);

+    ret_maj = gp_cred_allowed(&ret_min, gpcall, ich, target_name);

     if (ret_maj) {

         goto done;

     }

diff --git a/proxy/tests/t_impersonate.py b/proxy/tests/t_impersonate.py

index 3e25962..29f9a41 100755

--- a/proxy/tests/t_impersonate.py

+++ b/proxy/tests/t_impersonate.py

@@ -34,19 +34,20 @@ IMPERSONATE_CONF_TEMPLATE = '''

 '''

-def run_cmd(testdir, env, conf, name, socket, cmd, expected_failure):

+def run_cmd(testdir, env, conf, name, socket, cmd, keytab, expected_failure):

     logfile = conf['logfile']

     testenv = env.copy()

     testenv.update({'KRB5CCNAME': os.path.join(testdir, 't' + conf['prefix'] +

                                                '_impersonate.ccache'),

-                    'KRB5_KTNAME': os.path.join(testdir, PROXY_KTNAME),

+                    'KRB5_KTNAME': os.path.join(testdir, keytab),

                     'KRB5_TRACE': os.path.join(testdir, 't' + conf['prefix'] +

                                                '_impersonate.trace'),

                     'GSS_USE_PROXY': 'yes',

                     'GSSPROXY_SOCKET': socket,

                     'GSSPROXY_BEHAVIOR': 'REMOTE_FIRST'})

+    print("\nTesting: [%s]" % (name,), file=logfile)

     print("[COMMAND]\n%s\n[ENVIRONMENT]\n%s\n" % (cmd, testenv), file=logfile)

     logfile.flush()

@@ -74,45 +75,59 @@ def run(testdir, env, conf):

     rets = []

     # Test all permitted

+    msg = "Impersonate"

     socket = os.path.join(testdir, 'impersonate.socket')

     cmd = ["./tests/t_impersonate", USR_NAME, HOST_GSS, PROXY_GSS,

            path_prefix + 'impersonate.cache']

-    r = run_cmd(testdir, env, conf, "Impersonate", socket, cmd, False)

+    r = run_cmd(testdir, env, conf, msg, socket, cmd, PROXY_KTNAME, False)

     rets.append(r)

-    #Test fail

+    #Test self fail

+    msg = "Impersonate fail self"

     socket = os.path.join(testdir, 'impersonate-proxyonly.socket')

     cmd = ["./tests/t_impersonate", USR_NAME, HOST_GSS, PROXY_GSS,

            path_prefix + 'impersonate.cache']

-    r = run_cmd(testdir, env, conf, "Impersonate fail self", socket, cmd, True)

+    r = run_cmd(testdir, env, conf, msg, socket, cmd, PROXY_KTNAME, True)

     rets.append(r)

-    #Test fail

+    #Test proxy fail

+    msg = "Impersonate fail proxy"

     socket = os.path.join(testdir, 'impersonate-selfonly.socket')

     cmd = ["./tests/t_impersonate", USR_NAME, HOST_GSS, PROXY_GSS,

            path_prefix + 'impersonate.cache']

-    r = run_cmd(testdir, env, conf, "Impersonate fail proxy", socket, cmd, True)

+    r = run_cmd(testdir, env, conf, msg, socket, cmd, PROXY_KTNAME, True)

     rets.append(r)

     #Test s4u2self half succeed

+    msg = "s4u2self delegation"

     socket = os.path.join(testdir, 'impersonate-selfonly.socket')

     cmd = ["./tests/t_impersonate", USR_NAME, HOST_GSS, PROXY_GSS,

            path_prefix + 'impersonate.cache', 's4u2self']

-    r = run_cmd(testdir, env, conf, "s4u2self delegation", socket, cmd, False)

+    r = run_cmd(testdir, env, conf, msg, socket, cmd, PROXY_KTNAME, False)

+    rets.append(r)

+

+    #Test proxy to self succeed

+    msg = "Impersonate to self"

+    socket = os.path.join(testdir, 'impersonate-selfonly.socket')

+    cmd = ["./tests/t_impersonate", USR_NAME, HOST_GSS, HOST_GSS,

+           path_prefix + 'impersonate.cache', 's4u2proxy']

+    r = run_cmd(testdir, env, conf, msg, socket, cmd, SVC_KTNAME, False)

     rets.append(r)

     #Test s4u2proxy half fail

+    msg = "s4u2proxy fail"

     socket = os.path.join(testdir, 'impersonate-selfonly.socket')

     cmd = ["./tests/t_impersonate", USR_NAME, HOST_GSS, PROXY_GSS,

            path_prefix + 'impersonate.cache', 's4u2proxy']

-    r = run_cmd(testdir, env, conf, "s4u2proxy fail", socket, cmd, True)

+    r = run_cmd(testdir, env, conf, msg, socket, cmd, PROXY_KTNAME, True)

     rets.append(r)

     #Test s4u2proxy half succeed

+    msg = "s4u2proxy"

     socket = os.path.join(testdir, 'impersonate-proxyonly.socket')

     cmd = ["./tests/t_impersonate", USR_NAME, HOST_GSS, PROXY_GSS,

            path_prefix + 'impersonate.cache', 's4u2proxy']

-    r = run_cmd(testdir, env, conf, "s4u2proxy", socket, cmd, False)

+    r = run_cmd(testdir, env, conf, msg, socket, cmd, PROXY_KTNAME, False)

     rets.append(r)

     # Reset back gssproxy conf