Blame SOURCES/0088-KRB5-Do-not-switch_creds-if-already-the-specified-us.patch

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From 458ab6652130ebea1f305b5d383e263a2fbbcedc Mon Sep 17 00:00:00 2001
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From: Jakub Hrozek <jhrozek@redhat.com>
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Date: Sun, 19 Oct 2014 12:28:13 +0200
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Subject: [PATCH 88/92] KRB5: Do not switch_creds() if already the specified
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 user
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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The code didn't have to handle this case previously as sssd_be was always
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running as root and switching to the ccache as the user logging in.
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Also handle NULL creds on restore_creds() in case there was no switch.
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One less if-condition and fewer indentation levels.
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Related:
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https://fedorahosted.org/sssd/ticket/2370
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Reviewed-by: Sumit Bose <sbose@redhat.com>
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Reviewed-by: Lukáš Slebodník <lslebodn@redhat.com>
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---
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 src/tests/cwrap/test_become_user.c |  7 +++++++
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 src/util/become_user.c             | 29 +++++++++++++++++++++--------
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 2 files changed, 28 insertions(+), 8 deletions(-)
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diff --git a/src/tests/cwrap/test_become_user.c b/src/tests/cwrap/test_become_user.c
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index 06d3ad425c4928e9e9bff661fbb8f7b4536b8896..7ecea5aac34bb73ca81d94ad481f05b338e65ed0 100644
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--- a/src/tests/cwrap/test_become_user.c
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+++ b/src/tests/cwrap/test_become_user.c
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@@ -76,6 +76,7 @@ void test_switch_user(void **state)
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     struct passwd *sssd;
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     TALLOC_CTX *tmp_ctx;
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     struct sss_creds *saved_creds;
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+    struct sss_creds *saved_creds2 = NULL;
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     check_leaks_push(global_talloc_context);
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     tmp_ctx = talloc_new(global_talloc_context);
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@@ -102,6 +103,12 @@ void test_switch_user(void **state)
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     assert_int_equal(saved_creds->uid, 0);
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     assert_int_equal(saved_creds->gid, 0);
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+    /* Attempt to restore creds again */
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+    ret = switch_creds(tmp_ctx, sssd->pw_uid, sssd->pw_gid,
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+                       0, NULL, &saved_creds2);
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+    assert_int_equal(ret, EOK);
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+    assert_null(saved_creds2);
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+
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     /* restore root */
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     ret = restore_creds(saved_creds);
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     assert_int_equal(ret, EOK);
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diff --git a/src/util/become_user.c b/src/util/become_user.c
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index b5f94f993cd2c23bd3340fc502d36a530aa729fa..7dd2c752b1d0f289e7d82feee6d93e5974823f95 100644
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--- a/src/util/become_user.c
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+++ b/src/util/become_user.c
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@@ -90,9 +90,14 @@ errno_t switch_creds(TALLOC_CTX *mem_ctx,
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     struct sss_creds *ssc = NULL;
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     int size;
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     int ret;
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+    uid_t myuid;
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+    uid_t mygid;
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     DEBUG(SSSDBG_FUNC_DATA, "Switch user to [%d][%d].\n", uid, gid);
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+    myuid = geteuid();
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+    mygid = getegid();
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+
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     if (saved_creds) {
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         /* save current user credentials */
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         size = getgroups(0, NULL);
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@@ -124,8 +129,8 @@ errno_t switch_creds(TALLOC_CTX *mem_ctx,
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         }
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         /* we care only about effective ids */
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-        ssc->uid = geteuid();
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-        ssc->gid = getegid();
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+        ssc->uid = myuid;
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+        ssc->gid = mygid;
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     }
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     /* if we are regaining root set euid first so that we have CAP_SETUID back,
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@@ -141,7 +146,12 @@ errno_t switch_creds(TALLOC_CTX *mem_ctx,
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         }
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     }
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-    /* TODO: use prctl to get/set capabilities too ? */
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+    /* TODO: use libcap-ng if we need to get/set capabilities too ? */
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+
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+    if (myuid == uid && mygid == gid) {
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+        DEBUG(SSSDBG_FUNC_DATA, "Already user [%"SPRIuid"].\n", uid);
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+        return EOK;
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+    }
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     /* try to setgroups first should always work if CAP_SETUID is set,
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      * otherwise it will always fail, failure is not critical though as
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@@ -177,11 +187,9 @@ errno_t switch_creds(TALLOC_CTX *mem_ctx,
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 done:
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     if (ret) {
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-        if (ssc) {
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-            /* attempt to restore creds first */
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-            restore_creds(ssc);
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-            talloc_free(ssc);
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-        }
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+        /* attempt to restore creds first */
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+        restore_creds(ssc);
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+        talloc_free(ssc);
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     } else if (saved_creds) {
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         *saved_creds = ssc;
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     }
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@@ -190,6 +198,11 @@ done:
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 errno_t restore_creds(struct sss_creds *saved_creds)
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 {
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+    if (saved_creds == NULL) {
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+        /* In case save_creds was saved with the UID already dropped */
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+        return EOK;
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+    }
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+
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     return switch_creds(saved_creds,
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                         saved_creds->uid,
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                         saved_creds->gid,
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-- 
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1.9.3
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