On Tue, Aug 26, 2014 at 02:21:00PM +0200, Sumit Bose wrote:
> > > This is working as expected, but using krb5_cc_new_unique() and
> > > krb5_cc_get_name() from libkrb5 might even result in more simple code?
> >
> > In theory yes, I have a patch that I tested already:
> >
> > https://fedorapeople.org/cgit/jhrozek/public_git/sssd.git/commit/?h=ldapchild&id=b692d625202d7ee512f0affb2a38c49ec02403d6o
> >
> > But I'm not sure this approach will work well for us, because:
> > 1) The ccache is always created in /tmp when using
> > krb5_cc_new_unique(). In the krb5 code it looks like
> > krb5_cc_new_unique calls krb5_fcc_generate_new() which
> > unconditionally uses a templatized file in /tmp. Because on many
> > systems, tmp is a tmpfs, the rename errored out with error 18
> > (Invalid cross-device link).
> >
> > 2) Rename from one directory to another is not friedly to SELinux.
> >
> > So while the code is way cleaner than handling the templates ourselves,
> > I think we would have a way to tell krb5_cc_new_unique() to accept a
> > directory to create the ccache at..or copy the file ourselves.
>
> ah, sorry, I didn't realized that the hint option is unused. I agree
> that you original approach is better. But please free the temporary
> strings.
OK, done. I used a tmp_ctx for this change, because we have several
other temporary strings that suffer from the same. I also added the
extra debug message you requested earlier.
btw when I was testing the changes to make sure there is no
use-after-free, I realized we have many leaks in the ldap_child itself.
Using:
command = /usr/bin/valgrind --trace-children=yes /usr/libexec/sssd/sssd_be
--domain ipa.example.com --debug-level 3
in the domain section. I guess that's worth of a ticket, but not urgent
either.
>From bc66dc8829648456d2f69ea9533afa29a550938c Mon Sep 17 00:00:00 2001
From: Jakub Hrozek <jhro...@redhat.com>
Date: Tue, 26 Aug 2014 14:35:55 +0200
Subject: [PATCH 1/2] LDAP: Use tmp_ctx in ldap_child for temporary data
Using a global memory context for short-lived private data might lead to
memory growth.
---
src/providers/ldap/ldap_child.c | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)
diff --git a/src/providers/ldap/ldap_child.c b/src/providers/ldap/ldap_child.c
index
e2fe3f232b3f051bf1d94617c2c711b7087130c7..d0552d57c733b71fa2d901d6c9f0f9dd5cbbd8b5
100644
--- a/src/providers/ldap/ldap_child.c
+++ b/src/providers/ldap/ldap_child.c
@@ -184,6 +184,7 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX
*memctx,
int canonicalize = 0;
int kdc_time_offset_usec;
int ret;
+ TALLOC_CTX *tmp_ctx;
krberr = krb5_init_context(&context);
if (krberr) {
@@ -192,6 +193,12 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX
*memctx,
}
DEBUG(SSSDBG_TRACE_INTERNAL, "Kerberos context initialized\n");
+ tmp_ctx = talloc_new(memctx);
+ if (tmp_ctx == NULL) {
+ krberr = KRB5KRB_ERR_GENERIC;
+ goto done;
+ }
+
krberr = set_child_debugging(context);
if (krberr != EOK) {
DEBUG(SSSDBG_MINOR_FAILURE, "Cannot set krb5_child debugging\n");
@@ -205,14 +212,14 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX
*memctx,
goto done;
}
- realm_name = talloc_strdup(memctx, default_realm);
+ realm_name = talloc_strdup(tmp_ctx, default_realm);
krb5_free_default_realm(context, default_realm);
if (!realm_name) {
krberr = KRB5KRB_ERR_GENERIC;
goto done;
}
} else {
- realm_name = talloc_strdup(memctx, realm_str);
+ realm_name = talloc_strdup(tmp_ctx, realm_str);
if (!realm_name) {
krberr = KRB5KRB_ERR_GENERIC;
goto done;
@@ -223,10 +230,10 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX
*memctx,
if (princ_str) {
if (!strchr(princ_str, '@')) {
- full_princ = talloc_asprintf(memctx, "%s@%s",
+ full_princ = talloc_asprintf(tmp_ctx, "%s@%s",
princ_str, realm_name);
} else {
- full_princ = talloc_strdup(memctx, princ_str);
+ full_princ = talloc_strdup(tmp_ctx, princ_str);
}
} else {
char hostname[HOST_NAME_MAX + 1];
@@ -240,7 +247,7 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX
*memctx,
DEBUG(SSSDBG_TRACE_LIBS, "got hostname: [%s]\n", hostname);
- ret = select_principal_from_keytab(memctx, hostname, realm_name,
+ ret = select_principal_from_keytab(tmp_ctx, hostname, realm_name,
keytab_name, &full_princ, NULL, NULL);
if (ret) {
krberr = KRB5_KT_IOERR;
@@ -283,7 +290,7 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX
*memctx,
goto done;
}
- ccname = talloc_asprintf(memctx, "FILE:%s/ccache_%s", DB_PATH, realm_name);
+ ccname = talloc_asprintf(tmp_ctx, "FILE:%s/ccache_%s", DB_PATH,
realm_name);
if (!ccname) {
krberr = KRB5KRB_ERR_GENERIC;
goto done;
@@ -362,10 +369,11 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX
*memctx,
#endif
krberr = 0;
- *ccname_out = ccname;
+ *ccname_out = talloc_steal(memctx, ccname);
*expire_time_out = my_creds.times.endtime - kdc_time_offset;
done:
+ talloc_free(tmp_ctx);
if (krberr != 0) KRB5_SYSLOG(krberr);
if (keytab) krb5_kt_close(context, keytab);
if (context) krb5_free_context(context);
--
1.9.3
>From fe8401195007ef9ba7e28a0e4c9a107e8ca27354 Mon Sep 17 00:00:00 2001
From: Jakub Hrozek <jhro...@redhat.com>
Date: Tue, 26 Aug 2014 09:43:09 +0200
Subject: [PATCH 2/2] LDAP: Use randomized ccname for storing credentials
https://fedorahosted.org/sssd/ticket/2410
If two ldap_child processes attempt to prime the ccache at the same time
for the same domain, the ldap_child might fail with:
[ldap_child_get_tgt_sync] (0x0040): Failed to init ccache: Internal
credentials cache error
[main] (0x0020): ldap_child_get_tgt_sync failed.
To avoid the race-condition, the ldap_child process now creates the
ccache randomized and before returning to the caller, renames the
randomized ccache to a permanent one.
---
src/providers/ldap/ldap_child.c | 44 ++++++++++++++++++++++++++++++++++++-----
1 file changed, 39 insertions(+), 5 deletions(-)
diff --git a/src/providers/ldap/ldap_child.c b/src/providers/ldap/ldap_child.c
index
d0552d57c733b71fa2d901d6c9f0f9dd5cbbd8b5..6ef7bd204bb028b0dc1f0ccb8b6e52cdacf044f2
100644
--- a/src/providers/ldap/ldap_child.c
+++ b/src/providers/ldap/ldap_child.c
@@ -168,7 +168,9 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX
*memctx,
const char **ccname_out,
time_t *expire_time_out)
{
+ int fd;
char *ccname;
+ char *ccname_dummy;
char *realm_name = NULL;
char *full_princ = NULL;
char *default_realm = NULL;
@@ -185,6 +187,8 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX
*memctx,
int kdc_time_offset_usec;
int ret;
TALLOC_CTX *tmp_ctx;
+ char *ccname_file_dummy;
+ char *ccname_file;
krberr = krb5_init_context(&context);
if (krberr) {
@@ -290,14 +294,34 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX
*memctx,
goto done;
}
- ccname = talloc_asprintf(tmp_ctx, "FILE:%s/ccache_%s", DB_PATH,
realm_name);
- if (!ccname) {
- krberr = KRB5KRB_ERR_GENERIC;
+ ccname_file_dummy = talloc_asprintf(tmp_ctx, "%s/ccache_%s_XXXXXX",
+ DB_PATH, realm_name);
+ ccname_file = talloc_asprintf(tmp_ctx, "%s/ccache_%s",
+ DB_PATH, realm_name);
+ if (ccname_file_dummy == NULL || ccname_file == NULL) {
+ ret = ENOMEM;
goto done;
}
- DEBUG(SSSDBG_TRACE_INTERNAL, "keytab ccname: [%s]\n", ccname);
- krberr = krb5_cc_resolve(context, ccname, &ccache);
+ fd = mkstemp(ccname_file_dummy);
+ if (fd == -1) {
+ ret = errno;
+ goto done;
+ }
+ /* We only care about creating a unique file name here, we don't
+ * need the fd
+ */
+ close(fd);
+
+ ccname_dummy = talloc_asprintf(tmp_ctx, "FILE:%s", ccname_file_dummy);
+ ccname = talloc_asprintf(tmp_ctx, "FILE:%s", ccname_file);
+ if (ccname_dummy == NULL || ccname == NULL) {
+ krberr = ENOMEM;
+ goto done;
+ }
+ DEBUG(SSSDBG_TRACE_INTERNAL, "keytab ccname: [%s]\n", ccname_dummy);
+
+ krberr = krb5_cc_resolve(context, ccname_dummy, &ccache);
if (krberr) {
DEBUG(SSSDBG_OP_FAILURE, "Failed to set cache name: %s\n",
sss_krb5_get_error_message(context, krberr));
@@ -368,6 +392,16 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX
*memctx,
kdc_time_offset = 0;
#endif
+ DEBUG(SSSDBG_TRACE_INTERNAL,
+ "Renaming [%s] to [%s]\n", ccname_file_dummy, ccname_file);
+ ret = rename(ccname_file_dummy, ccname_file);
+ if (ret == -1) {
+ ret = errno;
+ DEBUG(SSSDBG_CRIT_FAILURE,
+ "rename failed [%d][%s].\n", ret, strerror(ret));
+ goto done;
+ }
+
krberr = 0;
*ccname_out = talloc_steal(memctx, ccname);
*expire_time_out = my_creds.times.endtime - kdc_time_offset;
--
1.9.3
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