From 954637494fc8453f71e2b5d93b3d1ea97e31d646 Mon Sep 17 00:00:00 2001
From: Jakub Hrozek <jhrozek@redhat.com>
Date: Sun, 19 Oct 2014 19:15:52 +0200
Subject: [PATCH 68/71] LDAP: Drop privileges after kinit in ldap_child
MIME-Version: 1.0
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After ldap_child initializes privileges using root-owned keytab, it
drops privileges to the SSSD user, minimizing the amount of code that
runs as root.
Reviewed-by: Michal Židek <mzidek@redhat.com>
---
Makefile.am | 4 +-
src/providers/ldap/ldap_child.c | 96 ++++++++++++++++++++-------------
src/providers/ldap/sdap_child_helpers.c | 8 ++-
3 files changed, 70 insertions(+), 38 deletions(-)
diff --git a/Makefile.am b/Makefile.am
index 02b087ea37b4e55da7eeb7fb199d282d72129e40..ea296c40f89c552d5825cbce8e95afdc517e8bb5 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -2517,7 +2517,9 @@ ldap_child_SOURCES = \
src/util/atomic_io.c \
src/util/authtok.c \
src/util/util.c \
- src/util/signal.c
+ src/util/signal.c \
+ src/util/become_user.c \
+ $(NULL)
ldap_child_CFLAGS = \
$(AM_CFLAGS) \
$(POPT_CFLAGS) \
diff --git a/src/providers/ldap/ldap_child.c b/src/providers/ldap/ldap_child.c
index e1abc9fd73f2ae95f0a0c28159589ebd36d2cf06..a922b181715c5e89301e9f50bdb81723d1ff2a6a 100644
--- a/src/providers/ldap/ldap_child.c
+++ b/src/providers/ldap/ldap_child.c
@@ -49,6 +49,8 @@ struct input_buffer {
const char *princ_str;
const char *keytab_name;
krb5_deltat lifetime;
+ uid_t uid;
+ gid_t gid;
};
static errno_t unpack_buffer(uint8_t *buf, size_t size,
@@ -99,6 +101,12 @@ static errno_t unpack_buffer(uint8_t *buf, size_t size,
SAFEALIGN_COPY_UINT32_CHECK(&ibuf->lifetime, buf + p, size, &p);
DEBUG(SSSDBG_TRACE_LIBS, "lifetime: %u\n", ibuf->lifetime);
+ /* UID and GID to run as */
+ SAFEALIGN_COPY_UINT32_CHECK(&ibuf->uid, buf + p, size, &p);
+ SAFEALIGN_COPY_UINT32_CHECK(&ibuf->gid, buf + p, size, &p);
+ DEBUG(SSSDBG_FUNC_DATA,
+ "Will run as [%"SPRIuid"][%"SPRIgid"].\n", ibuf->uid, ibuf->gid);
+
return EOK;
}
@@ -242,6 +250,8 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX *memctx,
const char *princ_str,
const char *keytab_name,
const krb5_deltat lifetime,
+ uid_t uid,
+ gid_t gid,
const char **ccname_out,
time_t *expire_time_out)
{
@@ -372,42 +382,6 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX *memctx,
goto done;
}
- 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;
- }
-
- old_umask = umask(077);
- fd = mkstemp(ccname_file_dummy);
- umask(old_umask);
- 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));
- goto done;
- }
-
memset(&my_creds, 0, sizeof(my_creds));
memset(&options, 0, sizeof(options));
@@ -423,8 +397,36 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX *memctx,
}
sss_krb5_get_init_creds_opt_set_canonicalize(&options, canonicalize);
+ ccname_file = talloc_asprintf(tmp_ctx, "%s/ccache_%s",
+ DB_PATH, realm_name);
+ if (ccname_file == NULL) {
+ ret = ENOMEM;
+ goto done;
+ }
+
+ ccname_file_dummy = talloc_asprintf(tmp_ctx, "%s/ccache_%s_XXXXXX",
+ DB_PATH, realm_name);
+ if (ccname_file_dummy == NULL) {
+ ret = ENOMEM;
+ goto done;
+ }
+
+ old_umask = umask(077);
+ fd = mkstemp(ccname_file_dummy);
+ umask(old_umask);
+ 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);
+
krberr = krb5_get_init_creds_keytab(context, &my_creds, kprinc,
keytab, 0, NULL, &options);
+ krb5_kt_close(context, keytab);
+ keytab = NULL;
if (krberr) {
DEBUG(SSSDBG_FATAL_FAILURE,
"Failed to init credentials: %s\n",
@@ -438,6 +440,27 @@ static krb5_error_code ldap_child_get_tgt_sync(TALLOC_CTX *memctx,
}
DEBUG(SSSDBG_TRACE_INTERNAL, "credentials initialized\n");
+ krberr = become_user(uid, gid);
+ if (krberr != 0) {
+ DEBUG(SSSDBG_CRIT_FAILURE, "become_user failed.\n");
+ goto done;
+ }
+
+ 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));
+ goto done;
+ }
+
/* Use updated principal if changed due to canonicalization. */
krberr = krb5_cc_initialize(context, ccache, my_creds.client);
if (krberr) {
@@ -643,6 +666,7 @@ int main(int argc, const char *argv[])
kerr = ldap_child_get_tgt_sync(main_ctx,
ibuf->realm_str, ibuf->princ_str,
ibuf->keytab_name, ibuf->lifetime,
+ ibuf->uid, ibuf->gid,
&ccname, &expire_time);
if (kerr != EOK) {
DEBUG(SSSDBG_CRIT_FAILURE, "ldap_child_get_tgt_sync failed.\n");
diff --git a/src/providers/ldap/sdap_child_helpers.c b/src/providers/ldap/sdap_child_helpers.c
index 448c5af10e9da8949bcaa39d8a3fa05ec309e16f..e5d46b9b756cd50fadb212da72ad1cc9bdd93330 100644
--- a/src/providers/ldap/sdap_child_helpers.c
+++ b/src/providers/ldap/sdap_child_helpers.c
@@ -152,7 +152,7 @@ static errno_t create_tgt_req_send_buffer(TALLOC_CTX *mem_ctx,
return ENOMEM;
}
- buf->size = 4 * sizeof(uint32_t);
+ buf->size = 6 * sizeof(uint32_t);
if (realm_str) {
buf->size += strlen(realm_str);
}
@@ -201,6 +201,12 @@ static errno_t create_tgt_req_send_buffer(TALLOC_CTX *mem_ctx,
/* lifetime */
SAFEALIGN_SET_UINT32(&buf->data[rp], lifetime, &rp);
+ /* UID and GID to drop privileges to, if needed. The ldap_child process runs as
+ * setuid if the back end runs unprivileged as it needs to access the keytab
+ */
+ SAFEALIGN_SET_UINT32(&buf->data[rp], geteuid(), &rp);
+ SAFEALIGN_SET_UINT32(&buf->data[rp], getegid(), &rp);
+
*io_buf = buf;
return EOK;
}
--
1.9.3