linux-kernel - [RFC PATCH] fips: check whether a module registering an alg or template is signed

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Date:	Tue, 5 Feb 2013 17:58:30 -0500
From:	Kyle McMartin <kyle@...hat.com>
To:	Stephan Mueller <stephan.mueller@...ec.com>
Cc:	linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>,
	rusty@...tcorp.com.au, jstancek@...hat.com,
	herbert@...dor.hengli.com.au
Subject: [RFC PATCH] fips: check whether a module registering an alg or
 template is signed

fips mode needs to prevent unsigned modules from registering crypto
algorithms, and currently panics if an unsigned module is attempted to
be loaded. Instead, forbid (by returning -EINVAL) registering a crypto
alg or template if fips mode is enabled and the module signature is not
valid.

crypto_sig_check should return 1 (and allow the registration) if any
of the following are true:
 1/ fips is not enabled (but CONFIG_CRYPTO_FIPS is enabled.)
 2/ the algorithm is built into the kernel (THIS_MODULE == NULL)
 3/ the algorithm is in a module, and the module sig check passes
and fail in any of the other cases.

Checking in crypto_check_alg and crypto_register_template seems to hit
the callpoints as far as I can see.

Signed-off-by: Kyle McMartin <kyle@...hat.com>

---

rusty,

How about something like this? It keeps the FIPS mess in the
crypto/fips.c file (aside from something that goes away entirely in the
!CONFIG_CRYPTO_FIPS case.)

regards, Kyle

--- a/crypto/algapi.c
+++ b/crypto/algapi.c
@@ -52,6 +52,9 @@ static int crypto_check_alg(struct crypto_alg *alg)
 	if (alg->cra_priority < 0)
 		return -EINVAL;
 
+	if (!crypto_sig_check(alg->cra_module))
+		return -EINVAL;
+
 	return crypto_set_driver_name(alg);
 }
 
@@ -435,6 +438,11 @@ int crypto_register_template(struct crypto_template *tmpl)
 			goto out;
 	}
 
+	if (!crypto_sig_check(tmpl->module)) {
+		err = -EINVAL;
+		goto out;
+	}
+
 	list_add(&tmpl->list, &crypto_template_list);
 	crypto_notify(CRYPTO_MSG_TMPL_REGISTER, tmpl);
 	err = 0;
diff --git a/crypto/fips.c b/crypto/fips.c
index 5539700..2ebbe0f 100644
--- a/crypto/fips.c
+++ b/crypto/fips.c
@@ -15,6 +15,19 @@
 int fips_enabled;
 EXPORT_SYMBOL_GPL(fips_enabled);
 
+/* forbid loading modules in fips mode if the module is not signed */
+int crypto_sig_check(struct module *m)
+{
+#if defined(CONFIG_MODULE_SIG)
+	if (!fips_enabled || !m || (m && m->sig_ok))
+		return 1;
+	else
+		return 0;
+#else
+	return 1;
+#endif
+}
+
 /* Process kernel command-line parameter at boot time. fips=0 or fips=1 */
 static int fips_enable(char *str)
 {
diff --git a/crypto/internal.h b/crypto/internal.h
index 9ebedae..937bfaf 100644
--- a/crypto/internal.h
+++ b/crypto/internal.h
@@ -139,5 +139,14 @@ static inline void crypto_notify(unsigned long val, void *v)
 	blocking_notifier_call_chain(&crypto_chain, val, v);
 }
 
+#if defined(CONFIG_CRYPTO_FIPS)
+int crypto_sig_check(struct module *m);
+#else
+static inline int crypto_sig_check(struct module *m)
+{
+	return 1;
+}
+#endif
+
 #endif	/* _CRYPTO_INTERNAL_H */
 
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