From 9f18a841939777c6a34d930eab2be37d53a12351 Mon Sep 17 00:00:00 2001
From: Michal Marek <mmarek@suse.com>
Date: Thu, 11 Feb 2016 16:23:38 +0100
Subject: [PATCH] MODSIGN: Support the old-style signature format
References: fate#319460
Patch-mainline: Never, SLE12 specific

... to be compatible with SLE12 tools. This is a partial revert of
3f1e1bea3474 ("MODSIGN: Use PKCS#7 messages as module signatures").

Signed-off-by: Michal Marek <mmarek@suse.com>
---
 kernel/module_signing.c | 242 ++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 232 insertions(+), 10 deletions(-)

diff --git a/kernel/module_signing.c b/kernel/module_signing.c
index 6528a79d998d..48ede9f3dd03 100644
--- a/kernel/module_signing.c
+++ b/kernel/module_signing.c
@@ -11,6 +11,9 @@
 
 #include <linux/kernel.h>
 #include <linux/errno.h>
+#include <crypto/public_key.h>
+#include <crypto/hash.h>
+#include <keys/asymmetric-type.h>
 #include <keys/system_keyring.h>
 #include <crypto/public_key.h>
 #include "module-internal.h"
@@ -26,15 +29,18 @@
  *	- Information block
  */
 struct module_signature {
-	u8	algo;		/* Public-key crypto algorithm [0] */
-	u8	hash;		/* Digest algorithm [0] */
-	u8	id_type;	/* Key identifier type [PKEY_ID_PKCS7] */
-	u8	signer_len;	/* Length of signer's name [0] */
-	u8	key_id_len;	/* Length of key identifier [0] */
+	u8	algo;		/* Public-key crypto algorithm [0|enum pkey_algo] */
+	u8	hash;		/* Digest algorithm [0|enum hash_algo] */
+	u8	id_type;	/* Key identifier type [PKEY_ID_PKCS7|PKEY_ID_X509] */
+	u8	signer_len;	/* Length of signer's name (PKEY_ID_X509 only) */
+	u8	key_id_len;	/* Length of key identifier (PKEY_ID_X509 only) */
 	u8	__pad[3];
 	__be32	sig_len;	/* Length of signature data */
 };
 
+static int old_mod_verify_sig(const void *mod, unsigned long *_modlen,
+                       const struct module_signature *ms);
+
 /*
  * Verify the signature on a module.
  */
@@ -50,6 +56,17 @@ int mod_verify_sig(const void *mod, unsigned long *_modlen)
 
 	memcpy(&ms, mod + (modlen - sizeof(ms)), sizeof(ms));
 	modlen -= sizeof(ms);
+	*_modlen = modlen;
+
+	switch (ms.id_type) {
+	case PKEY_ID_PKCS7:
+		break;
+	case PKEY_ID_X509:
+		return old_mod_verify_sig(mod, _modlen, &ms);
+	default:
+		pr_err("Module is not signed with expected signature type\n");
+		return -ENOPKG;
+	}
 
 	sig_len = be32_to_cpu(ms.sig_len);
 	if (sig_len >= modlen)
@@ -57,11 +74,6 @@ int mod_verify_sig(const void *mod, unsigned long *_modlen)
 	modlen -= sig_len;
 	*_modlen = modlen;
 
-	if (ms.id_type != PKEY_ID_PKCS7) {
-		pr_err("Module is not signed with expected PKCS#7 message\n");
-		return -ENOPKG;
-	}
-
 	if (ms.algo != 0 ||
 	    ms.hash != 0 ||
 	    ms.signer_len != 0 ||
@@ -76,3 +88,213 @@ int mod_verify_sig(const void *mod, unsigned long *_modlen)
 	return system_verify_data(mod, modlen, mod + modlen, sig_len,
 				  VERIFYING_MODULE_SIGNATURE);
 }
+
+/*
+ * pre-4.3 compat stuff
+ */
+
+/*
+ * Digest the module contents.
+ */
+static struct public_key_signature *mod_make_digest(enum hash_algo hash,
+						    const void *mod,
+						    unsigned long modlen)
+{
+	struct public_key_signature *pks;
+	struct crypto_shash *tfm;
+	struct shash_desc *desc;
+	size_t digest_size, desc_size;
+	int ret;
+
+	pr_devel("==>%s()\n", __func__);
+	
+	/* Allocate the hashing algorithm we're going to need and find out how
+	 * big the hash operational data will be.
+	 */
+	tfm = crypto_alloc_shash(hash_algo_name[hash], 0, 0);
+	if (IS_ERR(tfm))
+		return (PTR_ERR(tfm) == -ENOENT) ? ERR_PTR(-ENOPKG) : ERR_CAST(tfm);
+
+	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
+	digest_size = crypto_shash_digestsize(tfm);
+
+	/* We allocate the hash operational data storage on the end of our
+	 * context data and the digest output buffer on the end of that.
+	 */
+	ret = -ENOMEM;
+	pks = kzalloc(digest_size + sizeof(*pks) + desc_size, GFP_KERNEL);
+	if (!pks)
+		goto error_no_pks;
+
+	pks->pkey_hash_algo	= hash;
+	pks->digest		= (u8 *)pks + sizeof(*pks) + desc_size;
+	pks->digest_size	= digest_size;
+
+	desc = (void *)pks + sizeof(*pks);
+	desc->tfm   = tfm;
+	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
+
+	ret = crypto_shash_init(desc);
+	if (ret < 0)
+		goto error;
+
+	ret = crypto_shash_finup(desc, mod, modlen, pks->digest);
+	if (ret < 0)
+		goto error;
+
+	crypto_free_shash(tfm);
+	pr_devel("<==%s() = ok\n", __func__);
+	return pks;
+
+error:
+	kfree(pks);
+error_no_pks:
+	crypto_free_shash(tfm);
+	pr_devel("<==%s() = %d\n", __func__, ret);
+	return ERR_PTR(ret);
+}
+
+/*
+ * Extract an MPI array from the signature data.  This represents the actual
+ * signature.  Each raw MPI is prefaced by a BE 2-byte value indicating the
+ * size of the MPI in bytes.
+ *
+ * RSA signatures only have one MPI, so currently we only read one.
+ */
+static int mod_extract_mpi_array(struct public_key_signature *pks,
+				 const void *data, size_t len)
+{
+	size_t nbytes;
+	MPI mpi;
+
+	if (len < 3)
+		return -EBADMSG;
+	nbytes = ((const u8 *)data)[0] << 8 | ((const u8 *)data)[1];
+	data += 2;
+	len -= 2;
+	if (len != nbytes)
+		return -EBADMSG;
+
+	mpi = mpi_read_raw_data(data, nbytes);
+	if (!mpi)
+		return -ENOMEM;
+	pks->mpi[0] = mpi;
+	pks->nr_mpi = 1;
+	return 0;
+}
+
+/*
+ * Request an asymmetric key.
+ */
+static struct key *request_asymmetric_key(const char *signer, size_t signer_len,
+					  const u8 *key_id, size_t key_id_len)
+{
+	key_ref_t key;
+	size_t i;
+	char *id, *q;
+
+	pr_devel("==>%s(,%zu,,%zu)\n", __func__, signer_len, key_id_len);
+
+	/* Construct an identifier. */
+	id = kmalloc(signer_len + 2 + key_id_len * 2 + 1, GFP_KERNEL);
+	if (!id)
+		return ERR_PTR(-ENOKEY);
+
+	memcpy(id, signer, signer_len);
+
+	q = id + signer_len;
+	*q++ = ':';
+	*q++ = ' ';
+	for (i = 0; i < key_id_len; i++) {
+		*q++ = hex_asc[*key_id >> 4];
+		*q++ = hex_asc[*key_id++ & 0x0f];
+	}
+
+	*q = 0;
+
+	pr_debug("Look up: \"%s\"\n", id);
+
+	key = keyring_search(make_key_ref(system_trusted_keyring, 1),
+			     &key_type_asymmetric, id);
+	if (IS_ERR(key))
+		pr_warn("Request for unknown module key '%s' err %ld\n",
+			id, PTR_ERR(key));
+	kfree(id);
+
+	if (IS_ERR(key)) {
+		switch (PTR_ERR(key)) {
+			/* Hide some search errors */
+		case -EACCES:
+		case -ENOTDIR:
+		case -EAGAIN:
+			return ERR_PTR(-ENOKEY);
+		default:
+			return ERR_CAST(key);
+		}
+	}
+
+	pr_devel("<==%s() = 0 [%x]\n", __func__, key_serial(key_ref_to_ptr(key)));
+	return key_ref_to_ptr(key);
+}
+
+/*
+ * Verify the signature on a module
+ */
+static int old_mod_verify_sig(const void *mod, unsigned long *_modlen,
+                       const struct module_signature *ms)
+{
+	struct public_key_signature *pks;
+	struct key *key;
+	const void *sig;
+	size_t modlen = *_modlen, sig_len;
+	int ret;
+
+	pr_devel("==>%s(,%zu)\n", __func__, modlen);
+
+	sig_len = be32_to_cpu(ms->sig_len);
+	if (sig_len >= modlen)
+		return -EBADMSG;
+	modlen -= sig_len;
+	if ((size_t)ms->signer_len + ms->key_id_len >= modlen)
+		return -EBADMSG;
+	modlen -= (size_t)ms->signer_len + ms->key_id_len;
+
+	*_modlen = modlen;
+	sig = mod + modlen;
+
+	/* For the moment, only support RSA and X.509 identifiers */
+	if (ms->algo != PKEY_ALGO_RSA ||
+	    ms->id_type != PKEY_ID_X509)
+		return -ENOPKG;
+
+	if (ms->hash >= PKEY_HASH__LAST ||
+	    !hash_algo_name[ms->hash])
+		return -ENOPKG;
+
+	key = request_asymmetric_key(sig, ms->signer_len,
+				     sig + ms->signer_len, ms->key_id_len);
+	if (IS_ERR(key))
+		return PTR_ERR(key);
+
+	pks = mod_make_digest(ms->hash, mod, modlen);
+	if (IS_ERR(pks)) {
+		ret = PTR_ERR(pks);
+		goto error_put_key;
+	}
+
+	ret = mod_extract_mpi_array(pks, sig + ms->signer_len + ms->key_id_len,
+				    sig_len);
+	if (ret < 0)
+		goto error_free_pks;
+
+	ret = verify_signature(key, pks);
+	pr_devel("verify_signature() = %d\n", ret);
+
+error_free_pks:
+	mpi_free(pks->rsa.s);
+	kfree(pks);
+error_put_key:
+	key_put(key);
+	pr_devel("<==%s() = %d\n", __func__, ret);
+	return ret;	
+}
-- 
2.1.4