KEYS: Generalise system_verify_data() to provide access to internal content

Generalise system_verify_data() to provide access to internal content
through a callback. This allows all the PKCS#7 stuff to be hidden inside
this function and removed from the PE file parser and the PKCS#7 test key.

If external content is not required, NULL should be passed as data to the
function. If the callback is not required, that can be set to NULL.

The function is now called verify_pkcs7_signature() to contrast with
verify_pefile_signature() and the definitions of both have been moved into
linux/verification.h along with the key_being_used_for enum.

Signed-off-by: David Howells <[e-mail]>

arch/x86/kernel/kexec-bzimage64.c

···
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/efi.h>
-#include <linux/verify_pefile.h>
-#include <keys/system_keyring.h>
+#include <linux/verification.h>
 
 #include <asm/bootparam.h>
 #include <asm/setup.h>
···
 #ifdef CONFIG_KEXEC_BZIMAGE_VERIFY_SIG
 static int bzImage64_verify_sig(const char *kernel, unsigned long kernel_len)
 {
-	bool trusted;
-	int ret;
-
-	ret = verify_pefile_signature(kernel, kernel_len,
-				      system_trusted_keyring,
-				      VERIFYING_KEXEC_PE_SIGNATURE,
-				      &trusted);
-	if (ret < 0)
-		return ret;
-	if (!trusted)
-		return -EKEYREJECTED;
-	return 0;
+	return verify_pefile_signature(kernel, kernel_len,
+				       NULL,
+				       VERIFYING_KEXEC_PE_SIGNATURE);
 }
 #endif
 

certs/system_keyring.c

···
 #ifdef CONFIG_SYSTEM_DATA_VERIFICATION
 
 /**
- * Verify a PKCS#7-based signature on system data.
- * @data: The data to be verified.
+ * verify_pkcs7_signature - Verify a PKCS#7-based signature on system data.
+ * @data: The data to be verified (NULL if expecting internal data).
  * @len: Size of @data.
  * @raw_pkcs7: The PKCS#7 message that is the signature.
  * @pkcs7_len: The size of @raw_pkcs7.
+ * @trusted_keys: Trusted keys to use (NULL for system_trusted_keyring).
  * @usage: The use to which the key is being put.
+ * @view_content: Callback to gain access to content.
+ * @ctx: Context for callback.
  */
-int system_verify_data(const void *data, unsigned long len,
-		       const void *raw_pkcs7, size_t pkcs7_len,
-		       enum key_being_used_for usage)
+int verify_pkcs7_signature(const void *data, size_t len,
+			   const void *raw_pkcs7, size_t pkcs7_len,
+			   struct key *trusted_keys,
+			   int untrusted_error,
+			   enum key_being_used_for usage,
+			   int (*view_content)(void *ctx,
+					       const void *data, size_t len,
+					       size_t asn1hdrlen),
+			   void *ctx)
 {
 	struct pkcs7_message *pkcs7;
 	bool trusted;
···
 		return PTR_ERR(pkcs7);
 
 	/* The data should be detached - so we need to supply it. */
-	if (pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
+	if (data && pkcs7_supply_detached_data(pkcs7, data, len) < 0) {
 		pr_err("PKCS#7 signature with non-detached data\n");
 		ret = -EBADMSG;
 		goto error;
···
 	if (ret < 0)
 		goto error;
 
-	ret = pkcs7_validate_trust(pkcs7, system_trusted_keyring, &trusted);
+	if (!trusted_keys)
+		trusted_keys = system_trusted_keyring;
+	ret = pkcs7_validate_trust(pkcs7, trusted_keys, &trusted);
 	if (ret < 0)
 		goto error;
 
-	if (!trusted) {
+	if (!trusted && untrusted_error) {
 		pr_err("PKCS#7 signature not signed with a trusted key\n");
-		ret = -ENOKEY;
+		ret = untrusted_error;
+		goto error;
+	}
+
+	if (view_content) {
+		size_t asn1hdrlen;
+
+		ret = pkcs7_get_content_data(pkcs7, &data, &len, &asn1hdrlen);
+		if (ret < 0) {
+			if (ret == -ENODATA)
+				pr_devel("PKCS#7 message does not contain data\n");
+			goto error;
+		}
+
+		ret = view_content(ctx, data, len, asn1hdrlen);
 	}
 
 error:
···
 	pr_devel("<==%s() = %d\n", __func__, ret);
 	return ret;
 }
-EXPORT_SYMBOL_GPL(system_verify_data);
+EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
 
 #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */

crypto/asymmetric_keys/Kconfig

···
 
 config PKCS7_TEST_KEY
 	tristate "PKCS#7 testing key type"
-	depends on PKCS7_MESSAGE_PARSER
-	select SYSTEM_TRUSTED_KEYRING
+	depends on SYSTEM_DATA_VERIFICATION
 	help
 	  This option provides a type of key that can be loaded up from a
 	  PKCS#7 message - provided the message is signed by a trusted key.  If
···
 config SIGNED_PE_FILE_VERIFICATION
 	bool "Support for PE file signature verification"
 	depends on PKCS7_MESSAGE_PARSER=y
+	depends on SYSTEM_DATA_VERIFICATION
 	select ASN1
 	select OID_REGISTRY
 	help

crypto/asymmetric_keys/mscode_parser.c

···
 /*
  * Parse a Microsoft Individual Code Signing blob
  */
-int mscode_parse(struct pefile_context *ctx)
+int mscode_parse(void *_ctx, const void *content_data, size_t data_len,
+		 size_t asn1hdrlen)
 {
-	const void *content_data;
-	size_t data_len;
-	int ret;
+	struct pefile_context *ctx = _ctx;
 
-	ret = pkcs7_get_content_data(ctx->pkcs7, &content_data, &data_len, 1);
-
-	if (ret) {
-		pr_debug("PKCS#7 message does not contain data\n");
-		return ret;
-	}
-
+	content_data -= asn1hdrlen;
+	data_len += asn1hdrlen;
 	pr_devel("Data: %zu [%*ph]\n", data_len, (unsigned)(data_len),
 		 content_data);
 
···
 {
 	struct pefile_context *ctx = context;
 
-	ctx->digest = value;
-	ctx->digest_len = vlen;
-	return 0;
+	ctx->digest = kmemdup(value, vlen, GFP_KERNEL);
+	return ctx->digest ? 0 : -ENOMEM;
 }

crypto/asymmetric_keys/pkcs7_key_type.c

···
 #include <linux/key.h>
 #include <linux/err.h>
 #include <linux/module.h>
+#include <linux/verification.h>
 #include <linux/key-type.h>
-#include <keys/asymmetric-type.h>
-#include <crypto/pkcs7.h>
 #include <keys/user-type.h>
-#include <keys/system_keyring.h>
-#include "pkcs7_parser.h"
 
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("PKCS#7 testing key type");
···
 		 "Usage to specify when verifying the PKCS#7 message");
 
 /*
+ * Retrieve the PKCS#7 message content.
+ */
+static int pkcs7_view_content(void *ctx, const void *data, size_t len,
+			      size_t asn1hdrlen)
+{
+	struct key_preparsed_payload *prep = ctx;
+	const void *saved_prep_data;
+	size_t saved_prep_datalen;
+	int ret;
+
+	saved_prep_data = prep->data;
+	saved_prep_datalen = prep->datalen;
+	prep->data = data;
+	prep->datalen = len;
+
+	ret = user_preparse(prep);
+
+	prep->data = saved_prep_data;
+	prep->datalen = saved_prep_datalen;
+	return ret;
+}
+
+/*
  * Preparse a PKCS#7 wrapped and validated data blob.
  */
 static int pkcs7_preparse(struct key_preparsed_payload *prep)
 {
 	enum key_being_used_for usage = pkcs7_usage;
-	struct pkcs7_message *pkcs7;
-	const void *data, *saved_prep_data;
-	size_t datalen, saved_prep_datalen;
-	bool trusted;
-	int ret;
-
-	kenter("");
 
 	if (usage >= NR__KEY_BEING_USED_FOR) {
 		pr_err("Invalid usage type %d\n", usage);
 		return -EINVAL;
 	}
 
-	saved_prep_data = prep->data;
-	saved_prep_datalen = prep->datalen;
-	pkcs7 = pkcs7_parse_message(saved_prep_data, saved_prep_datalen);
-	if (IS_ERR(pkcs7)) {
-		ret = PTR_ERR(pkcs7);
-		goto error;
-	}
-
-	ret = pkcs7_verify(pkcs7, usage);
-	if (ret < 0)
-		goto error_free;
-
-	ret = pkcs7_validate_trust(pkcs7, system_trusted_keyring, &trusted);
-	if (ret < 0)
-		goto error_free;
-	if (!trusted)
-		pr_warn("PKCS#7 message doesn't chain back to a trusted key\n");
-
-	ret = pkcs7_get_content_data(pkcs7, &data, &datalen, false);
-	if (ret < 0)
-		goto error_free;
-
-	prep->data = data;
-	prep->datalen = datalen;
-	ret = user_preparse(prep);
-	prep->data = saved_prep_data;
-	prep->datalen = saved_prep_datalen;
-
-error_free:
-	pkcs7_free_message(pkcs7);
-error:
-	kleave(" = %d", ret);
-	return ret;
+	return verify_pkcs7_signature(NULL, 0,
+				      prep->data, prep->datalen,
+				      NULL, -ENOKEY, usage,
+				      pkcs7_view_content, prep);
 }
 
 /*

crypto/asymmetric_keys/pkcs7_parser.c

···
  * @pkcs7: The preparsed PKCS#7 message to access
  * @_data: Place to return a pointer to the data
  * @_data_len: Place to return the data length
- * @want_wrapper: True if the ASN.1 object header should be included in the data
+ * @_headerlen: Size of ASN.1 header not included in _data
  *
- * Get access to the data content of the PKCS#7 message, including, optionally,
- * the header of the ASN.1 object that contains it.  Returns -ENODATA if the
- * data object was missing from the message.
+ * Get access to the data content of the PKCS#7 message.  The size of the
+ * header of the ASN.1 object that contains it is also provided and can be used
+ * to adjust *_data and *_data_len to get the entire object.
+ *
+ * Returns -ENODATA if the data object was missing from the message.
  */
 int pkcs7_get_content_data(const struct pkcs7_message *pkcs7,
 			   const void **_data, size_t *_data_len,
-			   bool want_wrapper)
+			   size_t *_headerlen)
 {
-	size_t wrapper;
-
 	if (!pkcs7->data)
 		return -ENODATA;
 
-	wrapper = want_wrapper ? pkcs7->data_hdrlen : 0;
-	*_data = pkcs7->data - wrapper;
-	*_data_len = pkcs7->data_len + wrapper;
+	*_data = pkcs7->data;
+	*_data_len = pkcs7->data_len;
+	if (_headerlen)
+		*_headerlen = pkcs7->data_hdrlen;
 	return 0;
 }
 EXPORT_SYMBOL_GPL(pkcs7_get_content_data);

crypto/asymmetric_keys/verify_pefile.c

···
 #include <linux/err.h>
 #include <linux/pe.h>
 #include <linux/asn1.h>
-#include <crypto/pkcs7.h>
+#include <linux/verification.h>
 #include <crypto/hash.h>
 #include "verify_pefile.h"
 
···
  * verify_pefile_signature - Verify the signature on a PE binary image
  * @pebuf: Buffer containing the PE binary image
  * @pelen: Length of the binary image
- * @trust_keyring: Signing certificates to use as starting points
+ * @trust_keys: Signing certificate(s) to use as starting points
  * @usage: The use to which the key is being put.
- * @_trusted: Set to true if trustworth, false otherwise
  *
  * Validate that the certificate chain inside the PKCS#7 message inside the PE
  * binary image intersects keys we already know and trust.
···
  * May also return -ENOMEM.
  */
 int verify_pefile_signature(const void *pebuf, unsigned pelen,
-			    struct key *trusted_keyring,
-			    enum key_being_used_for usage,
-			    bool *_trusted)
+			    struct key *trusted_keys,
+			    enum key_being_used_for usage)
 {
-	struct pkcs7_message *pkcs7;
 	struct pefile_context ctx;
-	const void *data;
-	size_t datalen;
 	int ret;
 
 	kenter("");
···
 	if (ret < 0)
 		return ret;
 
-	pkcs7 = pkcs7_parse_message(pebuf + ctx.sig_offset, ctx.sig_len);
-	if (IS_ERR(pkcs7))
-		return PTR_ERR(pkcs7);
-	ctx.pkcs7 = pkcs7;
-
-	ret = pkcs7_get_content_data(ctx.pkcs7, &data, &datalen, false);
-	if (ret < 0 || datalen == 0) {
-		pr_devel("PKCS#7 message does not contain data\n");
-		ret = -EBADMSG;
-		goto error;
-	}
-
-	ret = mscode_parse(&ctx);
+	ret = verify_pkcs7_signature(NULL, 0,
+				     pebuf + ctx.sig_offset, ctx.sig_len,
+				     trusted_keys, -EKEYREJECTED, usage,
+				     mscode_parse, &ctx);
 	if (ret < 0)
 		goto error;
 
···
 	 * contents.
 	 */
 	ret = pefile_digest_pe(pebuf, pelen, &ctx);
-	if (ret < 0)
-		goto error;
-
-	ret = pkcs7_verify(pkcs7, usage);
-	if (ret < 0)
-		goto error;
-
-	ret = pkcs7_validate_trust(pkcs7, trusted_keyring, _trusted);
 
 error:
-	pkcs7_free_message(ctx.pkcs7);
+	kfree(ctx.digest);
 	return ret;
 }

crypto/asymmetric_keys/verify_pefile.h

···
  * 2 of the Licence, or (at your option) any later version.
  */
 
-#include <linux/verify_pefile.h>
 #include <crypto/pkcs7.h>
 #include <crypto/hash_info.h>
 
···
 	unsigned	sig_offset;
 	unsigned	sig_len;
 	const struct section_header *secs;
-	struct pkcs7_message *pkcs7;
 
 	/* PKCS#7 MS Individual Code Signing content */
 	const void	*digest;		/* Digest */
···
 /*
  * mscode_parser.c
  */
-extern int mscode_parse(struct pefile_context *ctx);
+extern int mscode_parse(void *_ctx, const void *content_data, size_t data_len,
+			size_t asn1hdrlen);

include/crypto/pkcs7.h

···
 #ifndef _CRYPTO_PKCS7_H
 #define _CRYPTO_PKCS7_H
 
+#include <linux/verification.h>
 #include <crypto/public_key.h>
 
 struct key;
···
 
 extern int pkcs7_get_content_data(const struct pkcs7_message *pkcs7,
 				  const void **_data, size_t *_datalen,
-				  bool want_wrapper);
+				  size_t *_headerlen);
 
 /*
  * pkcs7_trust.c

include/crypto/public_key.h

···
 #define _LINUX_PUBLIC_KEY_H
 
 /*
- * The use to which an asymmetric key is being put.
- */
-enum key_being_used_for {
-	VERIFYING_MODULE_SIGNATURE,
-	VERIFYING_FIRMWARE_SIGNATURE,
-	VERIFYING_KEXEC_PE_SIGNATURE,
-	VERIFYING_KEY_SIGNATURE,
-	VERIFYING_KEY_SELF_SIGNATURE,
-	VERIFYING_UNSPECIFIED_SIGNATURE,
-	NR__KEY_BEING_USED_FOR
-};
-extern const char *const key_being_used_for[NR__KEY_BEING_USED_FOR];
-
-/*
  * Cryptographic data for the public-key subtype of the asymmetric key type.
  *
  * Note that this may include private part of the key as well as the public

include/keys/asymmetric-type.h

···
 #define _KEYS_ASYMMETRIC_TYPE_H
 
 #include <linux/key-type.h>
+#include <linux/verification.h>
 
 extern struct key_type key_type_asymmetric;
 

include/keys/system_keyring.h

···
 #ifdef CONFIG_SYSTEM_TRUSTED_KEYRING
 
 #include <linux/key.h>
+#include <linux/verification.h>
 #include <crypto/public_key.h>
 
 extern struct key *system_trusted_keyring;
···
 {
 	return NULL;
 }
-#endif
-
-#ifdef CONFIG_SYSTEM_DATA_VERIFICATION
-extern int system_verify_data(const void *data, unsigned long len,
-			      const void *raw_pkcs7, size_t pkcs7_len,
-			      enum key_being_used_for usage);
 #endif
 
 #ifdef CONFIG_IMA_MOK_KEYRING

include/linux/verification.h

···
+/* Signature verification
+ *
+ * Copyright (C) 2014 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells ([e-mail])
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#ifndef _LINUX_VERIFICATION_H
+#define _LINUX_VERIFICATION_H
+
+/*
+ * The use to which an asymmetric key is being put.
+ */
+enum key_being_used_for {
+	VERIFYING_MODULE_SIGNATURE,
+	VERIFYING_FIRMWARE_SIGNATURE,
+	VERIFYING_KEXEC_PE_SIGNATURE,
+	VERIFYING_KEY_SIGNATURE,
+	VERIFYING_KEY_SELF_SIGNATURE,
+	VERIFYING_UNSPECIFIED_SIGNATURE,
+	NR__KEY_BEING_USED_FOR
+};
+extern const char *const key_being_used_for[NR__KEY_BEING_USED_FOR];
+
+#ifdef CONFIG_SYSTEM_DATA_VERIFICATION
+
+struct key;
+
+extern int verify_pkcs7_signature(const void *data, size_t len,
+				  const void *raw_pkcs7, size_t pkcs7_len,
+				  struct key *trusted_keys,
+				  int untrusted_error,
+				  enum key_being_used_for usage,
+				  int (*view_content)(void *ctx,
+						      const void *data, size_t len,
+						      size_t asn1hdrlen),
+				  void *ctx);
+
+#ifdef CONFIG_SIGNED_PE_FILE_VERIFICATION
+extern int verify_pefile_signature(const void *pebuf, unsigned pelen,
+				   struct key *trusted_keys,
+				   enum key_being_used_for usage);
+#endif
+
+#endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
+#endif /* _LINUX_VERIFY_PEFILE_H */

include/linux/verify_pefile.h

···
-/* Signed PE file verification
- *
- * Copyright (C) 2014 Red Hat, Inc. All Rights Reserved.
- * Written by David Howells ([e-mail])
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public Licence
- * as published by the Free Software Foundation; either version
- * 2 of the Licence, or (at your option) any later version.
- */
-
-#ifndef _LINUX_VERIFY_PEFILE_H
-#define _LINUX_VERIFY_PEFILE_H
-
-#include <crypto/public_key.h>
-
-extern int verify_pefile_signature(const void *pebuf, unsigned pelen,
-				   struct key *trusted_keyring,
-				   enum key_being_used_for usage,
-				   bool *_trusted);
-
-#endif /* _LINUX_VERIFY_PEFILE_H */

kernel/module_signing.c

···
 		return -EBADMSG;
 	}
 
-	return system_verify_data(mod, modlen, mod + modlen, sig_len,
-				  VERIFYING_MODULE_SIGNATURE);
+	return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
+				      NULL, -ENOKEY, VERIFYING_MODULE_SIGNATURE,
+				      NULL, NULL);
 }