keystore.c

linux 内核源代码

/**
 * eCryptfs: Linux filesystem encryption layer
 * In-kernel key management code.  Includes functions to parse and
 * write authentication token-related packets with the underlying
 * file.
 *
 * Copyright (C) 2004-2006 International Business Machines Corp.
 *   Author(s): Michael A. Halcrow <[e-mail]>
 *              Michael C. Thompson <[e-mail]>
 *              Trevor S. Highland <[e-mail]>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 * 02111-1307, USA.
 */

#include <linux/string.h>
#include <linux/syscalls.h>
#include <linux/pagemap.h>
#include <linux/key.h>
#include <linux/random.h>
#include <linux/crypto.h>
#include <linux/scatterlist.h>
#include "ecryptfs_kernel.h"

/**
 * request_key returned an error instead of a valid key address;
 * determine the type of error, make appropriate log entries, and
 * return an error code.
 */
static int process_request_key_err(long err_code)
{
	int rc = 0;

	switch (err_code) {
	case ENOKEY:
		ecryptfs_printk(KERN_WARNING, "No key\n");
		rc = -ENOENT;
		break;
	case EKEYEXPIRED:
		ecryptfs_printk(KERN_WARNING, "Key expired\n");
		rc = -ETIME;
		break;
	case EKEYREVOKED:
		ecryptfs_printk(KERN_WARNING, "Key revoked\n");
		rc = -EINVAL;
		break;
	default:
		ecryptfs_printk(KERN_WARNING, "Unknown error code: "
				"[0x%.16x]\n", err_code);
		rc = -EINVAL;
	}
	return rc;
}

/**
 * parse_packet_length
 * @data: Pointer to memory containing length at offset
 * @size: This function writes the decoded size to this memory
 *        address; zero on error
 * @length_size: The number of bytes occupied by the encoded length
 *
 * Returns zero on success; non-zero on error
 */
static int parse_packet_length(unsigned char *data, size_t *size,
			       size_t *length_size)
{
	int rc = 0;

	(*length_size) = 0;
	(*size) = 0;
	if (data[0] < 192) {
		/* One-byte length */
		(*size) = (unsigned char)data[0];
		(*length_size) = 1;
	} else if (data[0] < 224) {
		/* Two-byte length */
		(*size) = (((unsigned char)(data[0]) - 192) * 256);
		(*size) += ((unsigned char)(data[1]) + 192);
		(*length_size) = 2;
	} else if (data[0] == 255) {
		/* Five-byte length; we're not supposed to see this */
		ecryptfs_printk(KERN_ERR, "Five-byte packet length not "
				"supported\n");
		rc = -EINVAL;
		goto out;
	} else {
		ecryptfs_printk(KERN_ERR, "Error parsing packet length\n");
		rc = -EINVAL;
		goto out;
	}
out:
	return rc;
}

/**
 * write_packet_length
 * @dest: The byte array target into which to write the length. Must
 *        have at least 5 bytes allocated.
 * @size: The length to write.
 * @packet_size_length: The number of bytes used to encode the packet
 *                      length is written to this address.
 *
 * Returns zero on success; non-zero on error.
 */
static int write_packet_length(char *dest, size_t size,
			       size_t *packet_size_length)
{
	int rc = 0;

	if (size < 192) {
		dest[0] = size;
		(*packet_size_length) = 1;
	} else if (size < 65536) {
		dest[0] = (((size - 192) / 256) + 192);
		dest[1] = ((size - 192) % 256);
		(*packet_size_length) = 2;
	} else {
		rc = -EINVAL;
		ecryptfs_printk(KERN_WARNING,
				"Unsupported packet size: [%d]\n", size);
	}
	return rc;
}

static int
write_tag_64_packet(char *signature, struct ecryptfs_session_key *session_key,
		    char **packet, size_t *packet_len)
{
	size_t i = 0;
	size_t data_len;
	size_t packet_size_len;
	char *message;
	int rc;

	/*
	 *              ***** TAG 64 Packet Format *****
	 *    | Content Type                       | 1 byte       |
	 *    | Key Identifier Size                | 1 or 2 bytes |
	 *    | Key Identifier                     | arbitrary    |
	 *    | Encrypted File Encryption Key Size | 1 or 2 bytes |
	 *    | Encrypted File Encryption Key      | arbitrary    |
	 */
	data_len = (5 + ECRYPTFS_SIG_SIZE_HEX
		    + session_key->encrypted_key_size);
	*packet = kmalloc(data_len, GFP_KERNEL);
	message = *packet;
	if (!message) {
		ecryptfs_printk(KERN_ERR, "Unable to allocate memory\n");
		rc = -ENOMEM;
		goto out;
	}
	message[i++] = ECRYPTFS_TAG_64_PACKET_TYPE;
	rc = write_packet_length(&message[i], ECRYPTFS_SIG_SIZE_HEX,
				 &packet_size_len);
	if (rc) {
		ecryptfs_printk(KERN_ERR, "Error generating tag 64 packet "
				"header; cannot generate packet length\n");
		goto out;
	}
	i += packet_size_len;
	memcpy(&message[i], signature, ECRYPTFS_SIG_SIZE_HEX);
	i += ECRYPTFS_SIG_SIZE_HEX;
	rc = write_packet_length(&message[i], session_key->encrypted_key_size,
				 &packet_size_len);
	if (rc) {
		ecryptfs_printk(KERN_ERR, "Error generating tag 64 packet "
				"header; cannot generate packet length\n");
		goto out;
	}
	i += packet_size_len;
	memcpy(&message[i], session_key->encrypted_key,
	       session_key->encrypted_key_size);
	i += session_key->encrypted_key_size;
	*packet_len = i;
out:
	return rc;
}

static int
parse_tag_65_packet(struct ecryptfs_session_key *session_key, u16 *cipher_code,
		    struct ecryptfs_message *msg)
{
	size_t i = 0;
	char *data;
	size_t data_len;
	size_t m_size;
	size_t message_len;
	u16 checksum = 0;
	u16 expected_checksum = 0;
	int rc;

	/*
	 *              ***** TAG 65 Packet Format *****
	 *         | Content Type             | 1 byte       |
	 *         | Status Indicator         | 1 byte       |
	 *         | File Encryption Key Size | 1 or 2 bytes |
	 *         | File Encryption Key      | arbitrary    |
	 */
	message_len = msg->data_len;
	data = msg->data;
	if (message_len < 4) {
		rc = -EIO;
		goto out;
	}
	if (data[i++] != ECRYPTFS_TAG_65_PACKET_TYPE) {
		ecryptfs_printk(KERN_ERR, "Type should be ECRYPTFS_TAG_65\n");
		rc = -EIO;
		goto out;
	}
	if (data[i++]) {
		ecryptfs_printk(KERN_ERR, "Status indicator has non-zero value "
				"[%d]\n", data[i-1]);
		rc = -EIO;
		goto out;
	}
	rc = parse_packet_length(&data[i], &m_size, &data_len);
	if (rc) {
		ecryptfs_printk(KERN_WARNING, "Error parsing packet length; "
				"rc = [%d]\n", rc);
		goto out;
	}
	i += data_len;
	if (message_len < (i + m_size)) {
		ecryptfs_printk(KERN_ERR, "The received netlink message is "
				"shorter than expected\n");
		rc = -EIO;
		goto out;
	}
	if (m_size < 3) {
		ecryptfs_printk(KERN_ERR,
				"The decrypted key is not long enough to "
				"include a cipher code and checksum\n");
		rc = -EIO;
		goto out;
	}
	*cipher_code = data[i++];
	/* The decrypted key includes 1 byte cipher code and 2 byte checksum */
	session_key->decrypted_key_size = m_size - 3;
	if (session_key->decrypted_key_size > ECRYPTFS_MAX_KEY_BYTES) {
		ecryptfs_printk(KERN_ERR, "key_size [%d] larger than "
				"the maximum key size [%d]\n",
				session_key->decrypted_key_size,
				ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES);
		rc = -EIO;
		goto out;
	}
	memcpy(session_key->decrypted_key, &data[i],
	       session_key->decrypted_key_size);
	i += session_key->decrypted_key_size;
	expected_checksum += (unsigned char)(data[i++]) << 8;
	expected_checksum += (unsigned char)(data[i++]);
	for (i = 0; i < session_key->decrypted_key_size; i++)
		checksum += session_key->decrypted_key[i];
	if (expected_checksum != checksum) {
		ecryptfs_printk(KERN_ERR, "Invalid checksum for file "
				"encryption  key; expected [%x]; calculated "
				"[%x]\n", expected_checksum, checksum);
		rc = -EIO;
	}
out:
	return rc;
}


static int
write_tag_66_packet(char *signature, size_t cipher_code,
		    struct ecryptfs_crypt_stat *crypt_stat, char **packet,
		    size_t *packet_len)
{
	size_t i = 0;
	size_t j;
	size_t data_len;
	size_t checksum = 0;
	size_t packet_size_len;
	char *message;
	int rc;

	/*
	 *              ***** TAG 66 Packet Format *****
	 *         | Content Type             | 1 byte       |
	 *         | Key Identifier Size      | 1 or 2 bytes |
	 *         | Key Identifier           | arbitrary    |
	 *         | File Encryption Key Size | 1 or 2 bytes |
	 *         | File Encryption Key      | arbitrary    |
	 */
	data_len = (5 + ECRYPTFS_SIG_SIZE_HEX + crypt_stat->key_size);
	*packet = kmalloc(data_len, GFP_KERNEL);
	message = *packet;
	if (!message) {
		ecryptfs_printk(KERN_ERR, "Unable to allocate memory\n");
		rc = -ENOMEM;
		goto out;
	}
	message[i++] = ECRYPTFS_TAG_66_PACKET_TYPE;
	rc = write_packet_length(&message[i], ECRYPTFS_SIG_SIZE_HEX,
				 &packet_size_len);
	if (rc) {
		ecryptfs_printk(KERN_ERR, "Error generating tag 66 packet "
				"header; cannot generate packet length\n");
		goto out;
	}
	i += packet_size_len;
	memcpy(&message[i], signature, ECRYPTFS_SIG_SIZE_HEX);
	i += ECRYPTFS_SIG_SIZE_HEX;
	/* The encrypted key includes 1 byte cipher code and 2 byte checksum */
	rc = write_packet_length(&message[i], crypt_stat->key_size + 3,
				 &packet_size_len);
	if (rc) {
		ecryptfs_printk(KERN_ERR, "Error generating tag 66 packet "
				"header; cannot generate packet length\n");
		goto out;
	}
	i += packet_size_len;
	message[i++] = cipher_code;
	memcpy(&message[i], crypt_stat->key, crypt_stat->key_size);
	i += crypt_stat->key_size;
	for (j = 0; j < crypt_stat->key_size; j++)
		checksum += crypt_stat->key[j];
	message[i++] = (checksum / 256) % 256;
	message[i++] = (checksum % 256);
	*packet_len = i;
out:
	return rc;
}

static int
parse_tag_67_packet(struct ecryptfs_key_record *key_rec,
		    struct ecryptfs_message *msg)
{
	size_t i = 0;
	char *data;
	size_t data_len;
	size_t message_len;
	int rc;

	/*
	 *              ***** TAG 65 Packet Format *****
	 *    | Content Type                       | 1 byte       |
	 *    | Status Indicator                   | 1 byte       |
	 *    | Encrypted File Encryption Key Size | 1 or 2 bytes |
	 *    | Encrypted File Encryption Key      | arbitrary    |
	 */
	message_len = msg->data_len;
	data = msg->data;
	/* verify that everything through the encrypted FEK size is present */
	if (message_len < 4) {
		rc = -EIO;
		goto out;
	}
	if (data[i++] != ECRYPTFS_TAG_67_PACKET_TYPE) {
		ecryptfs_printk(KERN_ERR, "Type should be ECRYPTFS_TAG_67\n");
		rc = -EIO;
		goto out;
	}
	if (data[i++]) {
		ecryptfs_printk(KERN_ERR, "Status indicator has non zero value"
				" [%d]\n", data[i-1]);
		rc = -EIO;
		goto out;
	}
	rc = parse_packet_length(&data[i], &key_rec->enc_key_size, &data_len);
	if (rc) {
		ecryptfs_printk(KERN_WARNING, "Error parsing packet length; "
				"rc = [%d]\n", rc);
		goto out;
	}
	i += data_len;
	if (message_len < (i + key_rec->enc_key_size)) {
		ecryptfs_printk(KERN_ERR, "message_len [%d]; max len is [%d]\n",
				message_len, (i + key_rec->enc_key_size));
		rc = -EIO;
		goto out;
	}
	if (key_rec->enc_key_size > ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES) {
		ecryptfs_printk(KERN_ERR, "Encrypted key_size [%d] larger than "
				"the maximum key size [%d]\n",
				key_rec->enc_key_size,
				ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES);
		rc = -EIO;
		goto out;
	}
	memcpy(key_rec->enc_key, &data[i], key_rec->enc_key_size);
out:
	return rc;
}

static int
ecryptfs_get_auth_tok_sig(char **sig, struct ecryptfs_auth_tok *auth_tok)
{
	int rc = 0;

	(*sig) = NULL;
	switch (auth_tok->token_type) {
	case ECRYPTFS_PASSWORD:
		(*sig) = auth_tok->token.password.signature;
		break;
	case ECRYPTFS_PRIVATE_KEY:
		(*sig) = auth_tok->token.private_key.signature;
		break;
	default:
		printk(KERN_ERR "Cannot get sig for auth_tok of type [%d]\n",
		       auth_tok->token_type);
		rc = -EINVAL;
	}
	return rc;
}

/**
 * decrypt_pki_encrypted_session_key - Decrypt the session key with the given auth_tok.
 * @auth_tok: The key authentication token used to decrypt the session key
 * @crypt_stat: The cryptographic context
 *
 * Returns zero on success; non-zero error otherwise.
 */
static int
decrypt_pki_encrypted_session_key(struct ecryptfs_auth_tok *auth_tok,
				  struct ecryptfs_crypt_stat *crypt_stat)
{
	u16 cipher_code = 0;
	struct ecryptfs_msg_ctx *msg_ctx;
	struct ecryptfs_message *msg = NULL;
	char *auth_tok_sig;
	char *netlink_message;
	size_t netlink_message_length;
	int rc;

	rc = ecryptfs_get_auth_tok_sig(&auth_tok_sig, auth_tok);
	if (rc) {
		printk(KERN_ERR "Unrecognized auth tok type: [%d]\n",
		       auth_tok->token_type);
		goto out;
	}
	rc = write_tag_64_packet(auth_tok_sig, &(auth_tok->session_key),
				 &netlink_message, &netlink_message_length);
	if (rc) {
		ecryptfs_printk(KERN_ERR, "Failed to write tag 64 packet");
		goto out;
	}
	rc = ecryptfs_send_message(ecryptfs_transport, netlink_message,
				   netlink_message_length, &msg_ctx);
	if (rc) {
		ecryptfs_printk(KERN_ERR, "Error sending netlink message\n");
		goto out;
	}
	rc = ecryptfs_wait_for_response(msg_ctx, &msg);
	if (rc) {
		ecryptfs_printk(KERN_ERR, "Failed to receive tag 65 packet "
				"from the user space daemon\n");
		rc = -EIO;
		goto out;
	}
	rc = parse_tag_65_packet(&(auth_tok->session_key),
				 &cipher_code, msg);
	if (rc) {
		printk(KERN_ERR "Failed to parse tag 65 packet; rc = [%d]\n",
		       rc);
		goto out;
	}
	auth_tok->session_key.flags |= ECRYPTFS_CONTAINS_DECRYPTED_KEY;