crypto.c

linux 内核源代码

static void ecryptfs_set_default_crypt_stat_vals(
	struct ecryptfs_crypt_stat *crypt_stat,
	struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
{
	ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
						      mount_crypt_stat);
	ecryptfs_set_default_sizes(crypt_stat);
	strcpy(crypt_stat->cipher, ECRYPTFS_DEFAULT_CIPHER);
	crypt_stat->key_size = ECRYPTFS_DEFAULT_KEY_BYTES;
	crypt_stat->flags &= ~(ECRYPTFS_KEY_VALID);
	crypt_stat->file_version = ECRYPTFS_FILE_VERSION;
	crypt_stat->mount_crypt_stat = mount_crypt_stat;
}

/**
 * ecryptfs_new_file_context
 * @ecryptfs_dentry: The eCryptfs dentry
 *
 * If the crypto context for the file has not yet been established,
 * this is where we do that.  Establishing a new crypto context
 * involves the following decisions:
 *  - What cipher to use?
 *  - What set of authentication tokens to use?
 * Here we just worry about getting enough information into the
 * authentication tokens so that we know that they are available.
 * We associate the available authentication tokens with the new file
 * via the set of signatures in the crypt_stat struct.  Later, when
 * the headers are actually written out, we may again defer to
 * userspace to perform the encryption of the session key; for the
 * foreseeable future, this will be the case with public key packets.
 *
 * Returns zero on success; non-zero otherwise
 */
int ecryptfs_new_file_context(struct dentry *ecryptfs_dentry)
{
	struct ecryptfs_crypt_stat *crypt_stat =
	    &ecryptfs_inode_to_private(ecryptfs_dentry->d_inode)->crypt_stat;
	struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
	    &ecryptfs_superblock_to_private(
		    ecryptfs_dentry->d_sb)->mount_crypt_stat;
	int cipher_name_len;
	int rc = 0;

	ecryptfs_set_default_crypt_stat_vals(crypt_stat, mount_crypt_stat);
	crypt_stat->flags |= (ECRYPTFS_ENCRYPTED | ECRYPTFS_KEY_VALID);
	ecryptfs_copy_mount_wide_flags_to_inode_flags(crypt_stat,
						      mount_crypt_stat);
	rc = ecryptfs_copy_mount_wide_sigs_to_inode_sigs(crypt_stat,
							 mount_crypt_stat);
	if (rc) {
		printk(KERN_ERR "Error attempting to copy mount-wide key sigs "
		       "to the inode key sigs; rc = [%d]\n", rc);
		goto out;
	}
	cipher_name_len =
		strlen(mount_crypt_stat->global_default_cipher_name);
	memcpy(crypt_stat->cipher,
	       mount_crypt_stat->global_default_cipher_name,
	       cipher_name_len);
	crypt_stat->cipher[cipher_name_len] = '\0';
	crypt_stat->key_size =
		mount_crypt_stat->global_default_cipher_key_size;
	ecryptfs_generate_new_key(crypt_stat);
	rc = ecryptfs_init_crypt_ctx(crypt_stat);
	if (rc)
		ecryptfs_printk(KERN_ERR, "Error initializing cryptographic "
				"context for cipher [%s]: rc = [%d]\n",
				crypt_stat->cipher, rc);
out:
	return rc;
}

/**
 * contains_ecryptfs_marker - check for the ecryptfs marker
 * @data: The data block in which to check
 *
 * Returns one if marker found; zero if not found
 */
static int contains_ecryptfs_marker(char *data)
{
	u32 m_1, m_2;

	memcpy(&m_1, data, 4);
	m_1 = be32_to_cpu(m_1);
	memcpy(&m_2, (data + 4), 4);
	m_2 = be32_to_cpu(m_2);
	if ((m_1 ^ MAGIC_ECRYPTFS_MARKER) == m_2)
		return 1;
	ecryptfs_printk(KERN_DEBUG, "m_1 = [0x%.8x]; m_2 = [0x%.8x]; "
			"MAGIC_ECRYPTFS_MARKER = [0x%.8x]\n", m_1, m_2,
			MAGIC_ECRYPTFS_MARKER);
	ecryptfs_printk(KERN_DEBUG, "(m_1 ^ MAGIC_ECRYPTFS_MARKER) = "
			"[0x%.8x]\n", (m_1 ^ MAGIC_ECRYPTFS_MARKER));
	return 0;
}

struct ecryptfs_flag_map_elem {
	u32 file_flag;
	u32 local_flag;
};

/* Add support for additional flags by adding elements here. */
static struct ecryptfs_flag_map_elem ecryptfs_flag_map[] = {
	{0x00000001, ECRYPTFS_ENABLE_HMAC},
	{0x00000002, ECRYPTFS_ENCRYPTED},
	{0x00000004, ECRYPTFS_METADATA_IN_XATTR}
};

/**
 * ecryptfs_process_flags
 * @crypt_stat: The cryptographic context
 * @page_virt: Source data to be parsed
 * @bytes_read: Updated with the number of bytes read
 *
 * Returns zero on success; non-zero if the flag set is invalid
 */
static int ecryptfs_process_flags(struct ecryptfs_crypt_stat *crypt_stat,
				  char *page_virt, int *bytes_read)
{
	int rc = 0;
	int i;
	u32 flags;

	memcpy(&flags, page_virt, 4);
	flags = be32_to_cpu(flags);
	for (i = 0; i < ((sizeof(ecryptfs_flag_map)
			  / sizeof(struct ecryptfs_flag_map_elem))); i++)
		if (flags & ecryptfs_flag_map[i].file_flag) {
			crypt_stat->flags |= ecryptfs_flag_map[i].local_flag;
		} else
			crypt_stat->flags &= ~(ecryptfs_flag_map[i].local_flag);
	/* Version is in top 8 bits of the 32-bit flag vector */
	crypt_stat->file_version = ((flags >> 24) & 0xFF);
	(*bytes_read) = 4;
	return rc;
}

/**
 * write_ecryptfs_marker
 * @page_virt: The pointer to in a page to begin writing the marker
 * @written: Number of bytes written
 *
 * Marker = 0x3c81b7f5
 */
static void write_ecryptfs_marker(char *page_virt, size_t *written)
{
	u32 m_1, m_2;

	get_random_bytes(&m_1, (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2));
	m_2 = (m_1 ^ MAGIC_ECRYPTFS_MARKER);
	m_1 = cpu_to_be32(m_1);
	memcpy(page_virt, &m_1, (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2));
	m_2 = cpu_to_be32(m_2);
	memcpy(page_virt + (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2), &m_2,
	       (MAGIC_ECRYPTFS_MARKER_SIZE_BYTES / 2));
	(*written) = MAGIC_ECRYPTFS_MARKER_SIZE_BYTES;
}

static void
write_ecryptfs_flags(char *page_virt, struct ecryptfs_crypt_stat *crypt_stat,
		     size_t *written)
{
	u32 flags = 0;
	int i;

	for (i = 0; i < ((sizeof(ecryptfs_flag_map)
			  / sizeof(struct ecryptfs_flag_map_elem))); i++)
		if (crypt_stat->flags & ecryptfs_flag_map[i].local_flag)
			flags |= ecryptfs_flag_map[i].file_flag;
	/* Version is in top 8 bits of the 32-bit flag vector */
	flags |= ((((u8)crypt_stat->file_version) << 24) & 0xFF000000);
	flags = cpu_to_be32(flags);
	memcpy(page_virt, &flags, 4);
	(*written) = 4;
}

struct ecryptfs_cipher_code_str_map_elem {
	char cipher_str[16];
	u16 cipher_code;
};

/* Add support for additional ciphers by adding elements here. The
 * cipher_code is whatever OpenPGP applicatoins use to identify the
 * ciphers. List in order of probability. */
static struct ecryptfs_cipher_code_str_map_elem
ecryptfs_cipher_code_str_map[] = {
	{"aes",RFC2440_CIPHER_AES_128 },
	{"blowfish", RFC2440_CIPHER_BLOWFISH},
	{"des3_ede", RFC2440_CIPHER_DES3_EDE},
	{"cast5", RFC2440_CIPHER_CAST_5},
	{"twofish", RFC2440_CIPHER_TWOFISH},
	{"cast6", RFC2440_CIPHER_CAST_6},
	{"aes", RFC2440_CIPHER_AES_192},
	{"aes", RFC2440_CIPHER_AES_256}
};

/**
 * ecryptfs_code_for_cipher_string
 * @crypt_stat: The cryptographic context
 *
 * Returns zero on no match, or the cipher code on match
 */
u16 ecryptfs_code_for_cipher_string(struct ecryptfs_crypt_stat *crypt_stat)
{
	int i;
	u16 code = 0;
	struct ecryptfs_cipher_code_str_map_elem *map =
		ecryptfs_cipher_code_str_map;

	if (strcmp(crypt_stat->cipher, "aes") == 0) {
		switch (crypt_stat->key_size) {
		case 16:
			code = RFC2440_CIPHER_AES_128;
			break;
		case 24:
			code = RFC2440_CIPHER_AES_192;
			break;
		case 32:
			code = RFC2440_CIPHER_AES_256;
		}
	} else {
		for (i = 0; i < ARRAY_SIZE(ecryptfs_cipher_code_str_map); i++)
			if (strcmp(crypt_stat->cipher, map[i].cipher_str) == 0){
				code = map[i].cipher_code;
				break;
			}
	}
	return code;
}

/**
 * ecryptfs_cipher_code_to_string
 * @str: Destination to write out the cipher name
 * @cipher_code: The code to convert to cipher name string
 *
 * Returns zero on success
 */
int ecryptfs_cipher_code_to_string(char *str, u16 cipher_code)
{
	int rc = 0;
	int i;

	str[0] = '\0';
	for (i = 0; i < ARRAY_SIZE(ecryptfs_cipher_code_str_map); i++)
		if (cipher_code == ecryptfs_cipher_code_str_map[i].cipher_code)
			strcpy(str, ecryptfs_cipher_code_str_map[i].cipher_str);
	if (str[0] == '\0') {
		ecryptfs_printk(KERN_WARNING, "Cipher code not recognized: "
				"[%d]\n", cipher_code);
		rc = -EINVAL;
	}
	return rc;
}

int ecryptfs_read_and_validate_header_region(char *data,
					     struct inode *ecryptfs_inode)
{
	struct ecryptfs_crypt_stat *crypt_stat =
		&(ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat);
	int rc;

	rc = ecryptfs_read_lower(data, 0, crypt_stat->extent_size,
				 ecryptfs_inode);
	if (rc) {
		printk(KERN_ERR "%s: Error reading header region; rc = [%d]\n",
		       __FUNCTION__, rc);
		goto out;
	}
	if (!contains_ecryptfs_marker(data + ECRYPTFS_FILE_SIZE_BYTES)) {
		rc = -EINVAL;
		ecryptfs_printk(KERN_DEBUG, "Valid marker not found\n");
	}
out:
	return rc;
}

void
ecryptfs_write_header_metadata(char *virt,
			       struct ecryptfs_crypt_stat *crypt_stat,
			       size_t *written)
{
	u32 header_extent_size;
	u16 num_header_extents_at_front;

	header_extent_size = (u32)crypt_stat->extent_size;
	num_header_extents_at_front =
		(u16)crypt_stat->num_header_extents_at_front;
	header_extent_size = cpu_to_be32(header_extent_size);
	memcpy(virt, &header_extent_size, 4);
	virt += 4;
	num_header_extents_at_front = cpu_to_be16(num_header_extents_at_front);
	memcpy(virt, &num_header_extents_at_front, 2);
	(*written) = 6;
}

struct kmem_cache *ecryptfs_header_cache_0;
struct kmem_cache *ecryptfs_header_cache_1;
struct kmem_cache *ecryptfs_header_cache_2;

/**
 * ecryptfs_write_headers_virt
 * @page_virt: The virtual address to write the headers to
 * @size: Set to the number of bytes written by this function
 * @crypt_stat: The cryptographic context
 * @ecryptfs_dentry: The eCryptfs dentry
 *
 * Format version: 1
 *
 *   Header Extent:
 *     Octets 0-7:        Unencrypted file size (big-endian)
 *     Octets 8-15:       eCryptfs special marker
 *     Octets 16-19:      Flags
 *      Octet 16:         File format version number (between 0 and 255)
 *      Octets 17-18:     Reserved
 *      Octet 19:         Bit 1 (lsb): Reserved
 *                        Bit 2: Encrypted?
 *                        Bits 3-8: Reserved
 *     Octets 20-23:      Header extent size (big-endian)
 *     Octets 24-25:      Number of header extents at front of file
 *                        (big-endian)
 *     Octet  26:         Begin RFC 2440 authentication token packet set
 *   Data Extent 0:
 *     Lower data (CBC encrypted)
 *   Data Extent 1:
 *     Lower data (CBC encrypted)
 *   ...
 *
 * Returns zero on success
 */
static int ecryptfs_write_headers_virt(char *page_virt, size_t *size,
				       struct ecryptfs_crypt_stat *crypt_stat,
				       struct dentry *ecryptfs_dentry)
{
	int rc;
	size_t written;
	size_t offset;

	offset = ECRYPTFS_FILE_SIZE_BYTES;
	write_ecryptfs_marker((page_virt + offset), &written);
	offset += written;
	write_ecryptfs_flags((page_virt + offset), crypt_stat, &written);
	offset += written;
	ecryptfs_write_header_metadata((page_virt + offset), crypt_stat,
				       &written);
	offset += written;
	rc = ecryptfs_generate_key_packet_set((page_virt + offset), crypt_stat,
					      ecryptfs_dentry, &written,
					      PAGE_CACHE_SIZE - offset);
	if (rc)
		ecryptfs_printk(KERN_WARNING, "Error generating key packet "
				"set; rc = [%d]\n", rc);
	if (size) {
		offset += written;
		*size = offset;
	}
	return rc;
}

static int
ecryptfs_write_metadata_to_contents(struct ecryptfs_crypt_stat *crypt_stat,
				    struct dentry *ecryptfs_dentry,
				    char *page_virt)
{
	int current_header_page;
	int header_pages;
	int rc;

	rc = ecryptfs_write_lower(ecryptfs_dentry->d_inode, page_virt,
				  0, PAGE_CACHE_SIZE);
	if (rc) {
		printk(KERN_ERR "%s: Error attempting to write header "
		       "information to lower file; rc = [%d]\n", __FUNCTION__,
		       rc);
		goto out;
	}
	header_pages = ((crypt_stat->extent_size
			 * crypt_stat->num_header_extents_at_front)
			/ PAGE_CACHE_SIZE);
	memset(page_virt, 0, PAGE_CACHE_SIZE);
	current_header_page = 1;
	while (current_header_page < header_pages) {
		loff_t offset;

		offset = (((loff_t)current_header_page) << PAGE_CACHE_SHIFT);
		if ((rc = ecryptfs_write_lower(ecryptfs_dentry->d_inode,
					       page_virt, offset,
					       PAGE_CACHE_SIZE))) {
			printk(KERN_ERR "%s: Error attempting to write header "
			       "information to lower file; rc = [%d]\n",
			       __FUNCTION__, rc);
			goto out;
		}
		current_header_page++;
	}
out:
	return rc;
}

static int
ecryptfs_write_metadata_to_xattr(struct dentry *ecryptfs_dentry,
				 struct ecryptfs_crypt_stat *crypt_stat,
				 char *page_virt, size_t size)
{
	int rc;

	rc = ecryptfs_setxattr(ecryptfs_dentry, ECRYPTFS_XATTR_NAME, page_virt,
			       size, 0);
	return rc;
}

/**
 * ecryptfs_write_metadata
 * @ecryptfs_dentry: The eCryptfs dentry
 *
 * Write the file headers out.  This will likely involve a userspace
 * callout, in which the session key is encrypted with one or more
 * public keys and/or the passphrase necessary to do the encryption is
 * retrieved via a prompt.  Exactly what happens at this point should
 * be policy-dependent.
 *
 * TODO: Support header information spanning multiple pages
 *
 * Returns zero on success; non-zero on error
 */
int ecryptfs_write_metadata(struct dentry *ecryptfs_dentry)
{
	struct ecryptfs_crypt_stat *crypt_stat =
		&ecryptfs_inode_to_private(ecryptfs_dentry->d_inode)->crypt_stat;
	char *page_virt;
	size_t size = 0;
	int rc = 0;

	if (likely(crypt_stat->flags & ECRYPTFS_ENCRYPTED)) {
		if (!(crypt_stat->flags & ECRYPTFS_KEY_VALID)) {
			printk(KERN_ERR "Key is invalid; bailing out\n");
			rc = -EINVAL;
			goto out;
		}
	} else {
		rc = -EINVAL;
		ecryptfs_printk(KERN_WARNING,
				"Called with crypt_stat->encrypted == 0\n");
		goto out;
	}
	/* Released in this function */
	page_virt = kmem_cache_zalloc(ecryptfs_header_cache_0, GFP_USER);
	if (!page_virt) {
		ecryptfs_printk(KERN_ERR, "Out of memory\n");
		rc = -ENOMEM;
		goto out;
	}
	rc = ecryptfs_write_headers_virt(page_virt, &size, crypt_stat,
  					 ecryptfs_dentry);
	if (unlikely(rc)) {
		ecryptfs_printk(KERN_ERR, "Error whilst writing headers\n");
		memset(page_virt, 0, PAGE_CACHE_SIZE);
		goto out_free;
	}
	if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
		rc = ecryptfs_write_metadata_to_xattr(ecryptfs_dentry,
						      crypt_stat, page_virt,
						      size);
	else
		rc = ecryptfs_write_metadata_to_contents(crypt_stat,
							 ecryptfs_dentry,
							 page_virt);
	if (rc) {
		printk(KERN_ERR "Error writing metadata out to lower file; "
		       "rc = [%d]\n", rc);
		goto out_free;
	}
out_free:
	kmem_cache_free(ecryptfs_header_cache_0, page_virt);
out:
	return rc;
}