From 48399c0b0e6172888a2e2e36df1595ab1e049ba8 Mon Sep 17 00:00:00 2001 From: Tyler Hicks Date: Sat, 14 Jan 2012 16:46:46 +0100 Subject: [PATCH] eCryptfs: Replace miscdev read/write magic numbers ecryptfs_miscdev_read() and ecryptfs_miscdev_write() contained many magic numbers for specifying packet header field sizes and offsets. This patch defines those values and replaces the magic values. Signed-off-by: Tyler Hicks --- fs/ecryptfs/ecryptfs_kernel.h | 5 ++ fs/ecryptfs/keystore.c | 5 +- fs/ecryptfs/miscdev.c | 86 +++++++++++++++++++---------------- 3 files changed, 55 insertions(+), 41 deletions(-) diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h index a9f29b12fbf2..a2362df58ae8 100644 --- a/fs/ecryptfs/ecryptfs_kernel.h +++ b/fs/ecryptfs/ecryptfs_kernel.h @@ -151,6 +151,11 @@ ecryptfs_get_key_payload_data(struct key *key) * dentry name */ #define ECRYPTFS_TAG_73_PACKET_TYPE 0x49 /* FEK-encrypted filename as * metadata */ +#define ECRYPTFS_MIN_PKT_LEN_SIZE 1 /* Min size to specify packet length */ +#define ECRYPTFS_MAX_PKT_LEN_SIZE 2 /* Pass at least this many bytes to + * ecryptfs_parse_packet_length() and + * ecryptfs_write_packet_length() + */ /* Constraint: ECRYPTFS_FILENAME_MIN_RANDOM_PREPEND_BYTES >= * ECRYPTFS_MAX_IV_BYTES */ #define ECRYPTFS_FILENAME_MIN_RANDOM_PREPEND_BYTES 16 diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c index ac1ad48c2376..8e3b943e330f 100644 --- a/fs/ecryptfs/keystore.c +++ b/fs/ecryptfs/keystore.c @@ -109,7 +109,7 @@ int ecryptfs_parse_packet_length(unsigned char *data, size_t *size, (*size) += ((unsigned char)(data[1]) + 192); (*length_size) = 2; } else if (data[0] == 255) { - /* Five-byte length; we're not supposed to see this */ + /* If support is added, adjust ECRYPTFS_MAX_PKT_LEN_SIZE */ ecryptfs_printk(KERN_ERR, "Five-byte packet length not " "supported\n"); rc = -EINVAL; @@ -126,7 +126,7 @@ out: /** * ecryptfs_write_packet_length * @dest: The byte array target into which to write the length. Must - * have at least 5 bytes allocated. + * have at least ECRYPTFS_MAX_PKT_LEN_SIZE 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. @@ -146,6 +146,7 @@ int ecryptfs_write_packet_length(char *dest, size_t size, dest[1] = ((size - 192) % 256); (*packet_size_length) = 2; } else { + /* If support is added, adjust ECRYPTFS_MAX_PKT_LEN_SIZE */ rc = -EINVAL; ecryptfs_printk(KERN_WARNING, "Unsupported packet size: [%zd]\n", size); diff --git a/fs/ecryptfs/miscdev.c b/fs/ecryptfs/miscdev.c index 1145c58103e2..349209dc6a91 100644 --- a/fs/ecryptfs/miscdev.c +++ b/fs/ecryptfs/miscdev.c @@ -218,6 +218,29 @@ out_unlock: return rc; } +/* + * miscdevfs packet format: + * Octet 0: Type + * Octets 1-4: network byte order msg_ctx->counter + * Octets 5-N0: Size of struct ecryptfs_message to follow + * Octets N0-N1: struct ecryptfs_message (including data) + * + * Octets 5-N1 not written if the packet type does not include a message + */ +#define PKT_TYPE_SIZE 1 +#define PKT_CTR_SIZE 4 +#define MIN_NON_MSG_PKT_SIZE (PKT_TYPE_SIZE + PKT_CTR_SIZE) +#define MIN_MSG_PKT_SIZE (PKT_TYPE_SIZE + PKT_CTR_SIZE \ + + ECRYPTFS_MIN_PKT_LEN_SIZE) +/* 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES comes from tag 65 packet format */ +#define MAX_MSG_PKT_SIZE (PKT_TYPE_SIZE + PKT_CTR_SIZE \ + + ECRYPTFS_MAX_PKT_LEN_SIZE \ + + sizeof(struct ecryptfs_message) \ + + 4 + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES) +#define PKT_TYPE_OFFSET 0 +#define PKT_CTR_OFFSET PKT_TYPE_SIZE +#define PKT_LEN_OFFSET (PKT_TYPE_SIZE + PKT_CTR_SIZE) + /** * ecryptfs_miscdev_read - format and send message from queue * @file: fs/ecryptfs/euid miscdevfs handle (ignored) @@ -237,7 +260,7 @@ ecryptfs_miscdev_read(struct file *file, char __user *buf, size_t count, struct ecryptfs_daemon *daemon; struct ecryptfs_msg_ctx *msg_ctx; size_t packet_length_size; - char packet_length[3]; + char packet_length[ECRYPTFS_MAX_PKT_LEN_SIZE]; size_t i; size_t total_length; uid_t euid = current_euid(); @@ -305,15 +328,8 @@ check_list: packet_length_size = 0; msg_ctx->msg_size = 0; } - /* miscdevfs packet format: - * Octet 0: Type - * Octets 1-4: network byte order msg_ctx->counter - * Octets 5-N0: Size of struct ecryptfs_message to follow - * Octets N0-N1: struct ecryptfs_message (including data) - * - * Octets 5-N1 not written if the packet type does not - * include a message */ - total_length = (1 + 4 + packet_length_size + msg_ctx->msg_size); + total_length = (PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_length_size + + msg_ctx->msg_size); if (count < total_length) { rc = 0; printk(KERN_WARNING "%s: Only given user buffer of " @@ -324,9 +340,10 @@ check_list: rc = -EFAULT; if (put_user(msg_ctx->type, buf)) goto out_unlock_msg_ctx; - if (put_user(cpu_to_be32(msg_ctx->counter), (__be32 __user *)(buf + 1))) + if (put_user(cpu_to_be32(msg_ctx->counter), + (__be32 __user *)(&buf[PKT_CTR_OFFSET]))) goto out_unlock_msg_ctx; - i = 5; + i = PKT_TYPE_SIZE + PKT_CTR_SIZE; if (msg_ctx->msg) { if (copy_to_user(&buf[i], packet_length, packet_length_size)) goto out_unlock_msg_ctx; @@ -391,12 +408,6 @@ out: * @count: Amount of data in @buf * @ppos: Pointer to offset in file (ignored) * - * miscdevfs packet format: - * Octet 0: Type - * Octets 1-4: network byte order msg_ctx->counter (0's for non-response) - * Octets 5-N0: Size of struct ecryptfs_message to follow - * Octets N0-N1: struct ecryptfs_message (including data) - * * Returns the number of bytes read from @buf */ static ssize_t @@ -405,29 +416,25 @@ ecryptfs_miscdev_write(struct file *file, const char __user *buf, { __be32 counter_nbo; u32 seq; - size_t packet_size, packet_size_length, i; + size_t packet_size, packet_size_length; char *data; uid_t euid = current_euid(); - unsigned char packet_size_peek[3]; + unsigned char packet_size_peek[ECRYPTFS_MAX_PKT_LEN_SIZE]; ssize_t rc; if (count == 0) { return 0; - } else if (count == (1 + 4)) { + } else if (count == MIN_NON_MSG_PKT_SIZE) { /* Likely a harmless MSG_HELO or MSG_QUIT - no packet length */ goto memdup; - } else if (count < (1 + 4 + 1) - || count > (1 + 4 + 2 + sizeof(struct ecryptfs_message) + 4 - + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES)) { + } else if (count < MIN_MSG_PKT_SIZE || count > MAX_MSG_PKT_SIZE) { printk(KERN_WARNING "%s: Acceptable packet size range is " "[%d-%lu], but amount of data written is [%zu].", - __func__, (1 + 4 + 1), - (1 + 4 + 2 + sizeof(struct ecryptfs_message) + 4 - + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES), count); + __func__, MIN_MSG_PKT_SIZE, MAX_MSG_PKT_SIZE, count); return -EINVAL; } - if (copy_from_user(packet_size_peek, (buf + 1 + 4), + if (copy_from_user(packet_size_peek, &buf[PKT_LEN_OFFSET], sizeof(packet_size_peek))) { printk(KERN_WARNING "%s: Error while inspecting packet size\n", __func__); @@ -442,7 +449,8 @@ ecryptfs_miscdev_write(struct file *file, const char __user *buf, return rc; } - if ((1 + 4 + packet_size_length + packet_size) != count) { + if ((PKT_TYPE_SIZE + PKT_CTR_SIZE + packet_size_length + packet_size) + != count) { printk(KERN_WARNING "%s: Invalid packet size [%zu]\n", __func__, packet_size); return -EINVAL; @@ -455,25 +463,25 @@ memdup: __func__, PTR_ERR(data)); return PTR_ERR(data); } - i = 0; - switch (data[i++]) { + switch (data[PKT_TYPE_OFFSET]) { case ECRYPTFS_MSG_RESPONSE: - if (count < (1 + 4 + 1 + sizeof(struct ecryptfs_message))) { + if (count < (MIN_MSG_PKT_SIZE + + sizeof(struct ecryptfs_message))) { printk(KERN_WARNING "%s: Minimum acceptable packet " "size is [%zd], but amount of data written is " "only [%zd]. Discarding response packet.\n", __func__, - (1 + 4 + 1 + sizeof(struct ecryptfs_message)), - count); + (MIN_MSG_PKT_SIZE + + sizeof(struct ecryptfs_message)), count); rc = -EINVAL; goto out_free; } - memcpy(&counter_nbo, &data[i], 4); + memcpy(&counter_nbo, &data[PKT_CTR_OFFSET], PKT_CTR_SIZE); seq = be32_to_cpu(counter_nbo); - i += 4 + packet_size_length; - rc = ecryptfs_miscdev_response(&data[i], packet_size, - euid, current_user_ns(), - task_pid(current), seq); + rc = ecryptfs_miscdev_response( + &data[PKT_LEN_OFFSET + packet_size_length], + packet_size, euid, current_user_ns(), + task_pid(current), seq); if (rc) { printk(KERN_WARNING "%s: Failed to deliver miscdev " "response to requesting operation; rc = [%zd]\n", -- 2.20.1