From c59becfceea8de57c35a3de5ee45a7bb883cf90a Mon Sep 17 00:00:00 2001 From: Michael Halcrow Date: Tue, 16 Oct 2007 01:27:56 -0700 Subject: [PATCH] eCryptfs: fix Tag 3 parsing code Fix up the Tag 3 parsing code to handle size limits and boundaries more explicitly. Signed-off-by: Michael Halcrow Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/ecryptfs/keystore.c | 89 +++++++++++++++++------------------------- 1 file changed, 35 insertions(+), 54 deletions(-) diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c index f7debe6961d..72086141a6e 100644 --- a/fs/ecryptfs/keystore.c +++ b/fs/ecryptfs/keystore.c @@ -643,22 +643,30 @@ parse_tag_3_packet(struct ecryptfs_crypt_stat *crypt_stat, (*packet_size) = 0; (*new_auth_tok) = NULL; - - /* we check that: - * one byte for the Tag 3 ID flag - * two bytes for the body size - * do not exceed the maximum_packet_size + /** + *This format is inspired by OpenPGP; see RFC 2440 + * packet tag 3 + * + * Tag 3 identifier (1 byte) + * Max Tag 3 packet size (max 3 bytes) + * Version (1 byte) + * Cipher code (1 byte) + * S2K specifier (1 byte) + * Hash identifier (1 byte) + * Salt (ECRYPTFS_SALT_SIZE) + * Hash iterations (1 byte) + * Encrypted key (arbitrary) + * + * (ECRYPTFS_SALT_SIZE + 7) minimum packet size */ - if (unlikely((*packet_size) + 3 > max_packet_size)) { - ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n"); + if (max_packet_size < (ECRYPTFS_SALT_SIZE + 7)) { + printk(KERN_ERR "Max packet size too large\n"); rc = -EINVAL; goto out; } - - /* check for Tag 3 identifyer - one byte */ if (data[(*packet_size)++] != ECRYPTFS_TAG_3_PACKET_TYPE) { - ecryptfs_printk(KERN_ERR, "Enter w/ first byte != 0x%.2x\n", - ECRYPTFS_TAG_3_PACKET_TYPE); + printk(KERN_ERR "First byte != 0x%.2x; invalid packet\n", + ECRYPTFS_TAG_3_PACKET_TYPE); rc = -EINVAL; goto out; } @@ -667,56 +675,36 @@ parse_tag_3_packet(struct ecryptfs_crypt_stat *crypt_stat, auth_tok_list_item = kmem_cache_zalloc(ecryptfs_auth_tok_list_item_cache, GFP_KERNEL); if (!auth_tok_list_item) { - ecryptfs_printk(KERN_ERR, "Unable to allocate memory\n"); + printk(KERN_ERR "Unable to allocate memory\n"); rc = -ENOMEM; goto out; } (*new_auth_tok) = &auth_tok_list_item->auth_tok; - - /* check for body size - one to two bytes */ - rc = parse_packet_length(&data[(*packet_size)], &body_size, - &length_size); - if (rc) { - ecryptfs_printk(KERN_WARNING, "Error parsing packet length; " - "rc = [%d]\n", rc); + if ((rc = parse_packet_length(&data[(*packet_size)], &body_size, + &length_size))) { + printk(KERN_WARNING "Error parsing packet length; rc = [%d]\n", + rc); goto out_free; } - if (unlikely(body_size < (0x05 + ECRYPTFS_SALT_SIZE))) { - ecryptfs_printk(KERN_WARNING, "Invalid body size ([%d])\n", - body_size); + if (unlikely(body_size < (ECRYPTFS_SALT_SIZE + 5))) { + printk(KERN_WARNING "Invalid body size ([%d])\n", body_size); rc = -EINVAL; goto out_free; } (*packet_size) += length_size; - - /* now we know the length of the remainting Tag 3 packet size: - * 5 fix bytes for: version string, cipher, S2K ID, hash algo, - * number of hash iterations - * ECRYPTFS_SALT_SIZE bytes for salt - * body_size bytes minus the stuff above is the encrypted key size - */ if (unlikely((*packet_size) + body_size > max_packet_size)) { - ecryptfs_printk(KERN_ERR, "Packet size exceeds max\n"); + printk(KERN_ERR "Packet size exceeds max\n"); rc = -EINVAL; goto out_free; } - - /* There are 5 characters of additional information in the - * packet */ (*new_auth_tok)->session_key.encrypted_key_size = - body_size - (0x05 + ECRYPTFS_SALT_SIZE); - ecryptfs_printk(KERN_DEBUG, "Encrypted key size = [%d]\n", - (*new_auth_tok)->session_key.encrypted_key_size); - - /* Version 4 (from RFC2440) - one byte */ + (body_size - (ECRYPTFS_SALT_SIZE + 5)); if (unlikely(data[(*packet_size)++] != 0x04)) { - ecryptfs_printk(KERN_DEBUG, "Unknown version number " - "[%d]\n", data[(*packet_size) - 1]); + printk(KERN_WARNING "Unknown version number [%d]\n", + data[(*packet_size) - 1]); rc = -EINVAL; goto out_free; } - - /* cipher - one byte */ ecryptfs_cipher_code_to_string(crypt_stat->cipher, (u16)data[(*packet_size)]); /* A little extra work to differentiate among the AES key @@ -730,33 +718,26 @@ parse_tag_3_packet(struct ecryptfs_crypt_stat *crypt_stat, (*new_auth_tok)->session_key.encrypted_key_size; } ecryptfs_init_crypt_ctx(crypt_stat); - /* S2K identifier 3 (from RFC2440) */ if (unlikely(data[(*packet_size)++] != 0x03)) { - ecryptfs_printk(KERN_ERR, "Only S2K ID 3 is currently " - "supported\n"); + printk(KERN_WARNING "Only S2K ID 3 is currently supported\n"); rc = -ENOSYS; goto out_free; } - /* TODO: finish the hash mapping */ - /* hash algorithm - one byte */ switch (data[(*packet_size)++]) { case 0x01: /* See RFC2440 for these numbers and their mappings */ /* Choose MD5 */ - /* salt - ECRYPTFS_SALT_SIZE bytes */ memcpy((*new_auth_tok)->token.password.salt, &data[(*packet_size)], ECRYPTFS_SALT_SIZE); (*packet_size) += ECRYPTFS_SALT_SIZE; - /* This conversion was taken straight from RFC2440 */ - /* number of hash iterations - one byte */ (*new_auth_tok)->token.password.hash_iterations = ((u32) 16 + (data[(*packet_size)] & 15)) << ((data[(*packet_size)] >> 4) + 6); (*packet_size)++; - - /* encrypted session key - - * (body_size-5-ECRYPTFS_SALT_SIZE) bytes */ + /* Friendly reminder: + * (*new_auth_tok)->session_key.encrypted_key_size = + * (body_size - (ECRYPTFS_SALT_SIZE + 5)); */ memcpy((*new_auth_tok)->session_key.encrypted_key, &data[(*packet_size)], (*new_auth_tok)->session_key.encrypted_key_size); @@ -766,7 +747,7 @@ parse_tag_3_packet(struct ecryptfs_crypt_stat *crypt_stat, ~ECRYPTFS_CONTAINS_DECRYPTED_KEY; (*new_auth_tok)->session_key.flags |= ECRYPTFS_CONTAINS_ENCRYPTED_KEY; - (*new_auth_tok)->token.password.hash_algo = 0x01; + (*new_auth_tok)->token.password.hash_algo = 0x01; /* MD5 */ break; default: ecryptfs_printk(KERN_ERR, "Unsupported hash algorithm: " -- 2.41.1