diff options
Diffstat (limited to 'security/integrity/evm')
| -rw-r--r-- | security/integrity/evm/Kconfig | 73 | ||||
| -rw-r--r-- | security/integrity/evm/Makefile | 7 | ||||
| -rw-r--r-- | security/integrity/evm/evm.h | 71 | ||||
| -rw-r--r-- | security/integrity/evm/evm_crypto.c | 379 | ||||
| -rw-r--r-- | security/integrity/evm/evm_main.c | 604 | ||||
| -rw-r--r-- | security/integrity/evm/evm_posix_acl.c | 27 | ||||
| -rw-r--r-- | security/integrity/evm/evm_secfs.c | 327 |
7 files changed, 1488 insertions, 0 deletions
diff --git a/security/integrity/evm/Kconfig b/security/integrity/evm/Kconfig new file mode 100644 index 000000000..60221852b --- /dev/null +++ b/security/integrity/evm/Kconfig @@ -0,0 +1,73 @@ +config EVM + bool "EVM support" + select KEYS + select ENCRYPTED_KEYS + select CRYPTO_HMAC + select CRYPTO_SHA1 + select CRYPTO_HASH_INFO + default n + help + EVM protects a file's security extended attributes against + integrity attacks. + + If you are unsure how to answer this question, answer N. + +config EVM_ATTR_FSUUID + bool "FSUUID (version 2)" + default y + depends on EVM + help + Include filesystem UUID for HMAC calculation. + + Default value is 'selected', which is former version 2. + if 'not selected', it is former version 1 + + WARNING: changing the HMAC calculation method or adding + additional info to the calculation, requires existing EVM + labeled file systems to be relabeled. + +config EVM_EXTRA_SMACK_XATTRS + bool "Additional SMACK xattrs" + depends on EVM && SECURITY_SMACK + default n + help + Include additional SMACK xattrs for HMAC calculation. + + In addition to the original security xattrs (eg. security.selinux, + security.SMACK64, security.capability, and security.ima) included + in the HMAC calculation, enabling this option includes newly defined + Smack xattrs: security.SMACK64EXEC, security.SMACK64TRANSMUTE and + security.SMACK64MMAP. + + WARNING: changing the HMAC calculation method or adding + additional info to the calculation, requires existing EVM + labeled file systems to be relabeled. + +config EVM_ADD_XATTRS + bool "Add additional EVM extended attributes at runtime" + depends on EVM + default n + help + Allow userland to provide additional xattrs for HMAC calculation. + + When this option is enabled, root can add additional xattrs to the + list used by EVM by writing them into + /sys/kernel/security/integrity/evm/evm_xattrs. + +config EVM_LOAD_X509 + bool "Load an X509 certificate onto the '.evm' trusted keyring" + depends on EVM && INTEGRITY_TRUSTED_KEYRING + default n + help + Load an X509 certificate onto the '.evm' trusted keyring. + + This option enables X509 certificate loading from the kernel + onto the '.evm' trusted keyring. A public key can be used to + verify EVM integrity starting from the 'init' process. + +config EVM_X509_PATH + string "EVM X509 certificate path" + depends on EVM_LOAD_X509 + default "/etc/keys/x509_evm.der" + help + This option defines X509 certificate path. diff --git a/security/integrity/evm/Makefile b/security/integrity/evm/Makefile new file mode 100644 index 000000000..7393c415a --- /dev/null +++ b/security/integrity/evm/Makefile @@ -0,0 +1,7 @@ +# +# Makefile for building the Extended Verification Module(EVM) +# +obj-$(CONFIG_EVM) += evm.o + +evm-y := evm_main.o evm_crypto.o evm_secfs.o +evm-$(CONFIG_FS_POSIX_ACL) += evm_posix_acl.o diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h new file mode 100644 index 000000000..c3f437f5d --- /dev/null +++ b/security/integrity/evm/evm.h @@ -0,0 +1,71 @@ +/* + * Copyright (C) 2005-2010 IBM Corporation + * + * Authors: + * Mimi Zohar <zohar@us.ibm.com> + * Kylene Hall <kjhall@us.ibm.com> + * + * 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, version 2 of the License. + * + * File: evm.h + * + */ + +#ifndef __INTEGRITY_EVM_H +#define __INTEGRITY_EVM_H + +#include <linux/xattr.h> +#include <linux/security.h> + +#include "../integrity.h" + +#define EVM_INIT_HMAC 0x0001 +#define EVM_INIT_X509 0x0002 +#define EVM_ALLOW_METADATA_WRITES 0x0004 +#define EVM_SETUP_COMPLETE 0x80000000 /* userland has signaled key load */ + +#define EVM_KEY_MASK (EVM_INIT_HMAC | EVM_INIT_X509) +#define EVM_INIT_MASK (EVM_INIT_HMAC | EVM_INIT_X509 | EVM_SETUP_COMPLETE | \ + EVM_ALLOW_METADATA_WRITES) + +struct xattr_list { + struct list_head list; + char *name; +}; + +extern int evm_initialized; + +#define EVM_ATTR_FSUUID 0x0001 + +extern int evm_hmac_attrs; + +extern struct crypto_shash *hmac_tfm; +extern struct crypto_shash *hash_tfm; + +/* List of EVM protected security xattrs */ +extern struct list_head evm_config_xattrnames; + +struct evm_digest { + struct ima_digest_data hdr; + char digest[IMA_MAX_DIGEST_SIZE]; +} __packed; + +int evm_init_key(void); +int evm_update_evmxattr(struct dentry *dentry, + const char *req_xattr_name, + const char *req_xattr_value, + size_t req_xattr_value_len); +int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name, + const char *req_xattr_value, + size_t req_xattr_value_len, struct evm_digest *data); +int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name, + const char *req_xattr_value, + size_t req_xattr_value_len, char type, + struct evm_digest *data); +int evm_init_hmac(struct inode *inode, const struct xattr *xattr, + char *hmac_val); +int evm_init_secfs(void); + +#endif diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c new file mode 100644 index 000000000..fc142d04d --- /dev/null +++ b/security/integrity/evm/evm_crypto.c @@ -0,0 +1,379 @@ +/* + * Copyright (C) 2005-2010 IBM Corporation + * + * Authors: + * Mimi Zohar <zohar@us.ibm.com> + * Kylene Hall <kjhall@us.ibm.com> + * + * 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, version 2 of the License. + * + * File: evm_crypto.c + * Using root's kernel master key (kmk), calculate the HMAC + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/module.h> +#include <linux/crypto.h> +#include <linux/xattr.h> +#include <linux/evm.h> +#include <keys/encrypted-type.h> +#include <crypto/hash.h> +#include <crypto/hash_info.h> +#include "evm.h" + +#define EVMKEY "evm-key" +#define MAX_KEY_SIZE 128 +static unsigned char evmkey[MAX_KEY_SIZE]; +static int evmkey_len = MAX_KEY_SIZE; + +struct crypto_shash *hmac_tfm; +static struct crypto_shash *evm_tfm[HASH_ALGO__LAST]; + +static DEFINE_MUTEX(mutex); + +#define EVM_SET_KEY_BUSY 0 + +static unsigned long evm_set_key_flags; + +static char * const evm_hmac = "hmac(sha1)"; + +/** + * evm_set_key() - set EVM HMAC key from the kernel + * @key: pointer to a buffer with the key data + * @size: length of the key data + * + * This function allows setting the EVM HMAC key from the kernel + * without using the "encrypted" key subsystem keys. It can be used + * by the crypto HW kernel module which has its own way of managing + * keys. + * + * key length should be between 32 and 128 bytes long + */ +int evm_set_key(void *key, size_t keylen) +{ + int rc; + + rc = -EBUSY; + if (test_and_set_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags)) + goto busy; + rc = -EINVAL; + if (keylen > MAX_KEY_SIZE) + goto inval; + memcpy(evmkey, key, keylen); + evm_initialized |= EVM_INIT_HMAC; + pr_info("key initialized\n"); + return 0; +inval: + clear_bit(EVM_SET_KEY_BUSY, &evm_set_key_flags); +busy: + pr_err("key initialization failed\n"); + return rc; +} +EXPORT_SYMBOL_GPL(evm_set_key); + +static struct shash_desc *init_desc(char type, uint8_t hash_algo) +{ + long rc; + const char *algo; + struct crypto_shash **tfm; + struct shash_desc *desc; + + if (type == EVM_XATTR_HMAC) { + if (!(evm_initialized & EVM_INIT_HMAC)) { + pr_err_once("HMAC key is not set\n"); + return ERR_PTR(-ENOKEY); + } + tfm = &hmac_tfm; + algo = evm_hmac; + } else { + if (hash_algo >= HASH_ALGO__LAST) + return ERR_PTR(-EINVAL); + + tfm = &evm_tfm[hash_algo]; + algo = hash_algo_name[hash_algo]; + } + + if (IS_ERR_OR_NULL(*tfm)) { + mutex_lock(&mutex); + if (*tfm) + goto out; + *tfm = crypto_alloc_shash(algo, 0, + CRYPTO_ALG_ASYNC | CRYPTO_NOLOAD); + if (IS_ERR(*tfm)) { + rc = PTR_ERR(*tfm); + pr_err("Can not allocate %s (reason: %ld)\n", algo, rc); + *tfm = NULL; + mutex_unlock(&mutex); + return ERR_PTR(rc); + } + if (type == EVM_XATTR_HMAC) { + rc = crypto_shash_setkey(*tfm, evmkey, evmkey_len); + if (rc) { + crypto_free_shash(*tfm); + *tfm = NULL; + mutex_unlock(&mutex); + return ERR_PTR(rc); + } + } +out: + mutex_unlock(&mutex); + } + + desc = kmalloc(sizeof(*desc) + crypto_shash_descsize(*tfm), + GFP_KERNEL); + if (!desc) + return ERR_PTR(-ENOMEM); + + desc->tfm = *tfm; + desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP; + + rc = crypto_shash_init(desc); + if (rc) { + kfree(desc); + return ERR_PTR(rc); + } + return desc; +} + +/* Protect against 'cutting & pasting' security.evm xattr, include inode + * specific info. + * + * (Additional directory/file metadata needs to be added for more complete + * protection.) + */ +static void hmac_add_misc(struct shash_desc *desc, struct inode *inode, + char type, char *digest) +{ + struct h_misc { + unsigned long ino; + __u32 generation; + uid_t uid; + gid_t gid; + umode_t mode; + } hmac_misc; + + memset(&hmac_misc, 0, sizeof(hmac_misc)); + /* Don't include the inode or generation number in portable + * signatures + */ + if (type != EVM_XATTR_PORTABLE_DIGSIG) { + hmac_misc.ino = inode->i_ino; + hmac_misc.generation = inode->i_generation; + } + /* The hmac uid and gid must be encoded in the initial user + * namespace (not the filesystems user namespace) as encoding + * them in the filesystems user namespace allows an attack + * where first they are written in an unprivileged fuse mount + * of a filesystem and then the system is tricked to mount the + * filesystem for real on next boot and trust it because + * everything is signed. + */ + hmac_misc.uid = from_kuid(&init_user_ns, inode->i_uid); + hmac_misc.gid = from_kgid(&init_user_ns, inode->i_gid); + hmac_misc.mode = inode->i_mode; + crypto_shash_update(desc, (const u8 *)&hmac_misc, sizeof(hmac_misc)); + if ((evm_hmac_attrs & EVM_ATTR_FSUUID) && + type != EVM_XATTR_PORTABLE_DIGSIG) + crypto_shash_update(desc, &inode->i_sb->s_uuid.b[0], + sizeof(inode->i_sb->s_uuid)); + crypto_shash_final(desc, digest); +} + +/* + * Calculate the HMAC value across the set of protected security xattrs. + * + * Instead of retrieving the requested xattr, for performance, calculate + * the hmac using the requested xattr value. Don't alloc/free memory for + * each xattr, but attempt to re-use the previously allocated memory. + */ +static int evm_calc_hmac_or_hash(struct dentry *dentry, + const char *req_xattr_name, + const char *req_xattr_value, + size_t req_xattr_value_len, + uint8_t type, struct evm_digest *data) +{ + struct inode *inode = d_backing_inode(dentry); + struct xattr_list *xattr; + struct shash_desc *desc; + size_t xattr_size = 0; + char *xattr_value = NULL; + int error; + int size; + bool ima_present = false; + + if (!(inode->i_opflags & IOP_XATTR) || + inode->i_sb->s_user_ns != &init_user_ns) + return -EOPNOTSUPP; + + desc = init_desc(type, data->hdr.algo); + if (IS_ERR(desc)) + return PTR_ERR(desc); + + data->hdr.length = crypto_shash_digestsize(desc->tfm); + + error = -ENODATA; + list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) { + bool is_ima = false; + + if (strcmp(xattr->name, XATTR_NAME_IMA) == 0) + is_ima = true; + + if ((req_xattr_name && req_xattr_value) + && !strcmp(xattr->name, req_xattr_name)) { + error = 0; + crypto_shash_update(desc, (const u8 *)req_xattr_value, + req_xattr_value_len); + if (is_ima) + ima_present = true; + continue; + } + size = vfs_getxattr_alloc(dentry, xattr->name, + &xattr_value, xattr_size, GFP_NOFS); + if (size == -ENOMEM) { + error = -ENOMEM; + goto out; + } + if (size < 0) + continue; + + error = 0; + xattr_size = size; + crypto_shash_update(desc, (const u8 *)xattr_value, xattr_size); + if (is_ima) + ima_present = true; + } + hmac_add_misc(desc, inode, type, data->digest); + + /* Portable EVM signatures must include an IMA hash */ + if (type == EVM_XATTR_PORTABLE_DIGSIG && !ima_present) + error = -EPERM; +out: + kfree(xattr_value); + kfree(desc); + return error; +} + +int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name, + const char *req_xattr_value, size_t req_xattr_value_len, + struct evm_digest *data) +{ + return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value, + req_xattr_value_len, EVM_XATTR_HMAC, data); +} + +int evm_calc_hash(struct dentry *dentry, const char *req_xattr_name, + const char *req_xattr_value, size_t req_xattr_value_len, + char type, struct evm_digest *data) +{ + return evm_calc_hmac_or_hash(dentry, req_xattr_name, req_xattr_value, + req_xattr_value_len, type, data); +} + +static int evm_is_immutable(struct dentry *dentry, struct inode *inode) +{ + const struct evm_ima_xattr_data *xattr_data = NULL; + struct integrity_iint_cache *iint; + int rc = 0; + + iint = integrity_iint_find(inode); + if (iint && (iint->flags & EVM_IMMUTABLE_DIGSIG)) + return 1; + + /* Do this the hard way */ + rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0, + GFP_NOFS); + if (rc <= 0) { + if (rc == -ENODATA) + return 0; + return rc; + } + if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) + rc = 1; + else + rc = 0; + + kfree(xattr_data); + return rc; +} + + +/* + * Calculate the hmac and update security.evm xattr + * + * Expects to be called with i_mutex locked. + */ +int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name, + const char *xattr_value, size_t xattr_value_len) +{ + struct inode *inode = d_backing_inode(dentry); + struct evm_digest data; + int rc = 0; + + /* + * Don't permit any transformation of the EVM xattr if the signature + * is of an immutable type + */ + rc = evm_is_immutable(dentry, inode); + if (rc < 0) + return rc; + if (rc) + return -EPERM; + + data.hdr.algo = HASH_ALGO_SHA1; + rc = evm_calc_hmac(dentry, xattr_name, xattr_value, + xattr_value_len, &data); + if (rc == 0) { + data.hdr.xattr.sha1.type = EVM_XATTR_HMAC; + rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM, + &data.hdr.xattr.data[1], + SHA1_DIGEST_SIZE + 1, 0); + } else if (rc == -ENODATA && (inode->i_opflags & IOP_XATTR)) { + rc = __vfs_removexattr(dentry, XATTR_NAME_EVM); + } + return rc; +} + +int evm_init_hmac(struct inode *inode, const struct xattr *lsm_xattr, + char *hmac_val) +{ + struct shash_desc *desc; + + desc = init_desc(EVM_XATTR_HMAC, HASH_ALGO_SHA1); + if (IS_ERR(desc)) { + pr_info("init_desc failed\n"); + return PTR_ERR(desc); + } + + crypto_shash_update(desc, lsm_xattr->value, lsm_xattr->value_len); + hmac_add_misc(desc, inode, EVM_XATTR_HMAC, hmac_val); + kfree(desc); + return 0; +} + +/* + * Get the key from the TPM for the SHA1-HMAC + */ +int evm_init_key(void) +{ + struct key *evm_key; + struct encrypted_key_payload *ekp; + int rc; + + evm_key = request_key(&key_type_encrypted, EVMKEY, NULL); + if (IS_ERR(evm_key)) + return -ENOENT; + + down_read(&evm_key->sem); + ekp = evm_key->payload.data[0]; + + rc = evm_set_key(ekp->decrypted_data, ekp->decrypted_datalen); + + /* burn the original key contents */ + memset(ekp->decrypted_data, 0, ekp->decrypted_datalen); + up_read(&evm_key->sem); + key_put(evm_key); + return rc; +} diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c new file mode 100644 index 000000000..6d1efe135 --- /dev/null +++ b/security/integrity/evm/evm_main.c @@ -0,0 +1,604 @@ +/* + * Copyright (C) 2005-2010 IBM Corporation + * + * Author: + * Mimi Zohar <zohar@us.ibm.com> + * Kylene Hall <kjhall@us.ibm.com> + * + * 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, version 2 of the License. + * + * File: evm_main.c + * implements evm_inode_setxattr, evm_inode_post_setxattr, + * evm_inode_removexattr, and evm_verifyxattr + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/module.h> +#include <linux/crypto.h> +#include <linux/audit.h> +#include <linux/xattr.h> +#include <linux/integrity.h> +#include <linux/evm.h> +#include <linux/magic.h> + +#include <crypto/hash.h> +#include <crypto/hash_info.h> +#include <crypto/algapi.h> +#include "evm.h" + +int evm_initialized; + +static const char * const integrity_status_msg[] = { + "pass", "pass_immutable", "fail", "no_label", "no_xattrs", "unknown" +}; +int evm_hmac_attrs; + +static struct xattr_list evm_config_default_xattrnames[] = { +#ifdef CONFIG_SECURITY_SELINUX + {.name = XATTR_NAME_SELINUX}, +#endif +#ifdef CONFIG_SECURITY_SMACK + {.name = XATTR_NAME_SMACK}, +#ifdef CONFIG_EVM_EXTRA_SMACK_XATTRS + {.name = XATTR_NAME_SMACKEXEC}, + {.name = XATTR_NAME_SMACKTRANSMUTE}, + {.name = XATTR_NAME_SMACKMMAP}, +#endif +#endif +#ifdef CONFIG_SECURITY_APPARMOR + {.name = XATTR_NAME_APPARMOR}, +#endif +#ifdef CONFIG_IMA_APPRAISE + {.name = XATTR_NAME_IMA}, +#endif + {.name = XATTR_NAME_CAPS}, +}; + +LIST_HEAD(evm_config_xattrnames); + +static int evm_fixmode __ro_after_init; +static int __init evm_set_fixmode(char *str) +{ + if (strncmp(str, "fix", 3) == 0) + evm_fixmode = 1; + return 0; +} +__setup("evm=", evm_set_fixmode); + +static void __init evm_init_config(void) +{ + int i, xattrs; + + xattrs = ARRAY_SIZE(evm_config_default_xattrnames); + + pr_info("Initialising EVM extended attributes:\n"); + for (i = 0; i < xattrs; i++) { + pr_info("%s\n", evm_config_default_xattrnames[i].name); + list_add_tail(&evm_config_default_xattrnames[i].list, + &evm_config_xattrnames); + } + +#ifdef CONFIG_EVM_ATTR_FSUUID + evm_hmac_attrs |= EVM_ATTR_FSUUID; +#endif + pr_info("HMAC attrs: 0x%x\n", evm_hmac_attrs); +} + +static bool evm_key_loaded(void) +{ + return (bool)(evm_initialized & EVM_KEY_MASK); +} + +static int evm_find_protected_xattrs(struct dentry *dentry) +{ + struct inode *inode = d_backing_inode(dentry); + struct xattr_list *xattr; + int error; + int count = 0; + + if (!(inode->i_opflags & IOP_XATTR)) + return -EOPNOTSUPP; + + list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) { + error = __vfs_getxattr(dentry, inode, xattr->name, NULL, 0); + if (error < 0) { + if (error == -ENODATA) + continue; + return error; + } + count++; + } + + return count; +} + +/* + * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr + * + * Compute the HMAC on the dentry's protected set of extended attributes + * and compare it against the stored security.evm xattr. + * + * For performance: + * - use the previoulsy retrieved xattr value and length to calculate the + * HMAC.) + * - cache the verification result in the iint, when available. + * + * Returns integrity status + */ +static enum integrity_status evm_verify_hmac(struct dentry *dentry, + const char *xattr_name, + char *xattr_value, + size_t xattr_value_len, + struct integrity_iint_cache *iint) +{ + struct evm_ima_xattr_data *xattr_data = NULL; + struct signature_v2_hdr *hdr; + enum integrity_status evm_status = INTEGRITY_PASS; + struct evm_digest digest; + struct inode *inode; + int rc, xattr_len; + + if (iint && (iint->evm_status == INTEGRITY_PASS || + iint->evm_status == INTEGRITY_PASS_IMMUTABLE)) + return iint->evm_status; + + /* if status is not PASS, try to check again - against -ENOMEM */ + + /* first need to know the sig type */ + rc = vfs_getxattr_alloc(dentry, XATTR_NAME_EVM, (char **)&xattr_data, 0, + GFP_NOFS); + if (rc <= 0) { + evm_status = INTEGRITY_FAIL; + if (rc == -ENODATA) { + rc = evm_find_protected_xattrs(dentry); + if (rc > 0) + evm_status = INTEGRITY_NOLABEL; + else if (rc == 0) + evm_status = INTEGRITY_NOXATTRS; /* new file */ + } else if (rc == -EOPNOTSUPP) { + evm_status = INTEGRITY_UNKNOWN; + } + goto out; + } + + xattr_len = rc; + + /* check value type */ + switch (xattr_data->type) { + case EVM_XATTR_HMAC: + if (xattr_len != sizeof(struct evm_ima_xattr_data)) { + evm_status = INTEGRITY_FAIL; + goto out; + } + + digest.hdr.algo = HASH_ALGO_SHA1; + rc = evm_calc_hmac(dentry, xattr_name, xattr_value, + xattr_value_len, &digest); + if (rc) + break; + rc = crypto_memneq(xattr_data->digest, digest.digest, + SHA1_DIGEST_SIZE); + if (rc) + rc = -EINVAL; + break; + case EVM_IMA_XATTR_DIGSIG: + case EVM_XATTR_PORTABLE_DIGSIG: + /* accept xattr with non-empty signature field */ + if (xattr_len <= sizeof(struct signature_v2_hdr)) { + evm_status = INTEGRITY_FAIL; + goto out; + } + + hdr = (struct signature_v2_hdr *)xattr_data; + digest.hdr.algo = hdr->hash_algo; + rc = evm_calc_hash(dentry, xattr_name, xattr_value, + xattr_value_len, xattr_data->type, &digest); + if (rc) + break; + rc = integrity_digsig_verify(INTEGRITY_KEYRING_EVM, + (const char *)xattr_data, xattr_len, + digest.digest, digest.hdr.length); + if (!rc) { + inode = d_backing_inode(dentry); + + if (xattr_data->type == EVM_XATTR_PORTABLE_DIGSIG) { + if (iint) + iint->flags |= EVM_IMMUTABLE_DIGSIG; + evm_status = INTEGRITY_PASS_IMMUTABLE; + } else if (!IS_RDONLY(inode) && + !(inode->i_sb->s_readonly_remount) && + !IS_IMMUTABLE(inode)) { + evm_update_evmxattr(dentry, xattr_name, + xattr_value, + xattr_value_len); + } + } + break; + default: + rc = -EINVAL; + break; + } + + if (rc) + evm_status = (rc == -ENODATA) ? + INTEGRITY_NOXATTRS : INTEGRITY_FAIL; +out: + if (iint) + iint->evm_status = evm_status; + kfree(xattr_data); + return evm_status; +} + +static int evm_protected_xattr(const char *req_xattr_name) +{ + int namelen; + int found = 0; + struct xattr_list *xattr; + + namelen = strlen(req_xattr_name); + list_for_each_entry_lockless(xattr, &evm_config_xattrnames, list) { + if ((strlen(xattr->name) == namelen) + && (strncmp(req_xattr_name, xattr->name, namelen) == 0)) { + found = 1; + break; + } + if (strncmp(req_xattr_name, + xattr->name + XATTR_SECURITY_PREFIX_LEN, + strlen(req_xattr_name)) == 0) { + found = 1; + break; + } + } + + return found; +} + +/** + * evm_verifyxattr - verify the integrity of the requested xattr + * @dentry: object of the verify xattr + * @xattr_name: requested xattr + * @xattr_value: requested xattr value + * @xattr_value_len: requested xattr value length + * + * Calculate the HMAC for the given dentry and verify it against the stored + * security.evm xattr. For performance, use the xattr value and length + * previously retrieved to calculate the HMAC. + * + * Returns the xattr integrity status. + * + * This function requires the caller to lock the inode's i_mutex before it + * is executed. + */ +enum integrity_status evm_verifyxattr(struct dentry *dentry, + const char *xattr_name, + void *xattr_value, size_t xattr_value_len, + struct integrity_iint_cache *iint) +{ + if (!evm_key_loaded() || !evm_protected_xattr(xattr_name)) + return INTEGRITY_UNKNOWN; + + if (!iint) { + iint = integrity_iint_find(d_backing_inode(dentry)); + if (!iint) + return INTEGRITY_UNKNOWN; + } + return evm_verify_hmac(dentry, xattr_name, xattr_value, + xattr_value_len, iint); +} +EXPORT_SYMBOL_GPL(evm_verifyxattr); + +/* + * evm_verify_current_integrity - verify the dentry's metadata integrity + * @dentry: pointer to the affected dentry + * + * Verify and return the dentry's metadata integrity. The exceptions are + * before EVM is initialized or in 'fix' mode. + */ +static enum integrity_status evm_verify_current_integrity(struct dentry *dentry) +{ + struct inode *inode = d_backing_inode(dentry); + + if (!evm_key_loaded() || !S_ISREG(inode->i_mode) || evm_fixmode) + return 0; + return evm_verify_hmac(dentry, NULL, NULL, 0, NULL); +} + +/* + * evm_protect_xattr - protect the EVM extended attribute + * + * Prevent security.evm from being modified or removed without the + * necessary permissions or when the existing value is invalid. + * + * The posix xattr acls are 'system' prefixed, which normally would not + * affect security.evm. An interesting side affect of writing posix xattr + * acls is their modifying of the i_mode, which is included in security.evm. + * For posix xattr acls only, permit security.evm, even if it currently + * doesn't exist, to be updated unless the EVM signature is immutable. + */ +static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name, + const void *xattr_value, size_t xattr_value_len) +{ + enum integrity_status evm_status; + + if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) { + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + } else if (!evm_protected_xattr(xattr_name)) { + if (!posix_xattr_acl(xattr_name)) + return 0; + evm_status = evm_verify_current_integrity(dentry); + if ((evm_status == INTEGRITY_PASS) || + (evm_status == INTEGRITY_NOXATTRS)) + return 0; + goto out; + } + + evm_status = evm_verify_current_integrity(dentry); + if (evm_status == INTEGRITY_NOXATTRS) { + struct integrity_iint_cache *iint; + + iint = integrity_iint_find(d_backing_inode(dentry)); + if (iint && (iint->flags & IMA_NEW_FILE)) + return 0; + + /* exception for pseudo filesystems */ + if (dentry->d_sb->s_magic == TMPFS_MAGIC + || dentry->d_sb->s_magic == SYSFS_MAGIC) + return 0; + + integrity_audit_msg(AUDIT_INTEGRITY_METADATA, + dentry->d_inode, dentry->d_name.name, + "update_metadata", + integrity_status_msg[evm_status], + -EPERM, 0); + } +out: + if (evm_status != INTEGRITY_PASS) + integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry), + dentry->d_name.name, "appraise_metadata", + integrity_status_msg[evm_status], + -EPERM, 0); + return evm_status == INTEGRITY_PASS ? 0 : -EPERM; +} + +/** + * evm_inode_setxattr - protect the EVM extended attribute + * @dentry: pointer to the affected dentry + * @xattr_name: pointer to the affected extended attribute name + * @xattr_value: pointer to the new extended attribute value + * @xattr_value_len: pointer to the new extended attribute value length + * + * Before allowing the 'security.evm' protected xattr to be updated, + * verify the existing value is valid. As only the kernel should have + * access to the EVM encrypted key needed to calculate the HMAC, prevent + * userspace from writing HMAC value. Writing 'security.evm' requires + * requires CAP_SYS_ADMIN privileges. + */ +int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name, + const void *xattr_value, size_t xattr_value_len) +{ + const struct evm_ima_xattr_data *xattr_data = xattr_value; + + /* Policy permits modification of the protected xattrs even though + * there's no HMAC key loaded + */ + if (evm_initialized & EVM_ALLOW_METADATA_WRITES) + return 0; + + if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) { + if (!xattr_value_len) + return -EINVAL; + if (xattr_data->type != EVM_IMA_XATTR_DIGSIG && + xattr_data->type != EVM_XATTR_PORTABLE_DIGSIG) + return -EPERM; + } + return evm_protect_xattr(dentry, xattr_name, xattr_value, + xattr_value_len); +} + +/** + * evm_inode_removexattr - protect the EVM extended attribute + * @dentry: pointer to the affected dentry + * @xattr_name: pointer to the affected extended attribute name + * + * Removing 'security.evm' requires CAP_SYS_ADMIN privileges and that + * the current value is valid. + */ +int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name) +{ + /* Policy permits modification of the protected xattrs even though + * there's no HMAC key loaded + */ + if (evm_initialized & EVM_ALLOW_METADATA_WRITES) + return 0; + + return evm_protect_xattr(dentry, xattr_name, NULL, 0); +} + +static void evm_reset_status(struct inode *inode) +{ + struct integrity_iint_cache *iint; + + iint = integrity_iint_find(inode); + if (iint) + iint->evm_status = INTEGRITY_UNKNOWN; +} + +/** + * evm_inode_post_setxattr - update 'security.evm' to reflect the changes + * @dentry: pointer to the affected dentry + * @xattr_name: pointer to the affected extended attribute name + * @xattr_value: pointer to the new extended attribute value + * @xattr_value_len: pointer to the new extended attribute value length + * + * Update the HMAC stored in 'security.evm' to reflect the change. + * + * No need to take the i_mutex lock here, as this function is called from + * __vfs_setxattr_noperm(). The caller of which has taken the inode's + * i_mutex lock. + */ +void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name, + const void *xattr_value, size_t xattr_value_len) +{ + if (!evm_key_loaded() || (!evm_protected_xattr(xattr_name) + && !posix_xattr_acl(xattr_name))) + return; + + evm_reset_status(dentry->d_inode); + + evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len); +} + +/** + * evm_inode_post_removexattr - update 'security.evm' after removing the xattr + * @dentry: pointer to the affected dentry + * @xattr_name: pointer to the affected extended attribute name + * + * Update the HMAC stored in 'security.evm' to reflect removal of the xattr. + * + * No need to take the i_mutex lock here, as this function is called from + * vfs_removexattr() which takes the i_mutex. + */ +void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name) +{ + if (!evm_key_loaded() || !evm_protected_xattr(xattr_name)) + return; + + evm_reset_status(dentry->d_inode); + + evm_update_evmxattr(dentry, xattr_name, NULL, 0); +} + +/** + * evm_inode_setattr - prevent updating an invalid EVM extended attribute + * @dentry: pointer to the affected dentry + * + * Permit update of file attributes when files have a valid EVM signature, + * except in the case of them having an immutable portable signature. + */ +int evm_inode_setattr(struct dentry *dentry, struct iattr *attr) +{ + unsigned int ia_valid = attr->ia_valid; + enum integrity_status evm_status; + + /* Policy permits modification of the protected attrs even though + * there's no HMAC key loaded + */ + if (evm_initialized & EVM_ALLOW_METADATA_WRITES) + return 0; + + if (!(ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))) + return 0; + evm_status = evm_verify_current_integrity(dentry); + if ((evm_status == INTEGRITY_PASS) || + (evm_status == INTEGRITY_NOXATTRS)) + return 0; + integrity_audit_msg(AUDIT_INTEGRITY_METADATA, d_backing_inode(dentry), + dentry->d_name.name, "appraise_metadata", + integrity_status_msg[evm_status], -EPERM, 0); + return -EPERM; +} + +/** + * evm_inode_post_setattr - update 'security.evm' after modifying metadata + * @dentry: pointer to the affected dentry + * @ia_valid: for the UID and GID status + * + * For now, update the HMAC stored in 'security.evm' to reflect UID/GID + * changes. + * + * This function is called from notify_change(), which expects the caller + * to lock the inode's i_mutex. + */ +void evm_inode_post_setattr(struct dentry *dentry, int ia_valid) +{ + if (!evm_key_loaded()) + return; + + if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID)) + evm_update_evmxattr(dentry, NULL, NULL, 0); +} + +/* + * evm_inode_init_security - initializes security.evm HMAC value + */ +int evm_inode_init_security(struct inode *inode, + const struct xattr *lsm_xattr, + struct xattr *evm_xattr) +{ + struct evm_ima_xattr_data *xattr_data; + int rc; + + if (!(evm_initialized & EVM_INIT_HMAC) || + !evm_protected_xattr(lsm_xattr->name)) + return 0; + + xattr_data = kzalloc(sizeof(*xattr_data), GFP_NOFS); + if (!xattr_data) + return -ENOMEM; + + xattr_data->type = EVM_XATTR_HMAC; + rc = evm_init_hmac(inode, lsm_xattr, xattr_data->digest); + if (rc < 0) + goto out; + + evm_xattr->value = xattr_data; + evm_xattr->value_len = sizeof(*xattr_data); + evm_xattr->name = XATTR_EVM_SUFFIX; + return 0; +out: + kfree(xattr_data); + return rc; +} +EXPORT_SYMBOL_GPL(evm_inode_init_security); + +#ifdef CONFIG_EVM_LOAD_X509 +void __init evm_load_x509(void) +{ + int rc; + + rc = integrity_load_x509(INTEGRITY_KEYRING_EVM, CONFIG_EVM_X509_PATH); + if (!rc) + evm_initialized |= EVM_INIT_X509; +} +#endif + +static int __init init_evm(void) +{ + int error; + struct list_head *pos, *q; + struct xattr_list *xattr; + + evm_init_config(); + + error = integrity_init_keyring(INTEGRITY_KEYRING_EVM); + if (error) + goto error; + + error = evm_init_secfs(); + if (error < 0) { + pr_info("Error registering secfs\n"); + goto error; + } + +error: + if (error != 0) { + if (!list_empty(&evm_config_xattrnames)) { + list_for_each_safe(pos, q, &evm_config_xattrnames) { + xattr = list_entry(pos, struct xattr_list, + list); + list_del(pos); + } + } + } + + return error; +} + +late_initcall(init_evm); + +MODULE_DESCRIPTION("Extended Verification Module"); +MODULE_LICENSE("GPL"); diff --git a/security/integrity/evm/evm_posix_acl.c b/security/integrity/evm/evm_posix_acl.c new file mode 100644 index 000000000..46408b9e6 --- /dev/null +++ b/security/integrity/evm/evm_posix_acl.c @@ -0,0 +1,27 @@ +/* + * Copyright (C) 2011 IBM Corporation + * + * Author: + * Mimi Zohar <zohar@us.ibm.com> + * + * 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, version 2 of the License. + */ + +#include <linux/module.h> +#include <linux/xattr.h> +#include <linux/evm.h> + +int posix_xattr_acl(const char *xattr) +{ + int xattr_len = strlen(xattr); + + if ((strlen(XATTR_NAME_POSIX_ACL_ACCESS) == xattr_len) + && (strncmp(XATTR_NAME_POSIX_ACL_ACCESS, xattr, xattr_len) == 0)) + return 1; + if ((strlen(XATTR_NAME_POSIX_ACL_DEFAULT) == xattr_len) + && (strncmp(XATTR_NAME_POSIX_ACL_DEFAULT, xattr, xattr_len) == 0)) + return 1; + return 0; +} diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c new file mode 100644 index 000000000..c5c44203a --- /dev/null +++ b/security/integrity/evm/evm_secfs.c @@ -0,0 +1,327 @@ +/* + * Copyright (C) 2010 IBM Corporation + * + * Authors: + * Mimi Zohar <zohar@us.ibm.com> + * + * 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, version 2 of the License. + * + * File: evm_secfs.c + * - Used to signal when key is on keyring + * - Get the key and enable EVM + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/audit.h> +#include <linux/uaccess.h> +#include <linux/module.h> +#include <linux/mutex.h> +#include "evm.h" + +static struct dentry *evm_dir; +static struct dentry *evm_init_tpm; +static struct dentry *evm_symlink; + +#ifdef CONFIG_EVM_ADD_XATTRS +static struct dentry *evm_xattrs; +static DEFINE_MUTEX(xattr_list_mutex); +static int evm_xattrs_locked; +#endif + +/** + * evm_read_key - read() for <securityfs>/evm + * + * @filp: file pointer, not actually used + * @buf: where to put the result + * @count: maximum to send along + * @ppos: where to start + * + * Returns number of bytes read or error code, as appropriate + */ +static ssize_t evm_read_key(struct file *filp, char __user *buf, + size_t count, loff_t *ppos) +{ + char temp[80]; + ssize_t rc; + + if (*ppos != 0) + return 0; + + sprintf(temp, "%d", (evm_initialized & ~EVM_SETUP_COMPLETE)); + rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); + + return rc; +} + +/** + * evm_write_key - write() for <securityfs>/evm + * @file: file pointer, not actually used + * @buf: where to get the data from + * @count: bytes sent + * @ppos: where to start + * + * Used to signal that key is on the kernel key ring. + * - get the integrity hmac key from the kernel key ring + * - create list of hmac protected extended attributes + * Returns number of bytes written or error code, as appropriate + */ +static ssize_t evm_write_key(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + unsigned int i; + int ret; + + if (!capable(CAP_SYS_ADMIN) || (evm_initialized & EVM_SETUP_COMPLETE)) + return -EPERM; + + ret = kstrtouint_from_user(buf, count, 0, &i); + + if (ret) + return ret; + + /* Reject invalid values */ + if (!i || (i & ~EVM_INIT_MASK) != 0) + return -EINVAL; + + /* + * Don't allow a request to enable metadata writes if + * an HMAC key is loaded. + */ + if ((i & EVM_ALLOW_METADATA_WRITES) && + (evm_initialized & EVM_INIT_HMAC) != 0) + return -EPERM; + + if (i & EVM_INIT_HMAC) { + ret = evm_init_key(); + if (ret != 0) + return ret; + /* Forbid further writes after the symmetric key is loaded */ + i |= EVM_SETUP_COMPLETE; + } + + evm_initialized |= i; + + /* Don't allow protected metadata modification if a symmetric key + * is loaded + */ + if (evm_initialized & EVM_INIT_HMAC) + evm_initialized &= ~(EVM_ALLOW_METADATA_WRITES); + + return count; +} + +static const struct file_operations evm_key_ops = { + .read = evm_read_key, + .write = evm_write_key, +}; + +#ifdef CONFIG_EVM_ADD_XATTRS +/** + * evm_read_xattrs - read() for <securityfs>/evm_xattrs + * + * @filp: file pointer, not actually used + * @buf: where to put the result + * @count: maximum to send along + * @ppos: where to start + * + * Returns number of bytes read or error code, as appropriate + */ +static ssize_t evm_read_xattrs(struct file *filp, char __user *buf, + size_t count, loff_t *ppos) +{ + char *temp; + int offset = 0; + ssize_t rc, size = 0; + struct xattr_list *xattr; + + if (*ppos != 0) + return 0; + + rc = mutex_lock_interruptible(&xattr_list_mutex); + if (rc) + return -ERESTARTSYS; + + list_for_each_entry(xattr, &evm_config_xattrnames, list) + size += strlen(xattr->name) + 1; + + temp = kmalloc(size + 1, GFP_KERNEL); + if (!temp) { + mutex_unlock(&xattr_list_mutex); + return -ENOMEM; + } + + list_for_each_entry(xattr, &evm_config_xattrnames, list) { + sprintf(temp + offset, "%s\n", xattr->name); + offset += strlen(xattr->name) + 1; + } + + mutex_unlock(&xattr_list_mutex); + rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp)); + + kfree(temp); + + return rc; +} + +/** + * evm_write_xattrs - write() for <securityfs>/evm_xattrs + * @file: file pointer, not actually used + * @buf: where to get the data from + * @count: bytes sent + * @ppos: where to start + * + * Returns number of bytes written or error code, as appropriate + */ +static ssize_t evm_write_xattrs(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + int len, err; + struct xattr_list *xattr, *tmp; + struct audit_buffer *ab; + struct iattr newattrs; + struct inode *inode; + + if (!capable(CAP_SYS_ADMIN) || evm_xattrs_locked) + return -EPERM; + + if (*ppos != 0) + return -EINVAL; + + if (count > XATTR_NAME_MAX) + return -E2BIG; + + ab = audit_log_start(NULL, GFP_KERNEL, AUDIT_INTEGRITY_EVM_XATTR); + if (!ab) + return -ENOMEM; + + xattr = kmalloc(sizeof(struct xattr_list), GFP_KERNEL); + if (!xattr) { + err = -ENOMEM; + goto out; + } + + xattr->name = memdup_user_nul(buf, count); + if (IS_ERR(xattr->name)) { + err = PTR_ERR(xattr->name); + xattr->name = NULL; + goto out; + } + + /* Remove any trailing newline */ + len = strlen(xattr->name); + if (len && xattr->name[len-1] == '\n') + xattr->name[len-1] = '\0'; + + if (strcmp(xattr->name, ".") == 0) { + evm_xattrs_locked = 1; + newattrs.ia_mode = S_IFREG | 0440; + newattrs.ia_valid = ATTR_MODE; + inode = evm_xattrs->d_inode; + inode_lock(inode); + err = simple_setattr(evm_xattrs, &newattrs); + inode_unlock(inode); + audit_log_format(ab, "locked"); + if (!err) + err = count; + goto out; + } + + audit_log_format(ab, "xattr="); + audit_log_untrustedstring(ab, xattr->name); + + if (strncmp(xattr->name, XATTR_SECURITY_PREFIX, + XATTR_SECURITY_PREFIX_LEN) != 0) { + err = -EINVAL; + goto out; + } + + /* + * xattr_list_mutex guards against races in evm_read_xattrs(). + * Entries are only added to the evm_config_xattrnames list + * and never deleted. Therefore, the list is traversed + * using list_for_each_entry_lockless() without holding + * the mutex in evm_calc_hmac_or_hash(), evm_find_protected_xattrs() + * and evm_protected_xattr(). + */ + mutex_lock(&xattr_list_mutex); + list_for_each_entry(tmp, &evm_config_xattrnames, list) { + if (strcmp(xattr->name, tmp->name) == 0) { + err = -EEXIST; + mutex_unlock(&xattr_list_mutex); + goto out; + } + } + list_add_tail_rcu(&xattr->list, &evm_config_xattrnames); + mutex_unlock(&xattr_list_mutex); + + audit_log_format(ab, " res=0"); + audit_log_end(ab); + return count; +out: + audit_log_format(ab, " res=%d", err); + audit_log_end(ab); + if (xattr) { + kfree(xattr->name); + kfree(xattr); + } + return err; +} + +static const struct file_operations evm_xattr_ops = { + .read = evm_read_xattrs, + .write = evm_write_xattrs, +}; + +static int evm_init_xattrs(void) +{ + evm_xattrs = securityfs_create_file("evm_xattrs", 0660, evm_dir, NULL, + &evm_xattr_ops); + if (!evm_xattrs || IS_ERR(evm_xattrs)) + return -EFAULT; + + return 0; +} +#else +static int evm_init_xattrs(void) +{ + return 0; +} +#endif + +int __init evm_init_secfs(void) +{ + int error = 0; + + evm_dir = securityfs_create_dir("evm", integrity_dir); + if (!evm_dir || IS_ERR(evm_dir)) + return -EFAULT; + + evm_init_tpm = securityfs_create_file("evm", 0660, + evm_dir, NULL, &evm_key_ops); + if (!evm_init_tpm || IS_ERR(evm_init_tpm)) { + error = -EFAULT; + goto out; + } + + evm_symlink = securityfs_create_symlink("evm", NULL, + "integrity/evm/evm", NULL); + if (!evm_symlink || IS_ERR(evm_symlink)) { + error = -EFAULT; + goto out; + } + + if (evm_init_xattrs() != 0) { + error = -EFAULT; + goto out; + } + + return 0; +out: + securityfs_remove(evm_symlink); + securityfs_remove(evm_init_tpm); + securityfs_remove(evm_dir); + return error; +} |