diff options
Diffstat (limited to 'security/integrity/ima/ima_appraise.c')
| -rw-r--r-- | security/integrity/ima/ima_appraise.c | 387 |
1 files changed, 387 insertions, 0 deletions
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c new file mode 100644 index 00000000000..d3113d4aaa3 --- /dev/null +++ b/security/integrity/ima/ima_appraise.c @@ -0,0 +1,387 @@ +/* + * 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/file.h> +#include <linux/fs.h> +#include <linux/xattr.h> +#include <linux/magic.h> +#include <linux/ima.h> +#include <linux/evm.h> +#include <crypto/hash_info.h> + +#include "ima.h" + +static int __init default_appraise_setup(char *str) +{ + if (strncmp(str, "off", 3) == 0) + ima_appraise = 0; + else if (strncmp(str, "fix", 3) == 0) + ima_appraise = IMA_APPRAISE_FIX; + return 1; +} + +__setup("ima_appraise=", default_appraise_setup); + +/* + * ima_must_appraise - set appraise flag + * + * Return 1 to appraise + */ +int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func) +{ + if (!ima_appraise) + return 0; + + return ima_match_policy(inode, func, mask, IMA_APPRAISE); +} + +static int ima_fix_xattr(struct dentry *dentry, + struct integrity_iint_cache *iint) +{ + int rc, offset; + u8 algo = iint->ima_hash->algo; + + if (algo <= HASH_ALGO_SHA1) { + offset = 1; + iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST; + } else { + offset = 0; + iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG; + iint->ima_hash->xattr.ng.algo = algo; + } + rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA, + &iint->ima_hash->xattr.data[offset], + (sizeof(iint->ima_hash->xattr) - offset) + + iint->ima_hash->length, 0); + return rc; +} + +/* Return specific func appraised cached result */ +enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint, + int func) +{ + switch (func) { + case MMAP_CHECK: + return iint->ima_mmap_status; + case BPRM_CHECK: + return iint->ima_bprm_status; + case MODULE_CHECK: + return iint->ima_module_status; + case FILE_CHECK: + default: + return iint->ima_file_status; + } +} + +static void ima_set_cache_status(struct integrity_iint_cache *iint, + int func, enum integrity_status status) +{ + switch (func) { + case MMAP_CHECK: + iint->ima_mmap_status = status; + break; + case BPRM_CHECK: + iint->ima_bprm_status = status; + break; + case MODULE_CHECK: + iint->ima_module_status = status; + break; + case FILE_CHECK: + default: + iint->ima_file_status = status; + break; + } +} + +static void ima_cache_flags(struct integrity_iint_cache *iint, int func) +{ + switch (func) { + case MMAP_CHECK: + iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED); + break; + case BPRM_CHECK: + iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED); + break; + case MODULE_CHECK: + iint->flags |= (IMA_MODULE_APPRAISED | IMA_APPRAISED); + break; + case FILE_CHECK: + default: + iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED); + break; + } +} + +void ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, int xattr_len, + struct ima_digest_data *hash) +{ + struct signature_v2_hdr *sig; + + if (!xattr_value || xattr_len < 2) + return; + + switch (xattr_value->type) { + case EVM_IMA_XATTR_DIGSIG: + sig = (typeof(sig))xattr_value; + if (sig->version != 2 || xattr_len <= sizeof(*sig)) + return; + hash->algo = sig->hash_algo; + break; + case IMA_XATTR_DIGEST_NG: + hash->algo = xattr_value->digest[0]; + break; + case IMA_XATTR_DIGEST: + /* this is for backward compatibility */ + if (xattr_len == 21) { + unsigned int zero = 0; + if (!memcmp(&xattr_value->digest[16], &zero, 4)) + hash->algo = HASH_ALGO_MD5; + else + hash->algo = HASH_ALGO_SHA1; + } else if (xattr_len == 17) + hash->algo = HASH_ALGO_MD5; + break; + } +} + +int ima_read_xattr(struct dentry *dentry, + struct evm_ima_xattr_data **xattr_value) +{ + struct inode *inode = dentry->d_inode; + + if (!inode->i_op->getxattr) + return 0; + + return vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value, + 0, GFP_NOFS); +} + +/* + * ima_appraise_measurement - appraise file measurement + * + * Call evm_verifyxattr() to verify the integrity of 'security.ima'. + * Assuming success, compare the xattr hash with the collected measurement. + * + * Return 0 on success, error code otherwise + */ +int ima_appraise_measurement(int func, struct integrity_iint_cache *iint, + struct file *file, const unsigned char *filename, + struct evm_ima_xattr_data *xattr_value, + int xattr_len) +{ + static const char op[] = "appraise_data"; + char *cause = "unknown"; + struct dentry *dentry = file->f_dentry; + struct inode *inode = dentry->d_inode; + enum integrity_status status = INTEGRITY_UNKNOWN; + int rc = xattr_len, hash_start = 0; + + if (!ima_appraise) + return 0; + if (!inode->i_op->getxattr) + return INTEGRITY_UNKNOWN; + + if (rc <= 0) { + if (rc && rc != -ENODATA) + goto out; + + cause = "missing-hash"; + status = + (inode->i_size == 0) ? INTEGRITY_PASS : INTEGRITY_NOLABEL; + goto out; + } + + status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint); + if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) { + if ((status == INTEGRITY_NOLABEL) + || (status == INTEGRITY_NOXATTRS)) + cause = "missing-HMAC"; + else if (status == INTEGRITY_FAIL) + cause = "invalid-HMAC"; + goto out; + } + switch (xattr_value->type) { + case IMA_XATTR_DIGEST_NG: + /* first byte contains algorithm id */ + hash_start = 1; + case IMA_XATTR_DIGEST: + if (iint->flags & IMA_DIGSIG_REQUIRED) { + cause = "IMA signature required"; + status = INTEGRITY_FAIL; + break; + } + if (xattr_len - sizeof(xattr_value->type) - hash_start >= + iint->ima_hash->length) + /* xattr length may be longer. md5 hash in previous + version occupied 20 bytes in xattr, instead of 16 + */ + rc = memcmp(&xattr_value->digest[hash_start], + iint->ima_hash->digest, + iint->ima_hash->length); + else + rc = -EINVAL; + if (rc) { + cause = "invalid-hash"; + status = INTEGRITY_FAIL; + break; + } + status = INTEGRITY_PASS; + break; + case EVM_IMA_XATTR_DIGSIG: + iint->flags |= IMA_DIGSIG; + rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA, + (const char *)xattr_value, rc, + iint->ima_hash->digest, + iint->ima_hash->length); + if (rc == -EOPNOTSUPP) { + status = INTEGRITY_UNKNOWN; + } else if (rc) { + cause = "invalid-signature"; + status = INTEGRITY_FAIL; + } else { + status = INTEGRITY_PASS; + } + break; + default: + status = INTEGRITY_UNKNOWN; + cause = "unknown-ima-data"; + break; + } + +out: + if (status != INTEGRITY_PASS) { + if ((ima_appraise & IMA_APPRAISE_FIX) && + (!xattr_value || + xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { + if (!ima_fix_xattr(dentry, iint)) + status = INTEGRITY_PASS; + } + integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, + op, cause, rc, 0); + } else { + ima_cache_flags(iint, func); + } + ima_set_cache_status(iint, func, status); + return status; +} + +/* + * ima_update_xattr - update 'security.ima' hash value + */ +void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file) +{ + struct dentry *dentry = file->f_dentry; + int rc = 0; + + /* do not collect and update hash for digital signatures */ + if (iint->flags & IMA_DIGSIG) + return; + + rc = ima_collect_measurement(iint, file, NULL, NULL); + if (rc < 0) + return; + + ima_fix_xattr(dentry, iint); +} + +/** + * ima_inode_post_setattr - reflect file metadata changes + * @dentry: pointer to the affected dentry + * + * Changes to a dentry's metadata might result in needing to appraise. + * + * This function is called from notify_change(), which expects the caller + * to lock the inode's i_mutex. + */ +void ima_inode_post_setattr(struct dentry *dentry) +{ + struct inode *inode = dentry->d_inode; + struct integrity_iint_cache *iint; + int must_appraise, rc; + + if (!ima_initialized || !ima_appraise || !S_ISREG(inode->i_mode) + || !inode->i_op->removexattr) + return; + + must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR); + iint = integrity_iint_find(inode); + if (iint) { + iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED | + IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK | + IMA_ACTION_FLAGS); + if (must_appraise) + iint->flags |= IMA_APPRAISE; + } + if (!must_appraise) + rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA); + return; +} + +/* + * ima_protect_xattr - protect 'security.ima' + * + * Ensure that not just anyone can modify or remove 'security.ima'. + */ +static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name, + const void *xattr_value, size_t xattr_value_len) +{ + if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) { + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + return 1; + } + return 0; +} + +static void ima_reset_appraise_flags(struct inode *inode, int digsig) +{ + struct integrity_iint_cache *iint; + + if (!ima_initialized || !ima_appraise || !S_ISREG(inode->i_mode)) + return; + + iint = integrity_iint_find(inode); + if (!iint) + return; + + iint->flags &= ~IMA_DONE_MASK; + if (digsig) + iint->flags |= IMA_DIGSIG; + return; +} + +int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name, + const void *xattr_value, size_t xattr_value_len) +{ + const struct evm_ima_xattr_data *xvalue = xattr_value; + int result; + + result = ima_protect_xattr(dentry, xattr_name, xattr_value, + xattr_value_len); + if (result == 1) { + ima_reset_appraise_flags(dentry->d_inode, + (xvalue->type == EVM_IMA_XATTR_DIGSIG) ? 1 : 0); + result = 0; + } + return result; +} + +int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name) +{ + int result; + + result = ima_protect_xattr(dentry, xattr_name, NULL, 0); + if (result == 1) { + ima_reset_appraise_flags(dentry->d_inode, 0); + result = 0; + } + return result; +} |