| // SPDX-License-Identifier: GPL-2.0-only |
| /* |
| * Copyright (C) 2011 IBM Corporation |
| * |
| * Author: |
| * Mimi Zohar <zohar@us.ibm.com> |
| */ |
| #include <linux/init.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 <keys/system_keyring.h> |
| |
| #include "ima.h" |
| |
| static int __init default_appraise_setup(char *str) |
| { |
| #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM |
| bool sb_state = arch_ima_get_secureboot(); |
| int appraisal_state = ima_appraise; |
| |
| if (strncmp(str, "off", 3) == 0) |
| appraisal_state = 0; |
| else if (strncmp(str, "log", 3) == 0) |
| appraisal_state = IMA_APPRAISE_LOG; |
| else if (strncmp(str, "fix", 3) == 0) |
| appraisal_state = IMA_APPRAISE_FIX; |
| else if (strncmp(str, "enforce", 7) == 0) |
| appraisal_state = IMA_APPRAISE_ENFORCE; |
| else |
| pr_err("invalid \"%s\" appraise option", str); |
| |
| /* If appraisal state was changed, but secure boot is enabled, |
| * keep its default */ |
| if (sb_state) { |
| if (!(appraisal_state & IMA_APPRAISE_ENFORCE)) |
| pr_info("Secure boot enabled: ignoring ima_appraise=%s option", |
| str); |
| } else { |
| ima_appraise = appraisal_state; |
| } |
| #endif |
| return 1; |
| } |
| |
| __setup("ima_appraise=", default_appraise_setup); |
| |
| /* |
| * is_ima_appraise_enabled - return appraise status |
| * |
| * Only return enabled, if not in ima_appraise="fix" or "log" modes. |
| */ |
| bool is_ima_appraise_enabled(void) |
| { |
| return ima_appraise & IMA_APPRAISE_ENFORCE; |
| } |
| |
| /* |
| * ima_must_appraise - set appraise flag |
| * |
| * Return 1 to appraise or hash |
| */ |
| int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func) |
| { |
| u32 secid; |
| |
| if (!ima_appraise) |
| return 0; |
| |
| security_task_getsecid(current, &secid); |
| return ima_match_policy(inode, current_cred(), secid, func, mask, |
| IMA_APPRAISE | IMA_HASH, NULL, NULL, NULL); |
| } |
| |
| 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, |
| enum ima_hooks func) |
| { |
| switch (func) { |
| case MMAP_CHECK: |
| return iint->ima_mmap_status; |
| case BPRM_CHECK: |
| return iint->ima_bprm_status; |
| case CREDS_CHECK: |
| return iint->ima_creds_status; |
| case FILE_CHECK: |
| case POST_SETATTR: |
| return iint->ima_file_status; |
| case MODULE_CHECK ... MAX_CHECK - 1: |
| default: |
| return iint->ima_read_status; |
| } |
| } |
| |
| static void ima_set_cache_status(struct integrity_iint_cache *iint, |
| enum ima_hooks 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 CREDS_CHECK: |
| iint->ima_creds_status = status; |
| break; |
| case FILE_CHECK: |
| case POST_SETATTR: |
| iint->ima_file_status = status; |
| break; |
| case MODULE_CHECK ... MAX_CHECK - 1: |
| default: |
| iint->ima_read_status = status; |
| break; |
| } |
| } |
| |
| static void ima_cache_flags(struct integrity_iint_cache *iint, |
| enum ima_hooks 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 CREDS_CHECK: |
| iint->flags |= (IMA_CREDS_APPRAISED | IMA_APPRAISED); |
| break; |
| case FILE_CHECK: |
| case POST_SETATTR: |
| iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED); |
| break; |
| case MODULE_CHECK ... MAX_CHECK - 1: |
| default: |
| iint->flags |= (IMA_READ_APPRAISED | IMA_APPRAISED); |
| break; |
| } |
| } |
| |
| enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, |
| int xattr_len) |
| { |
| struct signature_v2_hdr *sig; |
| enum hash_algo ret; |
| |
| if (!xattr_value || xattr_len < 2) |
| /* return default hash algo */ |
| return ima_hash_algo; |
| |
| switch (xattr_value->type) { |
| case EVM_IMA_XATTR_DIGSIG: |
| sig = (typeof(sig))xattr_value; |
| if (sig->version != 2 || xattr_len <= sizeof(*sig)) |
| return ima_hash_algo; |
| return sig->hash_algo; |
| break; |
| case IMA_XATTR_DIGEST_NG: |
| /* first byte contains algorithm id */ |
| ret = xattr_value->data[0]; |
| if (ret < HASH_ALGO__LAST) |
| return ret; |
| break; |
| case IMA_XATTR_DIGEST: |
| /* this is for backward compatibility */ |
| if (xattr_len == 21) { |
| unsigned int zero = 0; |
| if (!memcmp(&xattr_value->data[16], &zero, 4)) |
| return HASH_ALGO_MD5; |
| else |
| return HASH_ALGO_SHA1; |
| } else if (xattr_len == 17) |
| return HASH_ALGO_MD5; |
| break; |
| } |
| |
| /* return default hash algo */ |
| return ima_hash_algo; |
| } |
| |
| int ima_read_xattr(struct dentry *dentry, |
| struct evm_ima_xattr_data **xattr_value) |
| { |
| ssize_t ret; |
| |
| ret = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value, |
| 0, GFP_NOFS); |
| if (ret == -EOPNOTSUPP) |
| ret = 0; |
| return ret; |
| } |
| |
| /* |
| * xattr_verify - verify xattr digest or signature |
| * |
| * Verify whether the hash or signature matches the file contents. |
| * |
| * Return 0 on success, error code otherwise. |
| */ |
| static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint, |
| struct evm_ima_xattr_data *xattr_value, int xattr_len, |
| enum integrity_status *status, const char **cause) |
| { |
| int rc = -EINVAL, hash_start = 0; |
| |
| switch (xattr_value->type) { |
| case IMA_XATTR_DIGEST_NG: |
| /* first byte contains algorithm id */ |
| hash_start = 1; |
| fallthrough; |
| case IMA_XATTR_DIGEST: |
| if (iint->flags & IMA_DIGSIG_REQUIRED) { |
| *cause = "IMA-signature-required"; |
| *status = INTEGRITY_FAIL; |
| break; |
| } |
| clear_bit(IMA_DIGSIG, &iint->atomic_flags); |
| 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->data[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: |
| set_bit(IMA_DIGSIG, &iint->atomic_flags); |
| rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA, |
| (const char *)xattr_value, |
| xattr_len, |
| iint->ima_hash->digest, |
| iint->ima_hash->length); |
| if (rc == -EOPNOTSUPP) { |
| *status = INTEGRITY_UNKNOWN; |
| break; |
| } |
| if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc && |
| func == KEXEC_KERNEL_CHECK) |
| rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM, |
| (const char *)xattr_value, |
| xattr_len, |
| iint->ima_hash->digest, |
| iint->ima_hash->length); |
| if (rc) { |
| *cause = "invalid-signature"; |
| *status = INTEGRITY_FAIL; |
| } else { |
| *status = INTEGRITY_PASS; |
| } |
| break; |
| default: |
| *status = INTEGRITY_UNKNOWN; |
| *cause = "unknown-ima-data"; |
| break; |
| } |
| |
| return rc; |
| } |
| |
| /* |
| * modsig_verify - verify modsig signature |
| * |
| * Verify whether the signature matches the file contents. |
| * |
| * Return 0 on success, error code otherwise. |
| */ |
| static int modsig_verify(enum ima_hooks func, const struct modsig *modsig, |
| enum integrity_status *status, const char **cause) |
| { |
| int rc; |
| |
| rc = integrity_modsig_verify(INTEGRITY_KEYRING_IMA, modsig); |
| if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc && |
| func == KEXEC_KERNEL_CHECK) |
| rc = integrity_modsig_verify(INTEGRITY_KEYRING_PLATFORM, |
| modsig); |
| if (rc) { |
| *cause = "invalid-signature"; |
| *status = INTEGRITY_FAIL; |
| } else { |
| *status = INTEGRITY_PASS; |
| } |
| |
| return rc; |
| } |
| |
| /* |
| * ima_check_blacklist - determine if the binary is blacklisted. |
| * |
| * Add the hash of the blacklisted binary to the measurement list, based |
| * on policy. |
| * |
| * Returns -EPERM if the hash is blacklisted. |
| */ |
| int ima_check_blacklist(struct integrity_iint_cache *iint, |
| const struct modsig *modsig, int pcr) |
| { |
| enum hash_algo hash_algo; |
| const u8 *digest = NULL; |
| u32 digestsize = 0; |
| int rc = 0; |
| |
| if (!(iint->flags & IMA_CHECK_BLACKLIST)) |
| return 0; |
| |
| if (iint->flags & IMA_MODSIG_ALLOWED && modsig) { |
| ima_get_modsig_digest(modsig, &hash_algo, &digest, &digestsize); |
| |
| rc = is_binary_blacklisted(digest, digestsize); |
| if ((rc == -EPERM) && (iint->flags & IMA_MEASURE)) |
| process_buffer_measurement(NULL, digest, digestsize, |
| "blacklisted-hash", NONE, |
| pcr, NULL); |
| } |
| |
| return rc; |
| } |
| |
| /* |
| * 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(enum ima_hooks func, |
| struct integrity_iint_cache *iint, |
| struct file *file, const unsigned char *filename, |
| struct evm_ima_xattr_data *xattr_value, |
| int xattr_len, const struct modsig *modsig) |
| { |
| static const char op[] = "appraise_data"; |
| const char *cause = "unknown"; |
| struct dentry *dentry = file_dentry(file); |
| struct inode *inode = d_backing_inode(dentry); |
| enum integrity_status status = INTEGRITY_UNKNOWN; |
| int rc = xattr_len; |
| bool try_modsig = iint->flags & IMA_MODSIG_ALLOWED && modsig; |
| |
| /* If not appraising a modsig, we need an xattr. */ |
| if (!(inode->i_opflags & IOP_XATTR) && !try_modsig) |
| return INTEGRITY_UNKNOWN; |
| |
| /* If reading the xattr failed and there's no modsig, error out. */ |
| if (rc <= 0 && !try_modsig) { |
| if (rc && rc != -ENODATA) |
| goto out; |
| |
| cause = iint->flags & IMA_DIGSIG_REQUIRED ? |
| "IMA-signature-required" : "missing-hash"; |
| status = INTEGRITY_NOLABEL; |
| if (file->f_mode & FMODE_CREATED) |
| iint->flags |= IMA_NEW_FILE; |
| if ((iint->flags & IMA_NEW_FILE) && |
| (!(iint->flags & IMA_DIGSIG_REQUIRED) || |
| (inode->i_size == 0))) |
| status = INTEGRITY_PASS; |
| goto out; |
| } |
| |
| status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint); |
| switch (status) { |
| case INTEGRITY_PASS: |
| case INTEGRITY_PASS_IMMUTABLE: |
| case INTEGRITY_UNKNOWN: |
| break; |
| case INTEGRITY_NOXATTRS: /* No EVM protected xattrs. */ |
| /* It's fine not to have xattrs when using a modsig. */ |
| if (try_modsig) |
| break; |
| fallthrough; |
| case INTEGRITY_NOLABEL: /* No security.evm xattr. */ |
| cause = "missing-HMAC"; |
| goto out; |
| case INTEGRITY_FAIL: /* Invalid HMAC/signature. */ |
| cause = "invalid-HMAC"; |
| goto out; |
| default: |
| WARN_ONCE(true, "Unexpected integrity status %d\n", status); |
| } |
| |
| if (xattr_value) |
| rc = xattr_verify(func, iint, xattr_value, xattr_len, &status, |
| &cause); |
| |
| /* |
| * If we have a modsig and either no imasig or the imasig's key isn't |
| * known, then try verifying the modsig. |
| */ |
| if (try_modsig && |
| (!xattr_value || xattr_value->type == IMA_XATTR_DIGEST_NG || |
| rc == -ENOKEY)) |
| rc = modsig_verify(func, modsig, &status, &cause); |
| |
| out: |
| /* |
| * File signatures on some filesystems can not be properly verified. |
| * When such filesystems are mounted by an untrusted mounter or on a |
| * system not willing to accept such a risk, fail the file signature |
| * verification. |
| */ |
| if ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) && |
| ((inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) || |
| (iint->flags & IMA_FAIL_UNVERIFIABLE_SIGS))) { |
| status = INTEGRITY_FAIL; |
| cause = "unverifiable-signature"; |
| integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, |
| op, cause, rc, 0); |
| } else if (status != INTEGRITY_PASS) { |
| /* Fix mode, but don't replace file signatures. */ |
| if ((ima_appraise & IMA_APPRAISE_FIX) && !try_modsig && |
| (!xattr_value || |
| xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { |
| if (!ima_fix_xattr(dentry, iint)) |
| status = INTEGRITY_PASS; |
| } |
| |
| /* Permit new files with file signatures, but without data. */ |
| if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE && |
| xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG) { |
| 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_dentry(file); |
| int rc = 0; |
| |
| /* do not collect and update hash for digital signatures */ |
| if (test_bit(IMA_DIGSIG, &iint->atomic_flags)) |
| return; |
| |
| if ((iint->ima_file_status != INTEGRITY_PASS) && |
| !(iint->flags & IMA_HASH)) |
| return; |
| |
| rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo, NULL); |
| if (rc < 0) |
| return; |
| |
| inode_lock(file_inode(file)); |
| ima_fix_xattr(dentry, iint); |
| inode_unlock(file_inode(file)); |
| } |
| |
| /** |
| * 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 = d_backing_inode(dentry); |
| struct integrity_iint_cache *iint; |
| int action; |
| |
| if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode) |
| || !(inode->i_opflags & IOP_XATTR)) |
| return; |
| |
| action = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR); |
| if (!action) |
| __vfs_removexattr(dentry, XATTR_NAME_IMA); |
| iint = integrity_iint_find(inode); |
| if (iint) { |
| set_bit(IMA_CHANGE_ATTR, &iint->atomic_flags); |
| if (!action) |
| clear_bit(IMA_UPDATE_XATTR, &iint->atomic_flags); |
| } |
| } |
| |
| /* |
| * 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_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)) |
| return; |
| |
| iint = integrity_iint_find(inode); |
| if (!iint) |
| return; |
| iint->measured_pcrs = 0; |
| set_bit(IMA_CHANGE_XATTR, &iint->atomic_flags); |
| if (digsig) |
| set_bit(IMA_DIGSIG, &iint->atomic_flags); |
| else |
| clear_bit(IMA_DIGSIG, &iint->atomic_flags); |
| } |
| |
| 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) { |
| if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST)) |
| return -EINVAL; |
| ima_reset_appraise_flags(d_backing_inode(dentry), |
| xvalue->type == EVM_IMA_XATTR_DIGSIG); |
| 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(d_backing_inode(dentry), 0); |
| result = 0; |
| } |
| return result; |
| } |