diff options
Diffstat (limited to 'security/integrity/ima/ima_appraise.c')
| -rw-r--r-- | security/integrity/ima/ima_appraise.c | 636 |
1 files changed, 510 insertions, 126 deletions
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index a2baa85ea2f5..5149ff4fd50d 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -1,37 +1,60 @@ +// SPDX-License-Identifier: GPL-2.0-only /* * 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/init.h> #include <linux/file.h> +#include <linux/binfmts.h> #include <linux/fs.h> #include <linux/xattr.h> #include <linux/magic.h> #include <linux/ima.h> #include <linux/evm.h> +#include <linux/fsverity.h> +#include <keys/system_keyring.h> +#include <uapi/linux/fsverity.h> #include "ima.h" -static int __init default_appraise_setup(char *str) -{ #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM +static char *ima_appraise_cmdline_default __initdata; +core_param(ima_appraise, ima_appraise_cmdline_default, charp, 0); + +void __init ima_appraise_parse_cmdline(void) +{ + const char *str = ima_appraise_cmdline_default; + bool sb_state = arch_ima_get_secureboot(); + int appraisal_state = ima_appraise; + + if (!str) + return; + if (strncmp(str, "off", 3) == 0) - ima_appraise = 0; + appraisal_state = 0; else if (strncmp(str, "log", 3) == 0) - ima_appraise = IMA_APPRAISE_LOG; + appraisal_state = IMA_APPRAISE_LOG; else if (strncmp(str, "fix", 3) == 0) - ima_appraise = IMA_APPRAISE_FIX; -#endif - return 1; + 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; + } } - -__setup("ima_appraise=", default_appraise_setup); +#endif /* * is_ima_appraise_enabled - return appraise status @@ -48,20 +71,21 @@ bool is_ima_appraise_enabled(void) * * Return 1 to appraise or hash */ -int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func) +int ima_must_appraise(struct mnt_idmap *idmap, struct inode *inode, + int mask, enum ima_hooks func) { - u32 secid; + struct lsm_prop prop; 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); + security_current_getlsmprop_subj(&prop); + return ima_match_policy(idmap, inode, current_cred(), &prop, + func, mask, IMA_APPRAISE | IMA_HASH, NULL, + NULL, NULL, NULL); } -static int ima_fix_xattr(struct dentry *dentry, - struct integrity_iint_cache *iint) +static int ima_fix_xattr(struct dentry *dentry, struct ima_iint_cache *iint) { int rc, offset; u8 algo = iint->ima_hash->algo; @@ -74,7 +98,7 @@ static int ima_fix_xattr(struct dentry *dentry, 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, + rc = __vfs_setxattr_noperm(&nop_mnt_idmap, dentry, XATTR_NAME_IMA, &iint->ima_hash->xattr.data[offset], (sizeof(iint->ima_hash->xattr) - offset) + iint->ima_hash->length, 0); @@ -82,11 +106,12 @@ static int ima_fix_xattr(struct dentry *dentry, } /* Return specific func appraised cached result */ -enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint, +enum integrity_status ima_get_cache_status(struct ima_iint_cache *iint, enum ima_hooks func) { switch (func) { case MMAP_CHECK: + case MMAP_CHECK_REQPROT: return iint->ima_mmap_status; case BPRM_CHECK: return iint->ima_bprm_status; @@ -101,12 +126,13 @@ enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint, } } -static void ima_set_cache_status(struct integrity_iint_cache *iint, +static void ima_set_cache_status(struct ima_iint_cache *iint, enum ima_hooks func, enum integrity_status status) { switch (func) { case MMAP_CHECK: + case MMAP_CHECK_REQPROT: iint->ima_mmap_status = status; break; case BPRM_CHECK: @@ -114,6 +140,7 @@ static void ima_set_cache_status(struct integrity_iint_cache *iint, break; case CREDS_CHECK: iint->ima_creds_status = status; + break; case FILE_CHECK: case POST_SETATTR: iint->ima_file_status = status; @@ -125,11 +152,11 @@ static void ima_set_cache_status(struct integrity_iint_cache *iint, } } -static void ima_cache_flags(struct integrity_iint_cache *iint, - enum ima_hooks func) +static void ima_cache_flags(struct ima_iint_cache *iint, enum ima_hooks func) { switch (func) { case MMAP_CHECK: + case MMAP_CHECK_REQPROT: iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED); break; case BPRM_CHECK: @@ -149,7 +176,7 @@ static void ima_cache_flags(struct integrity_iint_cache *iint, } } -enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, +enum hash_algo ima_get_hash_algo(const struct evm_ima_xattr_data *xattr_value, int xattr_len) { struct signature_v2_hdr *sig; @@ -160,14 +187,21 @@ enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, return ima_hash_algo; switch (xattr_value->type) { + case IMA_VERITY_DIGSIG: + sig = (typeof(sig))xattr_value; + if (sig->version != 3 || xattr_len <= sizeof(*sig) || + sig->hash_algo >= HASH_ALGO__LAST) + return ima_hash_algo; + return sig->hash_algo; case EVM_IMA_XATTR_DIGSIG: sig = (typeof(sig))xattr_value; - if (sig->version != 2 || xattr_len <= sizeof(*sig)) + if (sig->version != 2 || xattr_len <= sizeof(*sig) + || sig->hash_algo >= HASH_ALGO__LAST) return ima_hash_algo; return sig->hash_algo; - break; case IMA_XATTR_DIGEST_NG: - ret = xattr_value->digest[0]; + /* first byte contains algorithm id */ + ret = xattr_value->data[0]; if (ret < HASH_ALGO__LAST) return ret; break; @@ -175,7 +209,7 @@ enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, /* this is for backward compatibility */ if (xattr_len == 21) { unsigned int zero = 0; - if (!memcmp(&xattr_value->digest[16], &zero, 4)) + if (!memcmp(&xattr_value->data[16], &zero, 4)) return HASH_ALGO_MD5; else return HASH_ALGO_SHA1; @@ -189,112 +223,127 @@ enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, } int ima_read_xattr(struct dentry *dentry, - struct evm_ima_xattr_data **xattr_value) + struct evm_ima_xattr_data **xattr_value, int xattr_len) { - ssize_t ret; + int ret; - ret = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value, - 0, GFP_NOFS); + ret = vfs_getxattr_alloc(&nop_mnt_idmap, dentry, XATTR_NAME_IMA, + (char **)xattr_value, xattr_len, GFP_NOFS); if (ret == -EOPNOTSUPP) ret = 0; return ret; } /* - * ima_appraise_measurement - appraise file measurement + * calc_file_id_hash - calculate the hash of the ima_file_id struct data + * @type: xattr type [enum evm_ima_xattr_type] + * @algo: hash algorithm [enum hash_algo] + * @digest: pointer to the digest to be hashed + * @hash: (out) pointer to the hash * - * Call evm_verifyxattr() to verify the integrity of 'security.ima'. - * Assuming success, compare the xattr hash with the collected measurement. + * IMA signature version 3 disambiguates the data that is signed by + * indirectly signing the hash of the ima_file_id structure data. * - * Return 0 on success, error code otherwise + * Signing the ima_file_id struct is currently only supported for + * IMA_VERITY_DIGSIG type xattrs. + * + * 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) +static int calc_file_id_hash(enum evm_ima_xattr_type type, + enum hash_algo algo, const u8 *digest, + struct ima_digest_data *hash) { - 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, hash_start = 0; + struct ima_file_id file_id = { + .hash_type = IMA_VERITY_DIGSIG, .hash_algorithm = algo}; + unsigned int unused = HASH_MAX_DIGESTSIZE - hash_digest_size[algo]; - if (!(inode->i_opflags & IOP_XATTR)) - return INTEGRITY_UNKNOWN; + if (type != IMA_VERITY_DIGSIG) + return -EINVAL; - if (rc <= 0) { - if (rc && rc != -ENODATA) - goto out; + memcpy(file_id.hash, digest, hash_digest_size[algo]); - 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; - } + hash->algo = algo; + hash->length = hash_digest_size[algo]; - 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. */ - 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); - } + return ima_calc_buffer_hash(&file_id, sizeof(file_id) - unused, hash); +} + +/* + * 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 ima_iint_cache *iint, + struct evm_ima_xattr_data *xattr_value, int xattr_len, + enum integrity_status *status, const char **cause) +{ + struct ima_max_digest_data hash; + struct signature_v2_hdr *sig; + int rc = -EINVAL, hash_start = 0; + int mask; switch (xattr_value->type) { case IMA_XATTR_DIGEST_NG: /* first byte contains algorithm id */ hash_start = 1; - /* fall through */ + fallthrough; case IMA_XATTR_DIGEST: - if (iint->flags & IMA_DIGSIG_REQUIRED) { - cause = "IMA-signature-required"; - status = INTEGRITY_FAIL; - break; + if (*status != INTEGRITY_PASS_IMMUTABLE) { + if (iint->flags & IMA_DIGSIG_REQUIRED) { + if (iint->flags & IMA_VERITY_REQUIRED) + *cause = "verity-signature-required"; + else + *cause = "IMA-signature-required"; + *status = INTEGRITY_FAIL; + break; + } + clear_bit(IMA_DIGSIG, &iint->atomic_flags); + } else { + set_bit(IMA_DIGSIG, &iint->atomic_flags); } - 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 + /* + * 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], + 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; + *cause = "invalid-hash"; + *status = INTEGRITY_FAIL; break; } - status = INTEGRITY_PASS; + *status = INTEGRITY_PASS; break; case EVM_IMA_XATTR_DIGSIG: set_bit(IMA_DIGSIG, &iint->atomic_flags); + + mask = IMA_DIGSIG_REQUIRED | IMA_VERITY_REQUIRED; + if ((iint->flags & mask) == mask) { + *cause = "verity-signature-required"; + *status = INTEGRITY_FAIL; + break; + } + + sig = (typeof(sig))xattr_value; + if (sig->version >= 3) { + *cause = "invalid-signature-version"; + *status = INTEGRITY_FAIL; + break; + } 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; + *status = INTEGRITY_UNKNOWN; break; } if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc && @@ -305,18 +354,232 @@ int ima_appraise_measurement(enum ima_hooks func, iint->ima_hash->digest, iint->ima_hash->length); if (rc) { - cause = "invalid-signature"; - status = INTEGRITY_FAIL; + *cause = "invalid-signature"; + *status = INTEGRITY_FAIL; } else { - status = INTEGRITY_PASS; + *status = INTEGRITY_PASS; + } + break; + case IMA_VERITY_DIGSIG: + set_bit(IMA_DIGSIG, &iint->atomic_flags); + + if (iint->flags & IMA_DIGSIG_REQUIRED) { + if (!(iint->flags & IMA_VERITY_REQUIRED)) { + *cause = "IMA-signature-required"; + *status = INTEGRITY_FAIL; + break; + } + } + + sig = (typeof(sig))xattr_value; + if (sig->version != 3) { + *cause = "invalid-signature-version"; + *status = INTEGRITY_FAIL; + break; + } + + rc = calc_file_id_hash(IMA_VERITY_DIGSIG, iint->ima_hash->algo, + iint->ima_hash->digest, + container_of(&hash.hdr, + struct ima_digest_data, hdr)); + if (rc) { + *cause = "sigv3-hashing-error"; + *status = INTEGRITY_FAIL; + break; } + + rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA, + (const char *)xattr_value, + xattr_len, hash.digest, + hash.hdr.length); + if (rc) { + *cause = "invalid-verity-signature"; + *status = INTEGRITY_FAIL; + } else { + *status = INTEGRITY_PASS; + } + break; default: - status = INTEGRITY_UNKNOWN; - cause = "unknown-ima-data"; + *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 ima_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); + } else if (iint->flags & IMA_DIGSIG_REQUIRED && iint->ima_hash) + rc = is_binary_blacklisted(iint->ima_hash->digest, iint->ima_hash->length); + + if ((rc == -EPERM) && (iint->flags & IMA_MEASURE)) + process_buffer_measurement(&nop_mnt_idmap, NULL, digest, digestsize, + "blacklisted-hash", NONE, + pcr, NULL, false, NULL, 0); + + return rc; +} + +static bool is_bprm_creds_for_exec(enum ima_hooks func, struct file *file) +{ + struct linux_binprm *bprm; + + if (func == BPRM_CHECK) { + bprm = container_of(&file, struct linux_binprm, file); + return bprm->is_check; + } + return false; +} + +/* + * 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 ima_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"; + int audit_msgno = AUDIT_INTEGRITY_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; + + /* + * Unlike any of the other LSM hooks where the kernel enforces file + * integrity, enforcing file integrity for the bprm_creds_for_exec() + * LSM hook with the AT_EXECVE_CHECK flag is left up to the discretion + * of the script interpreter(userspace). Differentiate kernel and + * userspace enforced integrity audit messages. + */ + if (is_bprm_creds_for_exec(func, file)) + audit_msgno = AUDIT_INTEGRITY_USERSPACE; + + /* If reading the xattr failed and there's no modsig, error out. */ + if (rc <= 0 && !try_modsig) { + if (rc && rc != -ENODATA) + goto out; + + if (iint->flags & IMA_DIGSIG_REQUIRED) { + if (iint->flags & IMA_VERITY_REQUIRED) + cause = "verity-signature-required"; + else + cause = "IMA-signature-required"; + } else { + cause = "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 < 0 ? 0 : rc); + 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_IMMUTABLE: + set_bit(IMA_DIGSIG, &iint->atomic_flags); + cause = "invalid-fail-immutable"; + 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. @@ -329,24 +592,27 @@ out: (iint->flags & IMA_FAIL_UNVERIFIABLE_SIGS))) { status = INTEGRITY_FAIL; cause = "unverifiable-signature"; - integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, + integrity_audit_msg(audit_msgno, 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) && + 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. */ + /* + * Permit new files with file/EVM portable signatures, but + * without data. + */ if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE && - xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG) { + test_bit(IMA_DIGSIG, &iint->atomic_flags)) { status = INTEGRITY_PASS; } - integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, + integrity_audit_msg(audit_msgno, inode, filename, op, cause, rc, 0); } else { ima_cache_flags(iint, func); @@ -359,7 +625,7 @@ out: /* * ima_update_xattr - update 'security.ima' hash value */ -void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file) +void ima_update_xattr(struct ima_iint_cache *iint, struct file *file) { struct dentry *dentry = file_dentry(file); int rc = 0; @@ -372,7 +638,7 @@ void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file) !(iint->flags & IMA_HASH)) return; - rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo); + rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo, NULL); if (rc < 0) return; @@ -383,27 +649,28 @@ void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file) /** * ima_inode_post_setattr - reflect file metadata changes + * @idmap: idmap of the mount the inode was found from * @dentry: pointer to the affected dentry + * @ia_valid: for the UID and GID status * * 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) +static void ima_inode_post_setattr(struct mnt_idmap *idmap, + struct dentry *dentry, int ia_valid) { struct inode *inode = d_backing_inode(dentry); - struct integrity_iint_cache *iint; + struct ima_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); + action = ima_must_appraise(idmap, inode, MAY_ACCESS, POST_SETATTR); + iint = ima_iint_find(inode); if (iint) { set_bit(IMA_CHANGE_ATTR, &iint->atomic_flags); if (!action) @@ -427,50 +694,167 @@ static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name, return 0; } +/* + * ima_reset_appraise_flags - reset ima_iint_cache flags + * + * @digsig: whether to clear/set IMA_DIGSIG flag, tristate values + * 0: clear IMA_DIGSIG + * 1: set IMA_DIGSIG + * -1: don't change IMA_DIGSIG + * + */ static void ima_reset_appraise_flags(struct inode *inode, int digsig) { - struct integrity_iint_cache *iint; + struct ima_iint_cache *iint; if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)) return; - iint = integrity_iint_find(inode); + iint = ima_iint_find(inode); if (!iint) return; iint->measured_pcrs = 0; set_bit(IMA_CHANGE_XATTR, &iint->atomic_flags); - if (digsig) + if (digsig == 1) set_bit(IMA_DIGSIG, &iint->atomic_flags); - else + else if (digsig == 0) 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) +/** + * validate_hash_algo() - Block setxattr with unsupported hash algorithms + * @dentry: object of the setxattr() + * @xattr_value: userland supplied xattr value + * @xattr_value_len: length of xattr_value + * + * The xattr value is mapped to its hash algorithm, and this algorithm + * must be built in the kernel for the setxattr to be allowed. + * + * Emit an audit message when the algorithm is invalid. + * + * Return: 0 on success, else an error. + */ +static int validate_hash_algo(struct dentry *dentry, + const struct evm_ima_xattr_data *xattr_value, + size_t xattr_value_len) +{ + char *path = NULL, *pathbuf = NULL; + enum hash_algo xattr_hash_algo; + const char *errmsg = "unavailable-hash-algorithm"; + unsigned int allowed_hashes; + + xattr_hash_algo = ima_get_hash_algo(xattr_value, xattr_value_len); + + allowed_hashes = atomic_read(&ima_setxattr_allowed_hash_algorithms); + + if (allowed_hashes) { + /* success if the algorithm is allowed in the ima policy */ + if (allowed_hashes & (1U << xattr_hash_algo)) + return 0; + + /* + * We use a different audit message when the hash algorithm + * is denied by a policy rule, instead of not being built + * in the kernel image + */ + errmsg = "denied-hash-algorithm"; + } else { + if (likely(xattr_hash_algo == ima_hash_algo)) + return 0; + + /* allow any xattr using an algorithm built in the kernel */ + if (crypto_has_alg(hash_algo_name[xattr_hash_algo], 0, 0)) + return 0; + } + + pathbuf = kmalloc(PATH_MAX, GFP_KERNEL); + if (!pathbuf) + return -EACCES; + + path = dentry_path(dentry, pathbuf, PATH_MAX); + + integrity_audit_msg(AUDIT_INTEGRITY_DATA, d_inode(dentry), path, + "set_data", errmsg, -EACCES, 0); + + kfree(pathbuf); + + return -EACCES; +} + +static int ima_inode_setxattr(struct mnt_idmap *idmap, struct dentry *dentry, + const char *xattr_name, const void *xattr_value, + size_t xattr_value_len, int flags) { const struct evm_ima_xattr_data *xvalue = xattr_value; + int digsig = 0; int result; + int err; 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; + + err = validate_hash_algo(dentry, xvalue, xattr_value_len); + if (err) + return err; + + digsig = (xvalue->type == EVM_IMA_XATTR_DIGSIG); + } else if (!strcmp(xattr_name, XATTR_NAME_EVM) && xattr_value_len > 0) { + digsig = (xvalue->type == EVM_XATTR_PORTABLE_DIGSIG); + } else { + digsig = -1; + } + if (result == 1 || evm_revalidate_status(xattr_name)) { + ima_reset_appraise_flags(d_backing_inode(dentry), digsig); + if (result == 1) + result = 0; } return result; } -int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name) +static int ima_inode_set_acl(struct mnt_idmap *idmap, struct dentry *dentry, + const char *acl_name, struct posix_acl *kacl) { - int result; + if (evm_revalidate_status(acl_name)) + ima_reset_appraise_flags(d_backing_inode(dentry), -1); + + return 0; +} + +static int ima_inode_removexattr(struct mnt_idmap *idmap, struct dentry *dentry, + const char *xattr_name) +{ + int result, digsig = -1; result = ima_protect_xattr(dentry, xattr_name, NULL, 0); - if (result == 1) { - ima_reset_appraise_flags(d_backing_inode(dentry), 0); - result = 0; + if (result == 1 || evm_revalidate_status(xattr_name)) { + if (!strcmp(xattr_name, XATTR_NAME_IMA)) + digsig = 0; + ima_reset_appraise_flags(d_backing_inode(dentry), digsig); + if (result == 1) + result = 0; } return result; } + +static int ima_inode_remove_acl(struct mnt_idmap *idmap, struct dentry *dentry, + const char *acl_name) +{ + return ima_inode_set_acl(idmap, dentry, acl_name, NULL); +} + +static struct security_hook_list ima_appraise_hooks[] __ro_after_init = { + LSM_HOOK_INIT(inode_post_setattr, ima_inode_post_setattr), + LSM_HOOK_INIT(inode_setxattr, ima_inode_setxattr), + LSM_HOOK_INIT(inode_set_acl, ima_inode_set_acl), + LSM_HOOK_INIT(inode_removexattr, ima_inode_removexattr), + LSM_HOOK_INIT(inode_remove_acl, ima_inode_remove_acl), +}; + +void __init init_ima_appraise_lsm(const struct lsm_id *lsmid) +{ + security_add_hooks(ima_appraise_hooks, ARRAY_SIZE(ima_appraise_hooks), + lsmid); +} |