diff options
Diffstat (limited to 'security/integrity/ima/ima_main.c')
| -rw-r--r-- | security/integrity/ima/ima_main.c | 1242 |
1 files changed, 1128 insertions, 114 deletions
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index e9508d5bbfcf..5770cf691912 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -1,4 +1,7 @@ +// SPDX-License-Identifier: GPL-2.0-only /* + * Integrity Measurement Architecture + * * Copyright (C) 2005,2006,2007,2008 IBM Corporation * * Authors: @@ -7,115 +10,206 @@ * Kylene Hall <kylene@us.ibm.com> * 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: ima_main.c * implements the IMA hooks: ima_bprm_check, ima_file_mmap, * and ima_file_check. */ + #include <linux/module.h> #include <linux/file.h> #include <linux/binfmts.h> +#include <linux/kernel_read_file.h> #include <linux/mount.h> #include <linux/mman.h> #include <linux/slab.h> #include <linux/xattr.h> #include <linux/ima.h> +#include <linux/fs.h> +#include <linux/iversion.h> +#include <linux/evm.h> +#include <linux/crash_dump.h> #include "ima.h" -int ima_initialized; - #ifdef CONFIG_IMA_APPRAISE int ima_appraise = IMA_APPRAISE_ENFORCE; #else int ima_appraise; #endif -char *ima_hash = "sha1"; +int __ro_after_init ima_hash_algo = HASH_ALGO_SHA1; +static int hash_setup_done; +static int ima_disabled __ro_after_init; + +static struct notifier_block ima_lsm_policy_notifier = { + .notifier_call = ima_lsm_policy_change, +}; + +static int __init ima_setup(char *str) +{ + if (!is_kdump_kernel()) { + pr_info("Warning: ima setup option only permitted in kdump"); + return 1; + } + + if (strncmp(str, "off", 3) == 0) + ima_disabled = 1; + else if (strncmp(str, "on", 2) == 0) + ima_disabled = 0; + else + pr_err("Invalid ima setup option: \"%s\" , please specify ima=on|off.", str); + + return 1; +} +__setup("ima=", ima_setup); + static int __init hash_setup(char *str) { - if (strncmp(str, "md5", 3) == 0) - ima_hash = "md5"; + struct ima_template_desc *template_desc = ima_template_desc_current(); + int i; + + if (hash_setup_done) + return 1; + + if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) { + if (strncmp(str, "sha1", 4) == 0) { + ima_hash_algo = HASH_ALGO_SHA1; + } else if (strncmp(str, "md5", 3) == 0) { + ima_hash_algo = HASH_ALGO_MD5; + } else { + pr_err("invalid hash algorithm \"%s\" for template \"%s\"", + str, IMA_TEMPLATE_IMA_NAME); + return 1; + } + goto out; + } + + i = match_string(hash_algo_name, HASH_ALGO__LAST, str); + if (i < 0) { + pr_err("invalid hash algorithm \"%s\"", str); + return 1; + } + + ima_hash_algo = i; +out: + hash_setup_done = 1; return 1; } __setup("ima_hash=", hash_setup); +enum hash_algo ima_get_current_hash_algo(void) +{ + return ima_hash_algo; +} + +/* Prevent mmap'ing a file execute that is already mmap'ed write */ +static int mmap_violation_check(enum ima_hooks func, struct file *file, + char **pathbuf, const char **pathname, + char *filename) +{ + struct inode *inode; + int rc = 0; + + if ((func == MMAP_CHECK || func == MMAP_CHECK_REQPROT) && + mapping_writably_mapped(file->f_mapping)) { + rc = -ETXTBSY; + inode = file_inode(file); + + if (!*pathbuf) /* ima_rdwr_violation possibly pre-fetched */ + *pathname = ima_d_path(&file->f_path, pathbuf, + filename); + integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, *pathname, + "mmap_file", "mmapped_writers", rc, 0); + } + return rc; +} + /* * ima_rdwr_violation_check * * Only invalidate the PCR for measured files: - * - Opening a file for write when already open for read, + * - Opening a file for write when already open for read, * results in a time of measure, time of use (ToMToU) error. * - Opening a file for read when already open for write, - * could result in a file measurement error. + * could result in a file measurement error. * */ -static void ima_rdwr_violation_check(struct file *file) +static void ima_rdwr_violation_check(struct file *file, + struct ima_iint_cache *iint, + int must_measure, + char **pathbuf, + const char **pathname, + char *filename) { - struct dentry *dentry = file->f_path.dentry; struct inode *inode = file_inode(file); fmode_t mode = file->f_mode; - int must_measure; bool send_tomtou = false, send_writers = false; - char *pathbuf = NULL; - const char *pathname; - - if (!S_ISREG(inode->i_mode) || !ima_initialized) - return; - - mutex_lock(&inode->i_mutex); /* file metadata: permissions, xattr */ if (mode & FMODE_WRITE) { - if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) - send_tomtou = true; - goto out; - } + if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) { + if (!iint) + iint = ima_iint_find(inode); - must_measure = ima_must_measure(inode, MAY_READ, FILE_CHECK); - if (!must_measure) - goto out; + /* IMA_MEASURE is set from reader side */ + if (iint && test_and_clear_bit(IMA_MAY_EMIT_TOMTOU, + &iint->atomic_flags)) + send_tomtou = true; + } + } else { + if (must_measure) + set_bit(IMA_MAY_EMIT_TOMTOU, &iint->atomic_flags); - if (atomic_read(&inode->i_writecount) > 0) - send_writers = true; -out: - mutex_unlock(&inode->i_mutex); + /* Limit number of open_writers violations */ + if (inode_is_open_for_write(inode) && must_measure) { + if (!test_and_set_bit(IMA_EMITTED_OPENWRITERS, + &iint->atomic_flags)) + send_writers = true; + } + } if (!send_tomtou && !send_writers) return; - pathname = ima_d_path(&file->f_path, &pathbuf); - if (!pathname || strlen(pathname) > IMA_EVENT_NAME_LEN_MAX) - pathname = dentry->d_name.name; + *pathname = ima_d_path(&file->f_path, pathbuf, filename); if (send_tomtou) - ima_add_violation(inode, pathname, + ima_add_violation(file, *pathname, iint, "invalid_pcr", "ToMToU"); if (send_writers) - ima_add_violation(inode, pathname, + ima_add_violation(file, *pathname, iint, "invalid_pcr", "open_writers"); - kfree(pathbuf); } -static void ima_check_last_writer(struct integrity_iint_cache *iint, +static void ima_check_last_writer(struct ima_iint_cache *iint, struct inode *inode, struct file *file) { fmode_t mode = file->f_mode; + bool update; if (!(mode & FMODE_WRITE)) return; - mutex_lock(&inode->i_mutex); - if (atomic_read(&inode->i_writecount) == 1 && - iint->version != inode->i_version) { - iint->flags &= ~IMA_DONE_MASK; - if (iint->flags & IMA_APPRAISE) - ima_update_xattr(iint, file); + mutex_lock(&iint->mutex); + if (atomic_read(&inode->i_writecount) == 1) { + struct kstat stat; + + clear_bit(IMA_EMITTED_OPENWRITERS, &iint->atomic_flags); + + update = test_and_clear_bit(IMA_UPDATE_XATTR, + &iint->atomic_flags); + if ((iint->flags & IMA_NEW_FILE) || + vfs_getattr_nosec(&file->f_path, &stat, + STATX_CHANGE_COOKIE, + AT_STATX_SYNC_AS_STAT) || + !(stat.result_mask & STATX_CHANGE_COOKIE) || + stat.change_cookie != iint->real_inode.version) { + iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE); + iint->measured_pcrs = 0; + if (update) + ima_update_xattr(iint, file); + } } - mutex_unlock(&inode->i_mutex); + mutex_unlock(&iint->mutex); } /** @@ -124,96 +218,261 @@ static void ima_check_last_writer(struct integrity_iint_cache *iint, * * Flag files that changed, based on i_version */ -void ima_file_free(struct file *file) +static void ima_file_free(struct file *file) { struct inode *inode = file_inode(file); - struct integrity_iint_cache *iint; + struct ima_iint_cache *iint; - if (!iint_initialized || !S_ISREG(inode->i_mode)) + if (!ima_policy_flag || !S_ISREG(inode->i_mode)) return; - iint = integrity_iint_find(inode); + iint = ima_iint_find(inode); if (!iint) return; ima_check_last_writer(iint, inode, file); } -static int process_measurement(struct file *file, const char *filename, - int mask, int function) +static int process_measurement(struct file *file, const struct cred *cred, + struct lsm_prop *prop, char *buf, loff_t size, + int mask, enum ima_hooks func, + enum kernel_read_file_id read_id) { - struct inode *inode = file_inode(file); - struct integrity_iint_cache *iint; + struct inode *real_inode, *inode = file_inode(file); + struct ima_iint_cache *iint = NULL; + struct ima_template_desc *template_desc = NULL; + struct inode *metadata_inode; char *pathbuf = NULL; + char filename[NAME_MAX]; const char *pathname = NULL; - int rc = -ENOMEM, action, must_appraise, _func; + int rc = 0, action, must_appraise = 0; + int pcr = CONFIG_IMA_MEASURE_PCR_IDX; + struct evm_ima_xattr_data *xattr_value = NULL; + struct modsig *modsig = NULL; + int xattr_len = 0; + bool violation_check; + enum hash_algo hash_algo; + unsigned int allowed_algos = 0; - if (!ima_initialized || !S_ISREG(inode->i_mode)) + if (!ima_policy_flag || !S_ISREG(inode->i_mode)) return 0; /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action * bitmask based on the appraise/audit/measurement policy. * Included is the appraise submask. */ - action = ima_get_action(inode, mask, function); - if (!action) + action = ima_get_action(file_mnt_idmap(file), inode, cred, prop, + mask, func, &pcr, &template_desc, NULL, + &allowed_algos); + violation_check = ((func == FILE_CHECK || func == MMAP_CHECK || + func == MMAP_CHECK_REQPROT) && + (ima_policy_flag & IMA_MEASURE) && + ((action & IMA_MEASURE) || + (file->f_mode & FMODE_WRITE))); + if (!action && !violation_check) return 0; must_appraise = action & IMA_APPRAISE; /* Is the appraise rule hook specific? */ - _func = (action & IMA_FILE_APPRAISE) ? FILE_CHECK : function; + if (action & IMA_FILE_APPRAISE) + func = FILE_CHECK; - mutex_lock(&inode->i_mutex); + inode_lock(inode); - iint = integrity_inode_get(inode); - if (!iint) + if (action) { + iint = ima_inode_get(inode); + if (!iint) + rc = -ENOMEM; + } + + if (!rc && violation_check) + ima_rdwr_violation_check(file, iint, action & IMA_MEASURE, + &pathbuf, &pathname, filename); + + inode_unlock(inode); + + if (rc) + goto out; + if (!action) goto out; + mutex_lock(&iint->mutex); + + if (test_and_clear_bit(IMA_CHANGE_ATTR, &iint->atomic_flags)) + /* + * Reset appraisal flags (action and non-action rule-specific) + * if ima_inode_post_setattr was called. + */ + iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED | + IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK | + IMA_NONACTION_RULE_FLAGS); + + /* + * Re-evaulate the file if either the xattr has changed or the + * kernel has no way of detecting file change on the filesystem. + * (Limited to privileged mounted filesystems.) + */ + if (test_and_clear_bit(IMA_CHANGE_XATTR, &iint->atomic_flags) || + ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) && + !(inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) && + !(action & IMA_FAIL_UNVERIFIABLE_SIGS))) { + iint->flags &= ~IMA_DONE_MASK; + iint->measured_pcrs = 0; + } + + /* + * On stacked filesystems, detect and re-evaluate file data and + * metadata changes. + */ + real_inode = d_real_inode(file_dentry(file)); + if (real_inode != inode && + (action & IMA_DO_MASK) && (iint->flags & IMA_DONE_MASK)) { + if (!IS_I_VERSION(real_inode) || + integrity_inode_attrs_changed(&iint->real_inode, + real_inode)) { + iint->flags &= ~IMA_DONE_MASK; + iint->measured_pcrs = 0; + } + + /* + * Reset the EVM status when metadata changed. + */ + metadata_inode = d_inode(d_real(file_dentry(file), + D_REAL_METADATA)); + if (evm_metadata_changed(inode, metadata_inode)) + iint->flags &= ~(IMA_APPRAISED | + IMA_APPRAISED_SUBMASK); + } + /* Determine if already appraised/measured based on bitmask * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED, * IMA_AUDIT, IMA_AUDITED) */ iint->flags |= action; action &= IMA_DO_MASK; - action &= ~((iint->flags & IMA_DONE_MASK) >> 1); + action &= ~((iint->flags & (IMA_DONE_MASK ^ IMA_MEASURED)) >> 1); + + /* If target pcr is already measured, unset IMA_MEASURE action */ + if ((action & IMA_MEASURE) && (iint->measured_pcrs & (0x1 << pcr))) + action ^= IMA_MEASURE; + + /* HASH sets the digital signature and update flags, nothing else */ + if ((action & IMA_HASH) && + !(test_bit(IMA_DIGSIG, &iint->atomic_flags))) { + xattr_len = ima_read_xattr(file_dentry(file), + &xattr_value, xattr_len); + if ((xattr_value && xattr_len > 2) && + (xattr_value->type == EVM_IMA_XATTR_DIGSIG)) + set_bit(IMA_DIGSIG, &iint->atomic_flags); + iint->flags |= IMA_HASHED; + action ^= IMA_HASH; + set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags); + } /* Nothing to do, just return existing appraised status */ if (!action) { - if (must_appraise) - rc = ima_get_cache_status(iint, _func); - goto out_digsig; + if (must_appraise) { + rc = mmap_violation_check(func, file, &pathbuf, + &pathname, filename); + if (!rc) + rc = ima_get_cache_status(iint, func); + } + goto out_locked; + } + + if ((action & IMA_APPRAISE_SUBMASK) || + strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0) { + /* read 'security.ima' */ + xattr_len = ima_read_xattr(file_dentry(file), + &xattr_value, xattr_len); + + /* + * Read the appended modsig if allowed by the policy, and allow + * an additional measurement list entry, if needed, based on the + * template format and whether the file was already measured. + */ + if (iint->flags & IMA_MODSIG_ALLOWED) { + rc = ima_read_modsig(func, buf, size, &modsig); + + if (!rc && ima_template_has_modsig(template_desc) && + iint->flags & IMA_MEASURED) + action |= IMA_MEASURE; + } } - rc = ima_collect_measurement(iint, file); - if (rc != 0) - goto out_digsig; + hash_algo = ima_get_hash_algo(xattr_value, xattr_len); - pathname = !filename ? ima_d_path(&file->f_path, &pathbuf) : filename; - if (!pathname) - pathname = (const char *)file->f_dentry->d_name.name; + rc = ima_collect_measurement(iint, file, buf, size, hash_algo, modsig); + if (rc != 0 && rc != -EBADF && rc != -EINVAL) + goto out_locked; + + /* Defer measuring/appraising kernel modules to READING_MODULE */ + if (read_id == READING_MODULE_COMPRESSED) { + must_appraise = 0; + goto out_locked; + } + + if (!pathbuf) /* ima_rdwr_violation possibly pre-fetched */ + pathname = ima_d_path(&file->f_path, &pathbuf, filename); if (action & IMA_MEASURE) - ima_store_measurement(iint, file, pathname); - if (action & IMA_APPRAISE_SUBMASK) - rc = ima_appraise_measurement(_func, iint, file, pathname); + ima_store_measurement(iint, file, pathname, + xattr_value, xattr_len, modsig, pcr, + template_desc); + if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) { + rc = ima_check_blacklist(iint, modsig, pcr); + if (rc != -EPERM) { + inode_lock(inode); + rc = ima_appraise_measurement(func, iint, file, + pathname, xattr_value, + xattr_len, modsig); + inode_unlock(inode); + } + if (!rc) + rc = mmap_violation_check(func, file, &pathbuf, + &pathname, filename); + } if (action & IMA_AUDIT) ima_audit_measurement(iint, pathname); - kfree(pathbuf); -out_digsig: - if ((mask & MAY_WRITE) && (iint->flags & IMA_DIGSIG)) + + if ((file->f_flags & O_DIRECT) && (iint->flags & IMA_PERMIT_DIRECTIO)) + rc = 0; + + /* Ensure the digest was generated using an allowed algorithm */ + if (rc == 0 && must_appraise && allowed_algos != 0 && + (allowed_algos & (1U << hash_algo)) == 0) { rc = -EACCES; + + integrity_audit_msg(AUDIT_INTEGRITY_DATA, file_inode(file), + pathname, "collect_data", + "denied-hash-algorithm", rc, 0); + } +out_locked: + if ((mask & MAY_WRITE) && test_bit(IMA_DIGSIG, &iint->atomic_flags) && + !(iint->flags & IMA_NEW_FILE)) + rc = -EACCES; + mutex_unlock(&iint->mutex); + kfree(xattr_value); + ima_free_modsig(modsig); out: - mutex_unlock(&inode->i_mutex); - if ((rc && must_appraise) && (ima_appraise & IMA_APPRAISE_ENFORCE)) - return -EACCES; + if (pathbuf) + __putname(pathbuf); + if (must_appraise) { + if (rc && (ima_appraise & IMA_APPRAISE_ENFORCE)) + return -EACCES; + if (file->f_mode & FMODE_WRITE) + set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags); + } return 0; } /** * ima_file_mmap - based on policy, collect/store measurement. * @file: pointer to the file to be measured (May be NULL) - * @prot: contains the protection that will be applied by the kernel. + * @reqprot: protection requested by the application + * @prot: protection that will be applied by the kernel + * @flags: operational flags * * Measure files being mmapped executable based on the ima_must_measure() * policy decision. @@ -221,14 +480,92 @@ out: * On success return 0. On integrity appraisal error, assuming the file * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. */ -int ima_file_mmap(struct file *file, unsigned long prot) +static int ima_file_mmap(struct file *file, unsigned long reqprot, + unsigned long prot, unsigned long flags) { - if (file && (prot & PROT_EXEC)) - return process_measurement(file, NULL, MAY_EXEC, MMAP_CHECK); + struct lsm_prop prop; + int ret; + + if (!file) + return 0; + + security_current_getlsmprop_subj(&prop); + + if (reqprot & PROT_EXEC) { + ret = process_measurement(file, current_cred(), &prop, NULL, + 0, MAY_EXEC, MMAP_CHECK_REQPROT, 0); + if (ret) + return ret; + } + + if (prot & PROT_EXEC) + return process_measurement(file, current_cred(), &prop, NULL, + 0, MAY_EXEC, MMAP_CHECK, 0); + return 0; } /** + * ima_file_mprotect - based on policy, limit mprotect change + * @vma: vm_area_struct protection is set to + * @reqprot: protection requested by the application + * @prot: protection that will be applied by the kernel + * + * Files can be mmap'ed read/write and later changed to execute to circumvent + * IMA's mmap appraisal policy rules. Due to locking issues (mmap semaphore + * would be taken before i_mutex), files can not be measured or appraised at + * this point. Eliminate this integrity gap by denying the mprotect + * PROT_EXECUTE change, if an mmap appraise policy rule exists. + * + * On mprotect change success, return 0. On failure, return -EACESS. + */ +static int ima_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot, + unsigned long prot) +{ + struct ima_template_desc *template = NULL; + struct file *file; + char filename[NAME_MAX]; + char *pathbuf = NULL; + const char *pathname = NULL; + struct inode *inode; + struct lsm_prop prop; + int result = 0; + int action; + int pcr; + + /* Is mprotect making an mmap'ed file executable? */ + if (!(ima_policy_flag & IMA_APPRAISE) || !vma->vm_file || + !(prot & PROT_EXEC) || (vma->vm_flags & VM_EXEC)) + return 0; + + security_current_getlsmprop_subj(&prop); + inode = file_inode(vma->vm_file); + action = ima_get_action(file_mnt_idmap(vma->vm_file), inode, + current_cred(), &prop, MAY_EXEC, MMAP_CHECK, + &pcr, &template, NULL, NULL); + action |= ima_get_action(file_mnt_idmap(vma->vm_file), inode, + current_cred(), &prop, MAY_EXEC, + MMAP_CHECK_REQPROT, &pcr, &template, NULL, + NULL); + + /* Is the mmap'ed file in policy? */ + if (!(action & (IMA_MEASURE | IMA_APPRAISE_SUBMASK))) + return 0; + + if (action & IMA_APPRAISE_SUBMASK) + result = -EPERM; + + file = vma->vm_file; + pathname = ima_d_path(&file->f_path, &pathbuf, filename); + integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, pathname, + "collect_data", "failed-mprotect", result, 0); + if (pathbuf) + __putname(pathbuf); + + return result; +} + +/** * ima_bprm_check - based on policy, collect/store measurement. * @bprm: contains the linux_binprm structure * @@ -241,66 +578,743 @@ int ima_file_mmap(struct file *file, unsigned long prot) * On success return 0. On integrity appraisal error, assuming the file * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. */ -int ima_bprm_check(struct linux_binprm *bprm) +static int ima_bprm_check(struct linux_binprm *bprm) +{ + struct lsm_prop prop; + + security_current_getlsmprop_subj(&prop); + return process_measurement(bprm->file, current_cred(), + &prop, NULL, 0, MAY_EXEC, BPRM_CHECK, 0); +} + +/** + * ima_creds_check - based on policy, collect/store measurement. + * @bprm: contains the linux_binprm structure + * @file: contains the file descriptor of the binary being executed + * + * The OS protects against an executable file, already open for write, + * from being executed in deny_write_access() and an executable file, + * already open for execute, from being modified in get_write_access(). + * So we can be certain that what we verify and measure here is actually + * what is being executed. + * + * The difference from ima_bprm_check() is that ima_creds_check() is invoked + * only after determining the final binary to be executed without interpreter, + * and not when searching for intermediate binaries. The reason is that since + * commit 56305aa9b6fab ("exec: Compute file based creds only once"), the + * credentials to be applied to the process are calculated only at that stage + * (bprm_creds_from_file security hook instead of bprm_check_security). + * + * On success return 0. On integrity appraisal error, assuming the file + * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. + */ +static int ima_creds_check(struct linux_binprm *bprm, const struct file *file) { - return process_measurement(bprm->file, - (strcmp(bprm->filename, bprm->interp) == 0) ? - bprm->filename : bprm->interp, - MAY_EXEC, BPRM_CHECK); + struct lsm_prop prop; + + security_current_getlsmprop_subj(&prop); + return process_measurement((struct file *)file, bprm->cred, &prop, NULL, + 0, MAY_EXEC, CREDS_CHECK, 0); } /** - * ima_path_check - based on policy, collect/store measurement. + * ima_bprm_creds_for_exec - collect/store/appraise measurement. + * @bprm: contains the linux_binprm structure + * + * Based on the IMA policy and the execveat(2) AT_EXECVE_CHECK flag, measure + * and appraise the integrity of a file to be executed by script interpreters. + * Unlike any of the other LSM hooks where the kernel enforces file integrity, + * enforcing file integrity is left up to the discretion of the script + * interpreter (userspace). + * + * On success return 0. On integrity appraisal error, assuming the file + * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. + */ +static int ima_bprm_creds_for_exec(struct linux_binprm *bprm) +{ + /* + * As security_bprm_check() is called multiple times, both + * the script and the shebang interpreter are measured, appraised, + * and audited. Limit usage of this LSM hook to just measuring, + * appraising, and auditing the indirect script execution + * (e.g. ./sh example.sh). + */ + if (!bprm->is_check) + return 0; + + return ima_bprm_check(bprm); +} + +/** + * ima_file_check - based on policy, collect/store measurement. * @file: pointer to the file to be measured - * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE + * @mask: contains MAY_READ, MAY_WRITE, MAY_EXEC or MAY_APPEND * * Measure files based on the ima_must_measure() policy decision. * * On success return 0. On integrity appraisal error, assuming the file * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. */ -int ima_file_check(struct file *file, int mask) +static int ima_file_check(struct file *file, int mask) +{ + struct lsm_prop prop; + + security_current_getlsmprop_subj(&prop); + return process_measurement(file, current_cred(), &prop, NULL, 0, + mask & (MAY_READ | MAY_WRITE | MAY_EXEC | + MAY_APPEND), FILE_CHECK, 0); +} + +static int __ima_inode_hash(struct inode *inode, struct file *file, char *buf, + size_t buf_size) +{ + struct ima_iint_cache *iint = NULL, tmp_iint; + int rc, hash_algo; + + if (ima_policy_flag) { + iint = ima_iint_find(inode); + if (iint) + mutex_lock(&iint->mutex); + } + + if ((!iint || !(iint->flags & IMA_COLLECTED)) && file) { + if (iint) + mutex_unlock(&iint->mutex); + + memset(&tmp_iint, 0, sizeof(tmp_iint)); + mutex_init(&tmp_iint.mutex); + + rc = ima_collect_measurement(&tmp_iint, file, NULL, 0, + ima_hash_algo, NULL); + if (rc < 0) { + /* ima_hash could be allocated in case of failure. */ + if (rc != -ENOMEM) + kfree(tmp_iint.ima_hash); + + return -EOPNOTSUPP; + } + + iint = &tmp_iint; + mutex_lock(&iint->mutex); + } + + if (!iint) + return -EOPNOTSUPP; + + /* + * ima_file_hash can be called when ima_collect_measurement has still + * not been called, we might not always have a hash. + */ + if (!iint->ima_hash || !(iint->flags & IMA_COLLECTED)) { + mutex_unlock(&iint->mutex); + return -EOPNOTSUPP; + } + + if (buf) { + size_t copied_size; + + copied_size = min_t(size_t, iint->ima_hash->length, buf_size); + memcpy(buf, iint->ima_hash->digest, copied_size); + } + hash_algo = iint->ima_hash->algo; + mutex_unlock(&iint->mutex); + + if (iint == &tmp_iint) + kfree(iint->ima_hash); + + return hash_algo; +} + +/** + * ima_file_hash - return a measurement of the file + * @file: pointer to the file + * @buf: buffer in which to store the hash + * @buf_size: length of the buffer + * + * On success, return the hash algorithm (as defined in the enum hash_algo). + * If buf is not NULL, this function also outputs the hash into buf. + * If the hash is larger than buf_size, then only buf_size bytes will be copied. + * It generally just makes sense to pass a buffer capable of holding the largest + * possible hash: IMA_MAX_DIGEST_SIZE. + * The file hash returned is based on the entire file, including the appended + * signature. + * + * If the measurement cannot be performed, return -EOPNOTSUPP. + * If the parameters are incorrect, return -EINVAL. + */ +int ima_file_hash(struct file *file, char *buf, size_t buf_size) +{ + if (!file) + return -EINVAL; + + return __ima_inode_hash(file_inode(file), file, buf, buf_size); +} +EXPORT_SYMBOL_GPL(ima_file_hash); + +/** + * ima_inode_hash - return the stored measurement if the inode has been hashed + * and is in the iint cache. + * @inode: pointer to the inode + * @buf: buffer in which to store the hash + * @buf_size: length of the buffer + * + * On success, return the hash algorithm (as defined in the enum hash_algo). + * If buf is not NULL, this function also outputs the hash into buf. + * If the hash is larger than buf_size, then only buf_size bytes will be copied. + * It generally just makes sense to pass a buffer capable of holding the largest + * possible hash: IMA_MAX_DIGEST_SIZE. + * The hash returned is based on the entire contents, including the appended + * signature. + * + * If IMA is disabled or if no measurement is available, return -EOPNOTSUPP. + * If the parameters are incorrect, return -EINVAL. + */ +int ima_inode_hash(struct inode *inode, char *buf, size_t buf_size) +{ + if (!inode) + return -EINVAL; + + return __ima_inode_hash(inode, NULL, buf, buf_size); +} +EXPORT_SYMBOL_GPL(ima_inode_hash); + +/** + * ima_post_create_tmpfile - mark newly created tmpfile as new + * @idmap: idmap of the mount the inode was found from + * @inode: inode of the newly created tmpfile + * + * No measuring, appraising or auditing of newly created tmpfiles is needed. + * Skip calling process_measurement(), but indicate which newly, created + * tmpfiles are in policy. + */ +static void ima_post_create_tmpfile(struct mnt_idmap *idmap, + struct inode *inode) + +{ + struct ima_iint_cache *iint; + int must_appraise; + + if (!ima_policy_flag || !S_ISREG(inode->i_mode)) + return; + + must_appraise = ima_must_appraise(idmap, inode, MAY_ACCESS, + FILE_CHECK); + if (!must_appraise) + return; + + /* Nothing to do if we can't allocate memory */ + iint = ima_inode_get(inode); + if (!iint) + return; + + /* needed for writing the security xattrs */ + set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags); + iint->ima_file_status = INTEGRITY_PASS; +} + +/** + * ima_post_path_mknod - mark as a new inode + * @idmap: idmap of the mount the inode was found from + * @dentry: newly created dentry + * + * Mark files created via the mknodat syscall as new, so that the + * file data can be written later. + */ +static void ima_post_path_mknod(struct mnt_idmap *idmap, struct dentry *dentry) +{ + struct ima_iint_cache *iint; + struct inode *inode = dentry->d_inode; + int must_appraise; + + if (!ima_policy_flag || !S_ISREG(inode->i_mode)) + return; + + must_appraise = ima_must_appraise(idmap, inode, MAY_ACCESS, + FILE_CHECK); + if (!must_appraise) + return; + + /* Nothing to do if we can't allocate memory */ + iint = ima_inode_get(inode); + if (!iint) + return; + + /* needed for re-opening empty files */ + iint->flags |= IMA_NEW_FILE; +} + +/** + * ima_read_file - pre-measure/appraise hook decision based on policy + * @file: pointer to the file to be measured/appraised/audit + * @read_id: caller identifier + * @contents: whether a subsequent call will be made to ima_post_read_file() + * + * Permit reading a file based on policy. The policy rules are written + * in terms of the policy identifier. Appraising the integrity of + * a file requires a file descriptor. + * + * For permission return 0, otherwise return -EACCES. + */ +static int ima_read_file(struct file *file, enum kernel_read_file_id read_id, + bool contents) { - ima_rdwr_violation_check(file); - return process_measurement(file, NULL, - mask & (MAY_READ | MAY_WRITE | MAY_EXEC), - FILE_CHECK); + enum ima_hooks func; + struct lsm_prop prop; + + /* + * Do devices using pre-allocated memory run the risk of the + * firmware being accessible to the device prior to the completion + * of IMA's signature verification any more than when using two + * buffers? It may be desirable to include the buffer address + * in this API and walk all the dma_map_single() mappings to check. + */ + + /* + * There will be a call made to ima_post_read_file() with + * a filled buffer, so we don't need to perform an extra + * read early here. + */ + if (contents) + return 0; + + /* Read entire file for all partial reads. */ + func = read_idmap[read_id] ?: FILE_CHECK; + security_current_getlsmprop_subj(&prop); + return process_measurement(file, current_cred(), &prop, NULL, 0, + MAY_READ, func, 0); } -EXPORT_SYMBOL_GPL(ima_file_check); + +const int read_idmap[READING_MAX_ID] = { + [READING_FIRMWARE] = FIRMWARE_CHECK, + [READING_MODULE] = MODULE_CHECK, + [READING_MODULE_COMPRESSED] = MODULE_CHECK, + [READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK, + [READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK, + [READING_POLICY] = POLICY_CHECK +}; /** - * ima_module_check - based on policy, collect/store/appraise measurement. - * @file: pointer to the file to be measured/appraised + * ima_post_read_file - in memory collect/appraise/audit measurement + * @file: pointer to the file to be measured/appraised/audit + * @buf: pointer to in memory file contents + * @size: size of in memory file contents + * @read_id: caller identifier * - * Measure/appraise kernel modules based on policy. + * Measure/appraise/audit in memory file based on policy. Policy rules + * are written in terms of a policy identifier. * * On success return 0. On integrity appraisal error, assuming the file * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. */ -int ima_module_check(struct file *file) +static int ima_post_read_file(struct file *file, char *buf, loff_t size, + enum kernel_read_file_id read_id) { - if (!file) { -#ifndef CONFIG_MODULE_SIG_FORCE - if ((ima_appraise & IMA_APPRAISE_MODULES) && - (ima_appraise & IMA_APPRAISE_ENFORCE)) + enum ima_hooks func; + struct lsm_prop prop; + + /* permit signed certs */ + if (!file && read_id == READING_X509_CERTIFICATE) + return 0; + + if (!file || !buf || size == 0) { /* should never happen */ + if (ima_appraise & IMA_APPRAISE_ENFORCE) + return -EACCES; + return 0; + } + + func = read_idmap[read_id] ?: FILE_CHECK; + security_current_getlsmprop_subj(&prop); + return process_measurement(file, current_cred(), &prop, buf, size, + MAY_READ, func, read_id); +} + +/** + * ima_load_data - appraise decision based on policy + * @id: kernel load data caller identifier + * @contents: whether the full contents will be available in a later + * call to ima_post_load_data(). + * + * Callers of this LSM hook can not measure, appraise, or audit the + * data provided by userspace. Enforce policy rules requiring a file + * signature (eg. kexec'ed kernel image). + * + * For permission return 0, otherwise return -EACCES. + */ +static int ima_load_data(enum kernel_load_data_id id, bool contents) +{ + bool ima_enforce, sig_enforce; + + ima_enforce = + (ima_appraise & IMA_APPRAISE_ENFORCE) == IMA_APPRAISE_ENFORCE; + + switch (id) { + case LOADING_KEXEC_IMAGE: + if (IS_ENABLED(CONFIG_KEXEC_SIG) + && arch_ima_get_secureboot()) { + pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n"); + return -EACCES; + } + + if (ima_enforce && (ima_appraise & IMA_APPRAISE_KEXEC)) { + pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n"); return -EACCES; /* INTEGRITY_UNKNOWN */ -#endif - return 0; /* We rely on module signature checking */ + } + break; + case LOADING_FIRMWARE: + if (ima_enforce && (ima_appraise & IMA_APPRAISE_FIRMWARE) && !contents) { + pr_err("Prevent firmware sysfs fallback loading.\n"); + return -EACCES; /* INTEGRITY_UNKNOWN */ + } + break; + case LOADING_MODULE: + sig_enforce = is_module_sig_enforced(); + + if (ima_enforce && (!sig_enforce + && (ima_appraise & IMA_APPRAISE_MODULES))) { + pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n"); + return -EACCES; /* INTEGRITY_UNKNOWN */ + } + break; + default: + break; } - return process_measurement(file, NULL, MAY_EXEC, MODULE_CHECK); + return 0; } +/** + * ima_post_load_data - appraise decision based on policy + * @buf: pointer to in memory file contents + * @size: size of in memory file contents + * @load_id: kernel load data caller identifier + * @description: @load_id-specific description of contents + * + * Measure/appraise/audit in memory buffer based on policy. Policy rules + * are written in terms of a policy identifier. + * + * On success return 0. On integrity appraisal error, assuming the file + * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. + */ +static int ima_post_load_data(char *buf, loff_t size, + enum kernel_load_data_id load_id, + char *description) +{ + if (load_id == LOADING_FIRMWARE) { + if ((ima_appraise & IMA_APPRAISE_FIRMWARE) && + (ima_appraise & IMA_APPRAISE_ENFORCE)) { + pr_err("Prevent firmware loading_store.\n"); + return -EACCES; /* INTEGRITY_UNKNOWN */ + } + return 0; + } + + /* + * Measure the init_module syscall buffer containing the ELF image. + */ + if (load_id == LOADING_MODULE) + ima_measure_critical_data("modules", "init_module", + buf, size, true, NULL, 0); + + return 0; +} + +/** + * process_buffer_measurement - Measure the buffer or the buffer data hash + * @idmap: idmap of the mount the inode was found from + * @inode: inode associated with the object being measured (NULL for KEY_CHECK) + * @buf: pointer to the buffer that needs to be added to the log. + * @size: size of buffer(in bytes). + * @eventname: event name to be used for the buffer entry. + * @func: IMA hook + * @pcr: pcr to extend the measurement + * @func_data: func specific data, may be NULL + * @buf_hash: measure buffer data hash + * @digest: buffer digest will be written to + * @digest_len: buffer length + * + * Based on policy, either the buffer data or buffer data hash is measured + * + * Return: 0 if the buffer has been successfully measured, 1 if the digest + * has been written to the passed location but not added to a measurement entry, + * a negative value otherwise. + */ +int process_buffer_measurement(struct mnt_idmap *idmap, + struct inode *inode, const void *buf, int size, + const char *eventname, enum ima_hooks func, + int pcr, const char *func_data, + bool buf_hash, u8 *digest, size_t digest_len) +{ + int ret = 0; + const char *audit_cause = "ENOMEM"; + struct ima_template_entry *entry = NULL; + struct ima_iint_cache iint = {}; + struct ima_event_data event_data = {.iint = &iint, + .filename = eventname, + .buf = buf, + .buf_len = size}; + struct ima_template_desc *template; + struct ima_max_digest_data hash; + struct ima_digest_data *hash_hdr = container_of(&hash.hdr, + struct ima_digest_data, hdr); + char digest_hash[IMA_MAX_DIGEST_SIZE]; + int digest_hash_len = hash_digest_size[ima_hash_algo]; + int violation = 0; + int action = 0; + struct lsm_prop prop; + + if (digest && digest_len < digest_hash_len) + return -EINVAL; + + if (!ima_policy_flag && !digest) + return -ENOENT; + + template = ima_template_desc_buf(); + if (!template) { + ret = -EINVAL; + audit_cause = "ima_template_desc_buf"; + goto out; + } + + /* + * Both LSM hooks and auxiliary based buffer measurements are + * based on policy. To avoid code duplication, differentiate + * between the LSM hooks and auxiliary buffer measurements, + * retrieving the policy rule information only for the LSM hook + * buffer measurements. + */ + if (func) { + security_current_getlsmprop_subj(&prop); + action = ima_get_action(idmap, inode, current_cred(), + &prop, 0, func, &pcr, &template, + func_data, NULL); + if (!(action & IMA_MEASURE) && !digest) + return -ENOENT; + } + + if (!pcr) + pcr = CONFIG_IMA_MEASURE_PCR_IDX; + + iint.ima_hash = hash_hdr; + iint.ima_hash->algo = ima_hash_algo; + iint.ima_hash->length = hash_digest_size[ima_hash_algo]; + + ret = ima_calc_buffer_hash(buf, size, iint.ima_hash); + if (ret < 0) { + audit_cause = "hashing_error"; + goto out; + } + + if (buf_hash) { + memcpy(digest_hash, hash_hdr->digest, digest_hash_len); + + ret = ima_calc_buffer_hash(digest_hash, digest_hash_len, + iint.ima_hash); + if (ret < 0) { + audit_cause = "hashing_error"; + goto out; + } + + event_data.buf = digest_hash; + event_data.buf_len = digest_hash_len; + } + + if (digest) + memcpy(digest, iint.ima_hash->digest, digest_hash_len); + + if (!ima_policy_flag || (func && !(action & IMA_MEASURE))) + return 1; + + ret = ima_alloc_init_template(&event_data, &entry, template); + if (ret < 0) { + audit_cause = "alloc_entry"; + goto out; + } + + ret = ima_store_template(entry, violation, NULL, event_data.buf, pcr); + if (ret < 0) { + audit_cause = "store_entry"; + ima_free_template_entry(entry); + } + +out: + if (ret < 0) + integrity_audit_message(AUDIT_INTEGRITY_PCR, NULL, eventname, + func_measure_str(func), + audit_cause, ret, 0, ret); + + return ret; +} + +/** + * ima_kexec_cmdline - measure kexec cmdline boot args + * @kernel_fd: file descriptor of the kexec kernel being loaded + * @buf: pointer to buffer + * @size: size of buffer + * + * Buffers can only be measured, not appraised. + */ +void ima_kexec_cmdline(int kernel_fd, const void *buf, int size) +{ + if (!buf || !size) + return; + + CLASS(fd, f)(kernel_fd); + if (fd_empty(f)) + return; + + process_buffer_measurement(file_mnt_idmap(fd_file(f)), file_inode(fd_file(f)), + buf, size, "kexec-cmdline", KEXEC_CMDLINE, 0, + NULL, false, NULL, 0); +} + +/** + * ima_measure_critical_data - measure kernel integrity critical data + * @event_label: unique event label for grouping and limiting critical data + * @event_name: event name for the record in the IMA measurement list + * @buf: pointer to buffer data + * @buf_len: length of buffer data (in bytes) + * @hash: measure buffer data hash + * @digest: buffer digest will be written to + * @digest_len: buffer length + * + * Measure data critical to the integrity of the kernel into the IMA log + * and extend the pcr. Examples of critical data could be various data + * structures, policies, and states stored in kernel memory that can + * impact the integrity of the system. + * + * Return: 0 if the buffer has been successfully measured, 1 if the digest + * has been written to the passed location but not added to a measurement entry, + * a negative value otherwise. + */ +int ima_measure_critical_data(const char *event_label, + const char *event_name, + const void *buf, size_t buf_len, + bool hash, u8 *digest, size_t digest_len) +{ + if (!event_name || !event_label || !buf || !buf_len) + return -ENOPARAM; + + return process_buffer_measurement(&nop_mnt_idmap, NULL, buf, buf_len, + event_name, CRITICAL_DATA, 0, + event_label, hash, digest, + digest_len); +} +EXPORT_SYMBOL_GPL(ima_measure_critical_data); + +#ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS + +/** + * ima_kernel_module_request - Prevent crypto-pkcs1(rsa,*) requests + * @kmod_name: kernel module name + * + * Avoid a verification loop where verifying the signature of the modprobe + * binary requires executing modprobe itself. Since the modprobe iint->mutex + * is already held when the signature verification is performed, a deadlock + * occurs as soon as modprobe is executed within the critical region, since + * the same lock cannot be taken again. + * + * This happens when public_key_verify_signature(), in case of RSA algorithm, + * use alg_name to store internal information in order to construct an + * algorithm on the fly, but crypto_larval_lookup() will try to use alg_name + * in order to load a kernel module with same name. + * + * Since we don't have any real "crypto-pkcs1(rsa,*)" kernel modules, + * we are safe to fail such module request from crypto_larval_lookup(), and + * avoid the verification loop. + * + * Return: Zero if it is safe to load the kernel module, -EINVAL otherwise. + */ +static int ima_kernel_module_request(char *kmod_name) +{ + if (strncmp(kmod_name, "crypto-pkcs1(rsa,", 17) == 0) + return -EINVAL; + + return 0; +} + +#endif /* CONFIG_INTEGRITY_ASYMMETRIC_KEYS */ + static int __init init_ima(void) { int error; + /*Note that turning IMA off is intentionally limited to kdump kernel.*/ + if (ima_disabled && is_kdump_kernel()) { + pr_info("IMA functionality is disabled"); + return 0; + } + + ima_appraise_parse_cmdline(); + ima_init_template_list(); + hash_setup(CONFIG_IMA_DEFAULT_HASH); error = ima_init(); + + if (error && strcmp(hash_algo_name[ima_hash_algo], + CONFIG_IMA_DEFAULT_HASH) != 0) { + pr_info("Allocating %s failed, going to use default hash algorithm %s\n", + hash_algo_name[ima_hash_algo], CONFIG_IMA_DEFAULT_HASH); + hash_setup_done = 0; + hash_setup(CONFIG_IMA_DEFAULT_HASH); + error = ima_init(); + } + + if (error) + return error; + + error = register_blocking_lsm_notifier(&ima_lsm_policy_notifier); + if (error) + pr_warn("Couldn't register LSM notifier, error %d\n", error); + if (!error) - ima_initialized = 1; + ima_update_policy_flags(); + return error; } -late_initcall(init_ima); /* Start IMA after the TPM is available */ +static struct security_hook_list ima_hooks[] __ro_after_init = { + LSM_HOOK_INIT(bprm_check_security, ima_bprm_check), + LSM_HOOK_INIT(bprm_creds_for_exec, ima_bprm_creds_for_exec), + LSM_HOOK_INIT(bprm_creds_from_file, ima_creds_check), + LSM_HOOK_INIT(file_post_open, ima_file_check), + LSM_HOOK_INIT(inode_post_create_tmpfile, ima_post_create_tmpfile), + LSM_HOOK_INIT(file_release, ima_file_free), + LSM_HOOK_INIT(mmap_file, ima_file_mmap), + LSM_HOOK_INIT(file_mprotect, ima_file_mprotect), + LSM_HOOK_INIT(kernel_load_data, ima_load_data), + LSM_HOOK_INIT(kernel_post_load_data, ima_post_load_data), + LSM_HOOK_INIT(kernel_read_file, ima_read_file), + LSM_HOOK_INIT(kernel_post_read_file, ima_post_read_file), + LSM_HOOK_INIT(path_post_mknod, ima_post_path_mknod), +#ifdef CONFIG_IMA_MEASURE_ASYMMETRIC_KEYS + LSM_HOOK_INIT(key_post_create_or_update, ima_post_key_create_or_update), +#endif +#ifdef CONFIG_INTEGRITY_ASYMMETRIC_KEYS + LSM_HOOK_INIT(kernel_module_request, ima_kernel_module_request), +#endif + LSM_HOOK_INIT(inode_free_security_rcu, ima_inode_free_rcu), +}; + +static const struct lsm_id ima_lsmid = { + .name = "ima", + .id = LSM_ID_IMA, +}; + +static int __init init_ima_lsm(void) +{ + ima_iintcache_init(); + security_add_hooks(ima_hooks, ARRAY_SIZE(ima_hooks), &ima_lsmid); + init_ima_appraise_lsm(&ima_lsmid); + return 0; +} + +struct lsm_blob_sizes ima_blob_sizes __ro_after_init = { + .lbs_inode = sizeof(struct ima_iint_cache *), +}; -MODULE_DESCRIPTION("Integrity Measurement Architecture"); -MODULE_LICENSE("GPL"); +DEFINE_LSM(ima) = { + .id = &ima_lsmid, + .init = init_ima_lsm, + .order = LSM_ORDER_LAST, + .blobs = &ima_blob_sizes, + /* Start IMA after the TPM is available */ + .initcall_late = init_ima, +}; |