diff options
Diffstat (limited to 'security/integrity/ima/ima_main.c')
| -rw-r--r-- | security/integrity/ima/ima_main.c | 83 |
1 files changed, 74 insertions, 9 deletions
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index b028c501949c..cdd225f65a62 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -27,6 +27,7 @@ #include <linux/fs.h> #include <linux/iversion.h> #include <linux/evm.h> +#include <linux/crash_dump.h> #include "ima.h" @@ -38,11 +39,30 @@ int ima_appraise; 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) { struct ima_template_desc *template_desc = ima_template_desc_current(); @@ -129,16 +149,22 @@ static void ima_rdwr_violation_check(struct file *file, if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) { if (!iint) iint = ima_iint_find(inode); + /* IMA_MEASURE is set from reader side */ - if (iint && test_bit(IMA_MUST_MEASURE, - &iint->atomic_flags)) + if (iint && test_and_clear_bit(IMA_MAY_EMIT_TOMTOU, + &iint->atomic_flags)) send_tomtou = true; } } else { if (must_measure) - set_bit(IMA_MUST_MEASURE, &iint->atomic_flags); - if (inode_is_open_for_write(inode) && must_measure) - send_writers = true; + set_bit(IMA_MAY_EMIT_TOMTOU, &iint->atomic_flags); + + /* 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) @@ -167,6 +193,8 @@ static void ima_check_last_writer(struct ima_iint_cache *iint, 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) || @@ -237,7 +265,9 @@ static int process_measurement(struct file *file, const struct cred *cred, &allowed_algos); violation_check = ((func == FILE_CHECK || func == MMAP_CHECK || func == MMAP_CHECK_REQPROT) && - (ima_policy_flag & IMA_MEASURE)); + (ima_policy_flag & IMA_MEASURE) && + ((action & IMA_MEASURE) || + (file->f_mode & FMODE_WRITE))); if (!action && !violation_check) return 0; @@ -558,6 +588,34 @@ static int ima_bprm_check(struct linux_binprm *bprm) } /** + * 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, MAY_EXEC or MAY_APPEND @@ -986,9 +1044,9 @@ int process_buffer_measurement(struct mnt_idmap *idmap, } /* - * Both LSM hooks and auxilary based buffer measurements are - * based on policy. To avoid code duplication, differentiate - * between the LSM hooks and auxilary buffer measurements, + * 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. */ @@ -1148,6 +1206,12 @@ 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); @@ -1177,6 +1241,7 @@ static int __init init_ima(void) 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(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), |