Messages in this thread Patch in this message | | | From | Prakhar Srivastava <> | Subject | [PATCHv2] added ima hook for buffer, being enabled as a policy | Date | Fri, 19 Apr 2019 17:00:55 -0700 |
| |
From: Prakhar Srivastava <prsriva02@gmail.com>
Signed-off-by: Prakhar Srivastava <prsriva@microsoft.com> ---
This adds a new ima hook ima_buffer_check and a policy entry BUFFER_CHECK. This enables buffer has measurements into ima log
Documentation/ABI/testing/ima_policy | 1 + include/linux/ima.h | 13 +++- security/integrity/ima/ima.h | 1 + security/integrity/ima/ima_main.c | 95 ++++++++++++++++++++++++++++ security/integrity/ima/ima_policy.c | 14 +++- 5 files changed, 122 insertions(+), 2 deletions(-)
diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy index bb0f9a135e21..676088c7ab26 100644 --- a/Documentation/ABI/testing/ima_policy +++ b/Documentation/ABI/testing/ima_policy @@ -28,6 +28,7 @@ Description: base: func:= [BPRM_CHECK][MMAP_CHECK][FILE_CHECK][MODULE_CHECK] [FIRMWARE_CHECK] [KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK] + [BUFFER_CHECK] mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND] [[^]MAY_EXEC] fsmagic:= hex value diff --git a/include/linux/ima.h b/include/linux/ima.h index 7f6952f8d6aa..733d0cb9dedc 100644 --- a/include/linux/ima.h +++ b/include/linux/ima.h @@ -14,6 +14,12 @@ #include <linux/kexec.h> struct linux_binprm; +enum __buffer_id { + KERNEL_VERSION, + KEXEC_CMDLINE, + MAX_BUFFER_ID = KEXEC_CMDLINE +} buffer_id; + #ifdef CONFIG_IMA extern int ima_bprm_check(struct linux_binprm *bprm); extern int ima_file_check(struct file *file, int mask, int opened); @@ -23,7 +29,7 @@ extern int ima_read_file(struct file *file, enum kernel_read_file_id id); extern int ima_post_read_file(struct file *file, void *buf, loff_t size, enum kernel_read_file_id id); extern void ima_post_path_mknod(struct dentry *dentry); - +extern void ima_buffer_check(const void *buff, int size, enum buffer_id id); #ifdef CONFIG_IMA_KEXEC extern void ima_add_kexec_buffer(struct kimage *image); #endif @@ -65,6 +71,11 @@ static inline void ima_post_path_mknod(struct dentry *dentry) return; } +static inline void ima_buffer_check(const void *buff, int size, + enum buffer_id id) +{ + return; +} #endif /* CONFIG_IMA */ #ifndef CONFIG_IMA_KEXEC diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h index b563fbd4d122..b71f2f6f7421 100644 --- a/security/integrity/ima/ima.h +++ b/security/integrity/ima/ima.h @@ -181,6 +181,7 @@ enum ima_hooks { FIRMWARE_CHECK, KEXEC_KERNEL_CHECK, KEXEC_INITRAMFS_CHECK, + BUFFER_CHECK, POLICY_CHECK, MAX_CHECK }; diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 2aebb7984437..6408cadaadbb 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -155,6 +155,84 @@ void ima_file_free(struct file *file) ima_check_last_writer(iint, inode, file); } +/* + * process_buffer_measurement - Measure the buffer passed to ima log. + * (Instead of using the file hash the buffer hash is used). + * @buff - The buffer that needs to be added to the log + * @size - size of buffer(in bytes) + * @id - buffer id, this is differentiator for the various buffers + * that can be measured. + * + * The buffer passed is added to the ima logs. + * If the sig template is used, then the sig field contains the buffer. + * + * On success return 0. + * On error cases surface errors from ima calls. + */ +static int process_buffer_measurement(const void *buff, int size, + enum buffer_id id) +{ + int ret = -EINVAL; + struct ima_template_entry *entry = NULL; + struct integrity_iint_cache tmp_iint, *iint = &tmp_iint; + struct ima_event_data event_data = {iint, NULL, NULL, + NULL, 0, NULL}; + struct { + struct ima_digest_data hdr; + char digest[IMA_MAX_DIGEST_SIZE]; + } hash; + char *name = NULL; + int violation = 0; + int pcr = CONFIG_IMA_MEASURE_PCR_IDX; + + if (!buff || size == 0) + goto err_out; + + if (ima_get_action(NULL, 0, BUFFER_CHECK, &pcr) != IMA_MEASURE) + goto err_out; + + switch (buffer_id) { + case KERNEL_VERSION: + name = "Kernel-version"; + break; + case KEXEC_CMDLINE: + name = "Kexec-cmdline"; + break; + default: + goto err_out; + } + + memset(iint, 0, sizeof(*iint)); + memset(&hash, 0, sizeof(hash)); + + event_data.filename = name; + + 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(buff, size, iint->ima_hash); + if (ret < 0) + goto err_out; + + ret = ima_alloc_init_template(&event_data, &entry); + if (ret < 0) + goto err_out; + + ret = ima_store_template(entry, violation, NULL, + buff, pcr); + if (ret < 0) { + ima_free_template_entry(entry); + goto err_out; + } + + return 0; + +err_out: + pr_err("Error in adding buffer measure: %d\n", ret); + return ret; +} + static int process_measurement(struct file *file, char *buf, loff_t size, int mask, enum ima_hooks func, int opened) { @@ -370,6 +448,23 @@ int ima_read_file(struct file *file, enum kernel_read_file_id read_id) return 0; } +/** + * ima_buffer_check - based on policy, collect & store buffer measurement + * @buf: pointer to buffer + * @size: size of buffer + * @buffer_id: caller identifier + * + * Buffers can only be measured, not appraised. The buffer identifier + * is used as the measurement list entry name (eg. boot_cmdline). + */ +void ima_buffer_check(const void *buf, int size, enum buffer_id id) +{ + if (buf && size != 0) + process_buffer_measurement(buf, size, id); + + return; +} + static int read_idmap[READING_MAX_ID] = { [READING_FIRMWARE] = FIRMWARE_CHECK, [READING_MODULE] = MODULE_CHECK, diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index 3ab1067db624..cefe1a188f31 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -231,6 +231,12 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode, const struct cred *cred = current_cred(); int i; + // Incase of BUFFER_CHECK, Inode is NULL + if (!inode) { + if ((rule->flags & IMA_FUNC) && (rule->func == func)) + return true; + return false; + } if ((rule->flags & IMA_FUNC) && (rule->func != func && func != POST_SETATTR)) return false; @@ -665,6 +671,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) else if (strcmp(args[0].from, "KEXEC_INITRAMFS_CHECK") == 0) entry->func = KEXEC_INITRAMFS_CHECK; + else if (strcmp(args[0].from, "BUFFER_CHECK") == 0) + entry->func = BUFFER_CHECK; else if (strcmp(args[0].from, "POLICY_CHECK") == 0) entry->func = POLICY_CHECK; else @@ -944,7 +952,7 @@ enum { func_file = 0, func_mmap, func_bprm, func_module, func_firmware, func_post, func_kexec_kernel, func_kexec_initramfs, - func_policy + func_buffer, func_policy }; static char *func_tokens[] = { @@ -956,6 +964,7 @@ static char *func_tokens[] = { "POST_SETATTR", "KEXEC_KERNEL_CHECK", "KEXEC_INITRAMFS_CHECK", + "BUFFER_CHECK", "POLICY_CHECK" }; @@ -1027,6 +1036,9 @@ static void policy_func_show(struct seq_file *m, enum ima_hooks func) case KEXEC_INITRAMFS_CHECK: seq_printf(m, pt(Opt_func), ft(func_kexec_initramfs)); break; + case BUFFER_CHECK: + seq_printf(m, pt(Opt_func), ft(func_buffer)); + break; case POLICY_CHECK: seq_printf(m, pt(Opt_func), ft(func_policy)); break; -- 2.17.1
| |