Hi, Mimi
CCing kexec list, not all kexec people subscribed to IMA list.
I just subscribed to it since Vivek CCed me last time about the V1 of this
series.
On 12/23/15 at 06:55pm, Mimi Zohar wrote:
> This patch defines a new IMA hook ima_hash_and_process_file() for
> measuring and appraising files read by the kernel. The caller loads
> the file into memory before calling this function, which calculates
> the hash followed by the normal IMA policy based processing.
>
> Two new IMA policy functions named KEXEC_CHECK and INITRAMFS_CHECK
> are defined for measuring, appraising or auditing the kexec image
> and initramfs.
Could you help us understand why do we need it first.
I think I do not really understand the purpose of the IMA handling
about kexec kernel and initramfs.
* Does the files in disk space have already contains some hash values
and when kernel load it IMA functions will do some checking? But seems I do not
see such handling..
* Does it try to calculate the hash of the file buffer after copying,
and IMA will avoid future modification based on the hash calculated?
If this is the purpose I think it should be wrong because kexe file buffers
will be freed at the end of kexec_file_load syscall.
>
> Changelog v2:
> - Calculate the file hash from the in memory buffer (suggested by Dave Young)
> - Rename ima_read_and_process_file() to ima_hash_and_process_file()
> - replace individual case statements with range:
> KEXEC_CHECK ... IMA_MAX_READ_CHECK - 1
> v1:
> - Instead of ima_read_and_process_file() allocating memory, the caller
> allocates and frees the memory.
> - Moved the kexec measurement/appraisal call to copy_file_from_fd(). The
> same call now measures and appraises both the kexec image and initramfs.
>
> Signed-off-by: Mimi Zohar <zo...@linux.vnet.ibm.com>
> ---
> Documentation/ABI/testing/ima_policy | 2 +-
> include/linux/ima.h | 16 ++++++++++++++
> kernel/kexec_file.c | 24 ++++++++++++--------
> security/integrity/iint.c | 1 +
> security/integrity/ima/ima.h | 21 ++++++++++++------
> security/integrity/ima/ima_api.c | 6 +++--
> security/integrity/ima/ima_appraise.c | 11 ++++++++--
> security/integrity/ima/ima_main.c | 41
> ++++++++++++++++++++++++++++-------
> security/integrity/ima/ima_policy.c | 38 ++++++++++++++++++++++++--------
> security/integrity/integrity.h | 7 ++++--
> 10 files changed, 127 insertions(+), 40 deletions(-)
>
> diff --git a/Documentation/ABI/testing/ima_policy
> b/Documentation/ABI/testing/ima_policy
> index 0a378a8..e80f767 100644
> --- a/Documentation/ABI/testing/ima_policy
> +++ b/Documentation/ABI/testing/ima_policy
> @@ -26,7 +26,7 @@ Description:
> option: [[appraise_type=]] [permit_directio]
>
> base: func:=
> [BPRM_CHECK][MMAP_CHECK][FILE_CHECK][MODULE_CHECK]
> - [FIRMWARE_CHECK]
> + [FIRMWARE_CHECK] [KEXEC_CHECK] [INITRAMFS_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 120ccc5..020de0f 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -13,6 +13,12 @@
> #include <linux/fs.h>
> struct linux_binprm;
>
> +enum ima_read_hooks {
> + KEXEC_CHECK = 1,
> + INITRAMFS_CHECK,
> + IMA_MAX_READ_CHECK
> +};
> +
> #ifdef CONFIG_IMA
> extern int ima_bprm_check(struct linux_binprm *bprm);
> extern int ima_file_check(struct file *file, int mask, int opened);
> @@ -20,6 +26,9 @@ extern void ima_file_free(struct file *file);
> extern int ima_file_mmap(struct file *file, unsigned long prot);
> extern int ima_module_check(struct file *file);
> extern int ima_fw_from_file(struct file *file, char *buf, size_t size);
> +extern int ima_hash_and_process_file(struct file *file,
> + void *buf, size_t size,
> + enum ima_read_hooks read_func);
>
> #else
> static inline int ima_bprm_check(struct linux_binprm *bprm)
> @@ -52,6 +61,13 @@ static inline int ima_fw_from_file(struct file *file, char
> *buf, size_t size)
> return 0;
> }
>
> +static inline int ima_hash_and_process_file(struct file *file,
> + void *buf, size_t size,
> + enum ima_read_hooks read_func)
> +{
> + return 0;
> +}
> +
> #endif /* CONFIG_IMA */
>
> #ifdef CONFIG_IMA_APPRAISE
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index b70ada0..1d0d998 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -18,6 +18,7 @@
> #include <linux/kexec.h>
> #include <linux/mutex.h>
> #include <linux/list.h>
> +#include <linux/ima.h>
> #include <crypto/hash.h>
> #include <crypto/sha.h>
> #include <linux/syscalls.h>
> @@ -33,7 +34,8 @@ size_t __weak kexec_purgatory_size = 0;
>
> static int kexec_calculate_store_digests(struct kimage *image);
>
> -static int copy_file_from_fd(int fd, void **buf, unsigned long *buf_len)
> +static int copy_file_from_fd(int fd, void **buf, unsigned long *buf_len,
> + enum ima_read_hooks read_func)
> {
> struct fd f = fdget(fd);
> int ret;
> @@ -70,9 +72,8 @@ static int copy_file_from_fd(int fd, void **buf, unsigned
> long *buf_len)
> bytes = kernel_read(f.file, pos, (char *)(*buf) + pos,
> stat.size - pos);
> if (bytes < 0) {
> - vfree(*buf);
> ret = bytes;
> - goto out;
> + goto out_free;
> }
>
> if (bytes == 0)
> @@ -80,13 +81,17 @@ static int copy_file_from_fd(int fd, void **buf, unsigned
> long *buf_len)
> pos += bytes;
> }
>
> - if (pos != stat.size) {
> + if (pos != stat.size)
> ret = -EBADF;
> +
> + ret = ima_hash_and_process_file(f.file, *buf, stat.size, read_func);
> + if (!ret)
> + *buf_len = pos;
> +out_free:
> + if (ret < 0) {
> vfree(*buf);
> - goto out;
> + *buf = NULL;
> }
> -
> - *buf_len = pos;
> out:
> fdput(f);
> return ret;
> @@ -182,7 +187,7 @@ kimage_file_prepare_segments(struct kimage *image, int
> kernel_fd, int initrd_fd,
> void *ldata;
>
> ret = copy_file_from_fd(kernel_fd, &image->kernel_buf,
> - &image->kernel_buf_len);
> + &image->kernel_buf_len, KEXEC_CHECK);
> if (ret)
> return ret;
>
> @@ -205,7 +210,8 @@ kimage_file_prepare_segments(struct kimage *image, int
> kernel_fd, int initrd_fd,
> /* It is possible that there no initramfs is being loaded */
> if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {
> ret = copy_file_from_fd(initrd_fd, &image->initrd_buf,
> - &image->initrd_buf_len);
> + &image->initrd_buf_len,
> + INITRAMFS_CHECK);
> if (ret)
> goto out;
> }
> diff --git a/security/integrity/iint.c b/security/integrity/iint.c
> index 54b51a4..8a45576 100644
> --- a/security/integrity/iint.c
> +++ b/security/integrity/iint.c
> @@ -158,6 +158,7 @@ static void init_once(void *foo)
> iint->ima_mmap_status = INTEGRITY_UNKNOWN;
> iint->ima_bprm_status = INTEGRITY_UNKNOWN;
> iint->ima_module_status = INTEGRITY_UNKNOWN;
> + iint->ima_read_status = INTEGRITY_UNKNOWN;
> iint->evm_status = INTEGRITY_UNKNOWN;
> }
>
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index e3a5b7b..fa801fa 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -20,6 +20,7 @@
> #include <linux/types.h>
> #include <linux/crypto.h>
> #include <linux/security.h>
> +#include <linux/ima.h>
> #include <linux/hash.h>
> #include <linux/tpm.h>
> #include <linux/audit.h>
> @@ -143,7 +144,8 @@ static inline unsigned long ima_hash_key(u8 *digest)
> int ima_get_action(struct inode *inode, int mask, int function);
> int ima_must_measure(struct inode *inode, int mask, int function);
> int ima_collect_measurement(struct integrity_iint_cache *iint,
> - struct file *file, enum hash_algo algo);
> + struct file *file, void *buf, size_t buf_len,
> + enum hash_algo algo);
> void ima_store_measurement(struct integrity_iint_cache *iint, struct file
> *file,
> const unsigned char *filename,
> struct evm_ima_xattr_data *xattr_value,
> @@ -158,10 +160,16 @@ void ima_free_template_entry(struct ima_template_entry
> *entry);
> const char *ima_d_path(struct path *path, char **pathbuf);
>
> /* IMA policy related functions */
> -enum ima_hooks { FILE_CHECK = 1, MMAP_CHECK, BPRM_CHECK, MODULE_CHECK,
> FIRMWARE_CHECK, POST_SETATTR };
> +enum ima_hooks {
> + FILE_CHECK = IMA_MAX_READ_CHECK,
> + MMAP_CHECK,
> + BPRM_CHECK,
> + MODULE_CHECK,
> + FIRMWARE_CHECK,
> + POST_SETATTR
> +};
>
> -int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask,
> - int flags);
> +int ima_match_policy(struct inode *inode, int func, int mask, int flags);
> void ima_init_policy(void);
> void ima_update_policy(void);
> void ima_update_policy_flag(void);
> @@ -184,7 +192,7 @@ int ima_appraise_measurement(int func, struct
> integrity_iint_cache *iint,
> struct file *file, const unsigned char *filename,
> struct evm_ima_xattr_data *xattr_value,
> int xattr_len, int opened);
> -int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func);
> +int ima_must_appraise(struct inode *inode, int mask, int func);
> void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file);
> enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
> int func);
> @@ -204,8 +212,7 @@ static inline int ima_appraise_measurement(int func,
> return INTEGRITY_UNKNOWN;
> }
>
> -static inline int ima_must_appraise(struct inode *inode, int mask,
> - enum ima_hooks func)
> +static inline int ima_must_appraise(struct inode *inode, int mask, int func)
> {
> return 0;
> }
> diff --git a/security/integrity/ima/ima_api.c
> b/security/integrity/ima/ima_api.c
> index e7c7a5d..f3a5b0b 100644
> --- a/security/integrity/ima/ima_api.c
> +++ b/security/integrity/ima/ima_api.c
> @@ -188,7 +188,8 @@ int ima_get_action(struct inode *inode, int mask, int
> function)
> * Return 0 on success, error code otherwise
> */
> int ima_collect_measurement(struct integrity_iint_cache *iint,
> - struct file *file, enum hash_algo algo)
> + struct file *file, void *buf, unsigned long buf_len,
> + enum hash_algo algo)
> {
> const char *audit_cause = "failed";
> struct inode *inode = file_inode(file);
> @@ -210,7 +211,8 @@ int ima_collect_measurement(struct integrity_iint_cache
> *iint,
>
> hash.hdr.algo = algo;
>
> - result = ima_calc_file_hash(file, &hash.hdr);
> + result = (!buf) ? ima_calc_file_hash(file, &hash.hdr) :
> + ima_calc_buffer_hash(buf, buf_len, &hash.hdr);
> if (!result) {
> int length = sizeof(hash.hdr) + hash.hdr.length;
> void *tmpbuf = krealloc(iint->ima_hash, length,
> diff --git a/security/integrity/ima/ima_appraise.c
> b/security/integrity/ima/ima_appraise.c
> index 9c2b46b..3adf937 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -36,7 +36,7 @@ __setup("ima_appraise=", default_appraise_setup);
> *
> * Return 1 to appraise
> */
> -int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func)
> +int ima_must_appraise(struct inode *inode, int mask, int func)
> {
> if (!ima_appraise)
> return 0;
> @@ -78,6 +78,8 @@ enum integrity_status ima_get_cache_status(struct
> integrity_iint_cache *iint,
> return iint->ima_module_status;
> case FIRMWARE_CHECK:
> return iint->ima_firmware_status;
> + case KEXEC_CHECK ... IMA_MAX_READ_CHECK - 1:
> + return iint->ima_read_status;
> case FILE_CHECK:
> default:
> return iint->ima_file_status;
> @@ -100,6 +102,9 @@ static void ima_set_cache_status(struct
> integrity_iint_cache *iint,
> case FIRMWARE_CHECK:
> iint->ima_firmware_status = status;
> break;
> + case KEXEC_CHECK ... IMA_MAX_READ_CHECK - 1:
> + iint->ima_read_status = status;
> + break;
> case FILE_CHECK:
> default:
> iint->ima_file_status = status;
> @@ -122,6 +127,8 @@ static void ima_cache_flags(struct integrity_iint_cache
> *iint, int func)
> case FIRMWARE_CHECK:
> iint->flags |= (IMA_FIRMWARE_APPRAISED | IMA_APPRAISED);
> break;
> + case KEXEC_CHECK ... IMA_MAX_READ_CHECK - 1:
> + break;
> case FILE_CHECK:
> default:
> iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED);
> @@ -299,7 +306,7 @@ void ima_update_xattr(struct integrity_iint_cache *iint,
> struct file *file)
> if (iint->flags & IMA_DIGSIG)
> return;
>
> - rc = ima_collect_measurement(iint, file, ima_hash_algo);
> + rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo);
> if (rc < 0)
> return;
>
> diff --git a/security/integrity/ima/ima_main.c
> b/security/integrity/ima/ima_main.c
> index d9fc463..cd9c576 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -153,8 +153,8 @@ void ima_file_free(struct file *file)
> ima_check_last_writer(iint, inode, file);
> }
>
> -static int process_measurement(struct file *file, int mask, int function,
> - int opened)
> +static int process_measurement(struct file *file, char *buf, size_t buf_len,
> + int mask, int function, int opened)
> {
> struct inode *inode = file_inode(file);
> struct integrity_iint_cache *iint = NULL;
> @@ -226,7 +226,7 @@ static int process_measurement(struct file *file, int
> mask, int function,
>
> hash_algo = ima_get_hash_algo(xattr_value, xattr_len);
>
> - rc = ima_collect_measurement(iint, file, hash_algo);
> + rc = ima_collect_measurement(iint, file, buf, buf_len, hash_algo);
> if (rc != 0) {
> if (file->f_flags & O_DIRECT)
> rc = (iint->flags & IMA_PERMIT_DIRECTIO) ? 0 : -EACCES;
> @@ -273,7 +273,8 @@ out:
> int ima_file_mmap(struct file *file, unsigned long prot)
> {
> if (file && (prot & PROT_EXEC))
> - return process_measurement(file, MAY_EXEC, MMAP_CHECK, 0);
> + return process_measurement(file, NULL, 0, MAY_EXEC,
> + MMAP_CHECK, 0);
> return 0;
> }
>
> @@ -292,7 +293,8 @@ int ima_file_mmap(struct file *file, unsigned long prot)
> */
> int ima_bprm_check(struct linux_binprm *bprm)
> {
> - return process_measurement(bprm->file, MAY_EXEC, BPRM_CHECK, 0);
> + return process_measurement(bprm->file, NULL, 0, MAY_EXEC,
> + BPRM_CHECK, 0);
> }
>
> /**
> @@ -307,7 +309,7 @@ int ima_bprm_check(struct linux_binprm *bprm)
> */
> int ima_file_check(struct file *file, int mask, int opened)
> {
> - return process_measurement(file,
> + return process_measurement(file, NULL, 0,
> mask & (MAY_READ | MAY_WRITE | MAY_EXEC),
> FILE_CHECK, opened);
> }
> @@ -332,7 +334,7 @@ int ima_module_check(struct file *file)
> #endif
> return 0; /* We rely on module signature checking */
> }
> - return process_measurement(file, MAY_EXEC, MODULE_CHECK, 0);
> + return process_measurement(file, NULL, 0, MAY_EXEC, MODULE_CHECK, 0);
> }
>
> int ima_fw_from_file(struct file *file, char *buf, size_t size)
> @@ -343,7 +345,30 @@ int ima_fw_from_file(struct file *file, char *buf,
> size_t size)
> return -EACCES; /* INTEGRITY_UNKNOWN */
> return 0;
> }
> - return process_measurement(file, MAY_EXEC, FIRMWARE_CHECK, 0);
> + return process_measurement(file, NULL, 0, MAY_EXEC, FIRMWARE_CHECK, 0);
> +}
> +
> +/**
> + * ima_hash_and_process_file - in memory collect/appraise/audit measurement
> + * @file: pointer to the file to be measured/appraised/audit
> + * @buf: pointer to in memory file contents
> + * @buf_len: size of in memory file contents
> + * @read_func: caller identifier
> + *
> + * Measure/appraise/audit in memory file based on policy. Policy rules
> + * are written in terms of the read_func identifier (eg. KEXEC_CHECK,
> + * INITRAMFS_CHECK)
> + */
> +int ima_hash_and_process_file(struct file *file, void *buf, size_t buf_len,
> + enum ima_read_hooks read_func)
> +{
> + if (!file || !buf || buf_len == 0) { /* should never happen */
> + if (ima_appraise & IMA_APPRAISE_ENFORCE)
> + return -EACCES;
> + return 0;
> + }
> +
> + return process_measurement(file, buf, buf_len, MAY_READ, read_func, 0);
> }
>
> static int __init init_ima(void)
> diff --git a/security/integrity/ima/ima_policy.c
> b/security/integrity/ima/ima_policy.c
> index ba5d2fc..26e24df 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -53,7 +53,10 @@ struct ima_rule_entry {
> struct list_head list;
> int action;
> unsigned int flags;
> - enum ima_hooks func;
> + union {
> + enum ima_hooks func;
> + enum ima_read_hooks read_func;
> + };
> int mask;
> unsigned long fsmagic;
> u8 fsuuid[16];
> @@ -208,7 +211,7 @@ static void ima_lsm_update_rules(void)
> * Returns true on rule match, false on failure.
> */
> static bool ima_match_rules(struct ima_rule_entry *rule,
> - struct inode *inode, enum ima_hooks func, int mask)
> + struct inode *inode, int func, int mask)
> {
> struct task_struct *tsk = current;
> const struct cred *cred = current_cred();
> @@ -303,6 +306,8 @@ static int get_subaction(struct ima_rule_entry *rule, int
> func)
> return IMA_MODULE_APPRAISE;
> case FIRMWARE_CHECK:
> return IMA_FIRMWARE_APPRAISE;
> + case KEXEC_CHECK ... IMA_MAX_READ_CHECK - 1:
> + return IMA_READ_APPRAISE;
> case FILE_CHECK:
> default:
> return IMA_FILE_APPRAISE;
> @@ -322,8 +327,7 @@ static int get_subaction(struct ima_rule_entry *rule, int
> func)
> * list when walking it. Reads are many orders of magnitude more numerous
> * than writes so ima_match_policy() is classical RCU candidate.
> */
> -int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask,
> - int flags)
> +int ima_match_policy(struct inode *inode, int func, int mask, int flags)
> {
> struct ima_rule_entry *entry;
> int action = 0, actmask = flags | (flags << 1);
> @@ -604,6 +608,10 @@ static int ima_parse_rule(char *rule, struct
> ima_rule_entry *entry)
> entry->func = MMAP_CHECK;
> else if (strcmp(args[0].from, "BPRM_CHECK") == 0)
> entry->func = BPRM_CHECK;
> + else if (strcmp(args[0].from, "KEXEC_CHECK") == 0)
> + entry->read_func = KEXEC_CHECK;
> + else if (strcmp(args[0].from, "INITRAMFS_CHECK") == 0)
> + entry->read_func = INITRAMFS_CHECK;
> else
> result = -EINVAL;
> if (!result)
> @@ -847,7 +855,8 @@ static char *mask_tokens[] = {
>
> enum {
> func_file = 0, func_mmap, func_bprm,
> - func_module, func_firmware, func_post
> + func_module, func_firmware, func_post,
> + func_kexec, func_initramfs
> };
>
> static char *func_tokens[] = {
> @@ -856,7 +865,9 @@ static char *func_tokens[] = {
> "BPRM_CHECK",
> "MODULE_CHECK",
> "FIRMWARE_CHECK",
> - "POST_SETATTR"
> + "POST_SETATTR",
> + "KEXEC_CHECK",
> + "INITRAMFS_CHECK",
> };
>
> void *ima_policy_start(struct seq_file *m, loff_t *pos)
> @@ -937,9 +948,18 @@ int ima_policy_show(struct seq_file *m, void *v)
> seq_printf(m, pt(Opt_func), ft(func_post));
> break;
> default:
> - snprintf(tbuf, sizeof(tbuf), "%d", entry->func);
> - seq_printf(m, pt(Opt_func), tbuf);
> - break;
> + switch (entry->read_func) {
> + case KEXEC_CHECK:
> + seq_printf(m, pt(Opt_func), ft(func_kexec));
> + break;
> + case INITRAMFS_CHECK:
> + seq_printf(m, pt(Opt_func), ft(func_initramfs));
> + break;
> + default:
> + snprintf(tbuf, sizeof(tbuf), "%d", entry->func);
> + seq_printf(m, pt(Opt_func), tbuf);
> + break;
> + }
> }
> seq_puts(m, " ");
> }
> diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
> index 5413f22..645d5be 100644
> --- a/security/integrity/integrity.h
> +++ b/security/integrity/integrity.h
> @@ -49,12 +49,14 @@
> #define IMA_MODULE_APPRAISED 0x00008000
> #define IMA_FIRMWARE_APPRAISE 0x00010000
> #define IMA_FIRMWARE_APPRAISED 0x00020000
> +#define IMA_READ_APPRAISE 0x00040000
> +#define IMA_READ_APPRAISED 0x00080000
> #define IMA_APPRAISE_SUBMASK (IMA_FILE_APPRAISE | IMA_MMAP_APPRAISE | \
> IMA_BPRM_APPRAISE | IMA_MODULE_APPRAISE | \
> - IMA_FIRMWARE_APPRAISE)
> + IMA_FIRMWARE_APPRAISE | IMA_READ_APPRAISE)
> #define IMA_APPRAISED_SUBMASK (IMA_FILE_APPRAISED |
> IMA_MMAP_APPRAISED | \
> IMA_BPRM_APPRAISED | IMA_MODULE_APPRAISED | \
> - IMA_FIRMWARE_APPRAISED)
> + IMA_FIRMWARE_APPRAISED | IMA_READ_APPRAISED)
>
> enum evm_ima_xattr_type {
> IMA_XATTR_DIGEST = 0x01,
> @@ -111,6 +113,7 @@ struct integrity_iint_cache {
> enum integrity_status ima_bprm_status:4;
> enum integrity_status ima_module_status:4;
> enum integrity_status ima_firmware_status:4;
> + enum integrity_status ima_read_status:4;
> enum integrity_status evm_status:4;
> struct ima_digest_data *ima_hash;
> };
> --
> 2.1.0
>
>
> ------------------------------------------------------------------------------
> _______________________________________________
> Linux-ima-devel mailing list
> linux-ima-de...@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-ima-devel
Thanks
Dave
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