Re: [PATCH v3 11/22] ima: define a new hook to measure and appraise a file already in memory

[Dmitry Kasatkin <dmitry.kasatkin@gmail.com>]

On Wed, Feb 3, 2016 at 9:06 PM, Mimi Zohar <zohar@linux.vnet.ibm.com> wrote:
> This patch defines a new IMA hook ima_post_read_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.
>
> Changelog v3:
> - rename ima_hash_and_process_file() to ima_post_read_file()
>
> v1:
> - To simplify patch review, separate the IMA changes from the kexec
> and initramfs changes in "ima: measure and appraise kexec image and
> initramfs" patch.  This patch contains just the IMA changes.  The
> kexec and initramfs changes are with the rest of the kexec changes
> in "kexec: replace call to copy_file_from_fd() with kernel version".
>
> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

Acked-by: Dmitry Kasatkin <dmitry.kasatkin@huawei.com>

> ---
>  include/linux/ima.h                   |  8 +++++++
>  include/linux/security.h              |  1 +
>  security/integrity/ima/ima.h          |  4 +++-
>  security/integrity/ima/ima_api.c      |  6 +++--
>  security/integrity/ima/ima_appraise.c |  2 +-
>  security/integrity/ima/ima_main.c     | 45 ++++++++++++++++++++++++++++-------
>  security/integrity/ima/ima_policy.c   |  1 +
>  security/integrity/integrity.h        |  7 ++++--
>  security/security.c                   |  7 +++++-
>  9 files changed, 66 insertions(+), 15 deletions(-)
>
> diff --git a/include/linux/ima.h b/include/linux/ima.h
> index 120ccc5..d29a6a2 100644
> --- a/include/linux/ima.h
> +++ b/include/linux/ima.h
> @@ -20,6 +20,8 @@ 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_post_read_file(struct file *file, void *buf, loff_t size,
> +                             enum kernel_read_file_id id);
>
>  #else
>  static inline int ima_bprm_check(struct linux_binprm *bprm)
> @@ -52,6 +54,12 @@ static inline int ima_fw_from_file(struct file *file, char *buf, size_t size)
>         return 0;
>  }
>
> +static inline int ima_post_read_file(struct file *file, void *buf, loff_t size,
> +                                    enum kernel_read_file_id id)
> +{
> +       return 0;
> +}
> +
>  #endif /* CONFIG_IMA */
>
>  #ifdef CONFIG_IMA_APPRAISE
> diff --git a/include/linux/security.h b/include/linux/security.h
> index b68ce94..d920718 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -24,6 +24,7 @@
>
>  #include <linux/key.h>
>  #include <linux/capability.h>
> +#include <linux/fs.h>
>  #include <linux/slab.h>
>  #include <linux/err.h>
>  #include <linux/string.h>
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 2c5262f..0b7134c 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -19,6 +19,7 @@
>
>  #include <linux/types.h>
>  #include <linux/crypto.h>
> +#include <linux/fs.h>
>  #include <linux/security.h>
>  #include <linux/hash.h>
>  #include <linux/tpm.h>
> @@ -152,7 +153,8 @@ enum ima_hooks {
>  int ima_get_action(struct inode *inode, int mask, enum ima_hooks func);
>  int ima_must_measure(struct inode *inode, int mask, enum ima_hooks func);
>  int ima_collect_measurement(struct integrity_iint_cache *iint,
> -                           struct file *file, enum hash_algo algo);
> +                           struct file *file, void *buf, loff_t size,
> +                           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,
> diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
> index 8750254..370e42d 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, enum ima_hooks func)
>   * 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, loff_t size,
> +                           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, size, &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 2888449..cb0d0ff 100644
> --- a/security/integrity/ima/ima_appraise.c
> +++ b/security/integrity/ima/ima_appraise.c
> @@ -300,7 +300,7 @@ 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 78a80c8..bead94b 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,
> -                              enum ima_hooks func, int opened)
> +static int process_measurement(struct file *file, char *buf, loff_t size,
> +                              int mask, enum ima_hooks func, 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,
>
>         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, size, 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 +345,34 @@ 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_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/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_post_read_file(struct file *file, void *buf, loff_t size,
> +                      enum kernel_read_file_id read_id)
> +{
> +       enum ima_hooks func = FILE_CHECK;
> +
> +       if (!file && (!buf || size == 0)) { /* should never happen */
> +               if (ima_appraise & IMA_APPRAISE_ENFORCE)
> +                       return -EACCES;
> +               return 0;
> +       }
> +
> +       return process_measurement(file, buf, size, MAY_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 b089ebe..cfbe86f 100644
> --- a/security/integrity/ima/ima_policy.c
> +++ b/security/integrity/ima/ima_policy.c
> @@ -12,6 +12,7 @@
>   */
>  #include <linux/module.h>
>  #include <linux/list.h>
> +#include <linux/fs.h>
>  #include <linux/security.h>
>  #include <linux/magic.h>
>  #include <linux/parser.h>
> diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
> index 5efe2ec..9a0ea4c 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;
>  };
> diff --git a/security/security.c b/security/security.c
> index 796a261..ad87e8d 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -913,7 +913,12 @@ int security_kernel_module_from_file(struct file *file)
>  int security_kernel_post_read_file(struct file *file, char *buf, loff_t size,
>                                    enum kernel_read_file_id id)
>  {
> -       return call_int_hook(kernel_post_read_file, 0, file, buf, size, id);
> +       int ret;
> +
> +       ret = call_int_hook(kernel_post_read_file, 0, file, buf, size, id);
> +       if (ret)
> +               return ret;
> +       return ima_post_read_file(file, buf, size, id);
>  }
>
>  int security_task_fix_setuid(struct cred *new, const struct cred *old,
> --
> 2.1.0
>



-- 
Thanks,
Dmitry