Re: [PATCH v6 2/3] add a new ima template field buf

[Roberto Sassu <roberto.sassu@xxxxxxxxxx>]

On 5/21/2019 2:06 AM, Prakhar Srivastava wrote:
> A buffer(cmdline args) measured into ima cannot be appraised
> without already being aware of the buffer contents.Since we

Space before 'Since'.


> don't know what cmdline args will be passed (or need to validate
> what was passed) it is not possible to appraise it.
>
> Since hashs are non reversible the raw buffer is needed to
> recompute the hash.

Hashes.

> To regenrate the hash of the buffer and appraise the same

Regenerate.


> the contents of the buffer need to be available.
>
> A new template field buf is added to the existing ima template
> fields, which can be used to store/read the buffer itself.
> Two new fields are added to the ima_event_data to carry the
> buf and buf_len whenever necessary.
>
> Updated the process_buffer_measurement call to add the buf
> to the ima_event_data.
> process_buffer_measurement added in "Add a new ima hook
> ima_kexec_cmdline to measure cmdline args"
>
> - Add a new template field 'buf' to be used to store/read
> the buffer data.
> - Added two new fields to ima_event_data to hold the buf and
> buf_len [Suggested by Roberto]
> -Updated process_buffer_meaurement to add the buffer to

Space after -.


> ima_event_data
>
> Signed-off-by: Prakhar Srivastava <prsriva02@xxxxxxxxx>
> ---
>   Documentation/security/IMA-templates.rst  |  2 +-
>   security/integrity/ima/ima.h              |  2 ++
>   security/integrity/ima/ima_api.c          |  4 ++--
>   security/integrity/ima/ima_init.c         |  2 +-
>   security/integrity/ima/ima_main.c         |  4 +++-
>   security/integrity/ima/ima_template.c     |  2 ++
>   security/integrity/ima/ima_template_lib.c | 20 ++++++++++++++++++++
>   security/integrity/ima/ima_template_lib.h |  4 ++++
>   8 files changed, 35 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/security/IMA-templates.rst b/Documentation/security/IMA-templates.rst
> index 2cd0e273cc9a..9cddb66727ee 100644
> --- a/Documentation/security/IMA-templates.rst
> +++ b/Documentation/security/IMA-templates.rst
> @@ -70,7 +70,7 @@ descriptors by adding their identifier to the format string
>      prefix is shown only if the hash algorithm is not SHA1 or MD5);
>    - 'n-ng': the name of the event, without size limitations;
>    - 'sig': the file signature.

; instead of .


> -

Keep the new line.


Apart from that, the patch looks good to me.

Reviewed-by: Roberto Sassu <roberto.sassu@xxxxxxxxxx>

Roberto


> + - 'buf': the buffer data that was used to generate the hash without size limitations.
>   
>   Below, there is the list of defined template descriptors:
>   
> diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
> index 226a26d8de09..4a82541dc3b6 100644
> --- a/security/integrity/ima/ima.h
> +++ b/security/integrity/ima/ima.h
> @@ -65,6 +65,8 @@ struct ima_event_data {
>   	struct evm_ima_xattr_data *xattr_value;
>   	int xattr_len;
>   	const char *violation;
> +	const void *buf;
> +	int buf_len;
>   };
>   
>   /* IMA template field data definition */
> diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
> index 800d965232e5..c12f1cd38f8f 100644
> --- a/security/integrity/ima/ima_api.c
> +++ b/security/integrity/ima/ima_api.c
> @@ -134,7 +134,7 @@ void ima_add_violation(struct file *file, const unsigned char *filename,
>   	struct ima_template_entry *entry;
>   	struct inode *inode = file_inode(file);
>   	struct ima_event_data event_data = {iint, file, filename, NULL, 0,
> -					    cause};
> +					    cause, NULL, 0};
>   	int violation = 1;
>   	int result;
>   
> @@ -286,7 +286,7 @@ void ima_store_measurement(struct integrity_iint_cache *iint,
>   	struct inode *inode = file_inode(file);
>   	struct ima_template_entry *entry;
>   	struct ima_event_data event_data = {iint, file, filename, xattr_value,
> -					    xattr_len, NULL};
> +					    xattr_len, NULL, NULL, 0};
>   	int violation = 0;
>   
>   	if (iint->measured_pcrs & (0x1 << pcr))
> diff --git a/security/integrity/ima/ima_init.c b/security/integrity/ima/ima_init.c
> index 6c9295449751..0c34d3100b5b 100644
> --- a/security/integrity/ima/ima_init.c
> +++ b/security/integrity/ima/ima_init.c
> @@ -50,7 +50,7 @@ static int __init ima_add_boot_aggregate(void)
>   	struct ima_template_entry *entry;
>   	struct integrity_iint_cache tmp_iint, *iint = &tmp_iint;
>   	struct ima_event_data event_data = {iint, NULL, boot_aggregate_name,
> -					    NULL, 0, NULL};
> +					    NULL, 0, NULL, NULL, 0};
>   	int result = -ENOMEM;
>   	int violation = 0;
>   	struct {
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index a88c28918a63..6c5691b65b84 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -594,7 +594,7 @@ static void process_buffer_measurement(const void *buf, int size,
>   	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};
> +						NULL, 0, NULL, NULL, 0};
>   	struct {
>   		struct ima_digest_data hdr;
>   		char digest[IMA_MAX_DIGEST_SIZE];
> @@ -611,6 +611,8 @@ static void process_buffer_measurement(const void *buf, int size,
>   	memset(&hash, 0, sizeof(hash));
>   
>   	event_data.filename = eventname;
> +	event_data.buf = buf;
> +	event_data.buf_len = size;
>   
>   	iint->ima_hash = &hash.hdr;
>   	iint->ima_hash->algo = ima_hash_algo;
> diff --git a/security/integrity/ima/ima_template.c b/security/integrity/ima/ima_template.c
> index b631b8bc7624..a76d1c04162a 100644
> --- a/security/integrity/ima/ima_template.c
> +++ b/security/integrity/ima/ima_template.c
> @@ -43,6 +43,8 @@ static const struct ima_template_field supported_fields[] = {
>   	 .field_show = ima_show_template_string},
>   	{.field_id = "sig", .field_init = ima_eventsig_init,
>   	 .field_show = ima_show_template_sig},
> +	{.field_id = "buf", .field_init = ima_eventbuf_init,
> +	 .field_show = ima_show_template_buf},
>   };
>   #define MAX_TEMPLATE_NAME_LEN 15
>   
> diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
> index 513b457ae900..43d1404141c1 100644
> --- a/security/integrity/ima/ima_template_lib.c
> +++ b/security/integrity/ima/ima_template_lib.c
> @@ -162,6 +162,12 @@ void ima_show_template_sig(struct seq_file *m, enum ima_show_type show,
>   	ima_show_template_field_data(m, show, DATA_FMT_HEX, field_data);
>   }
>   
> +void ima_show_template_buf(struct seq_file *m, enum ima_show_type show,
> +				struct ima_field_data *field_data)
> +{
> +	ima_show_template_field_data(m, show, DATA_FMT_HEX, field_data);
> +}
> +
>   /**
>    * ima_parse_buf() - Parses lengths and data from an input buffer
>    * @bufstartp:       Buffer start address.
> @@ -389,3 +395,17 @@ int ima_eventsig_init(struct ima_event_data *event_data,
>   	return ima_write_template_field_data(xattr_value, event_data->xattr_len,
>   					     DATA_FMT_HEX, field_data);
>   }
> +
> +/*
> + *  ima_eventbuf_init - include the buffer(kexec-cmldine) as part of the
> + *  template data.
> + */
> +int ima_eventbuf_init(struct ima_event_data *event_data,
> +				struct ima_field_data *field_data)
> +{
> +	if ((!event_data->buf) || (event_data->buf_len == 0))
> +		return 0;
> +
> +	return ima_write_template_field_data(event_data->buf, event_data->buf_len,
> +					DATA_FMT_HEX, field_data);
> +}
> diff --git a/security/integrity/ima/ima_template_lib.h b/security/integrity/ima/ima_template_lib.h
> index 6a3d8b831deb..f0178bc60c55 100644
> --- a/security/integrity/ima/ima_template_lib.h
> +++ b/security/integrity/ima/ima_template_lib.h
> @@ -29,6 +29,8 @@ void ima_show_template_string(struct seq_file *m, enum ima_show_type show,
>   			      struct ima_field_data *field_data);
>   void ima_show_template_sig(struct seq_file *m, enum ima_show_type show,
>   			   struct ima_field_data *field_data);
> +void ima_show_template_buf(struct seq_file *m, enum ima_show_type show,
> +				struct ima_field_data *field_data);
>   int ima_parse_buf(void *bufstartp, void *bufendp, void **bufcurp,
>   		  int maxfields, struct ima_field_data *fields, int *curfields,
>   		  unsigned long *len_mask, int enforce_mask, char *bufname);
> @@ -42,4 +44,6 @@ int ima_eventname_ng_init(struct ima_event_data *event_data,
>   			  struct ima_field_data *field_data);
>   int ima_eventsig_init(struct ima_event_data *event_data,
>   		      struct ima_field_data *field_data);
> +int ima_eventbuf_init(struct ima_event_data *event_data,
> +				struct ima_field_data *field_data);
>   #endif /* __LINUX_IMA_TEMPLATE_LIB_H */

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