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SubjectRe: [PATCH 2/3 v5] add a new template field buf to contain the buffer
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On 5/11/2019 12:37 AM, Prakhar Srivastava wrote:
> From: Prakhar Srivastava <prsriva02@gmail.com>
>
> The buffer(cmdline args) added to the ima log cannot be attested
> without having the actual buffer. Thus to make the measured buffer
> available to stroe/read a new ima temaplate (buf) is added.

Hi Prakhar

please fix the typos. More comments below.


> The cmdline args used for soft reboot can then be read and attested
> later.
>
> The patch adds a new template field buf to store/read the buffer
> used while measuring kexec_cmdline args in the
> [PATCH 1/2 v5]: "add a new ima hook and policy to measure the cmdline".
> Signed-off-by: Prakhar Srivastava <prsriva02@gmail.com>
> ---
> security/integrity/ima/ima_main.c | 23 +++++++++++++++++++++++
> security/integrity/ima/ima_template.c | 2 ++
> security/integrity/ima/ima_template_lib.c | 21 +++++++++++++++++++++
> security/integrity/ima/ima_template_lib.h | 4 ++++
> security/integrity/integrity.h | 1 +
> 5 files changed, 51 insertions(+)
>
> diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
> index 1d186bda25fe..ca12885ca241 100644
> --- a/security/integrity/ima/ima_main.c
> +++ b/security/integrity/ima/ima_main.c
> @@ -605,10 +605,32 @@ static int process_buffer_measurement(const void *buf, int size,
> int pcr = CONFIG_IMA_MEASURE_PCR_IDX;
> int action = 0;
>
> + struct buffer_xattr {
> + enum evm_ima_xattr_type type;
> + u16 buf_length;
> + unsigned char buf[0];
> + };
> + struct buffer_xattr *buffer_event_data = NULL;
> + int alloc_length = 0;
> +
> action = ima_get_action(NULL, cred, secid, 0, KEXEC_CMDLINE, &pcr);
> if (!(action & IMA_AUDIT) && !(action & IMA_MEASURE))
> goto out;
>
> + alloc_length = sizeof(struct buffer_xattr) + size;
> + buffer_event_data = kzalloc(alloc_length, GFP_KERNEL);
> + if (!buffer_event_data) {
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + buffer_event_data->type = IMA_XATTR_BUFFER;
> + buffer_event_data->buf_length = size;
> + memcpy(buffer_event_data->buf, buf, size);
> +
> + event_data.xattr_value = (struct evm_ima_xattr_data *)buffer_event_data;
> + event_data.xattr_len = alloc_length;

I would prefer that you introduce two new fields in the ima_event_data
structure. You can initialize them directly with the parameters of
process_buffer_measurement(). ima_write_template_field_data() will make
a copy.


> +
> memset(iint, 0, sizeof(*iint));
> memset(&hash, 0, sizeof(hash));
>
> @@ -638,6 +660,7 @@ static int process_buffer_measurement(const void *buf, int size,
> }
>
> out:
> + kfree(buffer_event_data);
> return ret;
> }
>
> 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},

Please update Documentation/security/IMA-templates.rst

Thanks

Roberto


> };
> #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..95a827f42c18 100644
> --- a/security/integrity/ima/ima_template_lib.c
> +++ b/security/integrity/ima/ima_template_lib.c
> @@ -162,6 +162,11 @@ 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 +394,19 @@ 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)
> +{
> + struct evm_ima_xattr_data *xattr_value = event_data->xattr_value;
> +
> + if ((!xattr_value) || (xattr_value->type != IMA_XATTR_BUFFER))
> + return 0;
> +
> + return ima_write_template_field_data(xattr_value, event_data->xattr_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..12f1a8578b31 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 */
> diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
> index 7de59f44cba3..14ef904f091d 100644
> --- a/security/integrity/integrity.h
> +++ b/security/integrity/integrity.h
> @@ -74,6 +74,7 @@ enum evm_ima_xattr_type {
> EVM_IMA_XATTR_DIGSIG,
> IMA_XATTR_DIGEST_NG,
> EVM_XATTR_PORTABLE_DIGSIG,
> + IMA_XATTR_BUFFER,
> IMA_XATTR_LAST
> };
>
>

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