[PATCH 2/3 v5] add a new template field buf to contain the buffer

[Prakhar Srivastava]

From: Prakhar Srivastava <prsriva02@xxxxxxxxx>

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. 
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@xxxxxxxxx>
---
 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;
+
 	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},
 };
 #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
 };
 
-- 
2.20.1