ima: do not send field length to userspace for digest of ima template

This patch defines a new value for the 'ima_show_type' enumerator
(IMA_SHOW_BINARY_NO_FIELD_LEN) to prevent that the field length
is transmitted through the 'binary_runtime_measurements' interface
for the digest field of the 'ima' template.

Fixes commit: 3ce1217 ima: define template fields library and new helpers

Signed-off-by: Roberto Sassu <roberto.sassu@polito.it>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

3 files changed, 18 insertions, 5 deletions

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index a21cf706d213..9636e17c9f5d 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -26,7 +26,8 @@
 
 #include "../integrity.h"
 
-enum ima_show_type { IMA_SHOW_BINARY, IMA_SHOW_ASCII };
+enum ima_show_type { IMA_SHOW_BINARY, IMA_SHOW_BINARY_NO_FIELD_LEN,
+                     IMA_SHOW_ASCII };
 enum tpm_pcrs { TPM_PCR0 = 0, TPM_PCR8 = 8 };
 
 /* digest size for IMA, fits SHA1 or MD5 */
diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index d47a7c86a21d..db01125926bd 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -120,6 +120,7 @@ static int ima_measurements_show(struct seq_file *m, void *v)
         struct ima_template_entry *e;
         int namelen;
         u32 pcr = CONFIG_IMA_MEASURE_PCR_IDX;
+        bool is_ima_template = false;
         int i;
 
         /* get entry */
@@ -145,14 +146,21 @@ static int ima_measurements_show(struct seq_file *m, void *v)
         ima_putc(m, e->template_desc->name, namelen);
 
         /* 5th:  template length (except for 'ima' template) */
-        if (strcmp(e->template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0)
+        if (strcmp(e->template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0)
+                is_ima_template = true;
+
+        if (!is_ima_template)
                 ima_putc(m, &e->template_data_len,
                          sizeof(e->template_data_len));
 
         /* 6th:  template specific data */
         for (i = 0; i < e->template_desc->num_fields; i++) {
-                e->template_desc->fields[i]->field_show(m, IMA_SHOW_BINARY,
-                                                        &e->template_data[i]);
+                enum ima_show_type show = IMA_SHOW_BINARY;
+                struct ima_template_field *field = e->template_desc->fields[i];
+
+                if (is_ima_template && strcmp(field->field_id, "d") == 0)
+                        show = IMA_SHOW_BINARY_NO_FIELD_LEN;
+                field->field_show(m, show, &e->template_data[i]);
         }
         return 0;
 }
diff --git a/security/integrity/ima/ima_template_lib.c b/security/integrity/ima/ima_template_lib.c
index 6d66ad6ed265..c38adcc910fb 100644
--- a/security/integrity/ima/ima_template_lib.c
+++ b/security/integrity/ima/ima_template_lib.c
@@ -109,9 +109,12 @@ static void ima_show_template_data_binary(struct seq_file *m,
                                           enum data_formats datafmt,
                                           struct ima_field_data *field_data)
 {
-        ima_putc(m, &field_data->len, sizeof(u32));
+        if (show != IMA_SHOW_BINARY_NO_FIELD_LEN)
+                ima_putc(m, &field_data->len, sizeof(u32));
+
         if (!field_data->len)
                 return;
+
         ima_putc(m, field_data->data, field_data->len);
 }
 
@@ -125,6 +128,7 @@ static void ima_show_template_field_data(struct seq_file *m,
                 ima_show_template_data_ascii(m, show, datafmt, field_data);
                 break;
         case IMA_SHOW_BINARY:
+        case IMA_SHOW_BINARY_NO_FIELD_LEN:
                 ima_show_template_data_binary(m, show, datafmt, field_data);
                 break;
         default: