ima: add crypto agility support for template-hash algorithm

The template hash showed by the ascii_runtime_measurements and
binary_runtime_measurements is the one calculated using sha1 and there is
no possibility to change this value, despite the fact that the template
hash is calculated using the hash algorithms corresponding to all the PCR
banks configured in the TPM.

Add the support to retrieve the ima log with the template data hash
calculated with a specific hash algorithm.
Add a new file in the securityfs ima directory for each hash algo
configured in a PCR bank of the TPM. Each new file has the name with
the following structure:

        {binary, ascii}_runtime_measurements_<hash_algo_name>

Legacy files are kept, to avoid breaking existing applications, but as
symbolic links which point to {binary, ascii}_runtime_measurements_sha1
files. These two files are created even if a TPM chip is not detected or
the sha1 bank is not configured in the TPM.

As example, in the case a TPM chip is present and sha256 is the only
configured PCR bank, the listing of the securityfs ima directory is the
following:

lr--r--r-- [...] ascii_runtime_measurements -> ascii_runtime_measurements_sha1
-r--r----- [...] ascii_runtime_measurements_sha1
-r--r----- [...] ascii_runtime_measurements_sha256
lr--r--r-- [...] binary_runtime_measurements -> binary_runtime_measurements_sha1
-r--r----- [...] binary_runtime_measurements_sha1
-r--r----- [...] binary_runtime_measurements_sha256
--w------- [...] policy
-r--r----- [...] runtime_measurements_count
-r--r----- [...] violations

Signed-off-by: Enrico Bravi <enrico.bravi@polito.it>
Signed-off-by: Silvia Sisinni <silvia.sisinni@polito.it>
Reviewed-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

1 files changed, 122 insertions, 12 deletions

diff --git a/security/integrity/ima/ima_fs.c b/security/integrity/ima/ima_fs.c
index cd1683dad3bf..abdd22007ed8 100644
--- a/security/integrity/ima/ima_fs.c
+++ b/security/integrity/ima/ima_fs.c
@@ -116,9 +116,31 @@ void ima_putc(struct seq_file *m, void *data, int datalen)
 		seq_putc(m, *(char *)data++);
 }
 
+static struct dentry **ascii_securityfs_measurement_lists __ro_after_init;
+static struct dentry **binary_securityfs_measurement_lists __ro_after_init;
+static int securityfs_measurement_list_count __ro_after_init;
+
+static void lookup_template_data_hash_algo(int *algo_idx, enum hash_algo *algo,
+					   struct seq_file *m,
+					   struct dentry **lists)
+{
+	struct dentry *dentry;
+	int i;
+
+	dentry = file_dentry(m->file);
+
+	for (i = 0; i < securityfs_measurement_list_count; i++) {
+		if (dentry == lists[i]) {
+			*algo_idx = i;
+			*algo = ima_algo_array[i].algo;
+			break;
+		}
+	}
+}
+
 /* print format:
  *       32bit-le=pcr#
- *       char[20]=template digest
+ *       char[n]=template digest
  *       32bit-le=template name size
  *       char[n]=template name
  *       [eventdata length]
@@ -132,7 +154,15 @@ int ima_measurements_show(struct seq_file *m, void *v)
 	char *template_name;
 	u32 pcr, namelen, template_data_len; /* temporary fields */
 	bool is_ima_template = false;
-	int i;
+	enum hash_algo algo;
+	int i, algo_idx;
+
+	algo_idx = ima_sha1_idx;
+	algo = HASH_ALGO_SHA1;
+
+	if (m->file != NULL)
+		lookup_template_data_hash_algo(&algo_idx, &algo, m,
+					       binary_securityfs_measurement_lists);
 
 	/* get entry */
 	e = qe->entry;
@@ -151,7 +181,7 @@ int ima_measurements_show(struct seq_file *m, void *v)
 	ima_putc(m, &pcr, sizeof(e->pcr));
 
 	/* 2nd: template digest */
-	ima_putc(m, e->digests[ima_sha1_idx].digest, TPM_DIGEST_SIZE);
+	ima_putc(m, e->digests[algo_idx].digest, hash_digest_size[algo]);
 
 	/* 3rd: template name size */
 	namelen = !ima_canonical_fmt ? strlen(template_name) :
@@ -220,7 +250,15 @@ static int ima_ascii_measurements_show(struct seq_file *m, void *v)
 	struct ima_queue_entry *qe = v;
 	struct ima_template_entry *e;
 	char *template_name;
-	int i;
+	enum hash_algo algo;
+	int i, algo_idx;
+
+	algo_idx = ima_sha1_idx;
+	algo = HASH_ALGO_SHA1;
+
+	if (m->file != NULL)
+		lookup_template_data_hash_algo(&algo_idx, &algo, m,
+					       ascii_securityfs_measurement_lists);
 
 	/* get entry */
 	e = qe->entry;
@@ -233,8 +271,8 @@ static int ima_ascii_measurements_show(struct seq_file *m, void *v)
 	/* 1st: PCR used (config option) */
 	seq_printf(m, "%2d ", e->pcr);
 
-	/* 2nd: SHA1 template hash */
-	ima_print_digest(m, e->digests[ima_sha1_idx].digest, TPM_DIGEST_SIZE);
+	/* 2nd: template hash */
+	ima_print_digest(m, e->digests[algo_idx].digest, hash_digest_size[algo]);
 
 	/* 3th:  template name */
 	seq_printf(m, " %s", template_name);
@@ -379,6 +417,71 @@ static const struct seq_operations ima_policy_seqops = {
 };
 #endif
 
+static void __init remove_securityfs_measurement_lists(struct dentry **lists)
+{
+	int i;
+
+	if (lists) {
+		for (i = 0; i < securityfs_measurement_list_count; i++)
+			securityfs_remove(lists[i]);
+
+		kfree(lists);
+	}
+
+	securityfs_measurement_list_count = 0;
+}
+
+static int __init create_securityfs_measurement_lists(void)
+{
+	char file_name[NAME_MAX + 1];
+	struct dentry *dentry;
+	u16 algo;
+	int i;
+
+	securityfs_measurement_list_count = NR_BANKS(ima_tpm_chip);
+
+	if (ima_sha1_idx >= NR_BANKS(ima_tpm_chip))
+		securityfs_measurement_list_count++;
+
+	ascii_securityfs_measurement_lists =
+	    kcalloc(securityfs_measurement_list_count, sizeof(struct dentry *),
+		    GFP_KERNEL);
+	if (!ascii_securityfs_measurement_lists)
+		return -ENOMEM;
+
+	binary_securityfs_measurement_lists =
+	    kcalloc(securityfs_measurement_list_count, sizeof(struct dentry *),
+		    GFP_KERNEL);
+	if (!binary_securityfs_measurement_lists)
+		return -ENOMEM;
+
+	for (i = 0; i < securityfs_measurement_list_count; i++) {
+		algo = ima_algo_array[i].algo;
+
+		sprintf(file_name, "ascii_runtime_measurements_%s",
+			hash_algo_name[algo]);
+		dentry = securityfs_create_file(file_name, S_IRUSR | S_IRGRP,
+						ima_dir, NULL,
+						&ima_ascii_measurements_ops);
+		if (IS_ERR(dentry))
+			return PTR_ERR(dentry);
+
+		ascii_securityfs_measurement_lists[i] = dentry;
+
+		sprintf(file_name, "binary_runtime_measurements_%s",
+			hash_algo_name[algo]);
+		dentry = securityfs_create_file(file_name, S_IRUSR | S_IRGRP,
+						ima_dir, NULL,
+						&ima_measurements_ops);
+		if (IS_ERR(dentry))
+			return PTR_ERR(dentry);
+
+		binary_securityfs_measurement_lists[i] = dentry;
+	}
+
+	return 0;
+}
+
 /*
  * ima_open_policy: sequentialize access to the policy file
  */
@@ -454,6 +557,9 @@ int __init ima_fs_init(void)
 {
 	int ret;
 
+	ascii_securityfs_measurement_lists = NULL;
+	binary_securityfs_measurement_lists = NULL;
+
 	ima_dir = securityfs_create_dir("ima", integrity_dir);
 	if (IS_ERR(ima_dir))
 		return PTR_ERR(ima_dir);
@@ -465,19 +571,21 @@ int __init ima_fs_init(void)
 		goto out;
 	}
 
+	ret = create_securityfs_measurement_lists();
+	if (ret != 0)
+		goto out;
+
 	binary_runtime_measurements =
-	    securityfs_create_file("binary_runtime_measurements",
-				   S_IRUSR | S_IRGRP, ima_dir, NULL,
-				   &ima_measurements_ops);
+	    securityfs_create_symlink("binary_runtime_measurements", ima_dir,
+				      "binary_runtime_measurements_sha1", NULL);
 	if (IS_ERR(binary_runtime_measurements)) {
 		ret = PTR_ERR(binary_runtime_measurements);
 		goto out;
 	}
 
 	ascii_runtime_measurements =
-	    securityfs_create_file("ascii_runtime_measurements",
-				   S_IRUSR | S_IRGRP, ima_dir, NULL,
-				   &ima_ascii_measurements_ops);
+	    securityfs_create_symlink("ascii_runtime_measurements", ima_dir,
+				      "ascii_runtime_measurements_sha1", NULL);
 	if (IS_ERR(ascii_runtime_measurements)) {
 		ret = PTR_ERR(ascii_runtime_measurements);
 		goto out;
@@ -515,6 +623,8 @@ out:
 	securityfs_remove(runtime_measurements_count);
 	securityfs_remove(ascii_runtime_measurements);
 	securityfs_remove(binary_runtime_measurements);
+	remove_securityfs_measurement_lists(ascii_securityfs_measurement_lists);
+	remove_securityfs_measurement_lists(binary_securityfs_measurement_lists);
 	securityfs_remove(ima_symlink);
 	securityfs_remove(ima_dir);