ima: read and use signature hash algorithm

All files on the filesystem, currently, are hashed using the same hash
algorithm.  In preparation for files from different packages being
signed using different hash algorithms, this patch adds support for
reading the signature hash algorithm from the 'security.ima' extended
attribute and calculates the appropriate file data hash based on it.

Changelog:
- fix scripts Lindent and checkpatch msgs - Mimi
- fix md5 support for older version, which occupied 20 bytes in the
  xattr, not the expected 16 bytes.  Fix the comparison to compare
  only the first 16 bytes.

Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

diff --git a/security/integrity/digsig_asymmetric.c b/security/integrity/digsig_asymmetric.c
index b4754667659da1d6d8896a07f689c4b3f53fc2c8..9eae4809006be6f364ed9e5fe31ccb897381b856 100644 (file)
--- a/security/integrity/digsig_asymmetric.c
+++ b/security/integrity/digsig_asymmetric.c
@@ -19,17 +19,6 @@
 
 #include "integrity.h"
 
-/*
- * signature format v2 - for using with asymmetric keys
- */
-struct signature_v2_hdr {
-       uint8_t version;        /* signature format version */
-       uint8_t hash_algo;      /* Digest algorithm [enum pkey_hash_algo] */
-       uint32_t keyid;         /* IMA key identifier - not X509/PGP specific*/
-       uint16_t sig_size;      /* signature size */
-       uint8_t sig[0];         /* signature payload */
-} __packed;
-
 /*
  * Request an asymmetric key.
  */

diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index eb86032f4f1e5d05fef175467163bbcf2aba5dc0..efcdef2bf1bc364b446c1855dab05863cd63a8af 100644 (file)
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -99,7 +99,9 @@ static inline unsigned long ima_hash_key(u8 *digest)
 int ima_get_action(struct inode *inode, int mask, int function);
 int ima_must_measure(struct inode *inode, int mask, int function);
 int ima_collect_measurement(struct integrity_iint_cache *iint,
-                           struct file *file);
+                           struct file *file,
+                           struct evm_ima_xattr_data **xattr_value,
+                           int *xattr_len);
 void ima_store_measurement(struct integrity_iint_cache *iint, struct file *file,
                           const unsigned char *filename);
 void ima_audit_measurement(struct integrity_iint_cache *iint,
@@ -132,17 +134,25 @@ void ima_delete_rules(void);
 
 #ifdef CONFIG_IMA_APPRAISE
 int ima_appraise_measurement(int func, struct integrity_iint_cache *iint,
-                            struct file *file, const unsigned char *filename);
+                            struct file *file, const unsigned char *filename,
+                            struct evm_ima_xattr_data *xattr_value,
+                            int xattr_len);
 int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func);
 void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file);
 enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint,
                                           int func);
+void ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, int xattr_len,
+                      struct ima_digest_data *hash);
+int ima_read_xattr(struct dentry *dentry,
+                  struct evm_ima_xattr_data **xattr_value);
 
 #else
 static inline int ima_appraise_measurement(int func,
                                           struct integrity_iint_cache *iint,
                                           struct file *file,
-                                          const unsigned char *filename)
+                                          const unsigned char *filename,
+                                          struct evm_ima_xattr_data *xattr_value,
+                                          int xattr_len)
 {
        return INTEGRITY_UNKNOWN;
 }
@@ -163,6 +173,19 @@ static inline enum integrity_status ima_get_cache_status(struct integrity_iint_c
 {
        return INTEGRITY_UNKNOWN;
 }
+
+static inline void ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value,
+                                    int xattr_len,
+                                    struct ima_digest_data *hash)
+{
+}
+
+static inline int ima_read_xattr(struct dentry *dentry,
+                                struct evm_ima_xattr_data **xattr_value)
+{
+       return 0;
+}
+
 #endif
 
 /* LSM based policy rules require audit */

diff --git a/security/integrity/ima/ima_api.c b/security/integrity/ima/ima_api.c
index e531fe22e582476885b454ae5538b0c05004fce6..1dba98e2d7e99b6e2d83b1374427297d6a7c4011 100644 (file)
--- a/security/integrity/ima/ima_api.c
+++ b/security/integrity/ima/ima_api.c
@@ -139,17 +139,27 @@ int ima_must_measure(struct inode *inode, int mask, int function)
  * Return 0 on success, error code otherwise
  */
 int ima_collect_measurement(struct integrity_iint_cache *iint,
-                           struct file *file)
+                           struct file *file,
+                           struct evm_ima_xattr_data **xattr_value,
+                           int *xattr_len)
 {
        struct inode *inode = file_inode(file);
        const char *filename = file->f_dentry->d_name.name;
        int result = 0;
 
+       if (xattr_value)
+               *xattr_len = ima_read_xattr(file->f_dentry, xattr_value);
+
        if (!(iint->flags & IMA_COLLECTED)) {
                u64 i_version = file_inode(file)->i_version;
 
                /* use default hash algorithm */
                iint->ima_hash.algo = ima_hash_algo;
+
+               if (xattr_value)
+                       ima_get_hash_algo(*xattr_value, *xattr_len,
+                                         &iint->ima_hash);
+
                result = ima_calc_file_hash(file, &iint->ima_hash);
                if (!result) {
                        iint->version = i_version;

diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index 3833b0fa71084576eda8562187baaaa08a52c9a5..00708a3052cc3e50c0f4a991e33a2a9858ddddc4 100644 (file)
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -107,6 +107,34 @@ static void ima_cache_flags(struct integrity_iint_cache *iint, int func)
        }
 }
 
+void ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, int xattr_len,
+                      struct ima_digest_data *hash)
+{
+       struct signature_v2_hdr *sig;
+
+       if (!xattr_value || xattr_len < 0 || xattr_len <= 1 + sizeof(*sig))
+               return;
+
+       sig = (typeof(sig)) xattr_value->digest;
+
+       if (xattr_value->type != EVM_IMA_XATTR_DIGSIG || sig->version != 2)
+               return;
+
+       hash->algo = sig->hash_algo;
+}
+
+int ima_read_xattr(struct dentry *dentry,
+                  struct evm_ima_xattr_data **xattr_value)
+{
+       struct inode *inode = dentry->d_inode;
+
+       if (!inode->i_op->getxattr)
+               return 0;
+
+       return vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value,
+                                 0, GFP_NOFS);
+}
+
 /*
  * ima_appraise_measurement - appraise file measurement
  *
@@ -116,23 +144,22 @@ static void ima_cache_flags(struct integrity_iint_cache *iint, int func)
  * Return 0 on success, error code otherwise
  */
 int ima_appraise_measurement(int func, struct integrity_iint_cache *iint,
-                            struct file *file, const unsigned char *filename)
+                            struct file *file, const unsigned char *filename,
+                            struct evm_ima_xattr_data *xattr_value,
+                            int xattr_len)
 {
        struct dentry *dentry = file->f_dentry;
        struct inode *inode = dentry->d_inode;
-       struct evm_ima_xattr_data *xattr_value = NULL;
        enum integrity_status status = INTEGRITY_UNKNOWN;
        const char *op = "appraise_data";
        char *cause = "unknown";
-       int rc;
+       int rc = xattr_len;
 
        if (!ima_appraise)
                return 0;
        if (!inode->i_op->getxattr)
                return INTEGRITY_UNKNOWN;
 
-       rc = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)&xattr_value,
-                               0, GFP_NOFS);
        if (rc <= 0) {
                if (rc && rc != -ENODATA)
                        goto out;
@@ -159,7 +186,10 @@ int ima_appraise_measurement(int func, struct integrity_iint_cache *iint,
                        status = INTEGRITY_FAIL;
                        break;
                }
-               if (rc - 1 == iint->ima_hash.length)
+               if (xattr_len - 1 >= iint->ima_hash.length)
+                       /* xattr length may be longer. md5 hash in previous
+                          version occupied 20 bytes in xattr, instead of 16
+                        */
                        rc = memcmp(xattr_value->digest,
                                    iint->ima_hash.digest,
                                    iint->ima_hash.length);
@@ -207,7 +237,6 @@ out:
                ima_cache_flags(iint, func);
        }
        ima_set_cache_status(iint, func, status);
-       kfree(xattr_value);
        return status;
 }
 
@@ -223,7 +252,7 @@ void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file)
        if (iint->flags & IMA_DIGSIG)
                return;
 
-       rc = ima_collect_measurement(iint, file);
+       rc = ima_collect_measurement(iint, file, NULL, NULL);
        if (rc < 0)
                return;
 

diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index 7708c2120d9c8b7398f6389f7981028d2fcc4918..95b5df2c65011e12a38a7cc96a4407738e16ad04 100644 (file)
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -149,6 +149,8 @@ static int process_measurement(struct file *file, const char *filename,
        char *pathbuf = NULL;
        const char *pathname = NULL;
        int rc = -ENOMEM, action, must_appraise, _func;
+       struct evm_ima_xattr_data *xattr_value = NULL, **xattr_ptr = NULL;
+       int xattr_len = 0;
 
        if (!ima_initialized || !S_ISREG(inode->i_mode))
                return 0;
@@ -187,7 +189,10 @@ static int process_measurement(struct file *file, const char *filename,
                goto out_digsig;
        }
 
-       rc = ima_collect_measurement(iint, file);
+       if (action & IMA_APPRAISE_SUBMASK)
+               xattr_ptr = &xattr_value;
+
+       rc = ima_collect_measurement(iint, file, xattr_ptr, &xattr_len);
        if (rc != 0)
                goto out_digsig;
 
@@ -198,7 +203,8 @@ static int process_measurement(struct file *file, const char *filename,
        if (action & IMA_MEASURE)
                ima_store_measurement(iint, file, pathname);
        if (action & IMA_APPRAISE_SUBMASK)
-               rc = ima_appraise_measurement(_func, iint, file, pathname);
+               rc = ima_appraise_measurement(_func, iint, file, pathname,
+                                             xattr_value, xattr_len);
        if (action & IMA_AUDIT)
                ima_audit_measurement(iint, pathname);
        kfree(pathbuf);
@@ -207,6 +213,7 @@ out_digsig:
                rc = -EACCES;
 out:
        mutex_unlock(&inode->i_mutex);
+       kfree(xattr_value);
        if ((rc && must_appraise) && (ima_appraise & IMA_APPRAISE_ENFORCE))
                return -EACCES;
        return 0;

diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
index 0b02ea868e30ba49234e2268a757cb1ff7d2947f..ea2318983d97a933b15c39b5504a58f7427d2731 100644 (file)
--- a/security/integrity/integrity.h
+++ b/security/integrity/integrity.h
@@ -70,6 +70,17 @@ struct ima_digest_data {
        u8 digest[IMA_MAX_DIGEST_SIZE];
 } __packed;
 
+/*
+ * signature format v2 - for using with asymmetric keys
+ */
+struct signature_v2_hdr {
+       uint8_t version;        /* signature format version */
+       uint8_t hash_algo;      /* Digest algorithm [enum pkey_hash_algo] */
+       uint32_t keyid;         /* IMA key identifier - not X509/PGP specific */
+       uint16_t sig_size;      /* signature size */
+       uint8_t sig[0];         /* signature payload */
+} __packed;
+
 /* integrity data associated with an inode */
 struct integrity_iint_cache {
        struct rb_node rb_node; /* rooted in integrity_iint_tree */