Add the content type attribute to additional CMS signerinfo.

[openssl.git] / crypto / cms / cms_att.c

diff --git a/crypto/cms/cms_att.c b/crypto/cms/cms_att.c
index a68b9bced405362dbc6a75e394c51d963f3c7a14..e54818053b84a79b857d558fb7a72052d2c4355f 100644 (file)
--- a/crypto/cms/cms_att.c
+++ b/crypto/cms/cms_att.c
@@ -13,6 +13,56 @@
 #include <openssl/err.h>
 #include <openssl/cms.h>
 #include "cms_lcl.h"
+#include "internal/nelem.h"
+
+/*-
+ * Attribute flags.
+ * CMS attribute restrictions are discussed in
+ *  - RFC 5652 Section 11.
+ * ESS attribute restrictions are discussed in
+ *  - RFC 2634 Section 1.3.4  AND
+ *  - RFC 5035 Section 5.4
+ */
+/* This is a signed attribute */
+#define CMS_ATTR_F_SIGNED         0x01
+/* This is an unsigned attribute */
+#define CMS_ATTR_F_UNSIGNED       0x02
+/* Must be present if there are any other attributes of the same type */
+#define CMS_ATTR_F_REQUIRED_COND  0x10
+/* There can only be one instance of this attribute */
+#define CMS_ATTR_F_ONLY_ONE       0x20
+/* The Attribute's value must have exactly one entry */
+#define CMS_ATTR_F_ONE_ATTR_VALUE 0x40
+
+/* Attributes rules for different attributes */
+static const struct {
+    int nid;   /* The attribute id */
+    int flags;
+} cms_attribute_properties[] = {
+    /* See RFC Section 11 */
+    { NID_pkcs9_contentType, CMS_ATTR_F_SIGNED
+                             | CMS_ATTR_F_ONLY_ONE
+                             | CMS_ATTR_F_ONE_ATTR_VALUE
+                             | CMS_ATTR_F_REQUIRED_COND },
+    { NID_pkcs9_messageDigest, CMS_ATTR_F_SIGNED
+                               | CMS_ATTR_F_ONLY_ONE
+                               | CMS_ATTR_F_ONE_ATTR_VALUE
+                               | CMS_ATTR_F_REQUIRED_COND },
+    { NID_pkcs9_signingTime, CMS_ATTR_F_SIGNED
+                             | CMS_ATTR_F_ONLY_ONE
+                             | CMS_ATTR_F_ONE_ATTR_VALUE },
+    { NID_pkcs9_countersignature, CMS_ATTR_F_UNSIGNED },
+    /* ESS */
+    { NID_id_smime_aa_signingCertificate, CMS_ATTR_F_SIGNED
+                                          | CMS_ATTR_F_ONLY_ONE
+                                          | CMS_ATTR_F_ONE_ATTR_VALUE },
+    { NID_id_smime_aa_signingCertificateV2, CMS_ATTR_F_SIGNED
+                                            | CMS_ATTR_F_ONLY_ONE
+                                            | CMS_ATTR_F_ONE_ATTR_VALUE },
+    { NID_id_smime_aa_receiptRequest, CMS_ATTR_F_SIGNED
+                                      | CMS_ATTR_F_ONLY_ONE
+                                      | CMS_ATTR_F_ONE_ATTR_VALUE }
+};
 
 /* CMS SignedData Attribute utilities */
 
@@ -149,4 +199,86 @@ void *CMS_unsigned_get0_data_by_OBJ(CMS_SignerInfo *si, ASN1_OBJECT *oid,
     return X509at_get0_data_by_OBJ(si->unsignedAttrs, oid, lastpos, type);
 }
 
-/* Specific attribute cases */
+/*
+ * Retrieve an attribute by nid from a stack of attributes starting at index
+ * *lastpos + 1.
+ * Returns the attribute or NULL if there is no attribute.
+ * If an attribute was found *lastpos returns the index of the found attribute.
+ */
+static X509_ATTRIBUTE *cms_attrib_get(int nid,
+                                      const STACK_OF(X509_ATTRIBUTE) *attrs,
+                                      int *lastpos)
+{
+    X509_ATTRIBUTE *at;
+    int loc;
+
+    loc = X509at_get_attr_by_NID(attrs, nid, *lastpos);
+    if (loc < 0)
+        return NULL;
+
+    at = X509at_get_attr(attrs, loc);
+    *lastpos = loc;
+    return at;
+}
+
+static int cms_check_attribute(int nid, int flags, int type,
+                               const STACK_OF(X509_ATTRIBUTE) *attrs,
+                               int have_attrs)
+{
+    int lastpos = -1;
+    X509_ATTRIBUTE *at = cms_attrib_get(nid, attrs, &lastpos);
+
+    if (at != NULL) {
+        int count = X509_ATTRIBUTE_count(at);
+
+        /* Is this attribute allowed? */
+        if (((flags & type) == 0)
+            /* check if multiple attributes of the same type are allowed */
+            || (((flags & CMS_ATTR_F_ONLY_ONE) != 0)
+                && cms_attrib_get(nid, attrs, &lastpos) != NULL)
+            /* Check if attribute should have exactly one value in its set */
+            || (((flags & CMS_ATTR_F_ONE_ATTR_VALUE) != 0)
+                && count != 1)
+            /* There should be at least one value */
+            || count == 0)
+        return 0;
+    } else {
+        /* fail if a required attribute is missing */
+        if (have_attrs
+            && ((flags & CMS_ATTR_F_REQUIRED_COND) != 0)
+            && (flags & type) != 0)
+            return 0;
+    }
+    return 1;
+}
+
+/*
+ * Check that the signerinfo attributes obey the attribute rules which includes
+ * the following checks
+ * - If any signed attributes exist then there must be a Content Type
+ * and Message Digest attribute in the signed attributes.
+ * - The countersignature attribute is an optional unsigned attribute only.
+ * - Content Type, Message Digest, and Signing time attributes are signed
+ *     attributes. Only one instance of each is allowed, with each of these
+ *     attributes containing a single attribute value in its set.
+ */
+int CMS_si_check_attributes(const CMS_SignerInfo *si)
+{
+    int i;
+    int have_signed_attrs = (CMS_signed_get_attr_count(si) > 0);
+    int have_unsigned_attrs = (CMS_unsigned_get_attr_count(si) > 0);
+
+    for (i = 0; i < (int)OSSL_NELEM(cms_attribute_properties); ++i) {
+        int nid = cms_attribute_properties[i].nid;
+        int flags = cms_attribute_properties[i].flags;
+
+        if (!cms_check_attribute(nid, flags, CMS_ATTR_F_SIGNED,
+                                 si->signedAttrs, have_signed_attrs)
+            || !cms_check_attribute(nid, flags, CMS_ATTR_F_UNSIGNED,
+                                    si->unsignedAttrs, have_unsigned_attrs)) {
+            CMSerr(CMS_F_CMS_SI_CHECK_ATTRIBUTES, CMS_R_ATTRIBUTE_ERROR);
+            return 0;
+        }
+    }
+    return 1;
+}