NAME

       CMS_signed_get_attr_count, CMS_signed_get_attr_by_NID, CMS_signed_get_attr_by_OBJ,
       CMS_signed_get_attr, CMS_signed_delete_attr, CMS_signed_add1_attr,
       CMS_signed_add1_attr_by_OBJ, CMS_signed_add1_attr_by_NID, CMS_signed_add1_attr_by_txt,
       CMS_signed_get0_data_by_OBJ, CMS_unsigned_get_attr_count, CMS_unsigned_get_attr_by_NID,
       CMS_unsigned_get_attr_by_OBJ, CMS_unsigned_get_attr, CMS_unsigned_delete_attr,
       CMS_unsigned_add1_attr, CMS_unsigned_add1_attr_by_OBJ, CMS_unsigned_add1_attr_by_NID,
       CMS_unsigned_add1_attr_by_txt, CMS_unsigned_get0_data_by_OBJ - CMS signed and unsigned
       attribute functions

SYNOPSIS

        #include <openssl/cms.h>

        int CMS_signed_get_attr_count(const CMS_SignerInfo *si);
        int CMS_signed_get_attr_by_NID(const CMS_SignerInfo *si, int nid,
                                       int lastpos);
        int CMS_signed_get_attr_by_OBJ(const CMS_SignerInfo *si, const ASN1_OBJECT *obj,
                                       int lastpos);
        X509_ATTRIBUTE *CMS_signed_get_attr(const CMS_SignerInfo *si, int loc);
        X509_ATTRIBUTE *CMS_signed_delete_attr(CMS_SignerInfo *si, int loc);
        int CMS_signed_add1_attr(CMS_SignerInfo *si, X509_ATTRIBUTE *attr);
        int CMS_signed_add1_attr_by_OBJ(CMS_SignerInfo *si,
                                        const ASN1_OBJECT *obj, int type,
                                        const void *bytes, int len);
        int CMS_signed_add1_attr_by_NID(CMS_SignerInfo *si,
                                        int nid, int type,
                                        const void *bytes, int len);
        int CMS_signed_add1_attr_by_txt(CMS_SignerInfo *si,
                                        const char *attrname, int type,
                                        const void *bytes, int len);
        void *CMS_signed_get0_data_by_OBJ(const CMS_SignerInfo *si,
                                          const ASN1_OBJECT *oid,
                                          int lastpos, int type);

        int CMS_unsigned_get_attr_count(const CMS_SignerInfo *si);
        int CMS_unsigned_get_attr_by_NID(const CMS_SignerInfo *si, int nid,
                                         int lastpos);
        int CMS_unsigned_get_attr_by_OBJ(const CMS_SignerInfo *si,
                                         const ASN1_OBJECT *obj, int lastpos);
        X509_ATTRIBUTE *CMS_unsigned_get_attr(const CMS_SignerInfo *si, int loc);
        X509_ATTRIBUTE *CMS_unsigned_delete_attr(CMS_SignerInfo *si, int loc);
        int CMS_unsigned_add1_attr(CMS_SignerInfo *si, X509_ATTRIBUTE *attr);
        int CMS_unsigned_add1_attr_by_OBJ(CMS_SignerInfo *si,
                                          const ASN1_OBJECT *obj, int type,
                                          const void *bytes, int len);
        int CMS_unsigned_add1_attr_by_NID(CMS_SignerInfo *si,
                                          int nid, int type,
                                          const void *bytes, int len);
        int CMS_unsigned_add1_attr_by_txt(CMS_SignerInfo *si,
                                          const char *attrname, int type,
                                          const void *bytes, int len);
        void *CMS_unsigned_get0_data_by_OBJ(CMS_SignerInfo *si, ASN1_OBJECT *oid,
                                            int lastpos, int type);

DESCRIPTION

       CMS_signerInfo contains separate attribute lists for signed and unsigned attributes. Each
       CMS_signed_XXX() function is used for signed attributes, and each CMS_unsigned_XXX()
       function is used for unsigned attributes.  Since the CMS_unsigned_XXX() functions work in
       the same way as the CMS_signed_XXX() equivalents, only the CMS_signed_XXX() functions are
       described below.

       CMS_signed_get_attr_by_OBJ() finds the location of the first matching object obj in the
       SignerInfo's si signed attribute list. The search starts at the position after lastpos. If
       the returned value is positive then it can be used on the next call to
       CMS_signed_get_attr_by_OBJ() as the value of lastpos in order to iterate through the
       remaining attributes. lastpos can be set to any negative value on the first call, in order
       to start searching from the start of the signed attribute list.

       CMS_signed_get_attr_by_NID() is similar to CMS_signed_get_attr_by_OBJ() except that it
       passes the numerical identifier (NID) nid associated with the object.  See
       <openssl/obj_mac.h> for a list of NID_*.

       CMS_signed_get_attr() returns the X509_ATTRIBUTE object at index loc in the si signed
       attribute list. loc should be in the range from 0 to CMS_signed_get_attr_count() - 1.

       CMS_signed_delete_attr() removes the X509_ATTRIBUTE object at index loc in the si signed
       attribute list. An error occurs if the si attribute list is NULL.

       CMS_signed_add1_attr() pushes a copy of the passed in X509_ATTRIBUTE object to the si
       signed attribute list. A new signed attribute list is created if required. An error occurs
       if attr is NULL.

       CMS_signed_add1_attr_by_OBJ() creates a new signed X509_ATTRIBUTE using
       X509_ATTRIBUTE_set1_object() and X509_ATTRIBUTE_set1_data() to assign a new obj with type
       type and data bytes of length len and then pushes it to the key object's attribute list.

       CMS_signed_add1_attr_by_NID() is similar to CMS_signed_add1_attr_by_OBJ() except that it
       passes the numerical identifier (NID) nid associated with the object.  See
       <openssl/obj_mac.h> for a list of NID_*.

       CMS_signed_add1_attr_by_txt() is similar to CMS_signed_add1_attr_by_OBJ() except that it
       passes a name attrname associated with the object.  See <openssl/obj_mac.h> for a list of
       SN_* names.

       CMS_signed_get0_data_by_OBJ() finds the first attribute in a si signed attributes list
       that matches the obj starting at index lastpos and returns the data retrieved from the
       found attributes first ASN1_TYPE object. An error will occur if the attribute type type
       does not match the type of the ASN1_TYPE object OR if type is either V_ASN1_BOOLEAN or
       V_ASN1_NULL OR the attribute is not found.  If lastpos is less than -1 then an error will
       occur if there are multiple objects in the signed attribute list that match obj.  If
       lastpos is less than -2 then an error will occur if there is more than one ASN1_TYPE
       object in the found signed attribute.

       Refer to X509_ATTRIBUTE(3) for information related to attributes.

RETURN VALUES

       The CMS_unsigned_XXX() functions return values are similar to those of the equivalent
       CMS_signed_XXX() functions.

       CMS_signed_get_attr_count() returns the number of signed attributes in the SignerInfo si,
       or -1 if the signed attribute list is NULL.

       CMS_signed_get_attr_by_OBJ() returns -1 if either the signed attribute list of si is empty
       OR if obj is not found, otherwise it returns the location of the obj in the SignerInfo's
       si signed attribute list.

       CMS_signed_get_attr_by_NID() is similar to CMS_signed_get_attr_by_OBJ() except that it
       returns -2 if the nid is not known by OpenSSL.

       CMS_signed_get_attr() returns either a signed X509_ATTRIBUTE or NULL on error.

       CMS_signed_delete_attr() returns either the removed signed X509_ATTRIBUTE or NULL if there
       is a error.

       CMS_signed_add1_attr(), CMS_signed_add1_attr_by_OBJ(), CMS_signed_add1_attr_by_NID(),
       CMS_signed_add1_attr_by_txt(), return 1 on success or 0 on error.

       CMS_signed_get0_data_by_OBJ() returns the data retrieved from the found signed attributes
       first ASN1_TYPE object, or NULL if an error occurs.

NOTES

       Some attributes are added automatically during the signing process.

       Calling CMS_SignerInfo_sign() adds the NID_pkcs9_signingTime signed attribute.

       Calling CMS_final(), CMS_final_digest() or CMS_dataFinal() adds the
       NID_pkcs9_messageDigest signed attribute.

       The NID_pkcs9_contentType signed attribute is always added if the NID_pkcs9_signingTime
       attribute is added.

       Calling CMS_sign_ex(), CMS_sign_receipt() or CMS_add1_signer() may add attributes
       depending on the flags parameter. See CMS_add1_signer(3) for more information.

       OpenSSL applies special rules for the following attribute NIDs:

       CMS Signed Attributes
           NID_pkcs9_contentType NID_pkcs9_messageDigest NID_pkcs9_signingTime

       ESS Signed Attributes
           NID_id_smime_aa_signingCertificate NID_id_smime_aa_signingCertificateV2
           NID_id_smime_aa_receiptRequest

       CMS Unsigned Attributes
           NID_pkcs9_countersignature

       CMS_signed_add1_attr(), CMS_signed_add1_attr_by_OBJ(), CMS_signed_add1_attr_by_NID(),
       CMS_signed_add1_attr_by_txt() and the equivalent CMS_unsigned_add1_attrXXX() functions
       allow duplicate attributes to be added. The attribute rules are not checked during these
       function calls, and are deferred until the sign or verify process (i.e. during calls to
       any of CMS_sign_ex(), CMS_sign(), CMS_sign_receipt(), CMS_add1_signer(), CMS_Final(),
       CMS_dataFinal(), CMS_final_digest(), CMS_verify(), CMS_verify_receipt() or
       CMS_SignedData_verify()).

       For CMS attribute rules see RFC 5652 Section 11.  For ESS attribute rules see RFC 2634
       Section 1.3.4 and RFC 5035 Section 5.4.

SEE ALSO

       X509_ATTRIBUTE(3)

COPYRIGHT

       Copyright 2023-2024 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use this file except
       in compliance with the License.  You can obtain a copy in the file LICENSE in the source
       distribution or at <https://www.openssl.org/source/license.html>.