Add missing documentation for X509_ATTRIBUTE related functions.

Partial fix for #8026

Reviewed-by: Tom Cosgrove <tom.cosgrove@arm.com>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/22656)

(cherry picked from commit f1f0731ddf6cb31d62a2c0f406b009ae9817ed7f)

5 files changed, 725 insertions, 0 deletions

diff --git a/doc/build.info b/doc/build.info
index 00dc150721..e3ec1fe46b 100644
--- a/doc/build.info
+++ b/doc/build.info
@@ -843,6 +843,10 @@ DEPEND[html/man3/CMS_sign_receipt.html]=man3/CMS_sign_receipt.pod
 GENERATE[html/man3/CMS_sign_receipt.html]=man3/CMS_sign_receipt.pod
 DEPEND[man/man3/CMS_sign_receipt.3]=man3/CMS_sign_receipt.pod
 GENERATE[man/man3/CMS_sign_receipt.3]=man3/CMS_sign_receipt.pod
+DEPEND[html/man3/CMS_signed_get_attr.html]=man3/CMS_signed_get_attr.pod
+GENERATE[html/man3/CMS_signed_get_attr.html]=man3/CMS_signed_get_attr.pod
+DEPEND[man/man3/CMS_signed_get_attr.3]=man3/CMS_signed_get_attr.pod
+GENERATE[man/man3/CMS_signed_get_attr.3]=man3/CMS_signed_get_attr.pod
 DEPEND[html/man3/CMS_uncompress.html]=man3/CMS_uncompress.pod
 GENERATE[html/man3/CMS_uncompress.html]=man3/CMS_uncompress.pod
 DEPEND[man/man3/CMS_uncompress.3]=man3/CMS_uncompress.pod
@@ -1239,6 +1243,10 @@ DEPEND[html/man3/EVP_PKEY_fromdata.html]=man3/EVP_PKEY_fromdata.pod
 GENERATE[html/man3/EVP_PKEY_fromdata.html]=man3/EVP_PKEY_fromdata.pod
 DEPEND[man/man3/EVP_PKEY_fromdata.3]=man3/EVP_PKEY_fromdata.pod
 GENERATE[man/man3/EVP_PKEY_fromdata.3]=man3/EVP_PKEY_fromdata.pod
+DEPEND[html/man3/EVP_PKEY_get_attr.html]=man3/EVP_PKEY_get_attr.pod
+GENERATE[html/man3/EVP_PKEY_get_attr.html]=man3/EVP_PKEY_get_attr.pod
+DEPEND[man/man3/EVP_PKEY_get_attr.3]=man3/EVP_PKEY_get_attr.pod
+GENERATE[man/man3/EVP_PKEY_get_attr.3]=man3/EVP_PKEY_get_attr.pod
 DEPEND[html/man3/EVP_PKEY_get_default_digest_nid.html]=man3/EVP_PKEY_get_default_digest_nid.pod
 GENERATE[html/man3/EVP_PKEY_get_default_digest_nid.html]=man3/EVP_PKEY_get_default_digest_nid.pod
 DEPEND[man/man3/EVP_PKEY_get_default_digest_nid.3]=man3/EVP_PKEY_get_default_digest_nid.pod
@@ -2655,6 +2663,10 @@ DEPEND[html/man3/X509_ALGOR_dup.html]=man3/X509_ALGOR_dup.pod
 GENERATE[html/man3/X509_ALGOR_dup.html]=man3/X509_ALGOR_dup.pod
 DEPEND[man/man3/X509_ALGOR_dup.3]=man3/X509_ALGOR_dup.pod
 GENERATE[man/man3/X509_ALGOR_dup.3]=man3/X509_ALGOR_dup.pod
+DEPEND[html/man3/X509_ATTRIBUTE.html]=man3/X509_ATTRIBUTE.pod
+GENERATE[html/man3/X509_ATTRIBUTE.html]=man3/X509_ATTRIBUTE.pod
+DEPEND[man/man3/X509_ATTRIBUTE.3]=man3/X509_ATTRIBUTE.pod
+GENERATE[man/man3/X509_ATTRIBUTE.3]=man3/X509_ATTRIBUTE.pod
 DEPEND[html/man3/X509_CRL_get0_by_serial.html]=man3/X509_CRL_get0_by_serial.pod
 GENERATE[html/man3/X509_CRL_get0_by_serial.html]=man3/X509_CRL_get0_by_serial.pod
 DEPEND[man/man3/X509_CRL_get0_by_serial.3]=man3/X509_CRL_get0_by_serial.pod
@@ -2699,6 +2711,10 @@ DEPEND[html/man3/X509_PUBKEY_new.html]=man3/X509_PUBKEY_new.pod
 GENERATE[html/man3/X509_PUBKEY_new.html]=man3/X509_PUBKEY_new.pod
 DEPEND[man/man3/X509_PUBKEY_new.3]=man3/X509_PUBKEY_new.pod
 GENERATE[man/man3/X509_PUBKEY_new.3]=man3/X509_PUBKEY_new.pod
+DEPEND[html/man3/X509_REQ_get_attr.html]=man3/X509_REQ_get_attr.pod
+GENERATE[html/man3/X509_REQ_get_attr.html]=man3/X509_REQ_get_attr.pod
+DEPEND[man/man3/X509_REQ_get_attr.3]=man3/X509_REQ_get_attr.pod
+GENERATE[man/man3/X509_REQ_get_attr.3]=man3/X509_REQ_get_attr.pod
 DEPEND[html/man3/X509_SIG_get0.html]=man3/X509_SIG_get0.pod
 GENERATE[html/man3/X509_SIG_get0.html]=man3/X509_SIG_get0.pod
 DEPEND[man/man3/X509_SIG_get0.3]=man3/X509_SIG_get0.pod
@@ -2974,6 +2990,7 @@ html/man3/CMS_get0_type.html \
 html/man3/CMS_get1_ReceiptRequest.html \
 html/man3/CMS_sign.html \
 html/man3/CMS_sign_receipt.html \
+html/man3/CMS_signed_get_attr.html \
 html/man3/CMS_uncompress.html \
 html/man3/CMS_verify.html \
 html/man3/CMS_verify_receipt.html \
@@ -3073,6 +3090,7 @@ html/man3/EVP_PKEY_digestsign_supports_digest.html \
 html/man3/EVP_PKEY_encapsulate.html \
 html/man3/EVP_PKEY_encrypt.html \
 html/man3/EVP_PKEY_fromdata.html \
+html/man3/EVP_PKEY_get_attr.html \
 html/man3/EVP_PKEY_get_default_digest_nid.html \
 html/man3/EVP_PKEY_get_field_type.html \
 html/man3/EVP_PKEY_get_group_name.html \
@@ -3427,6 +3445,7 @@ html/man3/UI_new.html \
 html/man3/X509V3_get_d2i.html \
 html/man3/X509V3_set_ctx.html \
 html/man3/X509_ALGOR_dup.html \
+html/man3/X509_ATTRIBUTE.html \
 html/man3/X509_CRL_get0_by_serial.html \
 html/man3/X509_EXTENSION_set_object.html \
 html/man3/X509_LOOKUP.html \
@@ -3438,6 +3457,7 @@ html/man3/X509_NAME_get0_der.html \
 html/man3/X509_NAME_get_index_by_NID.html \
 html/man3/X509_NAME_print_ex.html \
 html/man3/X509_PUBKEY_new.html \
+html/man3/X509_REQ_get_attr.html \
 html/man3/X509_SIG_get0.html \
 html/man3/X509_STORE_CTX_get_error.html \
 html/man3/X509_STORE_CTX_new.html \
@@ -3577,6 +3597,7 @@ man/man3/CMS_get0_type.3 \
 man/man3/CMS_get1_ReceiptRequest.3 \
 man/man3/CMS_sign.3 \
 man/man3/CMS_sign_receipt.3 \
+man/man3/CMS_signed_get_attr.3 \
 man/man3/CMS_uncompress.3 \
 man/man3/CMS_verify.3 \
 man/man3/CMS_verify_receipt.3 \
@@ -3676,6 +3697,7 @@ man/man3/EVP_PKEY_digestsign_supports_digest.3 \
 man/man3/EVP_PKEY_encapsulate.3 \
 man/man3/EVP_PKEY_encrypt.3 \
 man/man3/EVP_PKEY_fromdata.3 \
+man/man3/EVP_PKEY_get_attr.3 \
 man/man3/EVP_PKEY_get_default_digest_nid.3 \
 man/man3/EVP_PKEY_get_field_type.3 \
 man/man3/EVP_PKEY_get_group_name.3 \
@@ -4030,6 +4052,7 @@ man/man3/UI_new.3 \
 man/man3/X509V3_get_d2i.3 \
 man/man3/X509V3_set_ctx.3 \
 man/man3/X509_ALGOR_dup.3 \
+man/man3/X509_ATTRIBUTE.3 \
 man/man3/X509_CRL_get0_by_serial.3 \
 man/man3/X509_EXTENSION_set_object.3 \
 man/man3/X509_LOOKUP.3 \
@@ -4041,6 +4064,7 @@ man/man3/X509_NAME_get0_der.3 \
 man/man3/X509_NAME_get_index_by_NID.3 \
 man/man3/X509_NAME_print_ex.3 \
 man/man3/X509_PUBKEY_new.3 \
+man/man3/X509_REQ_get_attr.3 \
 man/man3/X509_SIG_get0.3 \
 man/man3/X509_STORE_CTX_get_error.3 \
 man/man3/X509_STORE_CTX_new.3 \
diff --git a/doc/man3/CMS_signed_get_attr.pod b/doc/man3/CMS_signed_get_attr.pod
new file mode 100644
index 0000000000..833cfc441b
--- /dev/null
+++ b/doc/man3/CMS_signed_get_attr.pod
@@ -0,0 +1,214 @@
+=pod
+
+=head1 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
+
+=head1 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);
+
+=head1 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
+I<obj> in the SignerInfo's I<si> signed attribute list. The search starts at the
+position after I<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 I<lastpos> in
+order to iterate through the remaining attributes. I<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) I<nid> associated with the object.
+See <openssl/obj_mac.h> for a list of NID_*.
+
+CMS_signed_get_attr() returns the B<X509_ATTRIBUTE> object at index I<loc> in the
+I<si> signed attribute list. I<loc> should be in the range from 0 to
+CMS_signed_get_attr_count() - 1.
+
+CMS_signed_delete_attr() removes the B<X509_ATTRIBUTE> object at index I<loc> in
+the I<si> signed attribute list. An error occurs if the I<si> attribute list
+is NULL.
+
+CMS_signed_add1_attr() pushes a copy of the passed in B<X509_ATTRIBUTE> object
+to the I<si> signed attribute list. A new signed attribute list is created if
+required. An error occurs if I<attr> is NULL.
+
+CMS_signed_add1_attr_by_OBJ() creates a new signed B<X509_ATTRIBUTE> using
+X509_ATTRIBUTE_set1_object() and X509_ATTRIBUTE_set1_data() to assign a new
+I<obj> with type I<type> and data I<bytes> of length I<len> and then pushes it
+to the I<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) I<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 I<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 I<si> signed
+attributes list that matches the I<obj> starting at index I<lastpos>
+and returns the data retrieved from the found attributes first B<ASN1_TYPE>
+object. An error will occur if the attribute type I<type> does not match the
+type of the B<ASN1_TYPE> object OR if I<type> is either B<V_ASN1_BOOLEAN> or
+B<V_ASN1_NULL> OR the attribute is not found.
+If I<lastpos> is less than -1 then an error will occur if there are multiple
+objects in the signed attribute list that match I<obj>.
+If I<lastpos> is less than -2 then an error will occur if there is more than
+one B<ASN1_TYPE> object in the found signed attribute.
+
+Refer to L<X509_ATTRIBUTE(3)> for information related to attributes.
+
+=head1 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 I<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
+I<si> is empty OR if I<obj> is not found, otherwise it returns the location of
+the I<obj> in the SignerInfo's I<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 I<nid> is not known by OpenSSL.
+
+CMS_signed_get_attr() returns either a signed B<X509_ATTRIBUTE> or NULL on error.
+
+CMS_signed_delete_attr() returns either the removed signed B<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 B<ASN1_TYPE> object, or NULL if an error occurs.
+
+=head1 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 L<CMS_add1_signer(3)> for
+more information.
+
+OpenSSL applies special rules for the following attribute NIDs:
+
+=over 4
+
+=item CMS Signed Attributes
+
+NID_pkcs9_contentType
+NID_pkcs9_messageDigest
+NID_pkcs9_signingTime
+
+=item ESS Signed Attributes
+
+NID_id_smime_aa_signingCertificate
+NID_id_smime_aa_signingCertificateV2
+NID_id_smime_aa_receiptRequest
+
+=item CMS Unsigned Attributes
+
+NID_pkcs9_countersignature
+
+=back
+
+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.
+
+=head1 SEE ALSO
+
+L<X509_ATTRIBUTE(3)>
+
+=head1 COPYRIGHT
+
+Copyright 2023 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
+L<https://www.openssl.org/source/license.html>.
+
+=cut
diff --git a/doc/man3/EVP_PKEY_get_attr.pod b/doc/man3/EVP_PKEY_get_attr.pod
new file mode 100644
index 0000000000..101677422c
--- /dev/null
+++ b/doc/man3/EVP_PKEY_get_attr.pod
@@ -0,0 +1,113 @@
+=pod
+
+=head1 NAME
+
+EVP_PKEY_get_attr,
+EVP_PKEY_get_attr_count,
+EVP_PKEY_get_attr_by_NID, EVP_PKEY_get_attr_by_OBJ,
+EVP_PKEY_delete_attr,
+EVP_PKEY_add1_attr,
+EVP_PKEY_add1_attr_by_OBJ, EVP_PKEY_add1_attr_by_NID, EVP_PKEY_add1_attr_by_txt
+- EVP_PKEY B<X509_ATTRIBUTE> functions
+
+=head1 SYNOPSIS
+
+ #include <openssl/x509.h>
+
+ int EVP_PKEY_get_attr_count(const EVP_PKEY *key);
+ int EVP_PKEY_get_attr_by_NID(const EVP_PKEY *key, int nid, int lastpos);
+ int EVP_PKEY_get_attr_by_OBJ(const EVP_PKEY *key, const ASN1_OBJECT *obj,
+                              int lastpos);
+ X509_ATTRIBUTE *EVP_PKEY_get_attr(const EVP_PKEY *key, int loc);
+ X509_ATTRIBUTE *EVP_PKEY_delete_attr(EVP_PKEY *key, int loc);
+ int EVP_PKEY_add1_attr(EVP_PKEY *key, X509_ATTRIBUTE *attr);
+ int EVP_PKEY_add1_attr_by_OBJ(EVP_PKEY *key,
+                               const ASN1_OBJECT *obj, int type,
+                               const unsigned char *bytes, int len);
+ int EVP_PKEY_add1_attr_by_NID(EVP_PKEY *key,
+                               int nid, int type,
+                               const unsigned char *bytes, int len);
+ int EVP_PKEY_add1_attr_by_txt(EVP_PKEY *key,
+                               const char *attrname, int type,
+                               const unsigned char *bytes, int len);
+
+=head1 DESCRIPTION
+
+These functions are used by B<PKCS12>.
+
+EVP_PKEY_get_attr_by_OBJ() finds the location of the first matching object I<obj>
+in the I<key> attribute list. The search starts at the position after I<lastpos>.
+If the returned value is positive then it can be used on the next call to
+EVP_PKEY_get_attr_by_OBJ() as the value of I<lastpos> in order to iterate through
+the remaining attributes. I<lastpos> can be set to any negative value on the
+first call, in order to start searching from the start of the attribute list.
+
+EVP_PKEY_get_attr_by_NID() is similar to EVP_PKEY_get_attr_by_OBJ() except that
+it passes the numerical identifier (NID) I<nid> associated with the object.
+See <openssl/obj_mac.h> for a list of NID_*.
+
+EVP_PKEY_get_attr() returns the B<X509_ATTRIBUTE> object at index I<loc> in the
+I<key> attribute list. I<loc> should be in the range from 0 to
+EVP_PKEY_get_attr_count() - 1.
+
+EVP_PKEY_delete_attr() removes the B<X509_ATTRIBUTE> object at index I<loc> in
+the I<key> attribute list.
+
+EVP_PKEY_add1_attr() pushes a copy of the passed in B<X509_ATTRIBUTE> object
+to the I<key> attribute list. A new I<key> attribute list is created if required.
+An error occurs if either I<attr> is NULL, or the attribute already exists.
+
+EVP_PKEY_add1_attr_by_OBJ() creates a new B<X509_ATTRIBUTE> using
+X509_ATTRIBUTE_set1_object() and X509_ATTRIBUTE_set1_data() to assign a new
+I<obj> with type I<type> and data I<bytes> of length I<len> and then pushes it
+to the I<key> object's attribute list. If I<obj> already exists in the attribute
+list then an error occurs.
+
+EVP_PKEY_add1_attr_by_NID() is similar to EVP_PKEY_add1_attr_by_OBJ() except
+that it passes the numerical identifier (NID) I<nid> associated with the object.
+See <openssl/obj_mac.h> for a list of NID_*.
+
+EVP_PKEY_add1_attr_by_txt() is similar to EVP_PKEY_add1_attr_by_OBJ() except
+that it passes a name I<attrname> associated with the object.
+See <openssl/obj_mac.h> for a list of SN_* names.
+
+=head1 RETURN VALUES
+
+EVP_PKEY_get_attr_count() returns the number of attributes in the I<key> object
+attribute list or -1 if the attribute list is NULL.
+
+EVP_PKEY_get_attr_by_OBJ() returns -1 if either the list is empty OR the object
+is not found, otherwise it returns the location of the object in the list.
+
+EVP_PKEY_get_attr_by_NID() is similar to EVP_PKEY_get_attr_by_OBJ(), except that
+it returns -2 if the I<nid> is not known by OpenSSL.
+
+EVP_PKEY_get_attr() returns either a B<X509_ATTRIBUTE> or NULL if there is a
+error.
+
+EVP_PKEY_delete_attr() returns either the removed B<X509_ATTRIBUTE> or NULL if
+there is a error.
+
+EVP_PKEY_add1_attr(), EVP_PKEY_add1_attr_by_OBJ(), EVP_PKEY_add1_attr_by_NID()
+and EVP_PKEY_add1_attr_by_txt() return 1 on success or 0 otherwise.
+
+=head1 NOTES
+
+A B<EVP_PKEY> object's attribute list is initially NULL. All the above functions
+listed will return an error unless EVP_PKEY_add1_attr() is called.
+All functions listed assume that the I<key> is not NULL.
+
+=head1 SEE ALSO
+
+L<X509_ATTRIBUTE(3)>
+
+=head1 COPYRIGHT
+
+Copyright 2023 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
+L<https://www.openssl.org/source/license.html>.
+
+=cut
diff --git a/doc/man3/X509_ATTRIBUTE.pod b/doc/man3/X509_ATTRIBUTE.pod
new file mode 100644
index 0000000000..1eacf3ee3d
--- /dev/null
+++ b/doc/man3/X509_ATTRIBUTE.pod
@@ -0,0 +1,263 @@
+=pod
+
+=head1 NAME
+
+X509_ATTRIBUTE, X509at_get_attr,
+X509at_get_attr_count, X509at_get_attr_by_NID, X509at_get_attr_by_OBJ,
+X509at_delete_attr,
+X509at_add1_attr,
+X509at_add1_attr_by_OBJ, X509at_add1_attr_by_NID, X509at_add1_attr_by_txt,
+X509at_get0_data_by_OBJ,
+X509_ATTRIBUTE_create, X509_ATTRIBUTE_create_by_NID,
+X509_ATTRIBUTE_create_by_OBJ, X509_ATTRIBUTE_create_by_txt,
+X509_ATTRIBUTE_set1_object, X509_ATTRIBUTE_set1_data,
+X509_ATTRIBUTE_count,
+X509_ATTRIBUTE_get0_data, X509_ATTRIBUTE_get0_object, X509_ATTRIBUTE_get0_type
+- X509 attribute functions
+
+=head1 SYNOPSIS
+
+ #include <openssl/x509.h>
+
+ typedef struct x509_attributes_st X509_ATTRIBUTE;
+
+ int X509at_get_attr_count(const STACK_OF(X509_ATTRIBUTE) *x);
+ int X509at_get_attr_by_NID(const STACK_OF(X509_ATTRIBUTE) *x, int nid,
+                            int lastpos);
+ int X509at_get_attr_by_OBJ(const STACK_OF(X509_ATTRIBUTE) *sk,
+                            const ASN1_OBJECT *obj, int lastpos);
+ X509_ATTRIBUTE *X509at_get_attr(const STACK_OF(X509_ATTRIBUTE) *x, int loc);
+ X509_ATTRIBUTE *X509at_delete_attr(STACK_OF(X509_ATTRIBUTE) *x, int loc);
+ STACK_OF(X509_ATTRIBUTE) *X509at_add1_attr(STACK_OF(X509_ATTRIBUTE) **x,
+                                            X509_ATTRIBUTE *attr);
+ STACK_OF(X509_ATTRIBUTE) *X509at_add1_attr_by_OBJ(STACK_OF(X509_ATTRIBUTE)
+                                                   **x, const ASN1_OBJECT *obj,
+                                                   int type,
+                                                   const unsigned char *bytes,
+                                                   int len);
+ STACK_OF(X509_ATTRIBUTE) *X509at_add1_attr_by_NID(STACK_OF(X509_ATTRIBUTE)
+                                                   **x, int nid, int type,
+                                                   const unsigned char *bytes,
+                                                   int len);
+ STACK_OF(X509_ATTRIBUTE) *X509at_add1_attr_by_txt(STACK_OF(X509_ATTRIBUTE)
+                                                   **x, const char *attrname,
+                                                   int type,
+                                                   const unsigned char *bytes,
+                                                   int len);
+ void *X509at_get0_data_by_OBJ(const STACK_OF(X509_ATTRIBUTE) *x,
+                               const ASN1_OBJECT *obj, int lastpos, int type);
+ X509_ATTRIBUTE *X509_ATTRIBUTE_create(int nid, int atrtype, void *value);
+ X509_ATTRIBUTE *X509_ATTRIBUTE_create_by_NID(X509_ATTRIBUTE **attr, int nid,
+                                              int atrtype, const void *data,
+                                              int len);
+ X509_ATTRIBUTE *X509_ATTRIBUTE_create_by_OBJ(X509_ATTRIBUTE **attr,
+                                              const ASN1_OBJECT *obj,
+                                              int atrtype, const void *data,
+                                              int len);
+ X509_ATTRIBUTE *X509_ATTRIBUTE_create_by_txt(X509_ATTRIBUTE **attr,
+                                              const char *atrname, int type,
+                                              const unsigned char *bytes,
+                                              int len);
+ int X509_ATTRIBUTE_set1_object(X509_ATTRIBUTE *attr, const ASN1_OBJECT *obj);
+ int X509_ATTRIBUTE_set1_data(X509_ATTRIBUTE *attr, int attrtype,
+                              const void *data, int len);
+ void *X509_ATTRIBUTE_get0_data(X509_ATTRIBUTE *attr, int idx, int atrtype,
+                                void *data);
+ int X509_ATTRIBUTE_count(const X509_ATTRIBUTE *attr);
+ ASN1_OBJECT *X509_ATTRIBUTE_get0_object(X509_ATTRIBUTE *attr);
+ ASN1_TYPE *X509_ATTRIBUTE_get0_type(X509_ATTRIBUTE *attr, int idx);
+
+=head1 DESCRIPTION
+
+B<X509_ATTRIBUTE> objects are used by many standards including X509, X509_REQ,
+PKCS12, PKCS8, PKCS7 and CMS.
+
+The B<X509_ATTRIBUTE> object is used to represent the ASN.1 Attribute as defined
+in RFC 5280, i.e.
+
+ Attribute ::= SEQUENCE {
+   type             AttributeType,
+   values    SET OF AttributeValue }
+
+ AttributeType ::= OBJECT IDENTIFIER
+ AttributeValue ::= ANY -- DEFINED BY AttributeType
+
+For example CMS defines the signing-time attribute as:
+
+  id-signingTime OBJECT IDENTIFIER ::= { iso(1) member-body(2)
+      us(840) rsadsi(113549) pkcs(1) pkcs9(9) 5 }
+
+  SigningTime ::= Time
+
+  Time ::= CHOICE {
+    utcTime UTCTime,
+    generalizedTime GeneralizedTime }
+
+In OpenSSL B<AttributeType> maps to an B<ASN1_OBJECT> object
+and B<AttributeValue> maps to a list of B<ASN1_TYPE> objects.
+
+The following functions are used for B<X509_ATTRIBUTE> objects.
+
+X509at_get_attr_by_OBJ() finds the location of the first matching object I<obj>
+in a list of attributes I<sk>. The search starts at the position after I<lastpos>.
+If the returned value is positive then it can be used on the next call to
+X509at_get_attr_by_OBJ() as the value of I<lastpos> in order to iterate through
+the remaining attributes. I<lastpos> can be set to any negative value on the
+first call, in order to start searching from the start of the list.
+
+X509at_get_attr_by_NID() is similar to X509at_get_attr_by_OBJ() except that it
+passes the numerical identifier (NID) I<nid> associated with the object.
+See <openssl/obj_mac.h> for a list of NID_*.
+
+X509at_get_attr() returns the B<X509_ATTRIBUTE> object at index I<loc> in the
+list of attributes I<x>. I<loc> should be in the range from 0 to
+X509at_get_attr_count() - 1.
+
+X509at_delete_attr() removes the B<X509_ATTRIBUTE> object at index I<loc> in
+the list of attributes I<x>.
+
+X509at_add1_attr() pushes a copy of the passed in B<X509_ATTRIBUTE> object
+to the list I<x>.
+Both I<x> and I<attr> must be non NULL or an error will occur.
+If I<*x> is NULL then a new list is created, otherwise it uses the
+passed in list. An error will occur if an existing attribute (with the same
+attribute type) already exists in the attribute list.
+
+X509at_add1_attr_by_OBJ() creates a new B<X509_ATTRIBUTE> using
+X509_ATTRIBUTE_set1_object() and X509_ATTRIBUTE_set1_data() to assign a new
+I<obj> with type I<type> and data I<bytes> of length I<len> and then pushes it
+to the attribute list I<x>. Both I<x> and I<attr> must be non NULL or an error
+will occur. If I<*x> is NULL then a new attribute list is created. If I<obj>
+already exists in the attribute list then an error occurs.
+
+X509at_add1_attr_by_NID() is similar to X509at_add1_attr_by_OBJ() except that it
+passes the numerical identifier (NID) I<nid> associated with the object.
+See <openssl/obj_mac.h> for a list of NID_*.
+
+X509at_add1_attr_by_txt() is similar to X509at_add1_attr_by_OBJ() except that it
+passes a name I<attrname> associated with the object.
+See <openssl/obj_mac.h> for a list of SN_* names.
+
+X509_ATTRIBUTE_set1_object() assigns a B<ASN1_OBJECT> I<obj>
+to the attribute I<attr>. If I<attr> contained an existing B<ASN1_OBJECT> then
+it is freed. An error occurs if either I<attr> or I<obj> are NULL, or if
+the passed in I<obj> cannot be duplicated.
+
+X509_ATTRIBUTE_set1_data() pushes a new B<ASN1_TYPE> object onto the I<attr>
+attributes list. The new object is assigned a copy of the data in I<data> of
+size I<len>.
+If I<attrtype> has flag I<MBSTRING_FLAG> set then a table lookup using the
+I<attr> attributes NID is used to set an B<ASN1_STRING> using
+ASN1_STRING_set_by_NID(), and the passed in I<data> must be in the format
+required for that object type or an error will occur.
+If I<len> is not -1 then internally ASN1_STRING_type_new() is
+used with the passed in I<attrtype>.
+If I<attrtype> is 0 the call does nothing except return 1.
+
+X509_ATTRIBUTE_create() creates a new B<X509_ATTRIBUTE> using the I<nid>
+to set the B<ASN1_OBJECT> OID and the I<atrtype> and I<value> to set the
+B<ASN1_TYPE>.
+
+X509_ATTRIBUTE_create_by_OBJ() uses X509_ATTRIBUTE_set1_object() and
+X509_ATTRIBUTE_set1_data() to assign a new I<obj> with type I<atrtype> and
+data I<data> of length I<len>. If the passed in attribute I<attr> OR I<*attr> is
+NULL then a new B<X509_ATTRIBUTE> will be returned, otherwise the passed in
+B<X509_ATTRIBUTE> is used. Note that the ASN1_OBJECT I<obj> is pushed onto the
+attributes existing list of objects, which could be an issue if the attributes
+<ASN1_OBJECT> was different.
+
+X509_ATTRIBUTE_create_by_NID() is similar to X509_ATTRIBUTE_create_by_OBJ()
+except that it passes the numerical identifier (NID) I<nid> associated with the
+object. See <openssl/obj_mac.h> for a list of NID_*.
+
+X509_ATTRIBUTE_create_by_txt() is similar to X509_ATTRIBUTE_create_by_OBJ()
+except that it passes a name I<atrname> associated with the
+object. See <openssl/obj_mac.h> for a list of SN_* names.
+
+X509_ATTRIBUTE_count() returns the number of B<ASN1_TYPE> objects in an
+attribute I<attr>.
+
+X509_ATTRIBUTE_get0_type() returns the B<ASN1_TYPE> object at index I<idx> in
+the attribute list I<attr>. I<idx> should be in the
+range of 0 to X509_ATTRIBUTE_count() - 1 or an error will occur.
+
+X509_ATTRIBUTE_get0_data() returns the data of an B<ASN1_TYPE> object at
+index I<idx> in the attribute I<attr>. I<data> is unused and can be set to NULL.
+An error will occur if the attribute type I<atrtype> does not match the type of
+the B<ASN1_TYPE> object at index I<idx> OR if I<atrtype> is either
+B<V_ASN1_BOOLEAN> or B<V_ASN1_NULL> OR if the I<idx> is not in the
+range 0 to X509_ATTRIBUTE_count() - 1.
+
+X509at_get0_data_by_OBJ() finds the first attribute in an attribute list I<x>
+that matches the I<obj> starting at index I<lastpos> and returns the data
+retrieved from the found attributes first B<ASN1_TYPE> object. An error will
+occur if the attribute type I<type> does not match the type of the B<ASN1_TYPE>
+object OR if I<type> is either B<V_ASN1_BOOLEAN> or B<V_ASN1_NULL> OR the
+attribute is not found.
+If I<lastpos> is less than -1 then an error will occur if there are multiple
+objects in the list I<x> that match I<obj>.
+If I<lastpos> is less than -2 then an error will occur if there is more than
+one B<ASN1_TYPE> object in the found attribute.
+
+=head1 RETURN VALUES
+
+X509at_get_attr_count() returns the number of attributes in the list I<x> or -1
+if I<x> is NULL.
+
+X509at_get_attr_by_OBJ() returns -1 if either the list is empty OR the object
+is not found, otherwise it returns the location of the object in the list.
+
+X509at_get_attr_by_NID() is similar to X509at_get_attr_by_OBJ(), except that
+it returns -2 if the I<nid> is not known by OpenSSL.
+
+X509at_get_attr() returns either an B<X509_ATTRIBUTE> or NULL if there is a error.
+
+X509at_delete_attr() returns either the removed B<X509_ATTRIBUTE> or NULL if
+there is a error.
+
+X509_ATTRIBUTE_count() returns -1 on error, otherwise it returns the number
+of B<ASN1_TYPE> elements.
+
+X509_ATTRIBUTE_get0_type() returns NULL on error, otherwise it returns a
+B<ASN1_TYPE> object.
+
+X509_ATTRIBUTE_get0_data() returns NULL if an error occurs,
+otherwise it returns the data associated with an B<ASN1_TYPE> object.
+
+X509_ATTRIBUTE_set1_object() and X509_ATTRIBUTE_set1_data() returns 1 on
+success, or 0 otherwise.
+
+X509_ATTRIBUTE_create(), X509_ATTRIBUTE_create_by_OBJ(),
+X509_ATTRIBUTE_create_by_NID() and X509_ATTRIBUTE_create_by_txt() return either
+a B<X509_ATTRIBUTE> on success, or NULL if there is a error.
+
+X509at_add1_attr(), X509at_add1_attr_by_OBJ(), X509at_add1_attr_by_NID() and
+X509at_add1_attr_by_txt() return NULL on error, otherwise they return a list
+of B<X509_ATTRIBUTE>.
+
+X509at_get0_data_by_OBJ() returns the data retrieved from the found attributes
+first B<ASN1_TYPE> object, or NULL if an error occurs.
+
+=head1 SEE ALSO
+
+L<ASN1_TYPE_get(3)>,
+L<ASN1_INTEGER_get(3)>,
+L<ASN1_ENUMERATED_get(3)>,
+L<ASN1_STRING_get0_data(3)>,
+L<ASN1_STRING_length(3)>,
+L<ASN1_STRING_type(3)>,
+L<X509_REQ_get_attr(3)>,
+L<EVP_PKEY_get_attr(3)>,
+L<CMS_signed_get_attr(3)>,
+L<PKCS8_pkey_get0_attrs(3)>,
+
+=head1 COPYRIGHT
+
+Copyright 2023 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
+L<https://www.openssl.org/source/license.html>.
+
+=cut
diff --git a/doc/man3/X509_REQ_get_attr.pod b/doc/man3/X509_REQ_get_attr.pod
new file mode 100644
index 0000000000..a85d8399b0
--- /dev/null
+++ b/doc/man3/X509_REQ_get_attr.pod
@@ -0,0 +1,111 @@
+=pod
+
+=head1 NAME
+
+X509_REQ_get_attr_count,
+X509_REQ_get_attr_by_NID, X509_REQ_get_attr_by_OBJ, X509_REQ_get_attr,
+X509_REQ_delete_attr,
+X509_REQ_add1_attr, X509_REQ_add1_attr_by_OBJ, X509_REQ_add1_attr_by_NID,
+X509_REQ_add1_attr_by_txt
+- B<X509_ATTRIBUTE> support for signed certificate requests
+
+=head1 SYNOPSIS
+
+ #include <openssl/x509.h>
+
+ int X509_REQ_get_attr_count(const X509_REQ *req);
+ int X509_REQ_get_attr_by_NID(const X509_REQ *req, int nid, int lastpos);
+ int X509_REQ_get_attr_by_OBJ(const X509_REQ *req, const ASN1_OBJECT *obj,
+                              int lastpos);
+ X509_ATTRIBUTE *X509_REQ_get_attr(const X509_REQ *req, int loc);
+ X509_ATTRIBUTE *X509_REQ_delete_attr(X509_REQ *req, int loc);
+ int X509_REQ_add1_attr(X509_REQ *req, X509_ATTRIBUTE *attr);
+ int X509_REQ_add1_attr_by_OBJ(X509_REQ *req,
+                               const ASN1_OBJECT *obj, int type,
+                               const unsigned char *bytes, int len);
+ int X509_REQ_add1_attr_by_NID(X509_REQ *req,
+                               int nid, int type,
+                               const unsigned char *bytes, int len);
+ int X509_REQ_add1_attr_by_txt(X509_REQ *req,
+                               const char *attrname, int type,
+                               const unsigned char *bytes, int len);
+
+=head1 DESCRIPTION
+
+X509_REQ_get_attr_by_OBJ() finds the location of the first matching object I<obj>
+in the I<req> attribute list. The search starts at the position after I<lastpos>.
+If the returned value is positive then it can be used on the next call to
+X509_REQ_get_attr_by_OBJ() as the value of I<lastpos> in order to iterate through
+the remaining attributes. I<lastpos> can be set to any negative value on the
+first call, in order to start searching from the start of the attribute list.
+
+X509_REQ_get_attr_by_NID() is similar to X509_REQ_get_attr_by_OBJ() except that
+it passes the numerical identifier (NID) I<nid> associated with the object.
+See <openssl/obj_mac.h> for a list of NID_*.
+
+X509_REQ_get_attr() returns the B<X509_ATTRIBUTE> object at index I<loc> in the
+I<req> attribute list. I<loc> should be in the range from 0 to
+X509_REQ_get_attr_count() - 1.
+
+X509_REQ_delete_attr() removes the B<X509_ATTRIBUTE> object at index I<loc> in
+the I<req> objects list of attributes. An error occurs if I<req> is NULL.
+
+X509_REQ_add1_attr() pushes a copy of the passed in B<X509_ATTRIBUTE> I<>attr>
+to the I<req> object's attribute list. An error will occur if either the
+attribute list is NULL or the attribute already exists.
+
+X509_REQ_add1_attr_by_OBJ() creates a new B<X509_ATTRIBUTE> using
+X509_ATTRIBUTE_set1_object() and X509_ATTRIBUTE_set1_data() to assign a new
+I<obj> with type I<type> and data I<bytes> of length I<len> and then pushes it
+to the I<req> object's attribute list. I<req> must be non NULL or an error
+will occur. If I<obj> already exists in the attribute list then an error occurs.
+
+X509_REQ_add1_attr_by_NID() is similar to X509_REQ_add1_attr_by_OBJ() except
+that it passes the numerical identifier (NID) I<nid> associated with the object.
+See <openssl/obj_mac.h> for a list of NID_*.
+
+X509_REQ_add1_attr_by_txt() is similar to X509_REQ_add1_attr_by_OBJ() except
+that it passes a name I<attrname> associated with the object.
+See <openssl/obj_mac.h> for a list of SN_* name