Document that PKCS#12 functions assume UTF-8 for passwords

Part of issue openssl#3531

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from openssl#3535)
(cherry picked from commit cff85f3)

Author: dwmw2

doc/crypto/PKCS12_newpass.pod

@@ -17,6 +17,18 @@ PKCS12_newpass() changes the password of a PKCS12 structure.
 B<p12> is a pointer to a PKCS12 structure. B<oldpass> is the existing password
 and B<newpass> is the new password.
 
+=head1 NOTES
+
+Each of B<oldpass> and B<newpass> is independently interpreted as a string in
+the UTF-8 encoding. If it is not valid UTF-8, it is assumed to be ISO8859-1
+instead.
+
+In particular, this means that passwords in the locale character set
+(or code page on Windows) must potentially be converted to UTF-8 before
+use. This may include passwords from local text files, or input from
+the terminal or command line. Refer to the documentation of
+L<UI_OpenSSL(3)>, for example.
+
 =head1 RETURN VALUES
 
 PKCS12_newpass() returns 1 on success or 0 on failure. Applications can

doc/crypto/PKCS12_parse.pod

@@ -29,6 +29,15 @@ The B<friendlyName> and B<localKeyID> attributes (if present) on each
 certificate will be stored in the B<alias> and B<keyid> attributes of the
 B<X509> structure.
 
+The parameter B<pass> is interpreted as a string in the UTF-8 encoding. If it
+is not valid UTF-8, then it is assumed to be ISO8859-1 instead.
+
+In particular, this means that passwords in the locale character set
+(or code page on Windows) must potentially be converted to UTF-8 before
+use. This may include passwords from local text files, or input from
+the terminal or command line. Refer to the documentation of
+L<UI_OpenSSL(3)>, for example.
+
 =head1 RETURN VALUES
 
 PKCS12_parse() returns 1 for success and zero if an error occurred.