U g"@sddlZddlmZddlmZddlmZddlmZdZ ddZ ee e fe d d d Z d d ZddZddZedddZde eee dddZdS)N)md5)Union)generic) rc4_encrypts (N^NuAdNV..h>/ dSizc Cs|tdd}t|}||td|}|||||dkr\|s\|d|}|dkrtdD]} t|d|}qt|d|S)z{ Implementation of algorithm 3.2 of the PDF standard security handler, section 3.5.2 of the PDF 1.6 reference. N z]sz)compute_o_value_legacy..)compute_o_value_legacy_prepr rrbytes)Z owner_pwdZuser_pwdrrkeyvalnew_keyrr'rcompute_o_value_legacyGs   r.cCsR|tdd}t|}|}|dkrBtdD]}t|}q0|d|}|S)z$ Steps 1-4 of algorithm 3.3 Nrrr )r rrr)rrrrrrr+rrrr)ds  r)c Cs(t|dd|||dd}t|t}||fS){ Implementation of algorithm 3.4 of the PDF standard security handler, section 3.5.2 of the PDF 1.6 reference. Tr)rrr )rrrrr+urrrcompute_u_value_r2~s r4r2c s~t|||||||d}t}|t|||} t|| } tddD]$tfdd|D} t| | } qL| d|fS)r/r2r!r"c3s|]}|AVqdSr#rr$r'rrr(sz&compute_u_value_r34..s)rrr r rrrr*) rrrrrrrr+rrr,r-rr'rcompute_u_value_r34s$     r5F) shared_keyidnum generationrcCs~td|dd}td|dd}|||}t|t|dksLt|rX|d7}t|}|dtdt|dS)a Function that does the key derivation for PDF's legacy security handlers. :param shared_key: Global file encryption key. :param idnum: ID of the object being written. :param generation: Generation number of the object being written. :param use_aes: Boolean indicating whether the security handler uses RC4 or AES(-128). :return: zs(    1 9