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PASSPHRASE-ENCODING(7)		    OpenSSL		PASSPHRASE-ENCODING(7)

NAME
       passphrase-encoding - How diverse parts of OpenSSL treat	pass phrases
       character encoding

DESCRIPTION
       In a modern world with all sorts	of character encodings,	the treatment
       of pass phrases has become increasingly complex.	 This manual page
       attempts	to give	an overview over how this problem is currently
       addressed in different parts of the OpenSSL library.

   The general case
       The OpenSSL library doesn't treat pass phrases in any special way as a
       general rule, and trusts	the application	or user	to choose a suitable
       character set and stick to that throughout the lifetime of affected
       objects.	 This means that for an	object that was	encrypted using	a pass
       phrase encoded in ISO-8859-1, that object needs to be decrypted using a
       pass phrase encoded in ISO-8859-1.  Using the wrong encoding is
       expected	to cause a decryption failure.

   PKCS#12
       PKCS#12 is a bit	different regarding pass phrase	encoding.  The
       standard	stipulates that	the pass phrase	shall be encoded as an ASN.1
       BMPString, which	consists of the	code points of the basic multilingual
       plane, encoded in big endian (UCS-2 BE).

       OpenSSL tries to	adapt to this requirements in one of the following
       manners:

       1.  Treats the received pass phrase as UTF-8 encoded and	tries to re-
	   encode it to	UTF-16 (which is the same as UCS-2 for characters
	   U+0000 to U+D7FF and	U+E000 to U+FFFF, but becomes an expansion for
	   any other character), or failing that, proceeds with	step 2.

       2.  Assumes that	the pass phrase	is encoded in ASCII or ISO-8859-1 and
	   opportunistically prepends each byte	with a zero byte to obtain the
	   UCS-2 encoding of the characters, which it stores as	a BMPString.

	   Note	that since there is no check of	your locale, this may produce
	   UCS-2 / UTF-16 characters that do not correspond to the original
	   pass	phrase characters for other character sets, such as any
	   ISO-8859-X encoding other than ISO-8859-1 (or for Windows, CP 1252
	   with	exception for the extra	"graphical" characters in the
	   0x80-0x9F range).

       OpenSSL versions	older than 1.1.0 do variant 2 only, and	that is	the
       reason why OpenSSL still	does this, to be able to read files produced
       with older versions.

       It should be noted that this approach isn't entirely fault free.

       A pass phrase encoded in	ISO-8859-2 could very well have	a sequence
       such as 0xC3 0xAF (which	is the two characters "LATIN CAPITAL LETTER A
       WITH BREVE" and "LATIN CAPITAL LETTER Z WITH DOT	ABOVE" in ISO-8859-2
       encoding), but would be misinterpreted as the perfectly valid UTF-8
       encoded code point U+00EF (LATIN	SMALL LETTER I WITH DIAERESIS) if the
       pass phrase doesn't contain anything that would be invalid UTF-8.  A
       pass phrase that	contains this kind of byte sequence will give a
       different outcome in OpenSSL 1.1.0 and newer than in OpenSSL older than
       1.1.0.

	0x00 0xC3 0x00 0xAF		       # OpenSSL older than 1.1.0
	0x00 0xEF			       # OpenSSL 1.1.0 and newer

       On the same accord, anything encoded in UTF-8 that was given to OpenSSL
       older than 1.1.0	was misinterpreted as ISO-8859-1 sequences.

   OSSL_STORE
       ossl_store(7) acts as a general interface to access all kinds of
       objects,	potentially protected with a pass phrase, a PIN	or something
       else.  This API stipulates that pass phrases should be UTF-8 encoded,
       and that	any other pass phrase encoding may give	undefined results.
       This API	relies on the application to ensure UTF-8 encoding, and
       doesn't check that this is the case, so what it gets, it	will also pass
       to the underlying loader.

RECOMMENDATIONS
       This section assumes that you know what pass phrase was used for
       encryption, but that it may have	been encoded in	a different character
       encoding	than the one used by your current input	method.	 For example,
       the pass	phrase may have	been used at a time when your default encoding
       was ISO-8859-1 (i.e. "naieve" resulting in the byte sequence 0x6E 0x61
       0xEF 0x76 0x65),	and you're now in an environment where your default
       encoding	is UTF-8 (i.e. "naieve"	resulting in the byte sequence 0x6E
       0x61 0xC3 0xAF 0x76 0x65).  Whenever it's mentioned that	you should use
       a certain character encoding, it	should be understood that you either
       change the input	method to use the mentioned encoding when you type in
       your pass phrase, or use	some suitable tool to convert your pass	phrase
       from your default encoding to the target	encoding.

       Also note that the sub-sections below discuss human readable pass
       phrases.	 This is particularly relevant for PKCS#12 objects, where
       human readable pass phrases are assumed.	 For other objects, it's as
       legitimate to use any byte sequence (such as a sequence of bytes	from
       `/dev/urandom` that's been saved	away), which makes any character
       encoding	discussion irrelevant; in such cases, simply use the same byte
       sequence	as it is.

   Creating new	objects
       For creating new	pass phrase protected objects, make sure the pass
       phrase is encoded using UTF-8.  This is default on most modern Unixes,
       but may involve an effort on other platforms.  Specifically for
       Windows,	setting	the environment	variable OPENSSL_WIN32_UTF8 will have
       anything	entered	on [Windows] console prompt converted to UTF-8
       (command	line and separately prompted pass phrases alike).

   Opening existing objects
       For opening pass	phrase protected objects where you know	what character
       encoding	was used for the encryption pass phrase, make sure to use the
       same encoding again.

       For opening pass	phrase protected objects where the character encoding
       that was	used is	unknown, or where the producing	application is
       unknown,	try one	of the following:

       1.  Try the pass	phrase that you	have as	it is in the character
	   encoding of your environment.  It's possible	that its byte sequence
	   is exactly right.

       2.  Convert the pass phrase to UTF-8 and	try with the result.
	   Specifically	with PKCS#12, this should open up any object that was
	   created according to	the specification.

       3.  Do a	naieve (i.e. purely mathematical) ISO-8859-1 to	UTF-8
	   conversion and try with the result.	This differs from the previous
	   attempt because ISO-8859-1 maps directly to U+0000 to U+00FF, which
	   other non-UTF-8 character sets do not.

	   This	also takes care	of the case when a UTF-8 encoded string	was
	   used	with OpenSSL older than	1.1.0.	(for example, "ie", which is
	   0xC3	0xAF when encoded in UTF-8, would become 0xC3 0x83 0xC2	0xAF
	   when	re-encoded in the naieve manner.  The conversion to BMPString
	   would then yield 0x00 0xC3 0x00 0xA4	0x00 0x00, the
	   erroneous/non-compliant encoding used by OpenSSL older than 1.1.0)

SEE ALSO
       evp(7), ossl_store(7), EVP_BytesToKey(3), EVP_DecryptInit(3),
       PEM_do_header(3), PKCS12_parse(3), PKCS12_newpass(3),
       d2i_PKCS8PrivateKey_bio(3)

COPYRIGHT
       Copyright 2018-2020 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>.

3.0.0-alpha6			  2020-08-06		PASSPHRASE-ENCODING(7)

NAME | DESCRIPTION | RECOMMENDATIONS | SEE ALSO | COPYRIGHT

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