3187791ed3
[skip ci] Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from https://github.com/openssl/openssl/pull/7831)
180 lines
7 KiB
Text
180 lines
7 KiB
Text
=pod
|
|
|
|
=encoding utf8
|
|
|
|
=head1 NAME
|
|
|
|
passphrase-encoding
|
|
- How diverse parts of OpenSSL treat pass phrases character encoding
|
|
|
|
=head1 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.
|
|
|
|
=head2 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.
|
|
|
|
=head2 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:
|
|
|
|
=over 4
|
|
|
|
=item 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.
|
|
|
|
=item 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).
|
|
|
|
=back
|
|
|
|
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 DIARESIS) I<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.
|
|
|
|
=head2 OSSL_STORE
|
|
|
|
L<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.
|
|
|
|
=head1 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. "naïve" 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. "naïve" 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.
|
|
|
|
=head2 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
|
|
C<OPENSSL_WIN32_UTF8> will have anything entered on [Windows] console prompt
|
|
converted to UTF-8 (command line and separately prompted pass phrases alike).
|
|
|
|
=head2 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:
|
|
|
|
=over 4
|
|
|
|
=item 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.
|
|
|
|
=item 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.
|
|
|
|
=item 3.
|
|
|
|
Do a naïve (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, C<ï>, which is 0xC3 0xAF when encoded in UTF-8, would become 0xC3
|
|
0x83 0xC2 0xAF when re-encoded in the naïve 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)
|
|
|
|
=back
|
|
|
|
=head1 SEE ALSO
|
|
|
|
L<evp(7)>,
|
|
L<ossl_store(7)>,
|
|
L<EVP_BytesToKey(3)>, L<EVP_DecryptInit(3)>,
|
|
L<PEM_do_header(3)>,
|
|
L<PKCS12_parse(3)>, L<PKCS12_newpass(3)>,
|
|
L<d2i_PKCS8PrivateKey_bio(3)>
|
|
|
|
=head1 COPYRIGHT
|
|
|
|
Copyright 2018 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
|