The JPEG-2000 standard says that the file type box contains a series of compatibility list fields. It says this about each field:
This field is encoded as a four-byte string of ISO/IEC 646 characters.
Here is a compatibility list field from one JPEG-2000 file (hex bytes):
00 00 00 B5
How is that four-byte encoding of a string represented in XML, given that hex 00 (nul) is not a valid character in XML?
Related
When downloading the pdf file, I specified the password "123456789987654abc211234567899klm7654321". When opening, I can remove a few characters, for example,
"123456789987654abc211234567899kl" - file will open anyway! But if I use
"123456789987654abc211234567899k" - file not open
help me understand what is the problem
private static void encryptPdf(
InputStream inputStream,
OutputStream outputStream,
String ownerPassword,
String userPassword) throws Exception
{
PDDocument document = PDDocument.load(inputStream);
if (document.isEncrypted())
{
return;
}
AccessPermission accessPermission = new AccessPermission();
StandardProtectionPolicy spp =
new StandardProtectionPolicy(ownerPassword, userPassword, accessPermission);
spp.setEncryptionKeyLength(40);
document.protect(spp);
document.save(outputStream);
document.close();
}
The first step in calculating the encryption key from the password for pdf encryption up to revision 4 is
The password string is generated from host system codepage characters (or system scripts) by first converting the string to PDFDocEncoding. If the input is Unicode, first convert to a codepage encoding, and then to PDFDocEncoding for backward compatibility. Pad or truncate the resulting password string to exactly 32 bytes. If the password string is more than 32 bytes long, use only its first 32 bytes; if it is less than 32 bytes long, pad it by appending the required number of additional bytes from the beginning of the following padding string:
<28 BF 4E 5E 4E 75 8A 41 64 00 4E 56 FF FA 01 08
2E 2E 00 B6 D0 68 3E 80 2F 0C A9 FE 64 53 69 7A>
That is, if the password string is n bytes long, append the first 32 - n bytes of the padding string to the end of the password string. If the password string is empty (zero-length), meaning there is no user password, substitute the entire padding string in its place.
(ISO 32000-2 section 7.6.4.3.2 "Algorithm 2: Computing a file encryption key in order to encrypt a document (revision 4 and earlier)")
For more modern encryption types you have a restriction, too, but generally less harsh:
The UTF-8 password string shall be generated from Unicode input by processing the input string with the SASLprep (Internet RFC 4013) profile of stringprep (Internet RFC 3454) using the Normalize and BiDi options, and then converting to a UTF-8 representation.
Truncate the UTF-8 representation to 127 bytes if it is longer than 127 bytes.
(ISO 32000-2 section 7.6.4.3.3 "Algorithm 2.A: Retrieving the file encryption key from an encrypted document in order to decrypt it (revision 6 and later)")
Running a search in PHPMyAdmin for an ip address to unblock from a WordPress plug in, I get this on one of the tables:
Warning: #1300 Invalid utf8 character string: '\x8B\x08\x00\x00\x00\x00\x00\x00\x03\x14\xD6y8\x15\xEF\x17\x0...'
Warning: #1300 Invalid utf8 character string: '\x8B\x08\x00\x00\x00\x00\x00\x00\x03\x00\x1E\x80\xE1\x7Fa:2:{...'
I tried to search for part of the strings, but cannot find where they are in the db.
These look suspicious to me, I've had some SQL injection compromises in the past and I'm fearing that's what it may indicate.
How do I track down where these strings actually are in the db if I cannot find by the PHPMyAdmin search?
Thank you.
Those look like gzip headers which are missing their leading \x1f. I expect it's there but not part of the warning because \x1f is a valid UTF-8 character but \x8b is not.
1F 2-byte magic number of a gzip file
8B |
08 compression method (08 = deflate)
00 1 byte header flags (00 = it's probably compressed text)
00 4 byte timestamp
00 |
00 |
00 |
00 Extra flags
03 Operating System (03 = Unix)
After that, data begins.
Something is trying to read gzipped text as UTF-8.
I am trying to extract GPS metadata from hex following this tutorial, but cannot understand why at the end the latitude and longitude have length 24 and values 42 and 73:
http://itbrigadeinc.com/post/2012/03/06/Anatomy-of-a-JPG-image.aspx
http://www.itbrigadeinc.com/post/2012/03/16/Seeing-the-EXIF-data-for-a-JPG-image.aspx
I found the tags of latitude and longitude (00 02 00 05 00 00 00 03 00 00 02 42) and (00 04 00 05 00 00 00 03 00 00 02 5A). As I understood, if count = 3, then the values of both of them should follow in the last 4 bytes of tags. but 02 42 and 02 5A are not "42" and "73"...
Who could explain me what is wrong?
Please, don't recommend any tools - I need to do it manually.
You need to also consider the size of each value. The count is three, but the size of each is larger than one byte. Therefore it won't fit in the four bytes, and those four bytes represent an offset to the value.
GPS data is usually stored as three rational numbers, where each rational number is two 32-bit integers (numerator, denominator). Therefore you have three values for latitude, but each is 8 bytes. The 24 bytes won't fit within the TIFF tag, so it is stored somewhere else in the file, and the four bytes you're seeing are a pointer to it. You need to look into the spec to find out where that pointer is relative to, as it's probably not the start of the file.
Check out my metadata extractor libraries (in Java and C#) for reference.
Apparently the 24 bit data type is a PropertyTagTypeRational
https://msdn.microsoft.com/en-us/library/ms534414(v=vs.85).aspx
Specifies that the value data member is an array of pairs of unsigned long integers. Each pair represents a fraction; the first integer is the numerator and the second integer is the denominator.
Mostly gotten from: Getting GPS data from an image's EXIF in C#
This bit of python code might have a good hint too at how you can decode the data http://eran.sandler.co.il/2011/05/20/extract-gps-latitude-and-longitude-data-from-exif-using-python-imaging-library-pil/
I have a 'Subject' of SSL x.509 certificate given as
Subject: C=XX, ST=XX, L=XX, O=XX, OU=XX, emailAddress=admin#adobe.pw, CN=trustasia.asia
and I want to covert this to binary stream as found in SSL certificate when it is sent on wire, I know definition Subject field is given in RFC-5280 in ASN.1 notation and DER encoding rules given in x.609 are to covert this field to binary representation, these two documents and with little help from code(which gave hexadecimal representations of OID such as id-at-countryName:2.5.4.6:{0x55, 0x04, 0x06}) i was able to covert all the RDNs(RelativeDistinguishedNames) to their binary representation, but I am stuck with emailAdress filds.
I found its OID:1.2.840.113549.1.9.1 but don't know what it is hexadecimal representation.
Can you please guide me how can I covert this to binary representation.
I suspect that you are talking about OID encoding using ASN.1 Distinguished Encoding Rules (DER). I would suggest to check this article to get detailed information about OBJECT_IDENTIFIER encoding rules: OBJECT IDENTIFIER
OID string value conversion to ASN.1 DER will result in:
06 09 2A 86 48 86 F7 0D 01 09 01
where, 0x06 -- is OBJECT_IDENTIFIER tag identifer, 0x09 -- encoded OID value length in bytes, the rest bytes (2A 86 48 86 F7 0D 01 09 01) represent OID binary form
emailAddress is of type IA5String so it would appear in the certificate in the same form as shown in subject line: 'admin#adobe.pw'.
I'm writing a cookie authentication library that replicates that of an existing system. I'm able to create authentication tokens that work. However testing with a token with known value, created by the existing system, I encountered the following puzzle.
The original encoded string purports to be base64url encoded. And, in fact, using any of several base64url code modules and online tools, the decoded value is the expected result.
However base64url encoding the decoded value (again using any of several tools) doesn't reproduce the original string. Both encoded strings decode to the expected results, so apparently both representations are valid.
How? What's the difference?
How can I replicate the original encoded results?
original encoded string: YWRtaW46NTVGRDZDRUE6vtRbQoEXD9O6R4MYd8ro2o6Rzrc
my base64url decode: admin:55FD6CEA:[encrypted hash]
Encoding doesn't match original but the decoded strings match.
my base64url encode: YWRtaW46NTVGRDZDRUE677-977-9W0Lvv70XD9O6R--_vRh377-977-92o7vv73Otw
my base64url decode: admin:55FD6CEA:[encrypted hash]
(Sorry, SSE won't let me show the unicode representation of the hash. I assure you, they do match.)
This string:
YWRtaW46NTVGRDZDRUE6vtRbQoEXD9O6R4MYd8ro2o6Rzrc
is not exactly valid Base64. Valid Base64 consists in a sequence of characters among uppercase letters, lowercase letters, digits, '/' and '+'; it must also have a length which is a multiple of 4; 1 or 2 final '=' signs may appear as padding so that the length is indeed a multiple of 4. This string contains only Base64-valid characters, but only 47 of them, and 47 is not a multiple of 4. With an extra '=' sign at the end, this becomes valid Base64.
That string:
YWRtaW46NTVGRDZDRUE677-977-9W0Lvv70XD9O6R--_vRh377-977-92o7vv73Otw
is not valid Base64. It contains several '-' and one '_' sign, neither of which should appear in a Base64 string. If some tool is decoding that string into the "same" result as the previous string, then the tool is not implementing Base64 at all, but something else (and weird).
I suppose that your strings got garbled at some point through some copy&paste mishap, maybe related to a bad interpretation of bytes as characters. This is the important point: bytes are NOT characters.
It so happens that, traditionally, in older times, computers got on the habit of using so-called "code pages" which were direct mappings of characters onto bytes, with each character being encoded as exactly one byte. Thus came into existence some tools (such as Windows' notepad.exe) that purport to do the inverse, i.e. show the contents of a file (nominally, some bytes) as they character counterparts. This, however, fails when the bytes are not "printable characters" (while a code page such as "Windows-1252" maps each character to a byte value, there can be byte values that are not the mapping of a printable character). This also began to fail even more when people finally realized that there were only 256 possible byte values, and a lot more possible characters, especially when considering Chinese.
Unicode is an evolving standard that maps characters to code units (i.e. numbers), with a bit more than 100000 currently defined. Then some encoding rules (there are several of them, the most frequent being UTF-8) encode the characters into bytes. Crucially, one character can be encoded over several bytes.
In any case, a hash value (or whatever you call an "encrypted hash", which is probably a confusion, because hashing and encrypting are two distinct things) is a sequence of bytes, not characters, and thus is never guaranteed to be the encoding of a sequence of characters in any code page.
Armed with this knowledge, you may try to put some order into your strings and your question.
Edit: thanks to #marfarma for pointing out the URL-safe Base64 encoding where the '+' and '/' characters are replaced by '-' and '_'. This makes the situation clearer. When adding the needed '=' signs, the first string then decodes to:
00000000 61 64 6d 69 6e 3a 35 35 46 44 36 43 45 41 3a be |admin:55FD6CEA:.|
00000010 d4 5b 42 81 17 0f d3 ba 47 83 18 77 ca e8 da 8e |.[B.....G..w....|
00000020 91 ce b7 |...|
while the second becomes:
00000000 61 64 6d 69 6e 3a 35 35 46 44 36 43 45 41 3a ef |admin:55FD6CEA:.|
00000010 bf bd ef bf bd 5b 42 ef bf bd 17 0f d3 ba 47 ef |.....[B.......G.|
00000020 bf bd 18 77 ef bf bd ef bf bd da 8e ef bf bd ce |...w............|
00000030 b7 |.|
We now see what happened: the first string was decoded to bytes but someone fed these bytes to some display system or editors that really expected UTF-8. Some of these bytes were not valid UTF-8 encoding of anything, so they were replaced with the Unicode code point U+FEFF ZERO WIDTH NO-BREAK SPACE, i.e. a space character with no width (thus, nothingness on the screen). The characters where then reencoded as UTF-8, each U+FEFF yielding the EF BF BD sequence of three bytes.
Therefore, the hash value was badly mangled, but the bytes that were altered show up as nothing when interpreted (wrongly) as characters, and what was put in their place also shows up as nothing. Hence no visible difference on the screen.