php regex to get base64 string - php

Question

I have a file smime.p7m with many content. One or more of this Content is like this
--_3821f5f5-222-4a90-82e0-d8922ee62cc8_
Content-Type: application/pdf;
name="001235_0001.pdf"
Content-Transfer-Encoding: base64
Content-Disposition: attachment;
filename="001235_0001.pdf"
JVBERi0xLjMNCjMgMCBvYmoNCjw8DQogIC9UeXBlIC9YT2JqZWN0DQogIC9TdWJ0eXBlIC9J
bWFnZQ0KICAvRmlsdGVyIC9EQ1REZWNvZGUNCiAgL1dpZHRoIDI0MDkNCiAgL0hlaWdodCAz
AF6UAFACZoAUUAFABQA1TQAuaADGKAFoASgBaACgBKADpTAQnApAJ0oAdQAdKAD2oAXpQA3p
.........................................
0oAU9KAFHFABQAnSgBOaAFoAKACgAoAWgAoATGOlAAKAFoATpQAYoAO9AC0AFACZ7UAGKAFo
ZPi1JZBodj7GEjdqgELTq0RC7xeSu1yv+dwEltQFPoSMGcbiTf0cGyzbreEAAAAAAAA=
--------------ms021111111111111111111107--
Is there a way to get the filename for example with regex if it's a pDF and the BASE64 code below? It can happen that there is more than one PDF file in the file.
The Filename is not the problem. I get this with "filename="(.*).pdf". But I don't know how I get the base64code after the filename

Answer 1

base64 consists of characters A...Z a...z digits 0..9 symbols + and /. It also can have one or two = in the end and can be split to several lines.
if (preg_match('/filename=\"(?P<filename>[^"]*?\.pdf)\"\s*(?P<base64>([A-Za-z0-9+\/]+\s*)+=?=?)/', $s, $regres)) {
print("FileName: {$regres['filename']}\n");
print("Base64: {$regres['base64']}\n");
}

Answer 2

Use
(?im)^filename="([^"]*\.pdf)"\R+(.+(?:\R.+)+)
See proof
PHP:
preg_match_all('/^filename="([^"]*\.pdf)"\R+(.+(?:\R.+)+)/im', $str, $matches);
Explanation
--------------------------------------------------------------------------------
(?im) set flags for this block (case-
insensitive) (with ^ and $ matching start
and end of line) (with . not matching \n)
(matching whitespace and # normally)
--------------------------------------------------------------------------------
^ the beginning of a "line"
--------------------------------------------------------------------------------
filename=" 'filename="'
--------------------------------------------------------------------------------
( group and capture to \1:
--------------------------------------------------------------------------------
[^"]* any character except: '"' (0 or more
times (matching the most amount
possible))
--------------------------------------------------------------------------------
\. '.'
--------------------------------------------------------------------------------
pdf 'pdf'
--------------------------------------------------------------------------------
) end of \1
--------------------------------------------------------------------------------
" '"'
--------------------------------------------------------------------------------
\R+ any line break sequence (1 or more times (matching
the most amount possible))
--------------------------------------------------------------------------------
( group and capture to \2:
--------------------------------------------------------------------------------
.+ any character except \n (1 or more times
(matching the most amount possible))
--------------------------------------------------------------------------------
(?: group, but do not capture (1 or more
times (matching the most amount
possible)):
--------------------------------------------------------------------------------
\R any line break sequence
--------------------------------------------------------------------------------
.+ any character except \n (1 or more
times (matching the most amount
possible))
--------------------------------------------------------------------------------
)+ end of grouping
--------------------------------------------------------------------------------
) end of \2

Answer 3

I gather that this task is not about validation at all, and solely focuses on data extraction -- this makes sharpening the regex logic unnecessary.
You only need a pattern that will match filename=" at the start of a line, then capture the quote-wrapped substring (so long as it ends in .pdf), then after any number of whitespace characters, capture all characters until one or two = are encountered,
Using greedy negative character classes allows the regex engine to move quickly. The m pattern modifier tells the regex engine that the ^ meta character (not the ^ used inside of square braces) may match the start of a line in addition to the start of the string.
Perhaps you'd like to generate an associative array where the keys are the filename strings and the encoded strings are the values, array_column() does a snappy job of setting that up when there are qualifying matches.
Code: (Demo)
var_export(
preg_match_all(
'~^filename="([^"]+)\.pdf"\s*([^=]+={1,2})~m',
$fileContents,
$out,
PREG_SET_ORDER
)
? array_column($out, 2, 1)
: "no pdf's found"
);
Output:
array (
'001235_0001' => 'JVBERi0xLjMNCjMgMCBvYmoNCjw8DQogIC9UeXBlIC9YT2JqZWN0DQogIC9TdWJ0eXBlIC9J
bWFnZQ0KICAvRmlsdGVyIC9EQ1REZWNvZGUNCiAgL1dpZHRoIDI0MDkNCiAgL0hlaWdodCAz
AF6UAFACZoAUUAFABQA1TQAuaADGKAFoASgBaACgBKADpTAQnApAJ0oAdQAdKAD2oAXpQA3p
.........................................
0oAU9KAFHFABQAnSgBOaAFoAKACgAoAWgAoATGOlAAKAFoATpQAYoAO9AC0AFACZ7UAGKAFo
ZPi1JZBodj7GEjdqgELTq0RC7xeSu1yv+dwEltQFPoSMGcbiTf0cGyzbreEAAAAAAAA=',
)