Fix for unaligned chunks

Some time strangers mailers generates an encoded part for attachments in base64 wrapping the contents into chunks of size not module 4, causing an error in the decoding part.

I propose a fix to detect this cases and only decodes the mod 4 part of the message and store the other bytes into a temporary variable that can be added at the start of the next chunk to repeat the previous process (only decode the mod 4 part of the new part).

This case was detected with an email that contains a chunks of 998 bytes of base64 data in the first chunk and 997 bytes of base64 data in the others chunks.

Add the follow lines before the private functions definition:

var $body_fix_unaligned_chunks = '';

And replace the follow line:

$part['Data'] = base64_decode($this->body_buffer_position ? substr($this->body_buffer,$this->body_buffer_position) : $this->body_buffer);

By these lines:

$buffer = $this->body_buffer_position ? substr($this->body_buffer,$this->body_buffer_position) : $this->body_buffer;
$buffer = $this->body_fix_unaligned_chunks . str_replace([' ', "\n", "\r", "\t"], '', $buffer);
$this->body_fix_unaligned_chunks = '';
$remain = strlen($buffer) % 4;
if ($remain) {
$this->body_fix_unaligned_chunks = substr($buffer, -$remain);
$buffer = substr($buffer, 0, -$remain);
}
$part['Data'] = base64_decode($buffer);

With this code, the decoding action runs as expected without returning a corrupted file caused by the unaligned data in the base64 decode process.

Hello Josep,

Thank you for reporting.

Can you provide a sample MIME message that I can use to reproduce the issue?