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IDProjectCategoryView StatusDate SubmittedLast Update
000857810000-006: MappingsSpecpublic2023-01-12 08:342023-04-04 16:13
ReporterBernd Edlinger Assigned ToRandy Armstrong  
PrioritynormalSeverityminorReproducibilityhave not tried
Status closedResolutionno change required 
Product Version1.05.01 
Summary0008578: message footer / extra padding size description seems to be wrong
Description

reading https://reference.opcfoundation.org/Core/Part6/v105/docs/6.7.2.5.1
I found something that is not as our stack implements it:

ExtraPaddingSize Byte:
The most significant byte of a two-byte integer used to specify the padding size when the key used to encrypt the message chunk is larger than 2 048 bits. This field is omitted if the key length is less than or equal to 2 048 bits.

What we actually do is omit the field if the MaximumPlainTextSize is less than or equal to 256 bytes.
The problem is that the MaximumPlainTextSize is CipherTextSize - AsymmetricEncryptionOverhead

Where CipherTextSize = (KeyLength + 7)/8
AsymmetricEncryptionOverhead = 11 for Basic128Rsa15
AsymmetricEncryptionOverhead = 42 for Aes128Sha256RsaOaep, Basic256Sha256 and Basic256
AsymmetricEncryptionOverhead = 66 for Aes256Sha256RsaPss

I did a quick test with an RSA certificate of 2064 bits, and was able to connect with .NET, UAExpert, and CTT,
so other vendors did probably also use the MaximumPlainTextSize here.

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Randy Armstrong

2023-03-23 18:19

administrator   ~0019006

Only key sizes 1024, 2048, 3072 and 4096.

1024, 2048 => single byte padding.
3072 and 4096 => double byte padding

Spec should be fine as is.

Jim Luth

2023-04-04 16:13

administrator   ~0019098

Agreed to no-fix in web meeting.

Issue History

Date Modified Username Field Change
2023-01-12 08:34 Bernd Edlinger New Issue
2023-01-12 08:35 Bernd Edlinger Description Updated
2023-03-23 18:19 Randy Armstrong Assigned To => Randy Armstrong
2023-03-23 18:19 Randy Armstrong Status new => resolved
2023-03-23 18:19 Randy Armstrong Resolution open => no change required
2023-03-23 18:19 Randy Armstrong Note Added: 0019006
2023-04-04 16:13 Jim Luth Status resolved => closed
2023-04-04 16:13 Jim Luth Note Added: 0019098