[openssl-users] Is the structure of this CMS object correct?

[Stephan Mühlstrasser]

Bonjour Erwann,

Am 09.02.16 um 11:53 schrieb Erwann Abalea:
> Bonjour,
>
>> Le 9 févr. 2016 à 10:15, Stephan Mühlstrasser <stm at pdflib.com
>> <mailto:stm at pdflib.com>> a écrit :
>> ...
>>
>>       SET {
>>         [1] {
>>           SEQUENCE {
>>             INTEGER 3
>>             …
>
> This is the expression of an EXPLICIT tag.
>
>> I can match this to the following rules in RFC 5652:
>>
>> RecipientInfos ::= SET SIZE (1..MAX) OF RecipientInfo
>>
>> RecipientInfo ::= CHOICE {
>>        ktri KeyTransRecipientInfo,
>>        kari [1] KeyAgreeRecipientInfo,
>>        kekri [2] KEKRecipientInfo,
>>        pwri [3] PasswordRecipientinfo,
>>        ori [4] OtherRecipientInfo }
>>
>> KeyAgreeRecipientInfo ::= SEQUENCE {
>>        version CMSVersion,  -- always set to 3
>>        originator [0] EXPLICIT OriginatorIdentifierOrKey,
>>        ukm [1] EXPLICIT UserKeyingMaterial OPTIONAL,
>>        keyEncryptionAlgorithm KeyEncryptionAlgorithmIdentifier,
>>        recipientEncryptedKeys RecipientEncryptedKeys }
>
> See RFC5652 section 12.1.
> These data types are defined in a module with IMPLICIT TAGS (it was
> changed between PKCS#7v1.5 and RFC2630), so kari, kekri, pwri, and ori
> elements are associated to an IMPLICIT tag.
>
> Additional definition to read the dump.
>
> OriginatorIdentifierOrKey ::= CHOICE {
>       issuerAndSerialNumber IssuerAndSerialNumber,
>       subjectKeyIdentifier [0] SubjectKeyIdentifier,
>       originatorKey [1] OriginatorPublicKey }
>
> OriginatorPublicKey ::= SEQUENCE {
>       algorithm AlgorithmIdentifier,
>       publicKey BIT STRING }
>
>
>> If I dump a CMS object that was created with OpenSSL's CMS tool with
>> the same certificate as the problematic one, the structure of the
>> RecipientInfos object looks like this:
>>
>>       SET {
>>         [1] {
>>           INTEGER 3
>>           …
>
>> So the "SEQUENCE" element of the KeyAgreeRecipientInfo is not present
>> here.
>
> This is the correct behavior of an IMPLICIT tag.

many thanks for the analysis! One follow-up question:

I can also not decrypt the recipient.bin file with the "openssl smime" 
command. Do I understand it correctly then that the input file is 
neither a correct PKCS#7 file nor a correct CMS file?

--
Stephan