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Cisco Bug: CSCvi99989 - DKIM fails the signature with a semicolon and WSP before CRLF

Last Modified

Jun 07, 2018

Products (1)

  • Cisco Email Security Appliance

Known Affected Releases

10.0.1-020 11.0.1-027

Description (partial)

Symptom:
DKIM-Signature which ends with semicolon on the last tag=value and has an extra WSP before CRLF trigger a syntax error.


DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ciscolab.not;
 i=@ciscolab.not; 
 q=dns/txt; s=taclab; t=1523868659; h=from : to : subject; 
 bh=Ggz1hLY+ofr6ITyFfMEQMOwgw2EOBCMMe6OhhefHStg=; 
 b=vhG4tyyuNnnVmtvE5xnf7OUm0qtEG7GP8B20YBFcD0anjB5lvE7q8/nDHQy9fW9B13OtB1
 D+yFJB/QW42o+Wi0yu90tnBZ127VBO+hOUV3TDhgHQvh1Opo0Ey4/XqRIZKXRxytyjYNhXvi
 et+avXN8MKiuDUmEwUePC25IAgoIlbqo5qKgyaZS38Kkv2pmjIRoUr6pZVs1EviP77VKsJ3z
 5ZuRtHo56wZEZUG0dma6NM0iXagYdDyjXNDAAM4yogYsthbeG4xnTVIdNGV7dPCstNQIyrMF
 O7DmFSDcSSd+F7Ipwvy5ct3y8/vqufvGysTrc8etzUxETDcLCW8NxeQw==; <-- extra WSP before CRLF


It results with malformed signature information in the mail logs:

Info: MID 1255 DKIM: malformed signature - syntax error

Conditions:
DKIM-Signature which ends with semicolon and extra whitespace after  the last tag
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