--EncryptionKeysImpl.mesa
<<Last Edited by: Feigenbaum, May 31, 1984 3:46:19 pm PDT PDT PDT>>
<<Last Edited by: Greene, June 27, 1984 4:29:11 pm PDT>>
    <<Swinehart, July 5, 1985 2:06:27 pm PDT>>
<<    >>
<<>>
DIRECTORY
  Ascii USING [Lower],
  FS USING [StreamOpen, Error, Copy],
  IO USING [STREAM, EndOfStream, GetLineRope, PutRope, Close],
  MessageWindow USING [Append, Blink],                            
  BigCardinals USING [BigCARD, BigToDecimalRope, BigFromDecimalRope, BigToRope],
  EncryptionKeys,
  Rope USING [ROPE, Concat, Cat, Index, Equal, Substr, FromChar, Fetch, Length],
  RSA USING [KeyGenerate, Encrypt],
  UserCredentials USING [Get];
<<>>
 EncryptionKeysImpl: CEDAR PROGRAM 
  IMPORTS Ascii, FS, IO, RSA, BigCardinals, UserCredentials, Rope, MessageWindow EXPORTS EncryptionKeys =

BEGIN

KeyFail: PUBLIC ERROR [subclass: ATOM _ $Unspecified] = CODE;

 CreateKey: PUBLIC PROC[] ~ {  
    length: CARDINAL _ 17;   
    public, private: BigCardinals.BigCARD;
    PrivateFileName, PublicFileName, UserName: Rope.ROPE;
    PublicFile, PrivateFile: IO.STREAM;

    BEGIN

    [public, private] _ RSA.KeyGenerate[length];
    UserName _ UserCredentials.Get[].name;
    UserName _ Rope.Substr[UserName, 0, Rope.Index[UserName, 0, "."]];
    UserName _ ToLowerCase[UserName];
    PrivateFileName _ Rope.Cat["///Keys/", UserName, ".PrivateKey"];
    PrivateFile _ FS.StreamOpen[PrivateFileName, $create
        !FS.Error => IF error.group = user THEN GOTO CannotOpenPrivate;];                              
    IO.PutRope[PrivateFile, Rope.Concat[BigCardinals.BigToDecimalRope[private], "\n"]];
    PrivateFile.Close[]; 
    PublicFileName _ Rope.Cat["///Keys/", UserName, ".PublicKey"];
    PublicFile _ FS.StreamOpen[PublicFileName, $create
        !FS.Error => IF error.group = user THEN GOTO CannotOpenPublic;];
    IO.PutRope[PublicFile, Rope.Concat[BigCardinals.BigToDecimalRope[public], "\n"]];
    PublicFile.Close[];
    []_FS.Copy[PublicFileName, Rope.Cat["[Indigo]<Cryptography>Keys>", UserName, ".PublicKey"]
        !FS.Error => GOTO CannotCopy]; 

    EXITS
        CannotOpenPrivate => {
            MessageWindow.Append[Rope.Concat["Cannot Open ", PrivateFileName],
                   TRUE];
            MessageWindow.Blink; 
            ERROR KeyFail[$CannotOpenPrivate];
        };
        CannotOpenPublic => {
            MessageWindow.Append[Rope.Concat["Cannot Open  ", PublicFileName], TRUE];
            MessageWindow.Blink; 
            ERROR KeyFail[$CannotOpenPublic]; 
        };
        CannotCopy => {
            MessageWindow.Append["Cannot copy public key into [Indigo]<Cryptography>Keys>", TRUE];
            MessageWindow.Blink;
            ERROR KeyFail[$CannotCopy];
        };
    END;
 };

GetPrivateKey: PUBLIC PROC[] RETURNS[PrivateKey: BigCardinals.BigCARD] ~ {
    private, PrivateFileName, UserName: Rope.ROPE;
    PrivateFile: IO.STREAM;
    
    BEGIN
    
    UserName _ UserCredentials.Get[].name;
    UserName _ Rope.Substr[UserName, 0, Rope.Index[UserName, 0, "."]];
    UserName _ ToLowerCase[UserName];
    PrivateFileName _ Rope.Cat["///Keys/", UserName, ".PrivateKey"];    
    PrivateFile _ FS.StreamOpen[PrivateFileName
        !FS.Error => IF error.group = user THEN GOTO CannotOpenPrivate;];
    private _ IO.GetLineRope[PrivateFile !IO.EndOfStream => GOTO NoKey];
    PrivateFile.Close[];
    PrivateKey _ BigCardinals.BigFromDecimalRope[private];

    EXITS
        CannotOpenPrivate => {
            MessageWindow.Append[Rope.Concat["Cannot Open ", PrivateFileName],
                TRUE];
            MessageWindow.Blink; 
            ERROR KeyFail[$CannotOpenPrivate];
        };
        NoKey => {
            MessageWindow.Append[Rope.Concat[PrivateFileName, " Empty"],
                TRUE];
            MessageWindow.Blink; 
            ERROR KeyFail[$CannotOpenPrivate];
        };

    END;
 };

GetPublicKey:  PUBLIC PROC[sender: Rope.ROPE, authenticate: BOOLEAN _ FALSE] RETURNS[PublicKey: BigCardinals.BigCARD] ~ {
    public, PublicFileName, lCaseSender: Rope.ROPE; 
    PublicFile, masterFile: IO.STREAM;
  masterPublicKey, publicSignedByMaster: BigCardinals.BigCARD;
    
    BEGIN
     
    lCaseSender _ ToLowerCase[sender];
    PublicFileName _ Rope.Cat["[Indigo]<Cryptography>Keys>", lCaseSender, ".PublicKey"];
    PublicFile _ FS.StreamOpen[PublicFileName
        !FS.Error => IF error.group = user THEN GOTO KeyNotFound;];
    public _ IO.GetLineRope[PublicFile !IO.EndOfStream => GOTO NoPublicKey];
   PublicKey _ BigCardinals.BigFromDecimalRope[public];
   
   IF authenticate THEN 
      {publicSignedByMaster _ BigCardinals.BigFromDecimalRope[IO.GetLineRope[PublicFile ! IO.EndOfStream => GOTO Warning]];
      masterFile _ FS.StreamOpen["///Keys/MASTER.PublicKey"
        !FS.Error => IF error.group = user THEN GOTO MasterMissing];
      masterPublicKey _ BigCardinals.BigFromDecimalRope[IO.GetLineRope[masterFile ! IO.EndOfStream => GOTO MasterMissing]];
      masterFile.Close[];
      IF NOT Rope.Equal[
           BigCardinals.BigToRope[RSA.Encrypt[publicSignedByMaster, masterPublicKey]],
           Rope.Concat[lCaseSender, BigCardinals.BigToRope[PublicKey]]  ]
      THEN GOTO Trouble;
      };      
                
    PublicFile.Close[];
  
    EXITS
        KeyNotFound => { 
            MessageWindow.Append[Rope.Concat["Cannot Open ", PublicFileName], TRUE];
            MessageWindow.Blink; 
            ERROR KeyFail[$PublicKeyNotFound];       
        };
        NoPublicKey => { 
            MessageWindow.Append[Rope.Concat[PublicFileName, "Empty"], TRUE];
            MessageWindow.Blink; 
            ERROR KeyFail[$PublicKeyNotFound];       
        };
       Trouble => {
           MessageWindow.Append[Rope.Cat["Either ",
           PublicFileName, ", or ///Keys/MASTER.PublicKey has been tampered with."], TRUE];
            MessageWindow.Blink; 
            ERROR KeyFail[$PublicKeyNotAuthenticated];       
        };
       MasterMissing => {
           MessageWindow.Append[Rope.Concat["///Keys/MASTER.PublicKey is missing form local disk"], TRUE];
            MessageWindow.Blink; 
            ERROR KeyFail[$MasterNotFound];       
        };
       Warning => {
           MessageWindow.Append[Rope.Concat[sender, " must have his/her public key signed by MASTER for authenication to work"], 
TRUE];
            MessageWindow.Blink; 
        };
        
    END;
};

ToLowerCase: PUBLIC PROC[in: Rope.ROPE] RETURNS[out: Rope.ROPE] ~ {
    out _ NIL;

    FOR i: INT IN [0 .. Rope.Length[in]) DO
        IF in.Fetch[i] IN ['A..'Z] THEN out _ Rope.Concat[out, Rope.FromChar[Ascii.Lower[in.Fetch[i]]]] ELSE out _ Rope.Concat[out, 
Rope.FromChar[in.Fetch[i]]];
    ENDLOOP;
};

END.