[CryptNET Advisory] pgp4pine-1.75-6 - expired public keys

["V. Alex Brennen" <vab () CRYPTNET NET>]

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                          CryptNET Security Advisory
                           http://www.cryptnet.net/

Advisory Type:          Privacy - Programmatic Error
Synopsis:               pgp4pine may fail to identify expired public keys
Issue Date:             2001.02.20
Program:                pgp4pine-1.75-6 - http://pgp4pine.flatline.de/
Related Programs:       Gnu Privacy Guard (GnuPG) Version 1.0.4
                        Pine Version 4.2.1
Maintainer Response:    Attempts to contact the maintainer of the pgp4pine
                        package where unsuccessful.
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1.  Executive Summary

pgp4pine is a program which is used to interface various PGP implementations
with the popular Pine mail reading package.  Version 1.75-6 of pgp4pine fails
to properly identify expired keys when working with the Gnu Privacy Guard
program (GnuPG).  This failure may result in the transmission of sensitive
information in clear text across the network.


2.  Problem Description

Version 1.75-6 of pgp4pine does not include code to check if public keys
are expired when loading keys from the GnuPG openPGP implementation. If a
user has an expired public key in their keyring and attempts to encrypt a
message to a recipient with that expired public key, pgp4pine will fail to
recognize that the key is expired.  pgp4pine will then issue a command to
GnuPG to encrypt the email message with the expired key. The encryption
will not be successful, GnuPG will return an error message due to the
invalid key.  pgp4pine will not detect the error which occurred when
encrypting the text and will return program flow control to Pine.  Pine
will then transmit the message in the clear.  No notice that an error
occurred will be provided to the user by pgp4pine.

To duplicate the error on the command line:

bash$ pgp4pine -e -i /tmp/in.tmp -o /tmp/out.tmp -r (*R)

* Where R is a recipient with an expired public key in your keyring.


3.  Solution

A patch, written by V. Alex Brennen, has been provided with this advisory.
The patch consists of code modifications which allow pgp4pine to recognize
and ignore expired keys when working with GnuPG.


4.  About This Advisory

This advisory was produced as part of the CryptNET Free Cryptography
Auditing Project.  CryptNET is a group working on the development of
Free Software cryptographic solutions.  As part of its mission,
CryptNET has undertaken The Free Cryptography Auditing Project.  The
project is an effort to audit some of the more popular free software
cryptographic programs licensed under the GNU General Public License.
If you would like to become involved in this project, please see the
CryptNET web site.

John Sheehy, an IBM certified specialist with e-techservices.com
(http://www.e-techservices.com/), assisted with the discovery and
identification of this bug.

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[ENC: Patch]
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diff -urN pgp4pine-1.75/pgp4pine/keyrings.c vab.pgp4pine-1.75/pgp4pine/keyrings.c
- --- pgp4pine-1.75/pgp4pine/keyrings.c   Fri Aug 18 09:24:45 2000
+++ vab.pgp4pine-1.75/pgp4pine/keyrings.c       Mon Feb 12 21:03:09 2001
@@ -449,22 +449,36 @@
                        if (strchr(buf,':') != NULL) {
                                strncpy(keyType,getItem(buf,':',1),3);
                                lineType = 0;
- -                               if (strcmp(keyType,"sec") == 0) lineType = 1; /* secret line... */
- -                               if (strcmp(keyType,"pub") == 0) lineType = 2; /* public key     */
- -                               if (strcmp(keyType,"uid") == 0) lineType = 4; /* user id        */
- -
+                                /*
+                                        The letter e in the second field of the colon delimited GnuPG
+                                        output denotes that gpg asserts that the trust on this item
+                                        has expired (perhaps as the result of an expired openPGP type
+                                        0x13 or 0x18 signature packet).  If this line denotes a public
+                                        key, GnuPG will not function with this key.  So, we should
+                                        return with out adding it to the list.  We shouldn't check
+                                        expiration ourselves because GnuPG is the final authority.
+                                          - V. Alex Brennen, CryptNET FCAP [http://www.cryptnet.net/]
+                                            2001.02.13.01.13.47
+                                */
+                                strncpy(tmpString,getItem(buf,':',2),1);
+                                if (strcmp(tmpString,"e") == 0) lineType = -1; /* Line w/ expired trust */
+                               else if (strcmp(keyType,"sec") == 0) lineType = 1; /* secret line... */
+                               else if (strcmp(keyType,"pub") == 0) lineType = 2; /* public key     */
+                               else if (strcmp(keyType,"uid") == 0) lineType = 4; /* user id        */
+
                                if (lineType == 1) inSec = 1;
- -                               if (lineType == 2) inSec = 0;
+                               else if (lineType == 2) inSec = 0;

                                switch (lineType) {
                                case 1:
                                case 2:
                                        if (lineType == 2 && getSecretOnly) break;
+
                                        myNewKey = (struct pkiKey *) myMalloc(sizeof(pkiKeyStruct));
                                        if (firstKey == NULL) firstKey = myNewKey;
                                        if (oldKey != NULL) oldKey->nextKey = myNewKey;
                                        oldKey = myNewKey;
- -
+
                                        /* next, key size... */
                                        strncpy(tmpString,getItem(buf,':',3),KEY_SIZE_LENGTH);
                                        strncpy(myNewKey->keySize,tmpString,KEY_SIZE_LENGTH);
@@ -523,6 +537,8 @@
                                                
strncpy(myNewKey->emailAddress,extractEmailAddress(tmpString),EMAIL_ADDRESS_MAX_LENGTH);
                                        }
                                        break;
+                                default:
+                                        break;
                                }
                        }
                }
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                             End CryptNET Advisory
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- ---
V. Alex Brennen    [vab () cryptnet net]
  F A R  B E Y O N D  D R I V E N !
    [ http://www.cryptnet.net/ ]

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Attachment: vab.pgp4pine.patch
Description: pgp4pine patch as attachment