See ChangeLog: Thu Jul 27 12:01:00 CEST 2000 Werner Koch

NEWS

@@ -7,6 +7,10 @@ Noteworthy changes in the current CVS branch STABLE-BRANCH-1-0
 
     * Revoked user IDs are now marked in the output of --list-key
 
+    * New options --show-session-key and --override-session-key
+      to help the British folks to somewhat minimize the danger
+      of this Orwellian RIP bill.
+
 
 Noteworthy changes in version 1.0.2 (2000-07-12)
 ----------------------------------------------

doc/DETAILS

@@ -225,6 +225,11 @@ more arguments in future versions.
 		   (only the first character should be checked)
 	    class: 2 hex digits with the signature class
 
+    SESSION_KEY  <algo>:<hexdigits>
+	The session key used to decrypt the message.  This message will
+	only be emmited when the special option --show-session-key
+	is used.  The format is suitable to be passed to the option
+	--override-session-key
 
 
 Key generation

doc/gpg.sgml

@@ -1338,6 +1338,29 @@ the encoding used in old versions.  This may only happen for ElGamal signatures
 which are not widely used.
 </para></listitem></varlistentry>
 
+<varlistentry>
+<term>--show-session-key</term>
+<listitem><para>
+Display the session key used for one message. See --override-session-key
+for the counterpart of this option.
+</para>
+<para>
+We think that Key-Escrow is a Bad Thing; however the user should
+have the freedom to decide whether to go to prison or to reveal the content of
+one specific message without compromising all messages ever encrypted for one
+secret key. DON'T USE IT UNLESS YOU ARE REALLY FORCED TO DO SO.
+</para></listitem></varlistentry>
+
+<varlistentry>
+<term>--override-session-key &ParmString; </term>
+<listitem><para>
+Don't use the public key but the session key &ParmString;.  The format of this
+string is the same as the one printed by --show-session-key.  This option
+is normally not used but comes handy in case someone forces you to reveal the
+content of an encrypted message; using this option you can do this without
+handing out the secret key.
+</para></listitem></varlistentry>
+
 
 </variablelist>
 </refsect1>

g10/ChangeLog

@@ -1,3 +1,11 @@
+Thu Jul 27 12:01:00 CEST 2000  Werner Koch  <wk@openit.de>
+
+  * g10.c: New options --show-session-key and --override-session-key
+  * pubkey-enc.c (hextobyte): New.
+  (get_override_session_key): New.
+  * mainproc.c (proc_pubkey_enc): Add session-key stuff.
+  * status.h, status.c (STATUS_SESSION_KEY): New.
+
 Thu Jul 27 10:02:38 CEST 2000  Werner Koch  <wk@openit.de>
 
   * g10.c (main): Use setmode(O_BINARY) for MSDOS while generating random bytes

g10/g10.c

@@ -188,6 +188,8 @@ enum cmd_and_opt_values { aNull = 0,
     oFastListMode,
     oListOnly,
     oIgnoreTimeConflict,
+    oShowSessionKey,
+    oOverrideSessionKey,
     oNoRandomSeedFile,
     oNoAutoKeyRetrieve,
     oEmu3DESS2KBug,  /* will be removed in 1.1 */
@@ -370,6 +372,8 @@ static ARGPARSE_OPTS opts[] = {
     { oFastListMode,"fast-list-mode", 0, "@" },
     { oListOnly, "list-only", 0, "@"},
     { oIgnoreTimeConflict, "ignore-time-conflict", 0, "@" },
+    { oShowSessionKey, "show-session-key", 0, "@" },
+    { oOverrideSessionKey, "override-session-key", 2, "@" },
     { oNoRandomSeedFile,  "no-random-seed-file", 0, "@" },
     { oNoAutoKeyRetrieve, "no-auto-key-retrieve", 0, "@" },
     { oEmu3DESS2KBug,  "emulate-3des-s2k-bug", 0, "@"},
@@ -920,6 +924,10 @@ main( int argc, char **argv )
 	  case oIgnoreTimeConflict: opt.ignore_time_conflict = 1; break;
 	  case oNoRandomSeedFile: use_random_seed = 0; break;
 	  case oNoAutoKeyRetrieve: opt.auto_key_retrieve = 0; break;
+	  case oShowSessionKey: opt.show_session_key = 1; break;
+	  case oOverrideSessionKey:
+		opt.override_session_key = pargs.r.ret_str;
+		break;
 
 	  default : pargs.err = configfp? 1:2; break;
 	}

g10/mainproc.c

@@ -219,8 +219,17 @@ proc_pubkey_enc( CTX c, PACKET *pkt )
 	write_status_text( STATUS_ENC_TO, buf );
     }
 
-
+    if( !opt.list_only && opt.override_session_key ) {
-    if( is_ELGAMAL(enc->pubkey_algo)
+	/* It does not make nuch sense to store the session key in
+	 * secure memory because it has already been passed on the
+	 * command line and the GCHQ knows about it */
+	c->dek = m_alloc( sizeof *c->dek );
+	result = get_override_session_key ( c->dek, opt.override_session_key );
+	if ( result ) {
+	    m_free(c->dek); c->dek = NULL;
+	}
+    }
+    else if( is_ELGAMAL(enc->pubkey_algo)
 	|| enc->pubkey_algo == PUBKEY_ALGO_DSA
 	|| is_RSA(enc->pubkey_algo)  ) {
 	if ( !c->dek && ((!enc->keyid[0] && !enc->keyid[1])
@@ -246,6 +255,15 @@ proc_pubkey_enc( CTX c, PACKET *pkt )
     else if( !result ) {
 	if( opt.verbose > 1 )
 	    log_info( _("public key encrypted data: good DEK\n") );
+	if ( opt.show_session_key ) {
+	    int i;
+	    char *buf = m_alloc ( c->dek->keylen*2 + 20 );
+	    sprintf ( buf, "%d:", c->dek->algo );
+	    for(i=0; i < c->dek->keylen; i++ )
+		sprintf(buf+strlen(buf), "%02X", c->dek->key[i] );
+	    log_info( "session key: \"%s\"\n", buf );
+	    write_status_text ( STATUS_SESSION_KEY, buf );
+	}
     }
     else { /* store it for later display */
 	struct kidlist_item *x = m_alloc( sizeof *x );

g10/options.h

@@ -91,6 +91,8 @@ struct {
     int ignore_time_conflict;
     int command_fd;
     int auto_key_retrieve;
+    const char *override_session_key;
+    int show_session_key;
 } opt;
 
 

g10/packet.h

@@ -332,6 +332,7 @@ int protect_secret_key( PKT_secret_key *sk, DEK *dek );
 
 /*-- pubkey-enc.c --*/
 int get_session_key( PKT_pubkey_enc *k, DEK *dek );
+int get_override_session_key( DEK *dek, const char *string );
 
 /*-- compress.c --*/
 int handle_compressed( void *ctx, PKT_compressed *cd,

g10/pubkey-enc.c

@@ -221,3 +221,59 @@ get_it( PKT_pubkey_enc *k, DEK *dek, PKT_secret_key *sk, u32 *keyid )
 }
 
 
+static int
+hextobyte( const char *s )
+{
+    int c;
+
+    if( *s >= '0' && *s <= '9' )
+	c = 16 * (*s - '0');
+    else if( *s >= 'A' && *s <= 'F' )
+	c = 16 * (10 + *s - 'A');
+    else if( *s >= 'a' && *s <= 'f' )
+	c = 16 * (10 + *s - 'a');
+    else
+	return -1;
+    s++;
+    if( *s >= '0' && *s <= '9' )
+	c += *s - '0';
+    else if( *s >= 'A' && *s <= 'F' )
+	c += 10 + *s - 'A';
+    else if( *s >= 'a' && *s <= 'f' )
+	c += 10 + *s - 'a';
+    else
+	return -1;
+    return c;
+}
+
+/****************
+ * Get the session key from the given string.
+ * String is supposed to be formatted as this:
+ *  <algo-id>:<even-number-of-hex-digits>
+ */
+int
+get_override_session_key( DEK *dek, const char *string )
+{
+    const char *s;
+    int i;
+
+    if ( !string )
+	return G10ERR_BAD_KEY;
+    dek->algo = atoi(string);
+    if ( dek->algo < 1 )
+	return G10ERR_BAD_KEY;
+    if ( !(s = strchr ( string, ':' )) )
+	return G10ERR_BAD_KEY;
+    s++;
+    for(i=0; i < DIM(dek->key) && *s; i++, s +=2 ) {
+	int c = hextobyte ( s );
+	if (c == -1)
+	    return G10ERR_BAD_KEY;
+	dek->key[i] = c;
+    }
+    if ( *s )
+	return G10ERR_BAD_KEY;
+    dek->keylen = i;
+    return 0;
+}
+

g10/status.c

@@ -151,6 +151,7 @@ write_status_text ( int no, const char *text)
       case STATUS_DELETE_PROBLEM : s = "DELETE_PROBLEM\n"; break;
       case STATUS_PROGRESS	 : s = "PROGRESS\n"; break;
       case STATUS_SIG_CREATED	 : s = "SIG_CREATED\n"; break;
+      case STATUS_SESSION_KEY	 : s = "SESSION_KEY\n"; break;
       default: s = "?\n"; break;
     }
 

g10/status.h

@@ -81,6 +81,8 @@
 #define STATUS_GOT_IT		49
 #define STATUS_PROGRESS 	50
 #define STATUS_SIG_CREATED	51
+#define STATUS_SESSION_KEY	52
+
 
 /*-- status.c --*/
 void set_status_fd ( int fd );