Tale of how to make a time machine for a database and accidentally write an exploit

Background

Stone Age

Middle Ages

The era of scientific and technological progress

Era of New History

Era of Recent History

The fake per instance approach

export LD_PRELOAD=/usr/local/lib/faketime/libfaketime.so
export FAKETIME="+1d"
export FAKETIME_NO_CACHE=1

$ORACLE_HOME/bin/sqlplus @/home/oracle/scripts/restart_db.sql

The fake per process approach

#!/bin/sh

pid=$1

awk 'BEGIN {RS="\0"; ORS="\n"} $0' "/proc/$pid/environ"

#!/bin/sh

pid=$1
env_name=$2
env_val="$3"

out=`gdb -q -batch -ex "attach $pid" -ex 'call (int) setenv("'$env_name'", "'"$env_val"'", 1)' -ex "detach" 2>&1`

#!/bin/sh

pid=$1
var_name=$2

var_value=`gdb -q -batch -ex "attach $pid" -ex 'call (char*) getenv("'$var_name'")' -ex 'detach' | egrep '^\$1 ='`

if [ "$var_value" == '$1 = 0x0' ]
then
  # variable empty or does not exist
  echo -n
else
  # gdb returns $1 = hex_value "string value"
  var_hex=`echo "$var_value" | awk '{print $3}'`
  var_value=`echo "$var_value" | sed -r -e 's/^\$1 = '$var_hex' //;s/^"//;s/"$//'`
  
  echo -n "$var_value"
fi

An egg in a duck, a duck in a hare ...

public class Posix {

    private static native int setenv(String key, String value, boolean overwrite);

    private static native String getenv(String key);
    
    public static void stub() 
    {
        
    }
}

#  
javac Posix.java

#   Posix.h        JNI
javah Posix

#include <stdlib.h>
#include "Posix.h"

JNIEXPORT jint JNICALL Java_Posix_setenv(JNIEnv *env, jclass cls, jstring key, jstring value, jboolean overwrite)
{
    char* k = (char *) (*env)->GetStringUTFChars(env, key, NULL);
    char* v = (char *) (*env)->GetStringUTFChars(env, value, NULL);

    int err = setenv(k, v, overwrite);

    (*env)->ReleaseStringUTFChars(env, key, k);
    (*env)->ReleaseStringUTFChars(env, value, v);

    return err;
}

JNIEXPORT jstring JNICALL Java_Posix_getenv(JNIEnv *env, jclass cls, jstring key)
{
    char* k = (char *) (*env)->GetStringUTFChars(env, key, NULL);
    char* v = getenv(k);

    return (*env)->NewStringUTF(env, v);
}

gcc -I"$JAVA_HOME/include" -I"$JAVA_HOME/include/linux" -fPIC Posix.c -shared -o libPosix.so -Wl,-soname -Wl,--no-whole-archive

strip libPosix.so

• load binary class-file via loadjava utility
• compile class code from source using sqlplus

CREATE OR REPLACE AND RESOLVE JAVA SOURCE NAMED "Posix" AS
...
...
/

procedure set_env(var_name varchar2, var_value varchar2)
is
language java name 'Posix.set_env(java.lang.String, java.lang.String)';

begin
dbms_java.grant_permission( 'SYSTEM', 'SYS:java.lang.RuntimePermission', 'loadLibrary.Posix', '');
commit;
end;
/

ORA-29532: Java call terminated by uncaught Java exception: java.lang.SecurityException: policy table update

It's alive, alive

begin
dbms_output.enable(100000);
dbms_java.set_output(100000);
dbms_output.put_line('old time: '||to_char(sysdate, 'dd.mm.yyyy hh24:mi:ss'));
system.posix.set_env('FAKETIME','+1d');
dbms_output.put_line('new time: '||to_char(sysdate, 'dd.mm.yyyy hh24:mi:ss'));
end;
/

Conclusion

Bonus for those who read to the end