Patent Publication Number: US-11658956-B2

Title: Secure access to virtual machines in heterogeneous cloud environments

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Non-Provisional patent application Ser. No. 16/786,729, filed Feb. 10, 2020, which is a continuation of U.S. Non-Provisional patent application Ser. No. 16/032,572, filed Jul. 11, 2018, which is a division of U.S. Non-Provisional patent application Ser. No. 14/804,248, filed Jul. 20, 2015, the full disclosures of which are incorporated herein by reference in their entireties. 
    
    
     TECHNICAL FIELD 
     The present technology relates in general to the field of computer networks, and more specifically to providing secure access to virtual machines in heterogeneous cloud environment. 
     BACKGROUND 
     Industry trends indicate a growing movement among enterprises and other entities to hybrid cloud designs. These enterprises and other entities are choosing such designs to acquire additional on-demand computing, storage, and network resources, thereby eliminating the need to build for peak capacity within their own data centers. Public clouds do not have the same initial capital investments that may be necessary to build out a company&#39;s own private data center. In addition, a public cloud can better absorb a company&#39;s need for elasticity by providing almost unlimited pay-as-you-grow expansion. Although hybrid cloud models are conceptually and financially very attractive, customers are often reluctant to place their applications in the public cloud, away from their own premises. When an organization deploys an application or part of an application in the public cloud, it wants to be sure that the transition from the private data center to a hybrid model is not only operationally feasible, but also that the company retains data access and control in the new architecture. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe the manner in which the above-recited and other advantages and features of the disclosure can be obtained, a more particular description of the principles briefly described above will be rendered by reference to specific examples thereof which are illustrated in the appended drawings. Understanding that these drawings depict only examples of the disclosure and are not therefore to be considered to be limiting of its scope, the principles herein are described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
         FIG.  1    illustrates an example hybrid cloud environment that can be implemented in an example embodiment; 
         FIG.  2    illustrates an example hybrid cloud environment that can be implemented in an example embodiment; 
         FIG.  3    illustrates an example approach for migrating virtual machines from a first cloud environment to heterogeneous cloud environments according to an example embodiment; 
         FIGS.  4 A and  4 B  illustrate example processes for providing secure access to a virtual machine in a heterogeneous cloud environment according to an example embodiment; 
         FIG.  5    illustrates an example network device that can be used in various example embodiments; and 
         FIGS.  6 A and  6 B  illustrate example systems that can be used in various example embodiments. 
     
    
    
     DESCRIPTION OF EXAMPLE EMBODIMENTS 
     The detailed description set forth below is intended as a description of various configurations of example embodiments and is not intended to represent the only configurations in which the subject technology can be practiced. The appended drawings are incorporated herein and constitute a part of the detailed description. The detailed description includes specific details for the purpose of providing a more thorough understanding of the subject technology. However, it will be clear and apparent that the subject technology is not limited to the specific details set forth herein and may be practiced without these details. In some instances, structures and components are shown in block diagram form in order to avoid obscuring the concepts of the subject technology. 
     OVERVIEW 
     Secure access from a first cloud environment, such as a private cloud, to virtual machines in heterogeneous cloud environments, such as a plurality of public clouds, can be provided via Secure Shell (SSH). In an example embodiment, client credentials, such as a public key of a public-private key pair, are generated and inserted into a virtual machine in the first cloud environment. The virtual machine can be migrated from the first cloud network to a second cloud network. The virtual machine in the second cloud network can then be accessed from the first cloud network via SSH authentication using the client credentials. The client credentials can be updated (or rekeyed), and the updated client credentials can be used for later access to the virtual machine in the second cloud via SSH. 
     In some example embodiments, the virtual machine in the second cloud can be authenticated utilizing its host key. For example, the host key, such as a public-private key pair, can be generated and inserted into the virtual machine prior to migrating the virtual machine from the first cloud to the second cloud. Upon an initial attempt to login to the virtual machine in the second cloud via SSH, the identity of the virtual machine can be verified based at least in part on the host key or data relating to the host key, such as a public key of the host key or a fingerprint of the public key. After the virtual machine has been authenticated, such as by matching the public key or the fingerprint to an entry associated with the virtual machine in a database of known hosts, the host key can be rekeyed and the database can be updated with the new host key or the data relating to the host key. 
     DETAILED DESCRIPTION 
     A computer network is a geographically distributed collection of nodes interconnected by communication links and segments for transporting data between endpoints, such as personal computers and workstations. Many types of networks are available, with the types ranging from local area networks (LANs) and wide area networks (WANs) to overlay and software-defined networks, such as virtual extensible local area networks (VXLANs). 
     LANs typically connect nodes over dedicated private communications links located in the same general physical location, such as a building or campus. WANs, on the other hand, typically connect geographically dispersed nodes over long-distance communications links, such as common carrier telephone lines, optical lightpaths, synchronous optical networks (SONET), or synchronous digital hierarchy (SDH) links. LANs and WANs can include layer 2 (L2) and/or layer 3 (L3) networks and devices. 
     The Internet is an example of a WAN that connects disparate networks throughout the world, providing global communication between nodes on various networks. The nodes typically communicate over the network by exchanging discrete frames or packets of data according to predefined protocols, such as the Transmission Control Protocol/Internet Protocol (TCP/IP). In this context, a protocol can refer to a set of rules defining how the nodes interact with each other. Computer networks may be further interconnected by an intermediate network node, such as a router, to extend the effective “size” of each network. 
     Overlay networks generally allow virtual networks to be created and layered over a physical network infrastructure. Overlay network protocols, such as Virtual Extensible LAN (VXLAN), Network Virtualization using Generic Routing Encapsulation (NVGRE), Network Virtualization Overlays (NVO3), and Stateless Transport Tunneling (STT), provide a traffic encapsulation scheme which allows network traffic to be carried across L2 and L3 networks over a logical tunnel. Such logical tunnels can be originated and terminated through virtual tunnel end points (VTEPs). 
     Overlay networks can also include virtual segments, such as VXLAN segments in a VXLAN overlay network, which can include virtual L2 and/or L3 overlay networks over which virtual machines (VMs) communicate. The virtual segments can be identified through a virtual network identifier (VNI), such as a VXLAN network identifier, which can specifically identify an associated virtual segment or domain. 
     Network virtualization allows hardware and software resources to be combined in a virtual network. For example, network virtualization can allow multiple numbers of VMs to be attached to the physical network via respective virtual LANs (VLANs). The VMs can be grouped according to their respective VLAN, and can communicate with other VMs as well as other devices on the internal or external network. 
     Network segments, such as physical or virtual segments, networks, devices, ports, physical or logical links, and/or traffic in general can be grouped into a bridge or flood domain. A bridge domain or flood domain can represent a broadcast domain, such as an L2 broadcast domain. A bridge domain or flood domain can include a single subnet, but can also include multiple subnets. Moreover, a bridge domain can be associated with a bridge domain interface on a network device, such as a switch. A bridge domain interface can be a logical interface which supports traffic between an L2 bridged network and an L3 routed network. In addition, a bridge domain interface can support internet protocol (IP) termination, VPN termination, address resolution handling, MAC addressing, etc. Both bridge domains and bridge domain interfaces can be identified by a same index or identifier. 
     Cloud computing can also be provided in a network to provide computing services using shared resources. Cloud computing can generally include Internet-based computing in which computing resources are dynamically provisioned and allocated to client or user computers or other devices on-demand, from a collection of resources available via the network (e.g., “the cloud”). Cloud computing resources, for example, can include any type of resource, such as computing, storage, and networking, among others. For instance, resources may include service devices (firewalls, deep packet inspectors, traffic monitors, load balancers, etc.), compute/processing devices (servers, CPUs, GPUs, random access memory, caches, etc.), and storage devices (e.g., network attached storages, storage area network devices, hard disk drives, solid-state devices, etc.), among others. In addition, such resources may be used to support virtual networks, virtual machines, databases, applications (“apps”), etc. 
     Cloud computing resources may include a “private cloud,” a “public cloud,” and/or a “hybrid cloud.” A “private cloud” is a cloud infrastructure operated by an enterprise for use by the enterprise, while a “public cloud” is a cloud infrastructure that provides services and resources over a network for public use. A “hybrid cloud” is a cloud infrastructure composed of two or more clouds that inter-operate or federate through technology. A hybrid cloud can be thought of as an interaction between private and public clouds where a private cloud joins a public cloud and utilizes public cloud resources in a secure and scalable manner. Cloud computing resources can also be provisioned via virtual networks in an overlay network, such as a VXLAN. 
     Enterprises are increasingly implementing heterogeneous virtualization environments, and are thus potentially required to provide support for multiple types of hardware architectures, hypervisors, host and guest operating systems, and other virtualization infrastructure components, as well as seamless integration with multiple cloud providers. Utilizing multiple cloud providers, however, may increase complexity for matters such as compliance, control, and security. Incompatibility issues caused by heterogeneous virtualization environments can also have a negative impact on achieving universal access to public cloud providers. In addition, security concerns can prevent adoption or limit usage of hybrid cloud solutions. Those concerns can include unsecured connections and limited workload protection. 
     The disclosed technology addresses the need in the art to support heterogeneous virtualization infrastructures, ensure end-to-end security, and provide unified workload management and mobility across clouds. Disclosed are systems and methods for providing a secure mechanism to access virtual machines in a public cloud that is independent of the public cloud provider. A brief introductory description of example environments, as illustrated in  FIGS.  1 - 3   , is disclosed herein. A detailed description of enabling SSH access to virtual machines that are migrated from a first cloud to a second cloud, and example variations, will then follow. These variations shall be described as the various example embodiments are set forth. The disclosure now turns to  FIG.  1   . 
       FIG.  1    illustrates an example hybrid cloud network  100  comprising a plurality of networks or clouds, including a private cloud  105  (e.g., an enterprise datacenter) and a public cloud  110  separated by a public network, such as the Internet (not shown). Although a hybrid cloud is sometimes defined as consisting of a private cloud and a public cloud, it should be understood that many aspects of this disclosure can be practiced in various configurations (e.g., two or more clouds hosted by third party providers and/or two or more enterprise clouds located in different locations). The private cloud  105  and public cloud  110  can be connected via a communication link  170  between private cloud gateway  120  (e.g., an Intercloud Fabric™ Extender (ICX) from Cisco®, Systems, Inc. (Cisco) of San Jose, Calif.) and a public cloud gateway  130  (e.g., an Intercloud Fabric Switch (ICS) from Cisco) (the ICX/ICS pair forming an Intercloud Fabric Cloud (ICFCloud)). Data packets and traffic can be exchanged among the devices of the hybrid cloud network using predefined network communication protocols as will be understood by those skilled in the art. 
     As depicted in  FIG.  1   , each cloud can have a cloud gateway, such as private cloud gateway  120  (e.g., ICX) in the private cloud  105 , and public cloud gateway  130  (e.g., ICS) in the public cloud  110 . The private cloud gateway  120  can be configured as a VM for establishing the communication link  170 , which can be used to connect the components in the public cloud  110  with the private cloud  105 . Likewise, the public cloud gateway  130  can be configured as a VM running in the public cloud  110  to connect to the communication channel  170  for enabling the public cloud gateway  130  to communicate with cloud resources. 
     In some example embodiments, the private cloud gateway  120  (e.g., ICX) can establish a secure site-to-site tunnel to interconnect with the public cloud gateway  130  (e.g., ICS), and interact with the virtual supervisor module (VSM)  140  (e.g., a Cisco Nexus® 1000V switch). The VSM  140  can serve as a management interface for this secure cloud extension between the private cloud  105  and the public cloud  110 . In some example embodiments, the public cloud gateway  130  can establish a secure site-to-site tunnel to interconnect with the private cloud gateway  120  and secure access tunnels to connect the public cloud VMs, and monitor and report statistics for the public cloud VMs and any component failures in the public cloud  110 . In some example embodiments, the private cloud gateway  120  and the public cloud gateway  130  can be deployed as a high-availability pair to provide redundancy. In some example embodiments, the public gateway  130  can include a virtual Ethernet module (VEM) (not shown) that communicates with the VSM to retrieve VM-specific network policies (e.g., port profiles), switches network traffic between public cloud VMs, switches network traffic between public cloud VMs and the private cloud, applies network policies, and monitors and reports VEM-related statistics. 
       FIG.  1    also illustrates a hybrid cloud manager  180  within the private cloud  105 , which can be a management plane VM for auto-provisioning resources within the hybrid cloud network. The hybrid cloud manager  180 , in this example, is a management platform running in the private network  105 , and can be generally responsible for providing the hybrid cloud operations, translating between private cloud and public cloud interfaces, managing cloud resources, instantiating cloud gateways and cloud VMs though the private virtualization platform and public cloud provider application programming interfaces (APIs). The hybrid cloud manager  180  may also monitor the health of all of the components of the network (e.g., the cloud gateways, the one or more private application VMs, and the communication link  170 ), and ensure high availability of those components. 
     In some example embodiments, the hybrid cloud manager  180  is a VM that includes virtual appliances Intercloud Fabric™ Director (ICFD) and Cisco Prime™ Network Services Controller (PNSC) from Cisco. The ICFD is a single point of management and consumption for hybrid cloud solutions for end users as well as IT administrators. The ICFD offers a single console so that end users and IT administrators can provision workloads and associated policies. The ICFD also exposes northbound APIs, which allows customers to programmatically manage their workloads in the hybrid cloud environment or integrate with other cloud management platforms. The PNSC, through a single pane, can automate virtual network management to make configuration changes quickly and consistently. The PNSC supports greater scalability along with standardization and adherence to policies in complex environments. In some example embodiments, the ICFD communicates with the PNSC using the PNSC&#39;s northbound APIs, and customers and IT staff do not need to access the PNSC directly for workload creation or deployment. 
       FIG.  1    also illustrates a hypervisor  150  (also sometimes referred to as a virtual machine manager or a virtual machine monitor (VMM)) and VMs  160 ,  162  in the private cloud  105 . The hypervisor may be computer software, firmware, or hardware that creates and runs one or more VMs, such as VM 1   160  and VM 2   162 . Although VM 3   164  is not shown to be encapsulated by a hypervisor in this example, it will be appreciated that VMs may or may not be managed by a hypervisor. Each VM can host a private application, including VM 3   164  in the public cloud. The hypervisor  150  can be controlled by the hybrid cloud manager  180 , and can provide a respective operating system to one or more VMs. In some example embodiments, a public cloud VM can include an agent (e.g., Intercloud Fabric Agent (ICA) from Cisco) (not shown) that provides the network overlay for VMs in the public cloud. The agent can be deployed in the public cloud VM as a secure tunnel driver. The agent can establish a secure tunnel to connect the public cloud VM to a public cloud gateway (e.g., ICS), and monitor and report secure overlay-related statistics. 
     As discussed above,  FIG.  1    also illustrates communication link  170 . Communication link  170  can take several forms, such as various types of virtual private networks (VPNs) or Layer 2 (or “L2” of the illustrative and well-known Open Systems Interconnection model (OSI model)) tunneling protocols. For example, some example embodiments utilize an open VPN (e.g., OpenVPN) overlay or an IP security (IPSec) VPN based L3 network extension to provide communication link  170 . Some example embodiments utilize a secure transport layer (i.e., Layer 4 or “L4” of the OSI model) tunnel as the communication link  170  between a first cloud gateway in a private cloud and a second cloud gateway in a public cloud, where the secure transport layer tunnel is configured to provide a link layer (i.e., Layer 2 or “L2”) network extension between the private cloud and the public cloud. By establishing a secure transport layer (i.e., L4) tunnel  170  (e.g., transport layer security (TLS), datagram TLS (DTLS), secure socket layer (SSL), etc.) over the public network, the techniques herein build a secure L2 switch overlay that interconnects public cloud resources with private clouds (e.g., enterprise network backbones). In other words, the secure transport layer tunnel  170  provides a link layer network extension between the private cloud and the public cloud. 
     As noted, the cloud gateway  120  deployed in the private cloud  105  can use an L4 Secure Tunnel to connect to the cloud resources allocated in the public cloud  110 . The L4 secure tunnel may be well-suited for use with corporate firewalls and Network Address Translation (NAT) devices due to the nature of the transport level protocols (e.g., UDP/TCP) and the transport layer ports opened for HTTP/HTTPS in the firewall. The L2 network can thus be further extended and connected to each of the cloud VMs (e.g., VM 1   160 , VM 2   162 , VM 3   164 ) through the cloud gateway  130  deployed in the public cloud  110 . With an L2 network overlay, instances of a particular private application VM (e.g., VM 3   164 ) can be seamlessly migrated to the overlay network dynamically created in the public cloud  110 , without any impact to existing corporate infrastructure. In some example embodiments, virtual services can be deployed to provide firewall and routing support in the public cloud  110 . 
       FIG.  2    illustrates an example hybrid cloud environment  200 . Like reference numbers and designations indicate the same or functionally similar elements in  FIG.  1   . In this configuration, private cloud  205  and public clouds  210  and  215  are separated by a public network, such as the Internet (not shown). The private cloud  205  and the public cloud  210  can be connected via a communication link  270  between private cloud gateway  220  (e.g., ICX) and public cloud gateway  230  (e.g., ICS). Similarly, private cloud  205  and the public cloud  215  may be connected via a communication link  275  between private cloud gateway  225  and public cloud gateway  235 . 
       FIG.  2    also illustrates a hybrid cloud manager  280  (e.g., ICFD and PNSC) within the private cloud  205 . As discussed above, the hybrid cloud manager  280  can serve as the end user and IT administrator portal for provisioning and management of the hybrid cloud network  200 . The hybrid cloud manager can provide visibility into virtual machines in the private cloud  205  along with complete lifecycle management for virtual machines running in the public clouds  210  and  215 . The hybrid cloud manager  280  can also be used for managing cloud network services. The private cloud  205  also includes a VSM  240  (e.g., Cisco Nexus 1000V switch), a hypervisor  250 , and one or more VMs  260 ,  262 . As discussed above, the hybrid cloud manager  280  can be used to create VMs in the public or private cloud, such as VM 1   260 , VM 2   262 , VM 3   264 , and VM 4   266 . 
       FIG.  3    illustrates an example approach 300 for migrating virtual machines from a private cloud to public clouds in a hybrid cloud network similar to the environment illustrated in  FIG.  2   . Like reference numbers and designations indicate the same or functionally similar elements in  FIGS.  1  and  2   . In some example embodiments, VMs in the private cloud  205  may need to be scaled beyond the current resources of the private cloud,  205  or the private cloud  205  may need to be taken off-line for a period of time. In such situations, it can be desirable to migrate the VMs in the private cloud  205  to one or more of the public clouds  210 ,  215 . In particular,  FIG.  3    illustrates VM 1   260  in the private cloud  205  being migrated to the public cloud  210 , where VM 1  is illustrated as VM 1   260 ′. Similarly, VM 2  in the private cloud  205  is migrated to the public cloud  215 , where VM 2  is illustrated as VM 2   262 ′. Migration can be managed using hybrid cloud manager  280  (e.g., ICFD and PNSC) in communication with other components of the hybrid cloud network. 
     In an example embodiment, the migration process can include a series of steps. It should be understood that, for any process discussed herein, there can be additional, fewer, or alternative steps performed in similar or alternative orders, or in parallel, within the scope of the various example embodiments unless otherwise stated. Prior to migration, a secure tunnel driver (e.g., ICA) can be installed in the virtual machine to enable secure communication between public cloud VMs  260 ′,  262 ′,  264 , and  266  and public cloud gateways  230 ,  235  (e.g., ICS&#39;s). SSH public-private key pairs can also be generated and inserted into the images for the migrating VMs for purposes of user authentication (e.g., SSH public key) and server authentication (e.g., host key or information relating to the host key, such as a fingerprint of a public component of the host key) as discussed elsewhere herein. The migration process may begin by taking VM 1   260  and VM 2   262  offline or shutting them down in the private cloud. In other example embodiments, migration can occur “live” or substantially live as known to one of ordinary skill in the art. 
     Once the images for the migrating VMs have been prepared, they may be converted to a respective cloud format corresponding to the public clouds to which the VMs will be transferred. This can involve first “normalizing” or converting the images to raw image format, and then converting the normalized or raw images to the respective cloud format. Thereafter, the converted image for VM 1   260  can be uploaded to the public cloud  210 , and the converted image for VM 2   262  can be uploaded to the public cloud  215 . The migration process may conclude by instantiating or powering on the VMs  260 ′,  262 ′ in the public clouds  210 ,  215 , respectively. 
     As discussed above, enterprises are rapidly adopting cloud computing in order to meet dynamically changing business requirements. These deployments typically include both private and public clouds, resulting in the creation of hybrid clouds that are designed to rapidly scale up and down in response to user demands. Hybrid cloud models can also provide for economies of scale. In order to benefit from this environment, businesses may need to connect with these hybrid clouds more easily from their heterogeneous bases, and balance requirements for compliance and control against the desire to rapidly innovate and the ability to scale on demand. Systems and approaches in accordance with various example embodiments of the subject technology meet these needs. In particular, various example embodiments utilize SSH as a provider-independent, secure access mechanism for managing virtual machines in the public cloud. 
     SSH is an encryption-based networking protocol capable of initiating on remote computing systems command shell, port forwarding, file transfer, and data tunneling sessions, among other functions. SSH provides for secure network communications that can be less complex and expensive than other techniques, such as hardware-based VPN implementations or approaches based on a certificate authority or certification authority (CA). Further, SSH is available on most operating systems. SSH offers four security measures—user authentication, host authentication, data encryption, and data integrity. User authentication can be utilized for ensuring that access to a system is limited to credentialed users. Credentials can include passwords, private keys generated from public-key cryptography methods (e.g., Rivest-Shamir-Adleman (RSA), Digital Signature Algorithm (DSA), Elliptical Curve Digital Signature Algorithm (ECDSA), Diffie-Helman (DH), Elliptic Curve Diffie-Hellman (ECDH)), secret keys generated from symmetric-key cryptography methods (e.g., International Data Encryption Algorithm (IDEA), Data Encryption Standard (DES), Triple-DES, Advanced Encryption Standard (AES), ARCFOUR (RC4), Blowfish, Twofish, Carlisle Adams Stafford Tavares (CAST), etc.), among other types of credentials. However, SSH can be adapted to use other authentication methods (e.g., Kerberos, NT LAN Manager (NTLM), and keyboard-interactive, etc.), including new authentication methods as they become available. 
     Host authentication can be used by a server to establish its identity to a client, and by the client to determine whether the server is a known host. Host authentication may be used to prevent Man-in-the-Middle attacks and other security threats. An example of a Man-in-the-Middle attack involves a first valid user requesting a second valid user for the second user&#39;s public key; a malicious user intercepting the public key of the second user; the malicious user sending a forged message to the first user including the malicious user&#39;s public key; the first user sending an enciphered message encrypted using the malicious user&#39;s public key; and the malicious user intercepting the enciphered message, deciphering the enciphered message using the malicious user&#39;s private key, and re-encrypting the message using the second user&#39;s public key. Subsequent communications between the first user and the second user can be intercepted and modified by the malicious user. 
     Data encryption transforms plaintext to unreadable ciphertext using a cipher, and decryption reverts ciphertext to the original plaintext using the same cipher. In SSH, data encryption functions to protect communications between a client and a server during a session from sniffing or eavesdropping attacks. The symmetric-key algorithms discussed above can be utilized for encrypting the session communications. 
     Data integrity refers to ensuring that data sent from one of the valid SSH participants arrives unaltered to the other valid SSH participant. SSH can implement hash functions for maintaining data integrity (e.g., Cyclic Redundancy Check (32-bit) (CRC-32), Message Authentication Code (MAC), Universal hashing Message Authentication Code (UMAC), Message Digest algorithm number 5 (MD5), Secure Hash Algorithm (SHA-1), Research and Development in Advanced Communications Technologies ((RACE) Integrity Primitives Evaluation (RIPE)) Message Digest (160-bits) (RIPEMD-160), etc.). 
       FIG.  4 A  illustrates an example process  400  for providing secure access to virtual machines in heterogeneous cloud environments in accordance with an example embodiment. Method  400  begins at step  402  in which a first SSH authentication public-private key pair is generated using a public-key cryptography method (e.g., RSA, DSA, ECDSA, DH, ECDH, etc.). It will be appreciated that other example embodiments can utilize other credentials or other authentication methods (e.g., passwords, secret keys of symmetric-key cryptography algorithms, Kerberos, NTLM, keyboard-interactive, etc.). In this example embodiment, the first authentication public-private key pair is unique to this virtual machine. In other example embodiments, the first authentication public-private key pair can be shared globally with any virtual machine that will be migrated from a private cloud to a public cloud of a hybrid cloud network. After the first authentication public-private key pair is generated, the first authentication public key (or other credential(s)) is inserted into a virtual machine running in the private cloud  404 . For example, the first authentication public key can be added to a database or similar object (e.g., list) of authorized keys in the virtual machine. In some example embodiments, a secure tunnel driver (e.g., ICA) can also be installed or otherwise inserted into the virtual machine. The secure tunnel driver enables a secure tunnel to be established to connect the virtual machine to a public cloud gateway (e.g., ICS). 
     The process  400  can continue with migration of the virtual machine from the private cloud to a public cloud  406 , such one of many heterogeneous clouds operated by third party providers. As discussed above, migration can include normalizing or converting an image of the virtual machine to raw image format, converting the normalized or raw image to a cloud format of the public cloud, uploading the converted image to the public cloud, and powering on the virtual machine in the public cloud. In some example embodiments, migrating the virtual machine from the private cloud to the public cloud includes generating a template incorporating the virtual machine, and deploying the virtual machine to the public cloud using the template. A potential problem with this approach, however, is that the authentication public key becomes available to the cloud provider and other third parties. This can be resolved by re-keying the authentication public key as discussed further below. 
     The virtual machine, now running in the public cloud, can be accessed from the private cloud via SSH  408 , such as by a hybrid cloud manager (e.g., ICFD and PNSC) or similar system or user. Attempts to access the virtual machine will require authentication of the hybrid cloud manager. In this example embodiment, the virtual machine can send a challenge to the hybrid cloud manager. The hybrid cloud manager can respond to the challenge by encrypting the challenge or other data using the first authentication private key, and sending the encrypted challenge or other data to the virtual machine. The virtual machine can decrypt the encrypted challenge or other data using the first authentication public key to verify the identity of the hybrid cloud manager. For example, the virtual machine can compare the decrypted challenge or other data to the original challenge or other data. In other example embodiments, other authentication methods can be implemented as discussed elsewhere herein. 
     Once the hybrid cloud manager has successfully accessed the virtual machine in the public cloud, the hybrid cloud manager&#39;s authentication public key can be re-keyed. This can be achieved by generating a second SSH authentication public-private key pair  410 , and replacing the first authentication public key in the virtual machine with the second authentication public key  412 . The second authentication private key (or other credential(s)) can be saved and retained securely for subsequent access to the virtual machine  414  in a manner similar to step  408 . In this example embodiment, the second authentication public-private key pair is also unique to this virtual machine. In other example embodiments, the second public-private key pair can be shared by all of the virtual machines of this specific public cloud (e.g., ICFCloud). 
     The process  400  can be independently performed for each public cloud to which the private cloud is linked, enabling scalable management of virtual machines in a plurality of heterogeneous public clouds. However, process  400  may be susceptible to Man-in-the-Middle attacks. This can be improved by using SSH host authentication as discussed above.  FIG.  4 B  illustrates an example process  450  for providing secure access to virtual machines in heterogeneous cloud environments. In this example embodiment, the process  450  may be initiated by generating a first host key comprising a third public-private key pair  452  using a public-key algorithm (e.g., RSA, DSA, ECDSA, DH, ECDH, etc.), and inserting the first host key into a virtual machine running in a private cloud  454 . Although this example embodiment implements public-key cryptography, it should be understood that other example embodiments can utilize other credentials or other authentication methods (e.g., passwords, secret keys of symmetric-key cryptography algorithms, Kerberos, NTLM, keyboard-interactive, etc.) for host authentication. First information associating the host key or a first fingerprint of a public portion of the host key (i.e., third public key) can be stored to the private cloud  456 , such as in a database or similar object (e.g., list) of known hosts. In this example embodiment, the first fingerprint can be generated by performing a hash function (e.g., CRC-32, MAC, UMAC, MD5, SHA-1, RIPEMD-160, etc.) on the public portion of the host key (i.e., third public key). Other example embodiments may utilize other techniques for generating a fingerprint or signature of the host key as is known in the art. 
     Upon an initial login to the virtual machine, such as just prior to or contemporaneously with performing step  408  in  FIG.  4 A , the method  450  may proceed by receiving the public portion of the host key (i.e., third public key) or the first fingerprint to the private cloud, such as a hybrid cloud manager (e.g., ICFD and PNSC) or similar entity. This credential can be used for authenticating the virtual machine  458 . For example, the public portion of the first host key (i.e., third public key) or the first fingerprint can be matched to a portion of the first information stored in the database. After successfully accessing the virtual machine, such as following performance of step  408  in  FIG.  4 A , a second host key comprising a fourth public-private key pair can be generated  460  using public-key cryptography in a manner similar to step  452 . The second host key (i.e., fourth public-private key pair) can be used to replace the first host key (i.e., third public-private key pair) in the virtual machine in the public cloud  462 . 
     Second information associating the virtual machine to a public portion of the second host key (i.e., fourth public key) or a second fingerprint of the public portion of the second host key can also be stored to the known hosts database or similar object (e.g., list). In some example embodiments, the first information must also be explicitly removed from the known hosts database. Immediately prior to performing step  414  of  FIG.  4 A , the hybrid cloud manager can receive the public portion of the second host key (i.e., fourth public key) or the second fingerprint. This credential can be used to authenticate the virtual machine  464  in a manner similar to step  458 . 
       FIG.  5    illustrates an example network device  500  that can be used in accordance with various example embodiments. Network device  500  includes a master central processing unit (CPU)  502 , interfaces  504 , and a bus  506  (e.g., a PCI bus). When acting under the control of appropriate software or firmware, the CPU  502  is responsible for executing packet management, error detection, and/or routing functions, such policy enforcement, for example. The CPU  502  preferably accomplishes all these functions under the control of software including an operating system and any appropriate applications software. CPU  502  may include one or more processors  508  such as a processor from the Motorola family of microprocessors or the MIPS family of microprocessors. In an alternative embodiment, processor  508  is specially designed hardware for controlling the operations of device  500 . In a specific embodiment, a memory  510  (such as non-volatile RAM and/or ROM) also forms part of CPU  502 . However, there are many different ways in which memory could be coupled to the system. 
     The interfaces  504  are typically provided as interface cards (sometimes referred to as “line cards”). Generally, they control the sending and receiving of data packets over the network and sometimes support other peripherals used with the network device  500 . Among the interfaces that may be provided are Ethernet interfaces, frame relay interfaces, cable interfaces, DSL interfaces, token ring interfaces, and the like. In addition, various very high-speed interfaces may be provided such as fast token ring interfaces, wireless interfaces, Ethernet interfaces, Gigabit Ethernet interfaces, ATM interfaces, HSSI interfaces, POS interfaces, FDDI interfaces and the like. Generally, these interfaces may include ports appropriate for communication with the appropriate media. In some cases, they may also include an independent processor and, in some instances, volatile RAM. The independent processors may control such communications intensive tasks as packet switching, media control, and management. By providing separate processors for the communications intensive tasks, these interfaces allow the master microprocessor  502  to efficiently perform routing computations, network diagnostics, security functions, etc. 
     Although the system shown in  FIG.  5    is one specific network device, it is by no means the only network device architecture on which each embodiment can be implemented. For example, an architecture having a single processor that handles communications as well as routing computations, etc., is often used. Further, other types of interfaces and media could also be used with the router. 
     Regardless of the network device&#39;s configuration, it may employ one or more memories or memory modules (including memory  510 ) configured to store program instructions for the general-purpose network operations and mechanisms for roaming, route optimization and routing functions described herein. The program instructions may control the operation of an operating system and/or one or more applications, for example. The memory or memories may also be configured to store tables such as mobility binding, registration, and association tables, etc. 
       FIG.  6 A  and  FIG.  6 B  illustrate systems that can be used in various example embodiments. The more appropriate embodiment will be apparent to those of ordinary skill in the art when practicing the present technology. Persons of ordinary skill in the art will also readily appreciate that other embodiments are possible. 
       FIG.  6 A  illustrates a conventional system bus computing system architecture  600  wherein the components of the system are in electrical communication with each other using a bus  605 . Example system  600  includes a processing unit (CPU or processor)  610  and a system bus  605  that couples various system components including the system memory  615 , such as read only memory (ROM)  620  and random access memory (RAM)  625 , to the processor  610 . The system  600  can include a cache of high-speed memory connected directly with, in close proximity to, or integrated as part of the processor  610 . The system  600  can copy data from the memory  615  and/or the storage device  630  to the cache  612  for quick access by the processor  610 . In this way, the cache can provide a performance boost that avoids processor  610  delays while waiting for data. These and other modules can control or be configured to control the processor  610  to perform various actions. Other system memory  615  may be available for use as well. The memory  615  can include multiple different types of memory with different performance characteristics. The processor  610  can include any general purpose processor and a hardware module or software module, such as module  1   632 , module  2   634 , and module  3   636  stored in storage device  630 , configured to control the processor  610  as well as a special-purpose processor where software instructions are incorporated into the actual processor design. The processor  610  may essentially be a completely self-contained computing system, containing multiple cores or processors, a bus, memory controller, cache, etc. A multi-core processor may be symmetric or asymmetric. 
     To enable user interaction with the computing device  600 , an input device  645  can represent any number of input mechanisms, such as a microphone for speech, a touch-sensitive screen for gesture or graphical input, keyboard, mouse, motion input, speech, among others. An output device  635  can also be one or more of a number of output mechanisms known to those of skill in the art. In some instances, multimodal systems can enable a user to provide multiple types of input to communicate with the computing device  600 . The communications interface  640  can generally govern and manage the user input and system output. There is no restriction on operating on any particular hardware arrangement and therefore the basic features here may easily be substituted for improved hardware or firmware arrangements as they are developed. 
     Storage device  630  is a non-volatile memory and can be a hard disk or other types of computer readable media which can store data that are accessible by a computer, such as magnetic cassettes, flash memory cards, solid state memory devices, digital versatile disks, cartridges, random access memories (RAMs)  625 , read only memory (ROM)  620 , and hybrids thereof. 
     The storage device  630  can include software modules  632 ,  634 ,  636  for controlling the processor  610 . Other hardware or software modules are contemplated. The storage device  630  can be connected to the system bus  605 . In one aspect, a hardware module that performs a particular function can include the software component stored in a computer-readable medium in connection with the necessary hardware components, such as the processor  610 , bus  605 , display  635 , and so forth, to carry out the function. 
       FIG.  6 B  illustrates a computer system  650  having a chipset architecture that can be used in executing the described method and generating and displaying a graphical user interface (GUI). Computer system  650  is an example of computer hardware, software, and firmware that can be used to implement the disclosed technology. System  650  can include a processor  655 , representative of any number of physically and/or logically distinct resources capable of executing software, firmware, and hardware configured to perform identified computations. Processor  655  can communicate with a chipset  660  that can control input to and output from processor  655 . In this example, chipset  660  outputs information to output  665 , such as a display, and can read and write information to storage device  670 , which can include magnetic media, and solid state media, for example. Chipset  660  can also read data from and write data to RAM  675 . A bridge  680  for interfacing with a variety of user interface components  685  can be provided for interfacing with chipset  660 . Such user interface components  685  can include a keyboard, a microphone, touch detection and processing circuitry, a pointing device, such as a mouse, and so on. In general, inputs to system  650  can come from any of a variety of sources, machine generated and/or human generated. 
     Chipset  660  can also interface with one or more communication interfaces  690  that can have different physical interfaces. Such communication interfaces can include interfaces for wired and wireless local area networks, for broadband wireless networks, as well as personal area networks. Some applications of the methods for generating, displaying, and using the GUI disclosed herein can include receiving ordered datasets over the physical interface or be generated by the machine itself by processor  655  analyzing data stored in storage  670  or  675 . Further, the machine can receive inputs from a user via user interface components  685  and execute appropriate functions, such as browsing functions by interpreting these inputs using processor  655 . 
     It can be appreciated that example systems  600  and  650  can have more than one processor  610  or be part of a group or cluster of computing devices networked together to provide greater processing capability. 
     For clarity of explanation, in some instances the present technology may be presented as including individual functional blocks including functional blocks comprising devices, device components, steps or routines in a method embodied in software, or combinations of hardware and software. 
     Note that in certain example implementations, the optimization and/or placement functions outlined herein may be implemented by logic encoded in one or more tangible, non-transitory media (e.g., embedded logic provided in an application specific integrated circuit (ASIC), digital signal processor (DSP) instructions, software (potentially inclusive of object code and source code) to be executed by a processor, or other similar machine, etc.). The computer-readable storage devices, mediums, and memories can include a cable or wireless signal containing a bit stream and the like. However, when mentioned, non-transitory computer-readable storage media expressly exclude media such as energy, carrier signals, electromagnetic waves, and signals per se. 
     Methods according to the above-described examples can be implemented using computer-executable instructions that are stored or otherwise available from computer readable media. Such instructions can comprise, for example, instructions and data which cause or otherwise configure a general purpose computer, special purpose computer, or special purpose processing device to perform a certain function or group of functions. Portions of computer resources used can be accessible over a network. The computer executable instructions may be, for example, binaries, intermediate format instructions such as assembly language, firmware, or source code. Examples of computer-readable media that may be used to store instructions, information used, and/or information created during methods according to described examples include magnetic or optical disks, flash memory, USB devices provided with non-volatile memory, networked storage devices, and so on. 
     Devices implementing methods according to these disclosures can comprise hardware, firmware and/or software, and can take any of a variety of form factors. Typical examples of such form factors include laptops, smart phones, small form factor personal computers, personal digital assistants, and so on. Functionality described herein also can be embodied in peripherals or add-in cards. Such functionality can also be implemented on a circuit board among different chips or different processes executing in a single device, by way of further example. 
     The instructions, media for conveying such instructions, computing resources for executing them, and other structures for supporting such computing resources are means for providing the functions described in these disclosures. 
     Although a variety of examples and other information was used to explain aspects within the scope of the appended claims, no limitation of the claims should be implied based on particular features or arrangements in such examples, as one of ordinary skill would be able to use these examples to derive a wide variety of implementations. Further and although some subject matter may have been described in language specific to examples of structural features and/or method steps, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to these described features or acts. For example, such functionality can be distributed differently or performed in components other than those identified herein. Rather, the described features and steps are disclosed as examples of components of systems and methods within the scope of the appended claims.