Papers tagged as Attacks
  1. Practical State Recovery Attacks against Legacy RNG Implementations 2018 Attacks CCS SideChannels
    Shaanan N. Cohney, Matthew D. Green, and Nadia Heninger

    The ANSI X9.17/X9.31 pseudorandom number generator design was first standardized in 1985, with variants incorporated into numerous cryptographic standards over the next three decades. The design uses timestamps together with a statically keyed block cipher to produce pseudo-random output. It has been known since 1998 that the key must remain secret in order for the output to be secure. However, neither the FIPS 140-2 standardization process nor NIST’s later descriptions of the algorithm specified any process for key generation. We performed a systematic study of publicly available FIPS 140- 2 certifications for hundreds of products that implemented the ANSI X9.31 random number generator, and found twelve whose certification documents use of static, hard-coded keys in source code, leaving the implementation vulnerable to an attacker who can learn this key from the source code or binary. In order to demonstrate the practicality of such an attack, we develop a full passive decryption attack against FortiGate VPN gateway products using FortiOS v4 that recovers the private key in seconds. We measure the prevalence of this vulnerability on the visible Internet using active scans, and demonstrate state recovery and full private key recovery in the wild. Our work highlights the extent to which the validation and certification process has failed to provide even modest security guarantees.

  2. Fallout: Leaking Data on Meltdown-resistant CPUs 2019 Attacks CCS IntelSGX SideChannels
    Claudio Canella, Daniel Genkin, Lukas Giner, Daniel Gruss, Moritz Lipp, Marina Minkin, Daniel Moghimi, Frank Piessens, Michael Schwarz, Berk Sunar, Jo Van Bulck, and Yuval Yarom

    Meltdown and Spectre enable arbitrary data leakage from memory via various side channels. Short-term software mitigations for Meltdown are only a temporary solution with a significant performance overhead. Due to hardware fixes, these mitigations are disabled on recent processors. In this paper, we show that Meltdown-like attacks are still possible on recent CPUs which are not vulnerable to Meltdown. We identify two behaviors of the store buffer, a microarchitectural resource to reduce the latency for data stores, that enable powerful attacks. The first behavior, Write Transient Forwarding forwards data from stores to subsequent loads even when the load address differs from that of the store. The second, Store-to-Leak exploits the interaction between the TLB and the store buffer to leak metadata on store addresses. Based on these, we develop multiple attacks and demonstrate data leakage, control flow recovery, and attacks on ASLR. Our paper shows that Meltdown-like attacks are still possible, and software fixes with potentially significant performance overheads are still necessary to ensure proper isolation between the kernel and user space.

  3. Encrypted Databases: New Volume Attacks against Range Queries 2019 Attacks CCS EncryptedDatabases
    Zichen Gui, Oliver Johnson and Bogdan Warinschi

    We present a range of novel attacks which exploit information about the volume of answers to range queries in encrypted database. Our attacks rely on a strategy which is simple yet robust and effective. We illustrate the robustness of our strategy in a number of ways. We show how i) to adapt the attack for several variations of a basic usage scenario ii) to defeat countermeasures intended to thwart the premise of our basic attack and iii) to perform partial reconstruction of secret data when unique reconstruction is information theoretically impossible. Furthermore, over the state of the art, our attacks require one order of magnitude fewer queries. We show how to improve the attacks even further, under the assumption that some partial information is known to the adversary. We validate experimentally all of our attacks through extensive experiments on real-world medical data and justify theoretically the effectiveness of our strategy for the basic attack scenario. Our new attacks further underscore the difficulty of striking an appropriate functionality-security trade-off for encrypted databases.

  4. CryptoGuard: High Precision Detection of Cryptographic Vulnerabilities in Massive-sized Java Project 2019 Attacks CCS
    Sazzadur Rahaman, Ya Xiao, Sharmin Afrose, Fahad Shaon, Ke Tian, Miles Frantz, Danfeng (Daphne)Yao, Murat Kantarcioglu

    Cryptographic API misuses, such as exposed secrets, predictable random numbers, and vulnerable certificate verification, seriously threaten software security. The vision of automatically screening cryptographic API calls in massive-sized (e.g., millions of LoC) Java programs is not new. However, hindered by the practical difficulty of reducing false positives without compromising analysis quality, this goal has not been accomplished. State-of-the-art crypto API screening solutions are not designed to operate on a large scale.
    Our technical innovation is a set of fast and highly accurate slicing algorithms. Our algorithms refine program slices by identifying language-specific irrelevant elements. The refinements reduce false alerts by 76% to 80% in our experiments. Running our tool, CrytoGuard, on 46 high-impact large-scale Apache projects and 6,181 Android apps generate many security insights. Our findings helped multiple popular Apache projects to harden their code, including Spark, Ranger, and Ofbiz. We also have made substantial progress towards the science of analysis in this space, including: i) manually analyzing 1,295 Apache alerts and confirming 1,277 true positives (98.61% precision), ii) creating a benchmark with 38-unit basic cases and 74-unit advanced cases, iii) performing an in-depth comparison with leading solutions including CrySL, SpotBugs, and Coverity. We are in the process of integrating CryptoGuard with the Software Assurance Marketplace (SWAMP).

  5. Efail: Breaking S/MIME and OpenPGP Email Encryption using Exfiltration Channels 2018 Attacks PGP Usenix
    Damian Poddebniak, Christian Dresen, Jens Müller, Fabian Ising, Sebastian Schinzel, Simon Friedberger, Juraj Somorovsky and Jörg Schwenk

    OpenPGP and S/MIME are the two prime standards for providing end-to-end security for emails. We describe novel attacks built upon a technique we call malleability gadgets to reveal the plaintext of encrypted emails. We use CBC/CFB gadgets to inject malicious plaintext snippets into encrypted emails. These snippets abuse existing and standard conforming backchannels to exfiltrate the full plaintext after decryption. We describe malleability gadgets for emails using HTML, CSS, and X.509 functionality. The attack works for emails even if they were collected long ago, and it is triggered as soon as the recipient decrypts a single maliciously crafted email from the attacker.

    We devise working attacks for both OpenPGP and S/MIME encryption, and show that exfiltration channels exist for 23 of the 35 tested S/MIME email clients and 10 of the 28 tested OpenPGP email clients. While it is advisable to update the OpenPGP and S/MIME standards to fix these vulnerabilities, some clients had even more severe implementation flaws allowing straightforward exfiltration of the plaintext.

  6. The Dangers of Key Reuse: Practical Attacks on IPsec IKE 2018 Attacks IKE IPSec Usenix
    Dennis Felsch, Martin Grothe, Jörg Schwenk, Adam Czubak and Marcin Szymanek

    IPsec enables cryptographic protection of IP packets. It is commonly used to build VPNs (Virtual Private Networks). For key establishment, the IKE (Internet Key Exchange) protocol is used. IKE exists in two versions, each with different modes, different phases, several authentication methods, and configuration options.

    In this paper, we show that reusing a key pair across different versions and modes of IKE can lead to cross-protocol authentication bypasses, enabling the impersonation of a victim host or network by attackers. We exploit a Bleichenbacher oracle in an IKEv1 mode, where RSA encrypted nonces are used for authentication. Using this exploit, we break these RSA encryption based modes, and in addition break RSA signature based authentication in both IKEv1 and IKEv2. Additionally, we describe an offline dictionary attack against the PSK (Pre-Shared Key) based IKE modes, thus covering all available authentication mechanisms of IKE.

    We found Bleichenbacher oracles in the IKEv1 implementations of Cisco (CVE-2018-0131), Huawei (CVE-2017-17305), Clavister (CVE-2018-8753), and ZyXEL (CVE-2018-9129). All vendors published fixes or removed the particular authentication method from their devices’ firmwares in response to our reports.

  7. One&Done: A Single-Decryption EM-Based Attack on OpenSSL’s Constant-Time Blinded RSA 2018 Attacks SideChannels TLS Usenix
    Monjur Alam, Haider Adnan Khan, Moumita Dey, Nishith Sinha, Robert Callan, Alenka Zajic, and Milos Prvulovic

    This paper presents the first side channel attack approach that, without relying on the cache organization and/or timing, retrieves the secret exponent from a single decryption on arbitrary ciphertext in a modern (current version of OpenSSL) fixed-window constant-time implementation of RSA. Specifically, the attack recovers the exponent’s bits during modular exponentiation from analog signals that are unintentionally produced by the processor as it executes the constant-time code that constructs the value of each “window” in the exponent, rather than the signals that correspond to squaring/multiplication operations and/or cache behavior during multiplicand table lookup operations. The approach is demonstrated using electromagnetic (EM) emanations on two mobile phones and an embedded system, and after only one decryption in a fixed-window RSA implementation it recovers enough bits of the secret exponents to enable very efficient (within seconds) reconstruction of the full private RSA key.

    Since the value of the ciphertext is irrelevant to our attack, the attack succeeds even when the ciphertext is unknown and/or when message randomization (blinding) is used. Our evaluation uses signals obtained by demodulating the signal from a relatively narrow band (40 MHz) around the processor’s clock frequency (around 1GHz), which is within the capabilities of compact sub-$1,000 software-defined radio (SDR) receivers.

    Finally, we propose a mitigation where the bits of the exponent are only obtained from an exponent in integer-sized groups (tens of bits) rather than obtaining them one bit at a time. This mitigation is effective because it forces the attacker to attempt recovery of tens of bits from a single brief snippet of signal, rather than having a separate signal snippet for each individual bit. This mitigation has been submitted to OpenSSL and was merged into its master source code branch prior to the publication of this paper.

  8. Return Of Bleichenbacher’s Oracle Threat (ROBOT) 2018 Attacks TLS Usenix
    Hanno Böck, Juraj Somorovsky, and Craig Young

    In 1998 Bleichenbacher presented an adaptive chosen-ciphertext attack on the RSA PKCS#1 v1.5 padding scheme. The attack exploits the availability of a server which responds with different messages based on the ciphertext validity. This server is used as an oracle and allows the attacker to decrypt RSA ciphertexts. Given the importance of this attack, countermeasures were defined in TLS and other cryptographic standards using RSA PKCS#1 v1.5.

    We perform the first large-scale evaluation of Bleichenbacher’s RSA vulnerability. We show that this vulnerability is still very prevalent in the Internet and affected almost a third of the top 100 domains in the Alexa Top 1 Million list, including Facebook and Paypal.

    We identified vulnerable products from nine different vendors and open source projects, among them F5, Citrix, Radware, Palo Alto Networks, IBM, and Cisco. These implementations provide novel side-channels for constructing Bleichenbacher oracles: TCP resets, TCP timeouts, or duplicated alert messages. In order to prove the importance of this attack, we have demonstrated practical exploitation by signing a message with the private key of \texttt{}’s HTTPS certificate. Finally, we discuss countermeasures against Bleichenbacher attacks in TLS and recommend to deprecate the RSA encryption key exchange in TLS and the RSA PKCS~#1~v1.5 standard.

  9. Foreshadow: Extracting the Keys to the Intel SGX Kingdom with Transient Out-of-Order Execution 2018 Attacks IntelSGX TEE Usenix
    Jo Van Bulck, Marina Minkin, Ofir Weisse, Daniel Genkin, Baris Kasikci, Frank Piessens, Mark Silberstein, Thomas F. Wenisch, Yuval Yarom, and Raoul Strackx

    Trusted execution environments, and particularly the Software Guard eXtensions (SGX) included in recent Intel x86 processors, gained significant traction in recent years. A long track of research papers, and increasingly also real-world industry applications, take advantage of the strong hardware-enforced confidentiality and integrity guarantees provided by Intel SGX. Ultimately, enclaved execution holds the compelling potential of securely offloading sensitive computations to untrusted remote platforms.

    We present Foreshadow, a practical software-only microarchitectural attack that decisively dismantles the security objectives of current SGX implementations. Crucially, unlike previous SGX attacks, we do not make any assumptions on the victim enclave’s code and do not necessarily require kernel-level access. At its core, Foreshadow abuses a speculative execution bug in modern Intel processors, on top of which we develop a novel exploitation methodology to reliably leak plaintext enclave secrets from the CPU cache. We demonstrate our attacks by extracting full cryptographic keys from Intel’s vetted architectural enclaves, and validate their correctness by launching rogue production enclaves and forging arbitrary local and remote attestation responses. The extracted remote attestation keys affect millions of devices.

  10. Scalable Scanning and Automatic Classification of TLS Padding Oracle Vulnerabilities 2019 Attacks TLS Usenix
    Robert Merget, Juraj Somorovsky, Nimrod Aviram, Craig Young, Janis Fliegenschmidt, Jörg Schwenk, and Yuval Shavitt

    The TLS protocol provides encryption, data integrity, and authentication on the modern Internet. Despite the protocol’s importance, currently-deployed TLS versions use obsolete cryptographic algorithms which have been broken using various attacks. One prominent class of such attacks is CBC padding oracle attacks. These attacks allow an adversary to decrypt TLS traffic by observing different server behaviors which depend on the validity of CBC padding.

    We present the first large-scale scan for CBC padding oracle vulnerabilities in TLS implementations on the modern Internet. Our scan revealed vulnerabilities in 1.83% of the Alexa Top Million websites, detecting nearly 100 different vulnerabilities. Our scanner observes subtle differences in server behavior, such as responding with different TLS alerts, or with different TCP header flags.

    We used a novel scanning methodology consisting of three steps. First, we created a large set of probes that detect vulnerabilities at a considerable scanning cost. We then reduced the number of probes using a preliminary scan, such that a smaller set of probes has the same detection rate but is small enough to be used in large-scale scans. Finally, we used the reduced set to scan at scale, and clustered our findings with a novel approach using graph drawing algorithms.

    Contrary to common wisdom, exploiting CBC padding oracles does not necessarily require performing precise timing measurements. We detected vulnerabilities that can be exploited simply by observing the content of different server responses. These vulnerabilities pose a significantly larger threat in practice than previously assumed.

  11. CLKSCREW: Exposing the Perils of Security-Oblivious Energy Management 2017 Attacks TEE Usenix
    Adrian Tang, Simha Sethumadhavan, and Salvatore Stolfo

    The need for power- and energy-efficient computing has resulted in aggressive cooperative hardware-software energy management mechanisms on modern commodity devices. Most systems today, for example, allow software to control the frequency and voltage of the underlying hardware at a very fine granularity to extend battery life. Despite their benefits, these software-exposed energy management mechanisms pose grave security implications that have not been studied before.

    In this work, we present the CLKSCREW attack, a new class of fault attacks that exploit the security-obliviousness of energy management mechanisms to break security. A novel benefit for the attackers is that these fault attacks become more accessible since they can now be conducted without the need for physical access to the devices or fault injection equipment. We demonstrate CLKSCREW on commodity ARM/Android devices. We show that a malicious kernel driver (1) can extract secret cryptographic keys from Trustzone, and (2) can escalate its privileges by loading self-signed code into Trustzone. As the first work to show the security ramifications of energy management mechanisms, we urge the community to re-examine these security-oblivious designs.

  12. Learning to Reconstruct: Statistical Learning Theory and Encrypted Database Attacks 2019 Attacks EncryptedDatabases Oakland
    Paul Grubbs, Marie-Sarah Lacharite, Brice Minaud and Kenneth G. Paterson

    We show that the problem of reconstructing encrypted databases from access pattern leakage is closely related to statistical learning theory. This new viewpoint enables us to develop broader attacks that are supported by streamlined performance analyses. First, we address the problem of ε-approximate database reconstruction (ε-ADR) from range query leakage, giving attacks whose query cost scales only with the relative error ε, and is independent of the size of the database, or the number N of possible values of data items. This already goes significantly beyond the state-of-the-art for such attacks, as represented by Kellaris et al. (ACM CCS 2016) and Lacharité et al. (IEEE S&P 2018). We also study the new problem of ε-approximate order reconstruction (ε-AOR), where the adversary is tasked with reconstructing the order of records, except for records whose values are approximately equal. We show that as few as O(ε^−1 log ε^−1) uniformly random range queries suffice. Our analysis relies on an application of learning theory to PQ-trees, special data structures tuned to compactly record certain ordering constraints. We then show that when an auxiliary distribution is available, ε-AOR can be enhanced to achieve ε-ADR; using real data, we show that devastatingly small numbers of queries are needed to attain very accurate database reconstruction. Finally, we generalize from ranges to consider what learning theory tells us about the impact of access pattern leakage for other classes of queries, focusing on prefix and suffix queries. We illustrate this with both concrete attacks for prefix queries and with a general lower bound for all query classes. We also show a very general reduction from reconstruction with known or chosen queries to PAC learning.

  13. Improved Reconstruction Attacks on Encrypted Data Using Range Query Leakage 2018 Attacks EncryptedDatabases Oakland
    Marie-Sarah Lacharite, Brice Minaud and Kenneth G. Paterson

    We analyse the security of database encryption schemes supporting range queries against persistent adversaries. The bulk of our work applies to a generic setting, where the adversary’s view is limited to the set of records matched by each query (known as access pattern leakage). We also consider a more specific setting where rank information is also leaked, which is inherent inherent to multiple recent encryption schemes supporting range queries. We provide three attacks.

    First, we consider full reconstruction, which aims to recover the value of every record, fully negating encryption. We show that for dense datasets, full reconstruction is possible within an expected number of queries N log N + O(N), where N is the number of distinct plaintext values.
    This directly improves on a quadratic bound in the same setting by Kellaris et al. (CCS 2016).

    Second, we present an approximate reconstruction attack recovering all plaintext values in a dense dataset within a constant ratio of error, requiring the access pattern leakage of only O(N) queries.

    Third, we devise an attack in the common setting where the adversary has access to an auxiliary distribution for the target dataset. This third attack proves highly effective on age data from real-world medical data sets. In our experiments, observing only 25 queries was sufficient to reconstruct a majority of records to within 5 years.

    In combination, our attacks show that current approaches to enabling range queries offer little security when the threat model goes beyond snapshot attacks to include a persistent server-side adversary.

  14. Measuring small subgroup attacks against Diffie-Hellman 2017 Attacks Diffie-Hellman IPSec Measurement NDSS TLS
    Luke Valenta and David Adrian and Antonio Sanso and Shaanan Cohney and Joshua Fried and Marcella Hastings and J. Alex Halderman and Nadia Heninger

    Several recent standards, including NIST SP 800- 56A and RFC 5114, advocate the use of “DSA” parameters for Diffie-Hellman key exchange. While it is possible to use such parameters securely, additional validation checks are necessary to prevent well-known and potentially devastating attacks. In this paper, we observe that many Diffie-Hellman implementations do not properly validate key exchange inputs. Combined with other protocol properties and implementation choices, this can radically decrease security. We measure the prevalence of these parameter choices in the wild for HTTPS, POP3S, SMTP with STARTTLS, SSH, IKEv1, and IKEv2, finding millions of hosts using DSA and other non-“safe” primes for Diffie-Hellman key exchange, many of them in combination with potentially vulnerable behaviors. We examine over 20 open-source cryptographic libraries and applications and observe that until January 2016, not a single one validated subgroup orders by default. We found feasible full or partial key recovery vulnerabilities in OpenSSL, the Exim mail server, the Unbound DNS client, and Amazon’s load balancer, as well as susceptibility to weaker attacks in many other applications.

  15. Lucky Thirteen: Breaking the TLS and DTLS Record Protocols 2013 Attacks Oakland TLS
    N. J. Al Fardan and K. G. Paterson

    The Transport Layer Security (TLS) protocol aims to provide confidentiality and integrity of data in transit across untrusted networks. TLS has become the de facto secure protocol of choice for Internet and mobile applications. DTLS is a variant of TLS that is growing in importance. In this paper, we present distinguishing and plaintext recovery attacks against TLS and DTLS. The attacks are based on a delicate timing analysis of decryption processing in the two protocols. We include experimental results demonstrating the feasibility of the attacks in realistic network environments for several different implementations of TLS and DTLS, including the leading OpenSSL implementations. We provide countermeasures for the attacks. Finally, we discuss the wider implications of our attacks for the cryptographic design used by TLS and DTLS.