CVE-2023-3180: Vulnerability in QEMU Virtual Crypto Device May Lead to Heap Buffer Overflow

A security vulnerability, dubbed as CVE-2023-3180, has been discovered in the QEMU virtual crypto device's handling of data encryption/decryption requests. This flaw may potentially lead to a heap buffer overflow, which could be exploited by attackers to execute code or exfiltrate sensitive information. In this post, we will delve into the details of this vulnerability, share code snippets, provide links to original references, and discuss possible exploit scenarios.

The Vulnerability

The vulnerability lies in the virtio_crypto_handle_sym_req() function of hw/virtio/virtio-crypto.c file in the QEMU source code. This function handles the encryption and decryption of data submitted by guests, and passes the requests to virtio_crypto_sym_op_helper().
The problem arises because there is no check for the values of src_len and dst_len in virtio_crypto_sym_op_helper, which could lead to a heap buffer overflow if the two values differ.

Here is a code snippet displaying the affected function in hw/virtio/virtio-crypto.c

static int virtio_crypto_sym_op_helper(VirtIOCrypto *vcrypto,
                                       struct virtio_crypto_sym_op_req *in_req,
                                       struct virtio_crypto_sym_op_resp *out_resp)
{
    ...
    size_t src_len = le32_to_cpu(in_req->src_len);
    size_t dst_len = le32_to_cpu(in_req->dst_len);

    /* Handling input buffer */
    src_data = g_malloc(src_len);
    virtio_crypto_sym_op_get_data_in(vcrypto, in_req, src_data, src_len);

    /* Performing operation */
    ...
    out_data = g_malloc(dst_len);
    ...
    operation_func(src_data, src_len, out_data, &dst_len);

    /* Writing back output data */
    virtio_crypto_sym_op_put_data_back(vcrypto, out_resp, out_data, dst_len);

    ...
}

As seen in the code snippet above, the function allocates memory for both src_data and out_data, and reads the input data into the src_data buffer. It then calls the relevant cryptographic function (operation_func) to perform the operation on the input data, and writes the output of the operation back to the guest.

The vulnerability is that there is no check or constraint for the relationship between src_len and dst_len. If the destination length (dst_len) is greater than the source length (src_len), the operation_func may write more data to out_data than is allocated for it, resulting in a heap buffer overflow.

Exploiting the Vulnerability

An attacker may exploit this vulnerability by crafting a malicious guest on a vulnerable QEMU host. The guest can submit data encryption/decryption requests with manipulated values of src_len and dst_len, causing a heap buffer overflow. This can potentially allow the attacker to gain control over the host system, execute arbitrary code, or access sensitive information.

A patch has already been submitted to fix the problem in the QEMU source code. You can review the patch and the associated discussion in the QEMU mailing list archive.

To protect yourself from this vulnerability, we suggest you take the following steps

1. Update your QEMU instance to the latest version, which includes the patch for this vulnerability. If you are using a packaged version from a distribution, update to the latest available package.
2. Monitor the QEMU Security page for security-related updates and apply patches as recommended.
3. Enable proper access control measures on your host systems to prevent unauthorized access to QEMU instances.

In conclusion, CVE-2023-3180 is a security vulnerability in the QEMU virtual crypto device that can potentially lead to a heap buffer overflow. It is essential to stay up-to-date with the latest security patches and maintain proper access control measures to protect against this flaw.

Timeline

Published on: 08/03/2023 15:15:00 UTC
Last modified on: 10/13/2023 00:59:00 UTC