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+What: security/secrets/coco
+Date: February 2022
+Contact: Dov Murik <dovmurik@linux.ibm.com>
+Description:
+ Exposes confidential computing (coco) EFI secrets to
+ userspace via securityfs.
+
+ EFI can declare memory area used by confidential computing
+ platforms (such as AMD SEV and SEV-ES) for secret injection by
+ the Guest Owner during VM's launch. The secrets are encrypted
+ by the Guest Owner and decrypted inside the trusted enclave,
+ and therefore are not readable by the untrusted host.
+
+ The efi_secret module exposes the secrets to userspace. Each
+ secret appears as a file under <securityfs>/secrets/coco,
+ where the filename is the GUID of the entry in the secrets
+ table. This module is loaded automatically by the EFI driver
+ if the EFI secret area is populated.
+
+ Two operations are supported for the files: read and unlink.
+ Reading the file returns the content of secret entry.
+ Unlinking the file overwrites the secret data with zeroes and
+ removes the entry from the filesystem. A secret cannot be read
+ after it has been unlinked.
+
+ For example, listing the available secrets::
+
+ # modprobe efi_secret
+ # ls -l /sys/kernel/security/secrets/coco
+ -r--r----- 1 root root 0 Jun 28 11:54 736870e5-84f0-4973-92ec-06879ce3da0b
+ -r--r----- 1 root root 0 Jun 28 11:54 83c83f7f-1356-4975-8b7e-d3a0b54312c6
+ -r--r----- 1 root root 0 Jun 28 11:54 9553f55d-3da2-43ee-ab5d-ff17f78864d2
+ -r--r----- 1 root root 0 Jun 28 11:54 e6f5a162-d67f-4750-a67c-5d065f2a9910
+
+ Reading the secret data by reading a file::
+
+ # cat /sys/kernel/security/secrets/coco/e6f5a162-d67f-4750-a67c-5d065f2a9910
+ the-content-of-the-secret-data
+
+ Wiping a secret by unlinking a file::
+
+ # rm /sys/kernel/security/secrets/coco/e6f5a162-d67f-4750-a67c-5d065f2a9910
+ # ls -l /sys/kernel/security/secrets/coco
+ -r--r----- 1 root root 0 Jun 28 11:54 736870e5-84f0-4973-92ec-06879ce3da0b
+ -r--r----- 1 root root 0 Jun 28 11:54 83c83f7f-1356-4975-8b7e-d3a0b54312c6
+ -r--r----- 1 root root 0 Jun 28 11:54 9553f55d-3da2-43ee-ab5d-ff17f78864d2
+
+ Note: The binary format of the secrets table injected by the
+ Guest Owner is described in
+ drivers/virt/coco/efi_secret/efi_secret.c under "Structure of
+ the EFI secret area".