appended signatures: GRUB commands to manage the certificates
Introducing the following GRUB commands to manage the certificates.
1. append_list_db:
Show the list of trusted certificates from the db list
2. append_add_db_cert:
Add the trusted certificate to the db list
3. append_add_dbx_cert:
Add the distrusted certificate to the dbx list
4. append_verify:
Verify the signed file using db list
Note that if signature verification (check_appended_signatures) is set to yes,
the append_add_db_cert and append_add_dbx_cert commands only accept the file
‘X509_certificate’ that is signed with an appended signature.
Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>
Tested-by: Sridhar Markonda <sridharm@linux.ibm.com>
Reviewed-by: Avnish Chouhan <avnish@linux.ibm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Sudhakar Kuppusamy
Daniel Kiper
parent
ab7b177178
commit
6cb58b1c9e
@ -123,6 +123,9 @@ static bool append_key_mgmt = false;
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/* Platform KeyStore db and dbx. */
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static grub_pks_t *pks_keystore;
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/* Appended signature size. */
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static grub_size_t append_sig_len = 0;
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static grub_ssize_t
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pseudo_read (struct grub_file *file, char *buf, grub_size_t len)
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{
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@ -136,6 +139,65 @@ static struct grub_fs pseudo_fs = {
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.fs_read = pseudo_read
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};
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/*
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* We cannot use hexdump() to display hash data because it is typically displayed
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* in hexadecimal format, along with an ASCII representation of the same data.
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*
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* Example: sha256 hash data
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* 00000000 52 b5 90 49 64 de 22 d7 4e 5f 4f b4 1b 51 9c 34 |R..Id.".N_O..Q.4|
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* 00000010 b1 96 21 7c 91 78 a5 0d 20 8c e9 5c 22 54 53 f7 |..!|.x.. ..\"TS.|
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*
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* An appended signature only required to display the hexadecimal of the hash data
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* by separating each byte with ":". So, we introduced a new method hexdump_colon
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* to display it.
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*
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* Example: Sha256 hash data
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* 52:b5:90:49:64:de:22:d7:4e:5f:4f:b4:1b:51:9c:34:
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* b1:96:21:7c:91:78:a5:0d:20:8c:e9:5c:22:54:53:f7
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*/
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static void
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hexdump_colon (const grub_uint8_t *data, const grub_size_t length)
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{
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grub_size_t i, count = 0;
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for (i = 0; i < length - 1; i++)
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{
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grub_printf ("%02x:", data[i]);
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count++;
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if (count == 16)
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{
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grub_printf ("\n ");
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count = 0;
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}
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}
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grub_printf ("%02x\n", data[i]);
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}
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static void
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print_certificate (const grub_x509_cert_t *cert, const grub_uint32_t cert_num)
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{
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grub_uint32_t i;
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grub_printf ("\nCertificate: %u\n", cert_num);
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grub_printf (" Data:\n");
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grub_printf (" Version: %u (0x%u)\n", cert->version + 1, cert->version);
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grub_printf (" Serial Number:\n ");
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for (i = 0; i < cert->serial_len - 1; i++)
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grub_printf ("%02x:", cert->serial[i]);
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grub_printf ("%02x\n", cert->serial[cert->serial_len - 1]);
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grub_printf (" Issuer: %s\n", cert->issuer);
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grub_printf (" Subject: %s\n", cert->subject);
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grub_printf (" Subject Public Key Info:\n");
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grub_printf (" Public Key Algorithm: rsaEncryption\n");
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grub_printf (" RSA Public-Key: (%d bit)\n", cert->modulus_size);
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grub_printf (" Fingerprint: sha256\n ");
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hexdump_colon (&cert->fingerprint[GRUB_FINGERPRINT_SHA256][0],
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grub_strlen ((char *) cert->fingerprint[GRUB_FINGERPRINT_SHA256]));
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}
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/*
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* GUID can be used to determine the hashing function and generate the hash using
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* determined hashing function.
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@ -429,6 +491,61 @@ add_certificate (const grub_uint8_t *data, const grub_size_t data_size,
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return rc;
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}
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static void
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_remove_cert_from_db (const grub_x509_cert_t *cert)
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{
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grub_uint32_t i = 1;
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grub_x509_cert_t *curr_cert, *prev_cert;
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for (curr_cert = prev_cert = db.certs; curr_cert != NULL; curr_cert = curr_cert->next, i++)
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{
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if (is_cert_match (curr_cert, cert) == true)
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{
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if (i == 1) /* Match with first certificate in the db list. */
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db.certs = curr_cert->next;
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else
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prev_cert->next = curr_cert->next;
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grub_dprintf ("appendedsig",
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"removed distrusted certificate with CN: %s from the db list\n",
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curr_cert->subject);
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curr_cert->next = NULL;
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grub_x509_cert_release (curr_cert);
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grub_free (curr_cert);
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break;
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}
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else
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prev_cert = curr_cert;
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}
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}
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static grub_err_t
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remove_cert_from_db (const grub_uint8_t *data, const grub_size_t data_size)
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{
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grub_err_t rc;
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grub_x509_cert_t *cert;
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if (data == NULL || data_size == 0)
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return grub_error (GRUB_ERR_OUT_OF_RANGE, "certificate data or size is not available");
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cert = grub_zalloc (sizeof (grub_x509_cert_t));
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if (cert == NULL)
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return grub_error (GRUB_ERR_OUT_OF_MEMORY, "out of memory");
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rc = grub_x509_cert_parse (data, data_size, cert);
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if (rc != GRUB_ERR_NONE)
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{
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grub_dprintf ("appendedsig", "cannot remove an invalid certificate from the db list\n");
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grub_free (cert);
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return rc;
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}
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/* Remove certificate from the db list. */
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_remove_cert_from_db (cert);
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return rc;
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}
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static grub_err_t
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file_read_whole (grub_file_t file, grub_uint8_t **buf, grub_size_t *len)
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{
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@ -649,6 +766,7 @@ grub_verify_appended_signature (const grub_uint8_t *buf, grub_size_t bufsize)
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if (err != GRUB_ERR_NONE)
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return err;
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append_sig_len = sig.signature_len;
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datasize = bufsize - sig.signature_len;
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/*
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@ -709,6 +827,189 @@ grub_verify_appended_signature (const grub_uint8_t *buf, grub_size_t bufsize)
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return err;
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}
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static grub_err_t
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grub_cmd_verify_signature (grub_command_t cmd __attribute__ ((unused)), int argc, char **args)
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{
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grub_file_t signed_file;
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grub_err_t err;
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grub_uint8_t *signed_data = NULL;
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grub_size_t signed_data_size = 0;
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if (argc != 1)
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return grub_error (GRUB_ERR_BAD_ARGUMENT,
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"a signed file is expected\nExample:\n\tappend_verify <SIGNED FILE>\n");
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if (!grub_strlen (args[0]))
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return grub_error (GRUB_ERR_BAD_FILENAME, "missing signed file");
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grub_dprintf ("appendedsig", "verifying %s\n", args[0]);
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signed_file = grub_file_open (args[0], GRUB_FILE_TYPE_VERIFY_SIGNATURE);
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if (signed_file == NULL)
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return grub_error (GRUB_ERR_FILE_NOT_FOUND, "could not open %s file", args[0]);
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err = file_read_whole (signed_file, &signed_data, &signed_data_size);
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if (err == GRUB_ERR_NONE)
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{
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err = grub_verify_appended_signature (signed_data, signed_data_size);
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grub_free (signed_data);
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}
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grub_file_close (signed_file);
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return err;
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}
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/*
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* Checks the trusted certificate against dbx list if dynamic key management is
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* enabled. And add it to the db list if it is not already present.
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*
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* Note: When signature verification is enabled, this command only accepts the
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* trusted certificate that is signed with an appended signature.
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* The signature is verified by the appendedsig module. If verification succeeds,
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* the certificate is added to the db list. Otherwise, an error is posted and
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* the certificate is not added.
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* When signature verification is disabled, it accepts the trusted certificate
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* without an appended signature and add it to the db list.
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*
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* Also, note that the adding of the trusted certificate using this command does
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* not persist across reboots.
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*/
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static grub_err_t
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grub_cmd_db_cert (grub_command_t cmd __attribute__ ((unused)), int argc, char **args)
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{
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grub_err_t err;
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grub_file_t cert_file;
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grub_uint8_t *cert_data = NULL;
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grub_size_t cert_data_size = 0;
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if (argc != 1)
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return grub_error (GRUB_ERR_BAD_ARGUMENT,
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"a trusted X.509 certificate file is expected in DER format\n"
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"Example:\n\tappend_add_db_cert <X509_CERTIFICATE>\n");
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if (!grub_strlen (args[0]))
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return grub_error (GRUB_ERR_BAD_FILENAME, "missing trusted X.509 certificate file");
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cert_file = grub_file_open (args[0],
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GRUB_FILE_TYPE_CERTIFICATE_TRUST | GRUB_FILE_TYPE_NO_DECOMPRESS);
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if (cert_file == NULL)
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return grub_error (GRUB_ERR_BAD_FILE_TYPE, "could not open %s file", args[0]);
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err = file_read_whole (cert_file, &cert_data, &cert_data_size);
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grub_file_close (cert_file);
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if (err != GRUB_ERR_NONE)
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return err;
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/*
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* If signature verification is enabled (check_sigs is set to true), obtain
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* the actual certificate size by subtracting the appended signature size from
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* the certificate size because the certificate has an appended signature, and
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* this actual certificate size is used to get the X.509 certificate.
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*/
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if (check_sigs == true)
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cert_data_size -= append_sig_len;
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err = add_certificate (cert_data, cert_data_size, &db);
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grub_free (cert_data);
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return err;
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}
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/*
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* Remove the distrusted certificate from the db list if it is already present.
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* And add it to the dbx list if not present when dynamic key management is
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* enabled.
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*
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* Note: When signature verification is enabled, this command only accepts the
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* distrusted certificate that is signed with an appended signature.
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* The signature is verified by the appended sig module. If verification
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* succeeds, the certificate is removed from the db list. Otherwise, an error
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* is posted and the certificate is not removed.
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* When signature verification is disabled, it accepts the distrusted certificate
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* without an appended signature and removes it from the db list.
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*
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* Also, note that the removal of the distrusted certificate using this command
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* does not persist across reboots.
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*/
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static grub_err_t
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grub_cmd_dbx_cert (grub_command_t cmd __attribute__ ((unused)), int argc, char **args)
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{
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grub_err_t err;
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grub_file_t cert_file;
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grub_uint8_t *cert_data = NULL;
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grub_size_t cert_data_size = 0;
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if (argc != 1)
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return grub_error (GRUB_ERR_BAD_ARGUMENT,
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"a distrusted X.509 certificate file is expected in DER format\n"
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"Example:\n\tappend_add_dbx_cert <X509_CERTIFICATE>\n");
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if (!grub_strlen (args[0]))
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return grub_error (GRUB_ERR_BAD_FILENAME, "missing distrusted X.509 certificate file");
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cert_file = grub_file_open (args[0],
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GRUB_FILE_TYPE_CERTIFICATE_TRUST | GRUB_FILE_TYPE_NO_DECOMPRESS);
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if (cert_file == NULL)
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return grub_error (GRUB_ERR_BAD_FILE_TYPE, "could not open %s file", args[0]);
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err = file_read_whole (cert_file, &cert_data, &cert_data_size);
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grub_file_close (cert_file);
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if (err != GRUB_ERR_NONE)
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return err;
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/*
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* If signature verification is enabled (check_sigs is set to true), obtain
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* the actual certificate size by subtracting the appended signature size from
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* the certificate size because the certificate has an appended signature, and
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* this actual certificate size is used to get the X.509 certificate.
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*/
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if (check_sigs == true)
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cert_data_size -= append_sig_len;
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/* Remove distrusted certificate from the db list if present. */
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err = remove_cert_from_db (cert_data, cert_data_size);
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if (err != GRUB_ERR_NONE)
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{
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grub_free (cert_data);
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return err;
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}
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/* Only add the certificate to the dbx list if dynamic key management is enabled. */
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if (append_key_mgmt == true)
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err = add_certificate (cert_data, cert_data_size, &dbx);
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grub_free (cert_data);
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return err;
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}
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static grub_err_t
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grub_cmd_list_db (grub_command_t cmd __attribute__ ((unused)), int argc __attribute__ ((unused)),
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char **args __attribute__ ((unused)))
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{
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struct x509_certificate *cert;
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grub_uint32_t i, cert_num = 1;
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for (cert = db.certs; cert != NULL; cert = cert->next, cert_num++)
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print_certificate (cert, cert_num);
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if (append_key_mgmt == false)
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return GRUB_ERR_NONE;
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for (i = 0; i < db.hash_entries; i++)
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{
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if (db.hashes[i] != NULL)
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{
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grub_printf ("\nBinary hash: %u\n", i + 1);
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grub_printf (" Hash: sha%" PRIuGRUB_SIZE "\n ", db.hash_sizes[i] * 8);
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hexdump_colon (db.hashes[i], db.hash_sizes[i]);
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}
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}
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return GRUB_ERR_NONE;
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}
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/* Add the X.509 certificates/binary hash to the db list from PKS. */
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static grub_err_t
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load_pks2db (void)
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@ -1031,6 +1332,8 @@ struct grub_file_verifier grub_appendedsig_verifier = {
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.write = appendedsig_write,
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};
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static grub_command_t cmd_verify, cmd_list_db, cmd_dbx_cert, cmd_db_cert;
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GRUB_MOD_INIT (appendedsig)
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{
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grub_int32_t rc;
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@ -1100,6 +1403,15 @@ GRUB_MOD_INIT (appendedsig)
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db.cert_entries);
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}
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cmd_verify = grub_register_command ("append_verify", grub_cmd_verify_signature, N_("<SIGNED_FILE>"),
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N_("Verify SIGNED_FILE against the trusted X.509 certificates in the db list"));
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cmd_list_db = grub_register_command ("append_list_db", grub_cmd_list_db, 0,
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N_("Show the list of trusted X.509 certificates from the db list"));
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cmd_db_cert = grub_register_command ("append_add_db_cert", grub_cmd_db_cert, N_("<X509_CERTIFICATE>"),
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N_("Add trusted X509_CERTIFICATE to the db list"));
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cmd_dbx_cert = grub_register_command ("append_add_dbx_cert", grub_cmd_dbx_cert, N_("<X509_CERTIFICATE>"),
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N_("Add distrusted X509_CERTIFICATE to the dbx list"));
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grub_verifier_register (&grub_appendedsig_verifier);
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grub_dl_set_persistent (mod);
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}
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@ -1118,4 +1430,8 @@ GRUB_MOD_FINI (appendedsig)
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grub_register_variable_hook ("appendedsig_key_mgmt", NULL, NULL);
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grub_env_unset ("appendedsig_key_mgmt");
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grub_verifier_unregister (&grub_appendedsig_verifier);
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grub_unregister_command (cmd_verify);
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grub_unregister_command (cmd_list_db);
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grub_unregister_command (cmd_db_cert);
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grub_unregister_command (cmd_dbx_cert);
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}
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