[PATCH v7 03/17] efi_loader: add signature database parser

Heinrich Schuchardt xypron.glpk at gmx.de
Fri Apr 17 20:05:41 CEST 2020


On 4/14/20 4:51 AM, AKASHI Takahiro wrote:
> efi_signature_parse_sigdb() is a helper function will be used to parse
> signature database variable and instantiate a signature store structure
> in later patches.
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> ---
>  include/efi_loader.h           |   3 +
>  lib/efi_loader/efi_signature.c | 226 +++++++++++++++++++++++++++++++++
>  2 files changed, 229 insertions(+)
>
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index 8cf85d2fb7e2..fea2ead02e93 100644
> --- a/include/efi_loader.h
> +++ b/include/efi_loader.h
> @@ -750,6 +750,9 @@ bool efi_signature_verify_with_sigdb(struct efi_image_regions *regs,
>  efi_status_t efi_image_region_add(struct efi_image_regions *regs,
>  				  const void *start, const void *end,
>  				  int nocheck);
> +
> +void efi_sigstore_free(struct efi_signature_store *sigstore);
> +struct efi_signature_store *efi_sigstore_parse_sigdb(u16 *name);
>  #endif /* CONFIG_EFI_SECURE_BOOT */
>
>  #else /* CONFIG_IS_ENABLED(EFI_LOADER) */
> diff --git a/lib/efi_loader/efi_signature.c b/lib/efi_loader/efi_signature.c
> index 23dac94c0593..2d1f38980e5f 100644
> --- a/lib/efi_loader/efi_signature.c
> +++ b/lib/efi_loader/efi_signature.c
> @@ -580,4 +580,230 @@ efi_status_t efi_image_region_add(struct efi_image_regions *regs,
>
>  	return EFI_SUCCESS;
>  }
> +
> +/**
> + * efi_sigstore_free - free signature store
> + * @sigstore:	Pointer to signature store structure
> + *
> + * Feee all the memories held in signature store and itself,
> + * which were allocated by efi_sigstore_parse_sigdb().
> + */
> +void efi_sigstore_free(struct efi_signature_store *sigstore)
> +{
> +	struct efi_signature_store *sigstore_next;
> +	struct efi_sig_data *sig_data, *sig_data_next;
> +
> +	while (sigstore) {
> +		sigstore_next = sigstore->next;
> +
> +		sig_data = sigstore->sig_data_list;
> +		while (sig_data) {
> +			sig_data_next = sig_data->next;
> +			free(sig_data->data);
> +			free(sig_data);
> +			sig_data = sig_data_next;
> +		}
> +
> +		free(sigstore);
> +		sigstore = sigstore_next;
> +	}
> +}
> +
> +/**
> + * efi_sigstore_parse_siglist - parse a signature list
> + * @name:	Pointer to signature list
> + *
> + * Parse signature list and instantiate a signature store structure.
> + * Signature database is a simple concatenation of one or more
> + * signature list(s).
> + *
> + * Return:	Pointer to signature store on success, NULL on error
> + */
> +static struct efi_signature_store *
> +efi_sigstore_parse_siglist(struct efi_signature_list *esl)
> +{
> +	struct efi_signature_store *siglist = NULL;
> +	struct efi_sig_data *sig_data, *sig_data_next;
> +	struct efi_signature_data *esd;
> +	size_t left;
> +
> +	/*
> +	 * UEFI specification defines certificate types:
> +	 *   for non-signed images,
> +	 *	EFI_CERT_SHA256_GUID
> +	 *	EFI_CERT_RSA2048_GUID
> +	 *	EFI_CERT_RSA2048_SHA256_GUID
> +	 *	EFI_CERT_SHA1_GUID
> +	 *	EFI_CERT_RSA2048_SHA_GUID
> +	 *	EFI_CERT_SHA224_GUID
> +	 *	EFI_CERT_SHA384_GUID
> +	 *	EFI_CERT_SHA512_GUID
> +	 *
> +	 *   for signed images,
> +	 *	EFI_CERT_X509_GUID
> +	 *	NOTE: Each certificate will normally be in a separate
> +	 *	EFI_SIGNATURE_LIST as the size may vary depending on
> +	 *	its algo's.
> +	 *
> +	 *   for timestamp revocation of certificate,
> +	 *	EFI_CERT_X509_SHA512_GUID
> +	 *	EFI_CERT_X509_SHA256_GUID
> +	 *	EFI_CERT_X509_SHA384_GUID
> +	 */
> +
> +	if (esl->signature_list_size
> +			<= (sizeof(*esl) + esl->signature_header_size)) {
> +		debug("Siglist in wrong format\n");
> +		return NULL;
> +	}
> +
> +	/* Create a head */
> +	siglist = calloc(sizeof(*siglist), 1);
> +	if (!siglist) {
> +		debug("Out of memory\n");
> +		goto err;
> +	}
> +	memcpy(&siglist->sig_type, &esl->signature_type, sizeof(efi_guid_t));
> +
> +	/* Go through the list */
> +	sig_data_next = NULL;
> +	left = esl->signature_list_size
> +			- (sizeof(*esl) + esl->signature_header_size);
> +	esd = (struct efi_signature_data *)
> +			((u8 *)esl + sizeof(*esl) + esl->signature_header_size);
> +
> +	while ((left > 0) && left >= esl->signature_size) {
> +		/* Signature must exist if there is remaining data. */
> +		if (left < esl->signature_size) {

This code is unreachable (as indicated by cppcheck).

Please, send a follow-up patch.

Best regards

Heinrich

> +			debug("Certificate is too small\n");
> +			goto err;
> +		}
> +
> +		sig_data = calloc(esl->signature_size
> +					- sizeof(esd->signature_owner), 1);
> +		if (!sig_data) {
> +			debug("Out of memory\n");
> +			goto err;
> +		}
> +
> +		/* Append signature data */
> +		memcpy(&sig_data->owner, &esd->signature_owner,
> +		       sizeof(efi_guid_t));
> +		sig_data->size = esl->signature_size
> +					- sizeof(esd->signature_owner);
> +		sig_data->data = malloc(sig_data->size);
> +		if (!sig_data->data) {
> +			debug("Out of memory\n");
> +			goto err;
> +		}
> +		memcpy(sig_data->data, esd->signature_data, sig_data->size);
> +
> +		sig_data->next = sig_data_next;
> +		sig_data_next = sig_data;
> +
> +		/* Next */
> +		esd = (struct efi_signature_data *)
> +				((u8 *)esd + esl->signature_size);
> +		left -= esl->signature_size;
> +	}
> +	siglist->sig_data_list = sig_data_next;
> +
> +	return siglist;
> +
> +err:
> +	efi_sigstore_free(siglist);
> +
> +	return NULL;
> +}
> +
> +/**
> + * efi_sigstore_parse_sigdb - parse a signature database variable
> + * @name:	Variable's name
> + *
> + * Read in a value of signature database variable pointed to by
> + * @name, parse it and instantiate a signature store structure.
> + *
> + * Return:	Pointer to signature store on success, NULL on error
> + */
> +struct efi_signature_store *efi_sigstore_parse_sigdb(u16 *name)
> +{
> +	struct efi_signature_store *sigstore = NULL, *siglist;
> +	struct efi_signature_list *esl;
> +	const efi_guid_t *vendor;
> +	void *db;
> +	efi_uintn_t db_size;
> +	efi_status_t ret;
> +
> +	if (!u16_strcmp(name, L"PK") || !u16_strcmp(name, L"KEK")) {
> +		vendor = &efi_global_variable_guid;
> +	} else if (!u16_strcmp(name, L"db") || !u16_strcmp(name, L"dbx")) {
> +		vendor = &efi_guid_image_security_database;
> +	} else {
> +		debug("unknown signature database, %ls\n", name);
> +		return NULL;
> +	}
> +
> +	/* retrieve variable data */
> +	db_size = 0;
> +	ret = EFI_CALL(efi_get_variable(name, vendor, NULL, &db_size, NULL));
> +	if (ret == EFI_NOT_FOUND) {
> +		debug("variable, %ls, not found\n", name);
> +		sigstore = calloc(sizeof(*sigstore), 1);
> +		return sigstore;
> +	} else if (ret != EFI_BUFFER_TOO_SMALL) {
> +		debug("Getting variable, %ls, failed\n", name);
> +		return NULL;
> +	}
> +
> +	db = malloc(db_size);
> +	if (!db) {
> +		debug("Out of memory\n");
> +		return NULL;
> +	}
> +
> +	ret = EFI_CALL(efi_get_variable(name, vendor, NULL, &db_size, db));
> +	if (ret != EFI_SUCCESS) {
> +		debug("Getting variable, %ls, failed\n", name);
> +		goto err;
> +	}
> +
> +	/* Parse siglist list */
> +	esl = db;
> +	while (db_size > 0) {
> +		/* List must exist if there is remaining data. */
> +		if (db_size < sizeof(*esl)) {
> +			debug("variable, %ls, in wrong format\n", name);
> +			goto err;
> +		}
> +
> +		if (db_size < esl->signature_list_size) {
> +			debug("variable, %ls, in wrong format\n", name);
> +			goto err;
> +		}
> +
> +		/* Parse a single siglist. */
> +		siglist = efi_sigstore_parse_siglist(esl);
> +		if (!siglist) {
> +			debug("Parsing signature list of %ls failed\n", name);
> +			goto err;
> +		}
> +
> +		/* Append siglist */
> +		siglist->next = sigstore;
> +		sigstore = siglist;
> +
> +		/* Next */
> +		db_size -= esl->signature_list_size;
> +		esl = (void *)esl + esl->signature_list_size;
> +	}
> +	free(db);
> +
> +	return sigstore;
> +
> +err:
> +	efi_sigstore_free(sigstore);
> +	free(db);
> +
> +	return NULL;
> +}
>  #endif /* CONFIG_EFI_SECURE_BOOT */
>



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