[U-Boot] [PATCH 05/16] efi_loader: add signature verification functions

AKASHI Takahiro
2019-11-18T08:31:52Z

Heinrich,

On Sat, Nov 16, 2019 at 09:00:12PM +0100, Heinrich Schuchardt wrote:
> On 11/13/19 1:52 AM, AKASHI Takahiro wrote:
> >In this commit, implemented are a couple of helper functions which will be
> >used to materialize variable authentication as well as image authentication
> >in later patches.
>
> In which patch do you implement the unit tests for the new functions? I
> would expect them in /test/lib/ as tests invoked via the ut command.

As I said elsewhere, signature verification will be best exercised and
tested by image authentication or variable authentication (under pytest).
As you may see, the interfaces take arguments of complicated structures
and the code for setting up test environment and calling them properly
would be almost equal to writing image authentication and variable
authentication code.

> >
> >Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> >---
> > include/efi_api.h | 47 +++
> > include/efi_loader.h | 46 +++
> > lib/efi_loader/Makefile | 1 +
> > lib/efi_loader/efi_signature.c | 600 +++++++++++++++++++++++++++++++++
> > 4 files changed, 694 insertions(+)
> > create mode 100644 lib/efi_loader/efi_signature.c
> >
> >diff --git a/include/efi_api.h b/include/efi_api.h
> >index 22396172e15f..24d034246927 100644
> >--- a/include/efi_api.h
> >+++ b/include/efi_api.h
> >@@ -18,6 +18,7 @@
> >
> > #include <efi.h>
> > #include <charset.h>
> >+#include <pe.h>
> >
> > #ifdef CONFIG_EFI_LOADER
> > #include <asm/setjmp.h>
> >@@ -307,6 +308,10 @@ struct efi_runtime_services {
> > EFI_GUID(0x8be4df61, 0x93ca, 0x11d2, 0xaa, 0x0d, \
> > 0x00, 0xe0, 0x98, 0x03, 0x2b, 0x8c)
> >
> >+#define EFI_IMAGE_SECURITY_DATABASE_GUID \
> >+ EFI_GUID(0xd719b2cb, 0x3d3a, 0x4596, 0xa3, 0xbc, \
> >+ 0xda, 0xd0, 0x0e, 0x67, 0x65, 0x6f)
> >+
> > #define EFI_FDT_GUID \
> > EFI_GUID(0xb1b621d5, 0xf19c, 0x41a5, \
> > 0x83, 0x0b, 0xd9, 0x15, 0x2c, 0x69, 0xaa, 0xe0)
> >@@ -1616,4 +1621,46 @@ struct efi_unicode_collation_protocol {
> > #define LOAD_OPTION_CATEGORY_BOOT 0x00000000
> > #define LOAD_OPTION_CATEGORY_APP 0x00000100
> >
> >+/* Secure boot */
>
> Please, add a comment for each GUID.

There are bunch of GUID definitions here that have no
description. It is not very useful to do so since all those
macro's are already defined by UEFI specification.

> >+#define EFI_CERT_SHA256_GUID \
> >+ EFI_GUID(0xc1c41626, 0x504c, 0x4092, 0xac, 0xa9, \
> >+ 0x41, 0xf9, 0x36, 0x93, 0x43, 0x28)
> >+#define EFI_CERT_RSA2048_GUID \
> >+ EFI_GUID(0x3c5766e8, 0x269c, 0x4e34, 0xaa, 0x14, \
> >+ 0xed, 0x77, 0x6e, 0x85, 0xb3, 0xb6)
> >+#define EFI_CERT_X509_GUID \
> >+ EFI_GUID(0xa5c059a1, 0x94e4, 0x4aa7, 0x87, 0xb5, \
> >+ 0xab, 0x15, 0x5c, 0x2b, 0xf0, 0x72)
> >+#define EFI_CERT_X509_SHA256_GUID \
> >+ EFI_GUID(0x3bd2a492, 0x96c0, 0x4079, 0xb4, 0x20, \
> >+ 0xfc, 0xf9, 0x8e, 0xf1, 0x03, 0xed)
> >+#define EFI_CERT_TYPE_PKCS7_GUID \
> >+ EFI_GUID(0x4aafd29d, 0x68df, 0x49ee, 0x8a, 0xa9, \
> >+ 0x34, 0x7d, 0x37, 0x56, 0x65, 0xa7)
> >+
>
> Please add comments in Spinx style.
>
> What is the structure used for?
> What information do the fields hold?
>
> Same for all structures.

Okay.

> >+struct win_certificate_uefi_guid {
> >+ WIN_CERTIFICATE hdr;
>
> See comment to 01/16 (avoid typedefs).
>
> >+ efi_guid_t cert_type;
> >+ u8 cert_data[];
> >+} __attribute__((__packed__));
> >+
> >+struct efi_variable_authentication_2 {
> >+ struct efi_time time_stamp;
> >+ struct win_certificate_uefi_guid auth_info;
> >+} __attribute__((__packed__));
> >+
> >+struct efi_signature_data {
> >+ efi_guid_t signature_owner;
> >+ u8 signature_data[];
> >+} __attribute__((__packed__));
> >+
> >+struct efi_signature_list {
> >+ efi_guid_t signature_type;
> >+ u32 signature_list_size;
> >+ u32 signature_header_size;
> >+ u32 signature_size;
> >+/* u8 signature_header[signature_header_size]; */
> >+/* struct efi_signature_data signatures[...][signature_size]; */
> >+} __attribute__((__packed__));
> >+
> > #endif
> >diff --git a/include/efi_loader.h b/include/efi_loader.h
> >index 381da80cdce0..5a3df557e9f2 100644
> >--- a/include/efi_loader.h
> >+++ b/include/efi_loader.h
> >@@ -21,6 +21,7 @@ static inline int guidcmp(const void *g1, const void *g2)
> > #if CONFIG_IS_ENABLED(EFI_LOADER)
> >
> > #include <linux/list.h>
> >+#include <linux/oid_registry.h>
> >
> > /* Maximum number of configuration tables */
> > #define EFI_MAX_CONFIGURATION_TABLES 16
> >@@ -169,6 +170,11 @@ extern const efi_guid_t efi_guid_hii_config_routing_protocol;
> > extern const efi_guid_t efi_guid_hii_config_access_protocol;
> > extern const efi_guid_t efi_guid_hii_database_protocol;
> > extern const efi_guid_t efi_guid_hii_string_protocol;
> >+/* GUID for authentication */
>
> %s/GUID/GUIDs/g ?

Sure.

> >+extern const efi_guid_t efi_guid_image_security_database;
> >+extern const efi_guid_t efi_guid_sha256;
> >+extern const efi_guid_t efi_guid_cert_x509;
> >+extern const efi_guid_t efi_guid_cert_x509_sha256;
> >
> > extern unsigned int __efi_runtime_start, __efi_runtime_stop;
> > extern unsigned int __efi_runtime_rel_start, __efi_runtime_rel_stop;
> >@@ -650,6 +656,46 @@ void efi_deserialize_load_option(struct efi_load_option *lo, u8 *data);
> > unsigned long efi_serialize_load_option(struct efi_load_option *lo, u8 **data);
> > efi_status_t efi_bootmgr_load(efi_handle_t *handle);
> >
> >+#ifdef CONFIG_EFI_SECURE_BOOT
>
> Why do we need an #ifdef here?

Simply because those functions won't be defined if !CONFIG_EFI_SECURE_BOOT.

>
> >+#include <image.h>
> >+
> >+#define EFI_REGS_MAX 16 /* currently good enough */
> >+
>
> Do you mean: this could be exceeded in special cases?
>
> Can't we use a linked list for regions? We should not embed any
> unnecessary restrictions.

I will address this issue in the next version.

> Add comments explaining what the structures are used for.

Okay.

> >+struct efi_image_regions {
> >+ int num;
> >+ struct image_region reg[EFI_REGS_MAX];
> >+};
> >+
> >+struct efi_sig_data {
> >+ struct efi_sig_data *next;
> >+ efi_guid_t owner;
> >+ void *data;
> >+ size_t size;
> >+};
> >+
> >+struct efi_signature_store {
> >+ struct efi_signature_store *next;
> >+ efi_guid_t sig_type;
> >+ struct efi_sig_data *sig_data_list;
> >+};
> >+
> >+struct x509_certificate;
> >+struct pkcs7_message;
> >+
> >+bool efi_signature_verify_cert(struct x509_certificate *cert,
> >+ struct efi_signature_store *dbx);
> >+bool efi_signature_verify_signers(struct pkcs7_message *msg,
> >+ struct efi_signature_store *dbx);
> >+bool efi_signature_verify_with_sigdb(struct efi_image_regions *regs,
> >+ struct pkcs7_message *msg,
> >+ struct efi_signature_store *db,
> >+ struct x509_certificate **cert);
> >+
> >+efi_status_t efi_image_region_add(struct efi_image_regions *regs,
> >+ const void *start, const void *end,
> >+ int nocheck);
> >+#endif /* CONFIG_EFI_SECURE_BOOT */
> >+
> > #else /* CONFIG_IS_ENABLED(EFI_LOADER) */
> >
> > /* Without CONFIG_EFI_LOADER we don't have a runtime section, stub it out */
> >diff --git a/lib/efi_loader/Makefile b/lib/efi_loader/Makefile
> >index 01769ea58ba6..49c996c89052 100644
> >--- a/lib/efi_loader/Makefile
> >+++ b/lib/efi_loader/Makefile
> >@@ -39,3 +39,4 @@ obj-$(CONFIG_PARTITIONS) += efi_disk.o
> > obj-$(CONFIG_NET) += efi_net.o
> > obj-$(CONFIG_GENERATE_ACPI_TABLE) += efi_acpi.o
> > obj-$(CONFIG_GENERATE_SMBIOS_TABLE) += efi_smbios.o
> >+obj-y += efi_signature.o
> >diff --git a/lib/efi_loader/efi_signature.c b/lib/efi_loader/efi_signature.c
> >new file mode 100644
> >index 000000000000..04f43e47d1a3
> >--- /dev/null
> >+++ b/lib/efi_loader/efi_signature.c
> >@@ -0,0 +1,600 @@
> >+// SPDX-License-Identifier: GPL-2.0+
> >+/*
> >+ * Copyright (c) 2018 Patrick Wildt <patrick@blueri.se>
>
> From which upstream did you take the code?
>
> >+ * Copyright (c) 2019 Linaro Limited, Author: AKASHI Takahiro
> >+ */
> >+
>
> debug() checks the value of _DEBUG.
> Please, include common.h as first include.

Sure.

> Use the sequence of includes as defined in
> https://www.denx.de/wiki/U-Boot/CodingStyle
>
> >+#include <charset.h>
> >+#include <efi_loader.h>
> >+#include <image.h>
> >+#include <hexdump.h>
> >+#include <malloc.h>
> >+#include <pe.h>
> >+#include <linux/compat.h>
> >+#include <linux/oid_registry.h>
> >+#include <u-boot/rsa.h>
>
> Shouldn't we move all cryptography stuff into a directory crypto/?

On which part do you specifically have concerns?
The following code is UEFI specific, and I don't think that either crypto/
or lib/crypto, which I created for x509/pkcs7 parsers, is a right place.

> >+#include <u-boot/sha256.h>
> >+/*
> >+ * avoid duplicated inclusion:
> >+ * #include "../lib/crypto/x509_parser.h"
> >+ */
> >+#include "../lib/crypto/pkcs7_parser.h"
> >+
> >+const efi_guid_t efi_guid_image_security_database =
> >+ EFI_IMAGE_SECURITY_DATABASE_GUID;
> >+const efi_guid_t efi_guid_sha256 = EFI_CERT_SHA256_GUID;
> >+const efi_guid_t efi_guid_cert_rsa2048 = EFI_CERT_RSA2048_GUID;
> >+const efi_guid_t efi_guid_cert_x509 = EFI_CERT_X509_GUID;
> >+const efi_guid_t efi_guid_cert_x509_sha256 = EFI_CERT_X509_SHA256_GUID;
> >+
> >+#ifdef CONFIG_EFI_SECURE_BOOT
> >+static const unsigned char WinIndirectSha256[] = {
>
> We don't use camel case.

Okay, this one is a local variable. Fix it.

> >+ 0x30, 0x33, 0x06, 0x0a, 0x2b, 0x06, 0x01, 0x04, 0x01, 0x82, 0x37, 0x02,
> >+ 0x01, 0x0f, 0x30, 0x25, 0x03, 0x01, 0x00, 0xa0, 0x20, 0xa2, 0x1e, 0x80,
> >+ 0x1c, 0x00, 0x3c, 0x00, 0x3c, 0x00, 0x3c, 0x00, 0x4f, 0x00, 0x62, 0x00,
> >+ 0x73, 0x00, 0x6f, 0x00, 0x6c, 0x00, 0x65, 0x00, 0x74, 0x00, 0x65, 0x00,
> >+ 0x3e, 0x00, 0x3e, 0x00, 0x3e, 0x30, 0x31, 0x30, 0x0d, 0x06, 0x09, 0x60,
> >+ 0x86, 0x48, 0x01, 0x65, 0x03, 0x04, 0x02, 0x01, 0x05, 0x00, 0x04, 0x20
> >+};
>
> What secret sauce is this? - Please, add comments where applicable. Add
> references where needed for verification of correctness.

A similar technique is also used in EDK2.
I will add "decoded" version of data in a comment.

> Below you describe it as DER wrapper. So why call the variable Sha256?

Because it contains OID for sha256.

> >+
> >+/**
> >+ * efi_hash_regions - calculate a hash value
> >+ * @regs: List of regions
> >+ * @hash: Pointer to a pointer to buffer holding a hash value
> >+ * @size: Size of buffer to be returned
> >+ *
> >+ * Calculate a sha256 value of @regs and return a value in @hash.
>
> Is this a hash of the concatenation of all regions - or is this a list
> of hashes one for each regions?
>
> >+ *
> >+ * Return: true on success, false on error
> >+ */
> >+static bool efi_hash_regions(struct efi_image_regions *regs, void **hash,
> >+ size_t *size)
>
> Why use void** for hash? There should be a structure for SHA256 hashes.
>
> >+{
> >+ *size = 0;
> >+ *hash = calloc(1, SHA256_SUM_LEN);
> >+ if (!*hash) {
> >+ debug("Out of memory\n");
> >+ return false;
> >+ }
> >+ *size = SHA256_SUM_LEN;
> >+
> >+ hash_calculate("sha256", regs->reg, regs->num, *hash);
> >+#ifdef DEBUG
> >+ debug("hash calculated:\n");
>
> debug checks the value of _DEBUG not of DEBUG. So wouldn't you use
> #ifdef _DEBUG to be consistent?

It will be fixed once "common.h" (hence "log.h") is included.

> >+ print_hex_dump(" ", DUMP_PREFIX_OFFSET, 16, 1,
> >+ *hash, SHA256_SUM_LEN, false);
>
> This will fail to compile if CONFIG_HEXDUMP is not defined?

No. If CONFIG_HEXDUMP is not defined, print_hex_dump() will be nullified.
See lib/hexdump.c.

> >+#endif
> >+
> >+ return true;
> >+}
> >+
> >+/**
> >+ * efi_hash_regions_in_der - calculate a hash value
> >+ * @regs: List of regions
> >+ * @hash: Pointer to a pointer to buffer holding a hash value
> >+ * @size: Size of buffer to be returned
> >+ *
> >+ * Calculate a sha256 value of @regs and return a value in @hash.
> >+ * This function is a variant of efi_hash_regions(), and the data will
> >+ * be wrapped with some header in DER format before hash calculation.
> >+ * Message digest in signature of PE format will be calculated this way.
> >+ *
> >+ * Return: true on success, false on error
> >+ */
> >+static bool efi_hash_regions_in_der(struct efi_image_regions *regs, void **hash,
> >+ size_t *size)
> >+{
> >+ void *msg;
> >+ size_t msg_size;
> >+ struct image_region regtmp[2];
> >+
> >+ if (!efi_hash_regions(regs, &msg, &msg_size)) {
> >+ debug("Hash calculation failed\n");
> >+ return false;
> >+ ;
> >+ }
> >+
> >+ *size = 0;
> >+ *hash = calloc(1, SHA256_SUM_LEN);
> >+ if (!*hash) {
> >+ debug("Out of memory\n");
> >+ free(msg);
> >+ return false;
> >+ }
> >+ *size = SHA256_SUM_LEN;
> >+
> >+ /* File image hash is digested with some DER wrapper. */
> >+ regtmp[0].data = WinIndirectSha256;
> >+ regtmp[0].size = sizeof(WinIndirectSha256);
> >+ regtmp[1].data = msg;
> >+ regtmp[1].size = msg_size;
> >+
> >+ hash_calculate("sha256", regtmp, 2, *hash);
> >+#ifdef DEBUG
> >+ debug("hash calculated with extra header:\n");
> >+ print_hex_dump(" ", DUMP_PREFIX_OFFSET, 16, 1,
> >+ *hash, SHA256_SUM_LEN, false);
> >+#endif
> >+
> >+ free(msg);
> >+
> >+ return true;
> >+}
> >+
> >+/**
> >+ * efi_signature_verify - verify a signature with a certificate
> >+ * @regs: List of regions to be authenticated
> >+ * @signed_info: Pointer to PKCS7's signed_info
> >+ * @cert: x509 certificate
> >+ *
> >+ * Signature pointed to by @signed_info against image pointed to by @regs
> >+ * is verified by a certificate pointed to by @cert.
> >+ * @signed_info holds a signature, including a message digest which is to be
> >+ * compared with a hash value calculated from @regs.
> >+ *
> >+ * Return: true if signature is verified, false if not
> >+ */
> >+static bool efi_signature_verify(struct efi_image_regions *regs,
> >+ struct pkcs7_signed_info *ps_info,
> >+ struct x509_certificate *cert)
> >+{
> >+ struct image_sign_info info;
> >+ struct image_region regtmp[2];
> >+ void *hash;
> >+ size_t size;
> >+ char c;
> >+ bool verified;
> >+
> >+ debug("%s: Enter, %p, %p, %p(issuer: %s, subject: %s)\n", __func__,
> >+ regs, ps_info, cert, cert->issuer, cert->subject);
> >+
> >+ verified = false;
> >+
> >+ memset(&info, '\0', sizeof(info));
> >+ info.padding = image_get_padding_algo("pkcs-1.5");
> >+ /*
> >+ * Note: image_get_[checksum|crypto]_algo takes an string
> >+ * argument like "<checksum>,<crypto>"
> >+ * TODO: support other hash algorithms
> >+ */
> >+ if (!strcmp(ps_info->sig->hash_algo, "sha1")) {
> >+ info.checksum = image_get_checksum_algo("sha1,rsa2048");
> >+ info.name = "sha1,rsa2048";
> >+ } else if (!strcmp(ps_info->sig->hash_algo, "sha256")) {
> >+ info.checksum = image_get_checksum_algo("sha256,rsa2048");
> >+ info.name = "sha256,rsa2048";
> >+ } else {
> >+ debug("unknown msg digest algo: %s\n", ps_info->sig->hash_algo);
> >+ goto out;
> >+ }
> >+ info.crypto = image_get_crypto_algo(info.name);
> >+
> >+ info.key = cert->pub->key;
> >+ info.keylen = cert->pub->keylen;
> >+
> >+ /* verify signature */
> >+ debug("%s: crypto: %s, signature len:%x\n", __func__,
> >+ info.name, ps_info->sig->s_size);
> >+ if (ps_info->aa_set & (1UL << sinfo_has_message_digest)) {
> >+ debug("%s: RSA verify authentication attribute\n", __func__);
> >+ /*
> >+ * NOTE: This path will be executed only for
> >+ * PE image authentication
> >+ */
> >+
> >+ /* check if hash matches digest first */
> >+ debug("checking msg digest first, len:0x%x\n",
> >+ ps_info->msgdigest_len);
> >+
> >+#ifdef DEBUG
> >+ debug("hash in database:\n");
> >+ print_hex_dump(" ", DUMP_PREFIX_OFFSET, 16, 1,
> >+ ps_info->msgdigest, ps_info->msgdigest_len,
> >+ false);
> >+#endif
> >+ if (efi_hash_regions_in_der(regs, &hash, &size)) {
> >+ if (ps_info->msgdigest_len != size ||
> >+ memcmp(hash, ps_info->msgdigest, size)) {
> >+ debug("Digest doesn't match\n");
> >+ free(hash);
> >+ goto out;
> >+ }
> >+
> >+ free(hash);
> >+ } else {
> >+ debug("Digesting image failed\n");
> >+ goto out;
> >+ }
> >+
> >+ /* against digest */
> >+ c = 0x31;
> >+ regtmp[0].data = &c;
> >+ regtmp[0].size = 1;
> >+ regtmp[1].data = ps_info->authattrs;
> >+ regtmp[1].size = ps_info->authattrs_len;
> >+
> >+ if (!rsa_verify(&info, regtmp, 2,
> >+ ps_info->sig->s, ps_info->sig->s_size))
> >+ verified = true;
> >+ } else {
> >+ debug("%s: RSA verify content data\n", __func__);
> >+ /* against all data */
> >+ if (!rsa_verify(&info, regs->reg, regs->num,
> >+ ps_info->sig->s, ps_info->sig->s_size))
> >+ verified = true;
> >+ }
> >+
> >+out:
> >+ debug("%s: Exit, verified: %d\n", __func__, verified);
> >+ return verified;
> >+}
> >+
> >+/**
> >+ * efi_signature_verify_with_list - verify a signature with signature list
> >+ * @regs: List of regions to be authenticated
> >+ * @signed_info: Pointer to PKCS7's signed_info
> >+ * @siglist: Signature list for certificates
> >+ * @valid_cert: x509 certificate that verifies this signature
> >+ *
> >+ * Signature pointed to by @signed_info against image pointed to by @regs
> >+ * is verified by signature list pointed to by @siglist.
> >+ * Signature database is a simple concatenation of one or more
> >+ * signature list(s).
> >+ *
> >+ * Return: true if signature is verified, false if not
> >+ */
> >+static
> >+bool efi_signature_verify_with_list(struct efi_image_regions *regs,
> >+ struct pkcs7_signed_info *signed_info,
> >+ struct efi_signature_store *siglist,
> >+ struct x509_certificate **valid_cert)
> >+{
> >+ struct x509_certificate *cert;
> >+ struct efi_sig_data *sig_data;
> >+ bool verified = false;
> >+
> >+ debug("%s: Enter, %p, %p, %p, %p\n", __func__,
> >+ regs, signed_info, siglist, valid_cert);
>
> Shouldn't we use EFI_PRINT() to get proper indentation?
>
> >+
> >+ if (!signed_info) {
> >+ void *hash;
> >+ size_t size;
> >+
> >+ debug("%s: unsigned image\n", __func__);
>
> We already have indicated the function above.
>
> >+ /*
> >+ * verify based on calculated hash value
> >+ * TODO: support other hash algorithms
> >+ */
> >+ if (guidcmp(&siglist->sig_type, &efi_guid_sha256)) {
> >+ debug("Digest algorithm is not supported: %pUl\n",
> >+ &siglist->sig_type);
> >+ goto out;
> >+ }
> >+
> >+ if (!efi_hash_regions(regs, &hash, &size)) {
> >+ debug("Digesting unsigned image failed\n");
> >+ goto out;
> >+ }
> >+
> >+ /* go through the list */
> >+ for (sig_data = siglist->sig_data_list; sig_data;
> >+ sig_data = sig_data->next) {
> >+#ifdef DEBUG
> >+ debug("Msg digest in database:\n");
> >+ print_hex_dump(" ", DUMP_PREFIX_OFFSET, 16, 1,
> >+ sig_data->data, sig_data->size, false);
>
> Does this compile if CONFIG_HEXDUMP is not defined?
>
> >+#endif
> >+ if ((sig_data->size == size) &&
> >+ !memcmp(sig_data->data, hash, size)) {
> >+ verified = true;
> >+ free(hash);
> >+ goto out;
> >+ }
> >+ }
> >+ free(hash);
> >+ goto out;
> >+ }
> >+
> >+ debug("%s: signed image\n", __func__);
> >+ if (guidcmp(&siglist->sig_type, &efi_guid_cert_x509)) {
> >+ debug("Signature type is not supported: %pUl\n",
> >+ &siglist->sig_type);
> >+ goto out;
> >+ }
> >+
> >+ /* go through the list */
> >+ for (sig_data = siglist->sig_data_list; sig_data;
> >+ sig_data = sig_data->next) {
> >+ /* TODO: support owner check based on policy */
> >+
> >+ cert = x509_cert_parse(sig_data->data, sig_data->size);
> >+ if (IS_ERR(cert)) {
> >+ debug("Parsing x509 certificate failed\n");
> >+ goto out;
> >+ }
> >+
> >+ verified = efi_signature_verify(regs, signed_info, cert);
> >+
> >+ if (verified) {
> >+ if (valid_cert)
> >+ *valid_cert = cert;
> >+ else
> >+ x509_free_certificate(cert);
> >+ break;
> >+ } else {
> >+ x509_free_certificate(cert);
> >+ }
> >+ }
> >+
> >+out:
> >+ debug("%s: Exit, verified: %d\n", __func__, verified);
> >+ return verified;
> >+}
> >+
> >+/**
> >+ * efi_signature_verify_with_sigdb - verify a signature with db
> >+ * @regs: List of regions to be authenticated
> >+ * @msg: Signature
> >+ * @db: Signature database for trusted certificates
> >+ * @cert: x509 certificate that verifies this signature
> >+ *
> >+ * Signature pointed to by @msg against image pointed to by @regs
> >+ * is verified by signature database pointed to by @db.
> >+ *
> >+ * Return: true if signature is verified, false if not
> >+ */
> >+bool efi_signature_verify_with_sigdb(struct efi_image_regions *regs,
> >+ struct pkcs7_message *msg,
> >+ struct efi_signature_store *db,
> >+ struct x509_certificate **cert)
> >+{
> >+ struct pkcs7_signed_info *info;
> >+ struct efi_signature_store *siglist;
> >+ bool verified = false;
> >+
> >+ debug("%s: Enter, %p, %p, %p, %p\n", __func__, regs, msg, db, cert);
> >+
> >+ if (!db)
> >+ goto out;
> >+
> >+ if (!db->sig_data_list)
> >+ goto out;
> >+
> >+ /* for unsigned image */
> >+ if (!msg) {
> >+ debug("%s: Verify unsigned image with db\n", __func__);
> >+ for (siglist = db; siglist; siglist = siglist->next)
> >+ if (efi_signature_verify_with_list(regs, NULL,
> >+ siglist, cert)) {
> >+ verified = true;
> >+ goto out;
> >+ }
> >+
> >+ goto out;
> >+ }
> >+
> >+ /* for signed image or variable */
> >+ debug("%s: Verify signed image with db\n", __func__);
> >+ for (info = msg->signed_infos; info; info = info->next) {
> >+ debug("Signed Info: digest algo: %s, pkey algo: %s\n",
> >+ info->sig->hash_algo, info->sig->pkey_algo);
> >+
> >+ for (siglist = db; siglist; siglist = siglist->next) {
> >+ if (efi_signature_verify_with_list(regs, info,
> >+ siglist, cert)) {
> >+ verified = true;
> >+ goto out;
> >+ }
> >+ }
> >+ }
> >+
> >+out:
> >+ debug("%s: Exit, verified: %d\n", __func__, verified);
> >+ return verified;
> >+}
> >+
> >+/**
> >+ * efi_search_siglist - search signature list for a certificate
> >+ * @cert: x509 certificate
> >+ * @siglist: Signature list
> >+ * @revoc_time: Pointer to buffer for revocation time
> >+ *
> >+ * Search signature list pointed to by @siglist and find a certificate
> >+ * pointed to by @cert.
> >+ * If found, revocation time that is specified in signature database is
> >+ * returned in @revoc_time.
> >+ *
> >+ * Return: true if certificate is found, false if not
> >+ */
> >+static bool efi_search_siglist(struct x509_certificate *cert,
> >+ struct efi_signature_store *siglist,
> >+ time64_t *revoc_time)
> >+{
> >+ struct image_region reg[1];
> >+ void *hash = NULL, *msg = NULL;
> >+ struct efi_sig_data *sig_data;
> >+ bool found = false;
> >+
> >+ /* can be null */
> >+ if (!siglist->sig_data_list)
> >+ return false;
> >+
> >+ if (guidcmp(&siglist->sig_type, &efi_guid_cert_x509_sha256)) {
> >+ /* TODO: other hash algos */
> >+ debug("Certificate's digest type is not supported: %pUl\n",
> >+ &siglist->sig_type);
> >+ goto out;
> >+ }
> >+
> >+ /* calculate hash of TBSCertificate */
> >+ msg = calloc(1, SHA256_SUM_LEN);
> >+ if (!msg) {
> >+ debug("Out of memory\n");
> >+ goto out;
> >+ }
> >+
> >+ hash = calloc(1, SHA256_SUM_LEN);
> >+ if (!hash) {
> >+ debug("Out of memory\n");
> >+ goto out;
> >+ }
> >+
> >+ reg[0].data = cert->tbs;
> >+ reg[0].size = cert->tbs_size;
> >+ hash_calculate("sha256", reg, 1, msg);
> >+
> >+ /* go through signature list */
> >+ for (sig_data = siglist->sig_data_list; sig_data;
> >+ sig_data = sig_data->next) {
> >+ /*
> >+ * struct efi_cert_x509_sha256 {
> >+ * u8 tbs_hash[256/8];
> >+ * time64_t revocation_time;
> >+ * };
> >+ */
> >+ if ((sig_data->size == SHA256_SUM_LEN) &&
> >+ !memcmp(sig_data->data, hash, SHA256_SUM_LEN)) {
> >+ memcpy(revoc_time, sig_data->data + SHA256_SUM_LEN,
> >+ sizeof(*revoc_time));
> >+ found = true;
> >+ goto out;
> >+ }
> >+ }
> >+
> >+out:
> >+ free(hash);
> >+ free(msg);
> >+
> >+ return found;
> >+}
> >+
> >+/**
> >+ * efi_signature_verify_cert - verify a certificate with dbx
> >+ * @cert: x509 certificate
> >+ * @dbx: Signature database
> >+ *
> >+ * Search signature database pointed to by @dbx and find a certificate
> >+ * pointed to by @cert.
> >+ * This function is expected to be used against "dbx".
> >+ *
> >+ * Return: true if a certificate is not rejected, false otherwise.
> >+ */
> >+bool efi_signature_verify_cert(struct x509_certificate *cert,
> >+ struct efi_signature_store *dbx)
> >+{
> >+ struct efi_signature_store *siglist;
> >+ time64_t revoc_time;
> >+ bool found = false;
> >+
> >+ debug("%s: Enter, %p, %p\n", __func__, dbx, cert);
>
> EFI_PRINT() ?
>
> >+
> >+ if (!cert)
> >+ return false;
> >+
> >+ for (siglist = dbx; siglist; siglist = siglist->next) {
> >+ if (efi_search_siglist(cert, siglist, &revoc_time)) {
> >+ /* TODO */
> >+ /* compare signing time with revocation time */
>
> Is this a difficult thing to do? If not, please, fill the gap.

Actually, I have already implemented the prototype code
for revocation support. See my linaro repository described in
the cover letter.
But I won't include relevant patches in this patch series because:
1. The basic authentication mechanism should be upstreamed
first, yet it will provide enough function set.
2. Timestamp based revocation is quite complicated to understand.
So excluding it makes your reviews easier.
3. I haven't seen no strong demands for revocation support at the moment.

Thanks,
-Takahiro Akashi

> Best regards
>
> Heinrich
>
> >+
> >+ found = true;
> >+ break;
> >+ }
> >+ }
> >+
> >+ debug("%s: Exit, verified: %d\n", __func__, !found);
> >+ return !found;
> >+}
> >+
> >+/**
> >+ * efi_signature_verify_signers - verify signers' certificates with dbx
> >+ * @msg: Signature
> >+ * @dbx: Signature database
> >+ *
> >+ * Determine if any of signers' certificates in @msg may be verified
> >+ * by any of certificates in signature database pointed to by @dbx.
> >+ * This function is expected to be used against "dbx".
> >+ *
> >+ * Return: true if none of certificates is rejected, false otherwise.
> >+ */
> >+bool efi_signature_verify_signers(struct pkcs7_message *msg,
> >+ struct efi_signature_store *dbx)
> >+{
> >+ struct pkcs7_signed_info *info;
> >+ bool found = false;
> >+
> >+ debug("%s: Enter, %p, %p\n", __func__, msg, dbx);
> >+
> >+ if (!msg)
> >+ goto out;
> >+
> >+ for (info = msg->signed_infos; info; info = info->next) {
> >+ if (info->signer &&
> >+ !efi_signature_verify_cert(info->signer, dbx)) {
> >+ found = true;
> >+ goto out;
> >+ }
> >+ }
> >+out:
> >+ debug("%s: Exit, verified: %d\n", __func__, !found);
> >+ return !found;
> >+}
> >+
> >+/**
> >+ * efi_image_region_add - add an entry of region
> >+ * @regs: Pointer to array of regions
> >+ * @start: Start address of region
> >+ * @end: End address of region
> >+ * @nocheck: flag against overlapped regions
> >+ *
> >+ * Take one entry of region [@start, @end] and append it to the list
> >+ * pointed to by @regs. If @nocheck is false, overlapping among entries
> >+ * will be checked first.
> >+ *
> >+ * Return: 0 on success, status code (negative) on error
> >+ */
> >+efi_status_t efi_image_region_add(struct efi_image_regions *regs,
> >+ const void *start, const void *end,
> >+ int nocheck)
> >+{
> >+ struct image_region *reg;
> >+ int i, j;
> >+
> >+ if (regs->num >= EFI_REGS_MAX) {
> >+ debug("%s: no more room for regions\n", __func__);
> >+ return EFI_OUT_OF_RESOURCES;
> >+ }
> >+
> >+ if (end < start)
> >+ return EFI_INVALID_PARAMETER;
> >+
> >+ for (i = 0; i < regs->num; i++) {
> >+ reg = &regs->reg[i];
> >+ if (nocheck)
> >+ continue;
> >+
> >+ if (start > reg->data + reg->size)
> >+ continue;
> >+
> >+ if ((start >= reg->data && start < reg->data + reg->size) ||
> >+ (end > reg->data && end < reg->data + reg->size)) {
> >+ debug("%s: new region already part of another\n",
> >+ __func__);
> >+ return EFI_INVALID_PARAMETER;
> >+ }
> >+
> >+ if (start < reg->data && end < reg->data + reg->size) {
> >+ for (j = regs->num - 1; j >= i; j--)
> >+ memcpy(&regs->reg[j], &regs->reg[j + 1],
> >+ sizeof(*reg));
> >+ break;
> >+ }
> >+ }
> >+
> >+ reg = &regs->reg[i];
> >+ reg->data = start;
> >+ reg->size = end - start;
> >+ regs->num++;
> >+
> >+ return EFI_SUCCESS;
> >+}
> >+#endif /* CONFIG_EFI_SECURE_BOOT */
> >
>