[PATCH 1/2 v2] efi_loader: add sha384/512 on certificate revocation

Ilias Apalodimas ilias.apalodimas at linaro.org
Mon Apr 18 20:05:44 CEST 2022


Apologies for the noise.  Feel free to ignore this, I had a new
version with updated changelog.  I'll post them shortly

On Mon, 18 Apr 2022 at 08:53, Ilias Apalodimas
<ilias.apalodimas at linaro.org> wrote:
>
> Currently we don't support sha384/512 for the X.509
> certificate To-Be-Signed contents.  Moreover if we come across such a
> hash we skip the check and approve the image,  although the image
> might needs to be rejected.
>
> It's worth noting here that efi_hash_regions() can now be reused from
> efi_signature_lookup_digest() and add sha348/512 support there as well
>
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> ---
> changes since v1:
> - add an array of structs with the algo info info of a function
> - checking hash_calculate result in efi_hash_regions()
>
>  include/efi_api.h              |  6 +++
>  include/efi_loader.h           |  7 +++
>  lib/efi_loader/efi_helper.c    | 85 ++++++++++++++++++++++++++++++++++
>  lib/efi_loader/efi_signature.c | 76 +++++++++++++++++++++---------
>  4 files changed, 151 insertions(+), 23 deletions(-)
>
> diff --git a/include/efi_api.h b/include/efi_api.h
> index 982c2001728d..b9a04958f9ba 100644
> --- a/include/efi_api.h
> +++ b/include/efi_api.h
> @@ -1873,6 +1873,12 @@ struct efi_system_resource_table {
>  #define EFI_CERT_X509_SHA256_GUID \
>         EFI_GUID(0x3bd2a492, 0x96c0, 0x4079, 0xb4, 0x20, \
>                  0xfc, 0xf9, 0x8e, 0xf1, 0x03, 0xed)
> +#define EFI_CERT_X509_SHA384_GUID \
> +       EFI_GUID(0x7076876e, 0x80c2, 0x4ee6,            \
> +                0xaa, 0xd2, 0x28, 0xb3, 0x49, 0xa6, 0x86, 0x5b)
> +#define EFI_CERT_X509_SHA512_GUID \
> +       EFI_GUID(0x446dbf63, 0x2502, 0x4cda,            \
> +                0xbc, 0xfa, 0x24, 0x65, 0xd2, 0xb0, 0xfe, 0x9d)
>  #define EFI_CERT_TYPE_PKCS7_GUID \
>         EFI_GUID(0x4aafd29d, 0x68df, 0x49ee, 0x8a, 0xa9, \
>                  0x34, 0x7d, 0x37, 0x56, 0x65, 0xa7)
> diff --git a/include/efi_loader.h b/include/efi_loader.h
> index af36639ec6a7..ce221ee9317b 100644
> --- a/include/efi_loader.h
> +++ b/include/efi_loader.h
> @@ -300,6 +300,8 @@ 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 const efi_guid_t efi_guid_cert_x509_sha384;
> +extern const efi_guid_t efi_guid_cert_x509_sha512;
>  extern const efi_guid_t efi_guid_cert_type_pkcs7;
>
>  /* GUID of RNG protocol */
> @@ -671,6 +673,11 @@ efi_status_t efi_file_size(struct efi_file_handle *fh, efi_uintn_t *size);
>  /* get a device path from a Boot#### option */
>  struct efi_device_path *efi_get_dp_from_boot(const efi_guid_t guid);
>
> +/* get len, string (used in u-boot crypto from a guid */
> +const char *guid_to_sha_str(const efi_guid_t *guid);
> +int guid_to_sha_len(const efi_guid_t *guid);
> +int algo_to_len(const char *algo);
> +
>  /**
>   * efi_size_in_pages() - convert size in bytes to size in pages
>   *
> diff --git a/lib/efi_loader/efi_helper.c b/lib/efi_loader/efi_helper.c
> index 802d39ed97b6..c186ba4a3c01 100644
> --- a/lib/efi_loader/efi_helper.c
> +++ b/lib/efi_loader/efi_helper.c
> @@ -92,3 +92,88 @@ err:
>         free(var_value);
>         return NULL;
>  }
> +
> +const struct guid_to_hash_map {
> +       efi_guid_t guid;
> +       const char algo[32];
> +       u32 bits;
> +} guid_to_hash[] = {
> +       {
> +               EFI_CERT_X509_SHA256_GUID,
> +               "sha256",
> +               256,
> +       },
> +       {
> +               EFI_CERT_SHA256_GUID,
> +               "sha256",
> +               256,
> +       },
> +       {
> +               EFI_CERT_X509_SHA384_GUID,
> +               "sha384",
> +               384,
> +       },
> +       {
> +               EFI_CERT_X509_SHA512_GUID,
> +               "sha512",
> +               512,
> +       },
> +};
> +
> +#define MAX_GUID_TO_HASH_COUNT ARRAY_SIZE(guid_to_hash)
> +
> +/** guid_to_sha_str - return the sha string e.g "sha256" for a given guid
> + *                    used on EFI security databases
> + *
> + * @guid: guid to check
> + *
> + * Return: len or 0 if no match is found
> + */
> +const char *guid_to_sha_str(const efi_guid_t *guid)
> +{
> +       size_t i;
> +
> +       for (i = 0; i < MAX_GUID_TO_HASH_COUNT; i++) {
> +               if (!guidcmp(guid, &guid_to_hash[i].guid))
> +                       return guid_to_hash[i].algo;
> +       }
> +
> +       return NULL;
> +}
> +
> +/** guid_to_sha_len - return the sha size in bytes for a given guid
> + *                    used on EFI security databases
> + *
> + * @guid: guid to check
> + *
> + * Return: len or 0 if no match is found
> + */
> +int guid_to_sha_len(const efi_guid_t *guid)
> +{
> +       size_t i;
> +
> +       for (i = 0; i < MAX_GUID_TO_HASH_COUNT; i++) {
> +               if (!guidcmp(guid, &guid_to_hash[i].guid))
> +                       return guid_to_hash[i].bits / 8;
> +       }
> +
> +       return 0;
> +}
> +
> +/** algo_to_len - return the sha size in bytes for a given string
> + *
> + * @guid: string to check
> + *
> + * Return: len or 0 if no match is found
> + */
> +int algo_to_len(const char *algo)
> +{
> +       size_t i;
> +
> +       for (i = 0; i < MAX_GUID_TO_HASH_COUNT; i++) {
> +               if (!strcmp(algo, guid_to_hash[i].algo))
> +                       return guid_to_hash[i].bits / 8;
> +       }
> +
> +       return 0;
> +}
> diff --git a/lib/efi_loader/efi_signature.c b/lib/efi_loader/efi_signature.c
> index 79ed077ae7dd..cf01f21b4d04 100644
> --- a/lib/efi_loader/efi_signature.c
> +++ b/lib/efi_loader/efi_signature.c
> @@ -24,6 +24,8 @@ 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;
> +const efi_guid_t efi_guid_cert_x509_sha384 = EFI_CERT_X509_SHA384_GUID;
> +const efi_guid_t efi_guid_cert_x509_sha512 = EFI_CERT_X509_SHA512_GUID;
>  const efi_guid_t efi_guid_cert_type_pkcs7 = EFI_CERT_TYPE_PKCS7_GUID;
>
>  static u8 pkcs7_hdr[] = {
> @@ -124,23 +126,32 @@ struct pkcs7_message *efi_parse_pkcs7_header(const void *buf,
>   * Return:     true on success, false on error
>   */
>  static bool efi_hash_regions(struct image_region *regs, int count,
> -                            void **hash, size_t *size)
> +                            void **hash, const char *hash_algo, int *len)
>  {
> +       int ret;
> +
> +       if (!hash_algo || !len)
> +               return false;
> +
> +       *len = algo_to_len(hash_algo);
> +       if (!*len)
> +               return false;
> +
>         if (!*hash) {
> -               *hash = calloc(1, SHA256_SUM_LEN);
> +               *hash = calloc(1, *len);
>                 if (!*hash) {
>                         EFI_PRINT("Out of memory\n");
>                         return false;
>                 }
>         }
> -       if (size)
> -               *size = SHA256_SUM_LEN;
>
> -       hash_calculate("sha256", regs, count, *hash);
> +       ret = hash_calculate(hash_algo, regs, count, *hash);
> +       if (ret)
> +               return false;
>  #ifdef DEBUG
>         EFI_PRINT("hash calculated:\n");
>         print_hex_dump("    ", DUMP_PREFIX_OFFSET, 16, 1,
> -                      *hash, SHA256_SUM_LEN, false);
> +                      *hash, *len, false);
>  #endif
>
>         return true;
> @@ -190,7 +201,6 @@ bool efi_signature_lookup_digest(struct efi_image_regions *regs,
>         struct efi_signature_store *siglist;
>         struct efi_sig_data *sig_data;
>         void *hash = NULL;
> -       size_t size = 0;
>         bool found = false;
>         bool hash_done = false;
>
> @@ -200,6 +210,8 @@ bool efi_signature_lookup_digest(struct efi_image_regions *regs,
>                 goto out;
>
>         for (siglist = db; siglist; siglist = siglist->next) {
> +               int len = 0;
> +               const char *hash_algo = NULL;
>                 /*
>                  * if the hash algorithm is unsupported and we get an entry in
>                  * dbx reject the image
> @@ -215,8 +227,14 @@ bool efi_signature_lookup_digest(struct efi_image_regions *regs,
>                 if (guidcmp(&siglist->sig_type, &efi_guid_sha256))
>                         continue;
>
> +               hash_algo = guid_to_sha_str(&efi_guid_sha256);
> +               /*
> +                * We could check size and hash_algo but efi_hash_regions()
> +                * will do that for us
> +                */
>                 if (!hash_done &&
> -                   !efi_hash_regions(regs->reg, regs->num, &hash, &size)) {
> +                   !efi_hash_regions(regs->reg, regs->num, &hash, hash_algo,
> +                                     &len)) {
>                         EFI_PRINT("Digesting an image failed\n");
>                         break;
>                 }
> @@ -229,8 +247,8 @@ bool efi_signature_lookup_digest(struct efi_image_regions *regs,
>                         print_hex_dump("    ", DUMP_PREFIX_OFFSET, 16, 1,
>                                        sig_data->data, sig_data->size, false);
>  #endif
> -                       if (sig_data->size == size &&
> -                           !memcmp(sig_data->data, hash, size)) {
> +                       if (sig_data->size == len &&
> +                           !memcmp(sig_data->data, hash, len)) {
>                                 found = true;
>                                 free(hash);
>                                 goto out;
> @@ -263,8 +281,9 @@ static bool efi_lookup_certificate(struct x509_certificate *cert,
>         struct efi_sig_data *sig_data;
>         struct image_region reg[1];
>         void *hash = NULL, *hash_tmp = NULL;
> -       size_t size = 0;
> +       int len = 0;
>         bool found = false;
> +       const char *hash_algo = NULL;
>
>         EFI_PRINT("%s: Enter, %p, %p\n", __func__, cert, db);
>
> @@ -278,7 +297,11 @@ static bool efi_lookup_certificate(struct x509_certificate *cert,
>         /* calculate hash of TBSCertificate */
>         reg[0].data = cert->tbs;
>         reg[0].size = cert->tbs_size;
> -       if (!efi_hash_regions(reg, 1, &hash, &size))
> +
> +       /* We just need any sha256 algo to start the matching */
> +       hash_algo = guid_to_sha_str(&efi_guid_sha256);
> +       len = guid_to_sha_len(&efi_guid_sha256);
> +       if (!efi_hash_regions(reg, 1, &hash, hash_algo, &len))
>                 goto out;
>
>         EFI_PRINT("%s: searching for %s\n", __func__, cert->subject);
> @@ -290,6 +313,7 @@ static bool efi_lookup_certificate(struct x509_certificate *cert,
>                 for (sig_data = siglist->sig_data_list; sig_data;
>                      sig_data = sig_data->next) {
>                         struct x509_certificate *cert_tmp;
> +                       int len_tmp;
>
>                         cert_tmp = x509_cert_parse(sig_data->data,
>                                                    sig_data->size);
> @@ -300,12 +324,13 @@ static bool efi_lookup_certificate(struct x509_certificate *cert,
>                                   cert_tmp->subject);
>                         reg[0].data = cert_tmp->tbs;
>                         reg[0].size = cert_tmp->tbs_size;
> -                       if (!efi_hash_regions(reg, 1, &hash_tmp, NULL))
> +                       if (!efi_hash_regions(reg, 1, &hash_tmp, hash_algo,
> +                                             &len_tmp))
>                                 goto out;
>
>                         x509_free_certificate(cert_tmp);
>
> -                       if (!memcmp(hash, hash_tmp, size)) {
> +                       if (!memcmp(hash, hash_tmp, len)) {
>                                 found = true;
>                                 goto out;
>                         }
> @@ -400,9 +425,10 @@ static bool efi_signature_check_revocation(struct pkcs7_signed_info *sinfo,
>         struct efi_sig_data *sig_data;
>         struct image_region reg[1];
>         void *hash = NULL;
> -       size_t size = 0;
> +       int len = 0;
>         time64_t revoc_time;
>         bool revoked = false;
> +       const char *hash_algo = NULL;
>
>         EFI_PRINT("%s: Enter, %p, %p, %p\n", __func__, sinfo, cert, dbx);
>
> @@ -411,13 +437,14 @@ static bool efi_signature_check_revocation(struct pkcs7_signed_info *sinfo,
>
>         EFI_PRINT("Checking revocation against %s\n", cert->subject);
>         for (siglist = dbx; siglist; siglist = siglist->next) {
> -               if (guidcmp(&siglist->sig_type, &efi_guid_cert_x509_sha256))
> +               hash_algo = guid_to_sha_str(&siglist->sig_type);
> +               if (!hash_algo)
>                         continue;
>
>                 /* calculate hash of TBSCertificate */
>                 reg[0].data = cert->tbs;
>                 reg[0].size = cert->tbs_size;
> -               if (!efi_hash_regions(reg, 1, &hash, &size))
> +               if (!efi_hash_regions(reg, 1, &hash, hash_algo, &len))
>                         goto out;
>
>                 for (sig_data = siglist->sig_data_list; sig_data;
> @@ -429,18 +456,18 @@ static bool efi_signature_check_revocation(struct pkcs7_signed_info *sinfo,
>                          * };
>                          */
>  #ifdef DEBUG
> -                       if (sig_data->size >= size) {
> +                       if (sig_data->size >= len) {
>                                 EFI_PRINT("hash in db:\n");
>                                 print_hex_dump("    ", DUMP_PREFIX_OFFSET,
>                                                16, 1,
> -                                              sig_data->data, size, false);
> +                                              sig_data->data, len, false);
>                         }
>  #endif
> -                       if ((sig_data->size < size + sizeof(time64_t)) ||
> -                           memcmp(sig_data->data, hash, size))
> +                       if ((sig_data->size < len + sizeof(time64_t)) ||
> +                           memcmp(sig_data->data, hash, len))
>                                 continue;
>
> -                       memcpy(&revoc_time, sig_data->data + size,
> +                       memcpy(&revoc_time, sig_data->data + len,
>                                sizeof(revoc_time));
>                         EFI_PRINT("revocation time: 0x%llx\n", revoc_time);
>                         /*
> @@ -488,6 +515,7 @@ bool efi_signature_verify(struct efi_image_regions *regs,
>                 goto out;
>
>         for (sinfo = msg->signed_infos; sinfo; sinfo = sinfo->next) {
> +               int len;
>                 EFI_PRINT("Signed Info: digest algo: %s, pkey algo: %s\n",
>                           sinfo->sig->hash_algo, sinfo->sig->pkey_algo);
>
> @@ -500,7 +528,9 @@ bool efi_signature_verify(struct efi_image_regions *regs,
>                  */
>                 if (!msg->data &&
>                     !efi_hash_regions(regs->reg, regs->num,
> -                                     (void **)&sinfo->sig->digest, NULL)) {
> +                                     (void **)&sinfo->sig->digest,
> +                                     guid_to_sha_str(&efi_guid_sha256),
> +                                     &len)) {
>                         EFI_PRINT("Digesting an image failed\n");
>                         goto out;
>                 }
> --
> 2.32.0
>


More information about the U-Boot mailing list