tablet/grub
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
grub/grub-core/commands/appendedsig/x509.c
Sudhakar Kuppusamy e95c52f1f4 appended signatures: Parse X.509 certificates 
This code allows us to parse:

 - X.509 certificates: at least enough to verify the signatures on the PKCS#7
   messages. We expect that the certificates embedded in GRUB will be leaf
   certificates, not CA certificates. The parser enforces this.

 - X.509 certificates support the Extended Key Usage extension and handle it by
   verifying that the certificate has a Code Signing usage.

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com> # EKU support
Reported-by: Michal Suchanek <msuchanek@suse.com> # key usage issue
Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>
Reviewed-by: Avnish Chouhan <avnish@linux.ibm.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
2025-10-11 15:36:35 +02:00

971 lines
30 KiB
C
Raw Blame History

/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 2020, 2022 Free Software Foundation, Inc.
* Copyright (C) 2020, 2022, 2025 IBM Corporation
*
* GRUB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GRUB is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
*/
#include <libtasn1.h>
#include <grub/types.h>
#include <grub/err.h>
#include <grub/mm.h>
#include <grub/crypto.h>
#include <grub/misc.h>
#include <grub/gcrypt/gcrypt.h>
#include "appendedsig.h"
static char asn1_error[ASN1_MAX_ERROR_DESCRIPTION_SIZE];
/* RFC 3279 2.3.1 RSA Keys. */
static const char *rsaEncryption_oid = "1.2.840.113549.1.1.1";
/* RFC 5280 Appendix A. */
static const char *commonName_oid = "2.5.4.3";
/* RFC 5280 4.2.1.3 Key Usage. */
static const char *keyUsage_oid = "2.5.29.15";
static const grub_uint8_t digitalSignatureUsage = 0x80;
/* RFC 5280 4.2.1.9 Basic Constraints. */
static const char *basicConstraints_oid = "2.5.29.19";
/* RFC 5280 4.2.1.12 Extended Key Usage. */
static const char *extendedKeyUsage_oid = "2.5.29.37";
static const char *codeSigningUsage_oid = "1.3.6.1.5.5.7.3.3";
/*
* RFC 3279 2.3.1
*
* The RSA public key MUST be encoded using the ASN.1 type RSAPublicKey:
*
* RSAPublicKey ::= SEQUENCE {
* modulus INTEGER, -- n
* publicExponent INTEGER } -- e
*
* where modulus is the modulus n, and publicExponent is the public exponent e.
*/
static grub_err_t
grub_parse_rsa_pubkey (grub_uint8_t *der, grub_int32_t dersize, grub_x509_cert_t *certificate)
{
grub_int32_t result;
asn1_node spk = NULL;
grub_uint8_t *m_data, *e_data;
grub_int32_t m_size, e_size;
grub_err_t err = GRUB_ERR_NONE;
gcry_error_t gcry_err;
result = asn1_create_element (grub_gnutls_gnutls_asn, "GNUTLS.RSAPublicKey", &spk);
if (result != ASN1_SUCCESS)
return grub_error (GRUB_ERR_OUT_OF_MEMORY,
"cannot create storage for public key ASN.1 data");
result = asn1_der_decoding2 (&spk, der, &dersize, ASN1_DECODE_FLAG_STRICT_DER, asn1_error);
if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE,
"cannot decode certificate public key DER: %s", asn1_error);
goto cleanup;
}
m_data = grub_asn1_allocate_and_read (spk, "modulus", "RSA modulus", &m_size);
if (m_data == NULL)
{
err = grub_errno;
goto cleanup;
}
e_data = grub_asn1_allocate_and_read (spk, "publicExponent", "RSA public exponent", &e_size);
if (e_data == NULL)
{
err = grub_errno;
goto cleanup_m_data;
}
/*
* Convert m, e to mpi
*
* nscanned is not set for FMT_USG, it's only set for FMT_PGP, so we can't
* verify it.
*/
gcry_err = _gcry_mpi_scan (&certificate->mpis[0], GCRYMPI_FMT_USG, m_data, m_size, NULL);
if (gcry_err != GPG_ERR_NO_ERROR)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE,
"error loading RSA modulus into MPI structure: %d", gcry_err);
goto cleanup_e_data;
}
gcry_err = _gcry_mpi_scan (&certificate->mpis[1], GCRYMPI_FMT_USG, e_data, e_size, NULL);
if (gcry_err != GPG_ERR_NO_ERROR)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE,
"error loading RSA exponent into MPI structure: %d", gcry_err);
goto cleanup_m_mpi;
}
/* RSA key size in bits. */
certificate->modulus_size = (m_size * 8) - 8;
grub_free (e_data);
grub_free (m_data);
asn1_delete_structure (&spk);
return GRUB_ERR_NONE;
cleanup_m_mpi:
_gcry_mpi_release (certificate->mpis[0]);
cleanup_e_data:
grub_free (e_data);
cleanup_m_data:
grub_free (m_data);
cleanup:
asn1_delete_structure (&spk);
return err;
}
/*
* RFC 5280:
* SubjectPublicKeyInfo ::= SEQUENCE {
* algorithm AlgorithmIdentifier,
* subjectPublicKey BIT STRING }
*
* AlgorithmIdentifiers come from RFC 3279, we are not strictly compilant as we
* only support RSA Encryption.
*/
static grub_err_t
grub_x509_read_subject_public_key (asn1_node asn, grub_x509_cert_t *results)
{
grub_int32_t result;
grub_err_t err;
const char *algo_name = "tbsCertificate.subjectPublicKeyInfo.algorithm.algorithm";
const char *params_name = "tbsCertificate.subjectPublicKeyInfo.algorithm.parameters";
const char *pk_name = "tbsCertificate.subjectPublicKeyInfo.subjectPublicKey";
char algo_oid[GRUB_MAX_OID_LEN];
grub_int32_t algo_size = sizeof (algo_oid);
char params_value[2];
grub_int32_t params_size = sizeof (params_value);
grub_uint8_t *key_data = NULL;
grub_int32_t key_size = 0;
grub_uint32_t key_type;
/* Algorithm: see notes for rsaEncryption_oid. */
result = asn1_read_value (asn, algo_name, algo_oid, &algo_size);
if (result != ASN1_SUCCESS)
return grub_error (GRUB_ERR_BAD_FILE_TYPE, "error reading x509 public key algorithm: %s",
asn1_strerror (result));
if (grub_strncmp (algo_oid, rsaEncryption_oid, sizeof (rsaEncryption_oid)) != 0)
return grub_error (GRUB_ERR_NOT_IMPLEMENTED_YET,
"unsupported x509 public key algorithm: %s", algo_oid);
/*
* RFC 3279 2.3.1 : The rsaEncryption OID is intended to be used in the
* algorithm field of a value of type AlgorithmIdentifier. The parameters
* field MUST have ASN.1 type NULL for this algorithm identifier.
*/
result = asn1_read_value (asn, params_name, params_value, &params_size);
if (result != ASN1_SUCCESS)
return grub_error (GRUB_ERR_BAD_FILE_TYPE, "error reading x509 public key parameters: %s",
asn1_strerror (result));
if (params_value[0] != ASN1_TAG_NULL)
return grub_error (GRUB_ERR_BAD_FILE_TYPE,
"invalid x509 public key parameters: expected NULL");
/*
* RFC 3279 2.3.1: The DER encoded RSAPublicKey is the value of the BIT
* STRING subjectPublicKey.
*/
result = asn1_read_value_type (asn, pk_name, NULL, &key_size, &key_type);
if (result != ASN1_MEM_ERROR)
return grub_error (GRUB_ERR_BAD_FILE_TYPE, "error reading size of x509 public key: %s",
asn1_strerror (result));
if (key_type != ASN1_ETYPE_BIT_STRING)
return grub_error (GRUB_ERR_BAD_FILE_TYPE, "unexpected ASN.1 type when reading x509 public key: %x",
key_type);
/* Length is in bits. */
key_size = (key_size + 7) / 8;
key_data = grub_malloc (key_size);
if (key_data == NULL)
return grub_error (GRUB_ERR_OUT_OF_MEMORY, "out of memory for x509 public key");
result = asn1_read_value (asn, pk_name, key_data, &key_size);
if (result != ASN1_SUCCESS)
{
grub_free (key_data);
return grub_error (GRUB_ERR_BAD_FILE_TYPE, "error reading public key data");
}
key_size = (key_size + 7) / 8;
err = grub_parse_rsa_pubkey (key_data, key_size, results);
grub_free (key_data);
return err;
}
/* Decode a string as defined in Appendix A. */
static grub_err_t
decode_string (char *der, grub_int32_t der_size, char **string, grub_size_t *string_size)
{
asn1_node strasn;
grub_int32_t result;
char *choice;
grub_int32_t choice_size = 0;
grub_int32_t tmp_size = 0;
grub_err_t err = GRUB_ERR_NONE;
result = asn1_create_element (grub_gnutls_pkix_asn, "PKIX1.DirectoryString", &strasn);
if (result != ASN1_SUCCESS)
return grub_error (GRUB_ERR_OUT_OF_MEMORY,
"could not create ASN.1 structure for certificate: %s",
asn1_strerror (result));
result = asn1_der_decoding2 (&strasn, der, &der_size, ASN1_DECODE_FLAG_STRICT_DER, asn1_error);
if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE,
"could not parse DER for DirectoryString: %s", asn1_error);
goto cleanup;
}
choice = grub_asn1_allocate_and_read (strasn, "", "DirectoryString choice", &choice_size);
if (choice == NULL)
{
err = grub_errno;
goto cleanup;
}
if (grub_strncmp ("utf8String", choice, choice_size) == 0)
{
result = asn1_read_value (strasn, "utf8String", NULL, &tmp_size);
if (result != ASN1_MEM_ERROR)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "error reading size of UTF-8 string: %s",
asn1_strerror (result));
goto cleanup_choice;
}
}
else if (grub_strncmp ("printableString", choice, choice_size) == 0)
{
result = asn1_read_value (strasn, "printableString", NULL, &tmp_size);
if (result != ASN1_MEM_ERROR)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "error reading size of printableString: %s",
asn1_strerror (result));
goto cleanup_choice;
}
}
else
{
err = grub_error (GRUB_ERR_NOT_IMPLEMENTED_YET,
"only UTF-8 and printable DirectoryStrings are supported, got %s",
choice);
goto cleanup_choice;
}
/* Read size does not include trailing NUL. */
tmp_size++;
*string = grub_malloc (tmp_size);
if (*string == NULL)
{
err = grub_error (GRUB_ERR_OUT_OF_MEMORY,
"cannot allocate memory for DirectoryString contents");
goto cleanup_choice;
}
result = asn1_read_value (strasn, choice, *string, &tmp_size);
if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "error reading out %s in DirectoryString: %s",
choice, asn1_strerror (result));
grub_free (*string);
*string = NULL;
goto cleanup_choice;
}
*string_size = tmp_size + 1;
(*string)[tmp_size] = '\0';
cleanup_choice:
grub_free (choice);
cleanup:
asn1_delete_structure (&strasn);
return err;
}
/*
* TBSCertificate ::= SEQUENCE {
* version [0] EXPLICIT Version DEFAULT v1,
* ...
*
* Version ::= INTEGER { v1(0), v2(1), v3(2) }
*/
static grub_err_t
check_version (asn1_node certificate, grub_x509_cert_t *results)
{
grub_int32_t rc;
const char *name = "tbsCertificate.version";
grub_uint8_t version;
grub_int32_t len = sizeof (version);
rc = asn1_read_value (certificate, name, &version, &len);
/* Require version 3. */
if (rc != ASN1_SUCCESS || len != 1)
return grub_error (GRUB_ERR_BAD_FILE_TYPE, "error reading certificate version");
if (version != 0x02)
return grub_error (GRUB_ERR_BAD_FILE_TYPE,
"invalid x509 certificate version, expected v3 (0x02), got 0x%02x.",
version);
results->version = version;
return GRUB_ERR_NONE;
}
/* we extract only the CN and issuer. */
static grub_err_t
read_name (asn1_node asn, const char *name_path, char **name, grub_size_t *name_size)
{
grub_int32_t seq_components, set_components;
grub_int32_t result;
grub_int32_t i, j;
char *top_path, *set_path, *type_path, *val_path;
char type[GRUB_MAX_OID_LEN];
grub_int32_t type_len = sizeof (type);
grub_int32_t string_size = 0;
char *string_der;
grub_err_t err;
*name = NULL;
top_path = grub_xasprintf ("%s.rdnSequence", name_path);
if (top_path == NULL)
return grub_error (GRUB_ERR_OUT_OF_MEMORY,
"could not allocate memory for %s name parsing path", name_path);
result = asn1_number_of_elements (asn, top_path, &seq_components);
if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "error counting name components: %s",
asn1_strerror (result));
goto cleanup;
}
for (i = 1; i <= seq_components; i++)
{
set_path = grub_xasprintf ("%s.?%d", top_path, i);
if (set_path == NULL)
{
err = grub_error (GRUB_ERR_OUT_OF_MEMORY,
"could not allocate memory for %s name set parsing path",
name_path);
goto cleanup_set;
}
/* This brings us, hopefully, to a set. */
result = asn1_number_of_elements (asn, set_path, &set_components);
if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE,
"error counting name sub-components components (element %d): %s",
i, asn1_strerror (result));
goto cleanup_set;
}
for (j = 1; j <= set_components; j++)
{
type_path = grub_xasprintf ("%s.?%d.?%d.type", top_path, i, j);
if (type_path == NULL)
{
err = grub_error (GRUB_ERR_OUT_OF_MEMORY,
"could not allocate memory for %s name component type path",
name_path);
goto cleanup_set;
}
type_len = sizeof (type);
result = asn1_read_value (asn, type_path, type, &type_len);
if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "error reading %s name component type: %s",
name_path, asn1_strerror (result));
goto cleanup_type;
}
if (grub_strncmp (type, commonName_oid, type_len) != 0)
{
grub_free (type_path);
continue;
}
val_path = grub_xasprintf ("%s.?%d.?%d.value", top_path, i, j);
if (val_path == NULL)
{
err = grub_error (GRUB_ERR_OUT_OF_MEMORY,
"could not allocate memory for %s name component value path",
name_path);
goto cleanup_type;
}
string_der = grub_asn1_allocate_and_read (asn, val_path, name_path, &string_size);
if (string_der == NULL)
{
err = grub_errno;
goto cleanup_val_path;
}
err = decode_string (string_der, string_size, name, name_size);
if (err)
goto cleanup_string;
grub_free (string_der);
grub_free (type_path);
grub_free (val_path);
break;
}
grub_free (set_path);
if (*name)
break;
}
grub_free (top_path);
return GRUB_ERR_NONE;
cleanup_string:
grub_free (string_der);
cleanup_val_path:
grub_free (val_path);
cleanup_type:
grub_free (type_path);
cleanup_set:
grub_free (set_path);
cleanup:
grub_free (top_path);
return err;
}
/* Verify the Key Usage extension. We require the Digital Signature usage. */
static grub_err_t
verify_key_usage (grub_uint8_t *value, grub_int32_t value_size)
{
asn1_node usageasn;
grub_int32_t result;
grub_err_t err = GRUB_ERR_NONE;
grub_uint8_t usage = 0xff;
grub_int32_t usage_size = sizeof (usage_size);
result = asn1_create_element (grub_gnutls_pkix_asn, "PKIX1.KeyUsage", &usageasn);
if (result != ASN1_SUCCESS)
return grub_error (GRUB_ERR_OUT_OF_MEMORY,
"could not create ASN.1 structure for key usage");
result = asn1_der_decoding2 (&usageasn, value, &value_size,
ASN1_DECODE_FLAG_STRICT_DER, asn1_error);
if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE,
"error parsing DER for Key Usage: %s", asn1_error);
goto cleanup;
}
result = asn1_read_value (usageasn, "", &usage, &usage_size);
if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "error reading Key Usage value: %s",
asn1_strerror (result));
goto cleanup;
}
if (!(usage & digitalSignatureUsage))
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE,
"key usage (0x%x) missing Digital Signature usage", usage);
goto cleanup;
}
cleanup:
asn1_delete_structure (&usageasn);
return err;
}
/*
* BasicConstraints ::= SEQUENCE {
* cA BOOLEAN DEFAULT FALSE,
* pathLenConstraint INTEGER (0..MAX) OPTIONAL }
*/
static grub_err_t
verify_basic_constraints (grub_uint8_t *value, grub_int32_t value_size)
{
asn1_node basicasn;
grub_int32_t result;
grub_err_t err = GRUB_ERR_NONE;
char cA[6]; /* FALSE or TRUE. */
grub_int32_t cA_size = sizeof (cA);
result = asn1_create_element (grub_gnutls_pkix_asn, "PKIX1.BasicConstraints", &basicasn);
if (result != ASN1_SUCCESS)
return grub_error (GRUB_ERR_OUT_OF_MEMORY,
"could not create ASN.1 structure for Basic Constraints");
result = asn1_der_decoding2 (&basicasn, value, &value_size,
ASN1_DECODE_FLAG_STRICT_DER, asn1_error);
if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE,
"error parsing DER for Basic Constraints: %s", asn1_error);
goto cleanup;
}
result = asn1_read_value (basicasn, "cA", cA, &cA_size);
if (result == ASN1_ELEMENT_NOT_FOUND)
{
/* Not present, default is False, so this is OK. */
err = GRUB_ERR_NONE;
goto cleanup;
}
else if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "error reading Basic Constraints cA value: %s",
asn1_strerror (result));
goto cleanup;
}
/* The certificate must not be a CA certificate. */
if (grub_strncmp ("FALSE", cA, cA_size) != 0)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "unexpected CA value: %s", cA);
goto cleanup;
}
cleanup:
asn1_delete_structure (&basicasn);
return err;
}
/*
* Verify the Extended Key Usage extension. We require the Code Signing usage.
*
* ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId
*
* KeyPurposeId ::= OBJECT IDENTIFIER
*/
static grub_err_t
verify_extended_key_usage (grub_uint8_t *value, grub_int32_t value_size)
{
asn1_node extendedasn;
grub_int32_t result, count, i = 0;
grub_err_t err = GRUB_ERR_NONE;
char usage[GRUB_MAX_OID_LEN], name[3];
grub_int32_t usage_size = sizeof (usage);
result = asn1_create_element (grub_gnutls_pkix_asn, "PKIX1.ExtKeyUsageSyntax", &extendedasn);
if (result != ASN1_SUCCESS)
return grub_error (GRUB_ERR_OUT_OF_MEMORY,
"could not create ASN.1 structure for Extended Key Usage");
result = asn1_der_decoding2 (&extendedasn, value, &value_size,
ASN1_DECODE_FLAG_STRICT_DER, asn1_error);
if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE,
"error parsing DER for Extended Key Usage: %s", asn1_error);
goto cleanup;
}
/* If EKUs are present, it checks the presents of Code Signing usage. */
result = asn1_number_of_elements (extendedasn, "", &count);
if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "error counting number of Extended Key Usages: %s",
asn1_strerror (result));
goto cleanup;
}
for (i = 1; i < count + 1; i++)
{
grub_memset (name, 0, sizeof (name));
grub_snprintf (name, sizeof (name), "?%d", i);
result = asn1_read_value (extendedasn, name, usage, &usage_size);
if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "error reading Extended Key Usage: %s",
asn1_strerror (result));
goto cleanup;
}
if (grub_strncmp (codeSigningUsage_oid, usage, usage_size) == 0)
goto cleanup;
}
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "extended key usage missing Code Signing usage");
cleanup:
asn1_delete_structure (&extendedasn);
return err;
}
/*
* Extensions ::= SEQUENCE SIZE (1..MAX) OF Extension
*
* Extension ::= SEQUENCE {
* extnID OBJECT IDENTIFIER,
* critical BOOLEAN DEFAULT FALSE,
* extnValue OCTET STRING
* -- contains the DER encoding of an ASN.1 value
* -- corresponding to the extension type identified
* -- by extnID
* }
*
* A certificate must:
* - contain the Digital Signature usage
* - not be a CA
* - contain no extended usages, or contain the Code Signing extended usage
* - not contain any other critical extensions (RFC 5280 s 4.2)
*/
static grub_err_t
verify_extensions (asn1_node cert)
{
grub_int32_t result;
grub_int32_t ext, num_extensions = 0;
grub_int32_t usage_present = 0, constraints_present = 0, extended_usage_present = 0;
char *oid_path, *critical_path, *value_path;
char extnID[GRUB_MAX_OID_LEN];
grub_int32_t extnID_size;
grub_err_t err;
char critical[6]; /* We get either "TRUE" or "FALSE". */
grub_int32_t critical_size;
grub_uint8_t *value;
grub_int32_t value_size;
result = asn1_number_of_elements (cert, "tbsCertificate.extensions", &num_extensions);
if (result != ASN1_SUCCESS)
return grub_error (GRUB_ERR_BAD_FILE_TYPE, "error counting number of extensions: %s",
asn1_strerror (result));
if (num_extensions < 2)
return grub_error (GRUB_ERR_BAD_FILE_TYPE,
"insufficient number of extensions for certificate, need at least 2, got %d",
num_extensions);
for (ext = 1; ext <= num_extensions; ext++)
{
oid_path = grub_xasprintf ("tbsCertificate.extensions.?%d.extnID", ext);
if (oid_path == NULL)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "error extension OID path is empty");
return err;
}
extnID_size = sizeof (extnID);
result = asn1_read_value (cert, oid_path, extnID, &extnID_size);
if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "error reading extension OID: %s",
asn1_strerror (result));
goto cleanup_oid_path;
}
critical_path = grub_xasprintf ("tbsCertificate.extensions.?%d.critical", ext);
if (critical_path == NULL)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "error critical path is empty");
goto cleanup_oid_path;
}
critical_size = sizeof (critical);
result = asn1_read_value (cert, critical_path, critical, &critical_size);
if (result == ASN1_ELEMENT_NOT_FOUND)
critical[0] = '\0';
else if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "error reading extension criticality: %s",
asn1_strerror (result));
goto cleanup_critical_path;
}
value_path = grub_xasprintf ("tbsCertificate.extensions.?%d.extnValue", ext);
if (value_path == NULL)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE, "error extnValue path is empty");
goto cleanup_critical_path;
}
value = grub_asn1_allocate_and_read (cert, value_path,
"certificate extension value", &value_size);
if (value == NULL)
{
err = grub_errno;
goto cleanup_value_path;
}
/*
* Now we must see if we recognise the OID. If we have an unrecognised
* critical extension we MUST bail.
*/
if (grub_strncmp (keyUsage_oid, extnID, extnID_size) == 0)
{
err = verify_key_usage (value, value_size);
if (err != GRUB_ERR_NONE)
goto cleanup_value;
usage_present++;
}
else if (grub_strncmp (basicConstraints_oid, extnID, extnID_size) == 0)
{
err = verify_basic_constraints (value, value_size);
if (err != GRUB_ERR_NONE)
goto cleanup_value;
constraints_present++;
}
else if (grub_strncmp (extendedKeyUsage_oid, extnID, extnID_size) == 0)
{
err = verify_extended_key_usage (value, value_size);
if (err != GRUB_ERR_NONE)
goto cleanup_value;
extended_usage_present++;
}
else if (grub_strncmp ("TRUE", critical, critical_size) == 0)
{
/*
* Per the RFC, we must not process a certificate with a critical
* extension we do not understand.
*/
err = grub_error (GRUB_ERR_BAD_FILE_TYPE,
"unhandled critical x509 extension with OID %s", extnID);
goto cleanup_value;
}
grub_free (value);
grub_free (value_path);
grub_free (critical_path);
grub_free (oid_path);
}
if (usage_present != 1)
return grub_error (GRUB_ERR_BAD_FILE_TYPE,
"unexpected number of Key Usage extensions - expected 1, got %d",
usage_present);
if (constraints_present != 1)
return grub_error (GRUB_ERR_BAD_FILE_TYPE,
"unexpected number of basic constraints extensions - expected 1, got %d",
constraints_present);
if (extended_usage_present > 1)
return grub_error (GRUB_ERR_BAD_FILE_TYPE,
"unexpected number of Extended Key Usage extensions - expected 0 or 1, got %d",
extended_usage_present);
return GRUB_ERR_NONE;
cleanup_value:
grub_free (value);
cleanup_value_path:
grub_free (value_path);
cleanup_critical_path:
grub_free (critical_path);
cleanup_oid_path:
grub_free (oid_path);
return err;
}
static void
add_cert_fingerprint (const void *data, const grub_size_t data_size,
grub_x509_cert_t *const cert)
{
/* Add SHA256 hash of certificate. */
grub_crypto_hash ((gcry_md_spec_t *) &_gcry_digest_spec_sha256,
&cert->fingerprint[GRUB_FINGERPRINT_SHA256], data, data_size);
/* Add SHA384 hash of certificate. */
grub_crypto_hash ((gcry_md_spec_t *) &_gcry_digest_spec_sha384,
&cert->fingerprint[GRUB_FINGERPRINT_SHA384], data, data_size);
/* Add SHA512 hash of certificate. */
grub_crypto_hash ((gcry_md_spec_t *) &_gcry_digest_spec_sha512,
&cert->fingerprint[GRUB_FINGERPRINT_SHA512], data, data_size);
}
/*
* Parse a certificate whose DER-encoded form is in @data, of size @data_size.
* Return the results in @results, which must point to an allocated x509
* certificate.
*/
grub_err_t
grub_x509_cert_parse (const void *data, grub_size_t data_size, grub_x509_cert_t *results)
{
grub_int32_t result = 0;
asn1_node cert;
grub_err_t err;
grub_int32_t tmp_size;
grub_int32_t size = (grub_int32_t) data_size;
if (data_size > GRUB_UINT_MAX)
return grub_error (GRUB_ERR_OUT_OF_RANGE,
"cannot parse a certificate where data size > GRUB_UINT_MAX");
result = asn1_create_element (grub_gnutls_pkix_asn, "PKIX1.Certificate", &cert);
if (result != ASN1_SUCCESS)
return grub_error (GRUB_ERR_OUT_OF_MEMORY,
"could not create ASN.1 structure for certificate: %s",
asn1_strerror (result));
result = asn1_der_decoding2 (&cert, data, &size, ASN1_DECODE_FLAG_STRICT_DER, asn1_error);
if (result != ASN1_SUCCESS)
{
err = grub_error (GRUB_ERR_BAD_FILE_TYPE,
"could not parse DER for certificate: %s", asn1_error);
goto cleanup;
}
/*
* TBSCertificate ::= SEQUENCE {
* version [0] EXPLICIT Version DEFAULT v1
*/
err = check_version (cert, results);
if (err != GRUB_ERR_NONE)
goto cleanup;
/*
* serialNumber CertificateSerialNumber,
*
* CertificateSerialNumber ::= INTEGER
*/
results->serial = grub_asn1_allocate_and_read (cert, "tbsCertificate.serialNumber",
"certificate serial number", &tmp_size);
if (results->serial == NULL)
{
err = grub_errno;
goto cleanup;
}
/*
* It's safe to cast the signed int to an unsigned here, we know
* length is non-negative.
*/
results->serial_len = tmp_size;
/*
* signature AlgorithmIdentifier,
*
* We don't load the signature or issuer at the moment,
* as we don't attempt x509 verification.
*/
/*
* validity Validity,
*
* Validity ::= SEQUENCE {
* notBefore Time,
* notAfter Time }
*
* We can't validate this reasonably, we have no true time source on several
* platforms. For now we do not parse them.
*/
/*
* issuer Name,
*
* This is an X501 name, we parse out just the issuer.
*/
err = read_name (cert, "tbsCertificate.issuer", &results->issuer, &results->issuer_len);
if (err != GRUB_ERR_NONE)
goto cleanup_serial;
/*
* subject Name,
*
* This is an X501 name, we parse out just the CN.
*/
err = read_name (cert, "tbsCertificate.subject", &results->subject, &results->subject_len);
if (err != GRUB_ERR_NONE)
goto cleanup_issuer;
/*
* TBSCertificate ::= SEQUENCE {
* ...
* subjectPublicKeyInfo SubjectPublicKeyInfo,
* ...
*/
err = grub_x509_read_subject_public_key (cert, results);
if (err != GRUB_ERR_NONE)
goto cleanup_name;
/*
* TBSCertificate ::= SEQUENCE {
* ...
* extensions [3] EXPLICIT Extensions OPTIONAL
* -- If present, version MUST be v3
* }
*/
err = verify_extensions (cert);
if (err != GRUB_ERR_NONE)
goto cleanup_mpis;
/*
* We do not read or check the signature on the certificate:
* as discussed we do not try to validate the certificate but trust
* it implictly.
*/
asn1_delete_structure (&cert);
/* Add the fingerprint of the certificate. */
add_cert_fingerprint (data, data_size, results);
return GRUB_ERR_NONE;
cleanup_mpis:
_gcry_mpi_release (results->mpis[GRUB_RSA_PK_MODULUS]);
_gcry_mpi_release (results->mpis[GRUB_RSA_PK_EXPONENT]);
cleanup_name:
grub_free (results->subject);
cleanup_issuer:
grub_free (results->issuer);
cleanup_serial:
grub_free (results->serial);
cleanup:
asn1_delete_structure (&cert);
return err;
}
/*
* Release all the storage associated with the x509 certificate. If the caller
* dynamically allocated the certificate, it must free it. The caller is also
* responsible for maintenance of the linked list.
*/
void
grub_x509_cert_release (grub_x509_cert_t *cert)
{
grub_free (cert->issuer);
grub_free (cert->subject);
grub_free (cert->serial);
_gcry_mpi_release (cert->mpis[GRUB_RSA_PK_MODULUS]);
_gcry_mpi_release (cert->mpis[GRUB_RSA_PK_EXPONENT]);
}
Reference in New Issue View Git Blame Copy Permalink