cms.c

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/*
 * Copyright (C) 2012 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program 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 2 of the
 * License, or any later version.
 *
 * This program 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 this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 *
 * You can also choose to distribute this program under the terms of
 * the Unmodified Binary Distribution Licence (as given in the file
 * COPYING.UBDL), provided that you have satisfied its requirements.
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

/** @file
 *
 * Cryptographic Message Syntax (PKCS #7)
 *
 * The format of CMS messages is defined in RFC 5652.
 *
 */

#include <stdint.h>
#include <string.h>
#include <time.h>
#include <errno.h>
#include <ipxe/asn1.h>
#include <ipxe/x509.h>
#include <ipxe/malloc.h>
#include <ipxe/uaccess.h>
#include <ipxe/cms.h>

/* Disambiguate the various error causes */
#define EACCES_NON_SIGNING \
        __einfo_error ( EINFO_EACCES_NON_SIGNING )
#define EINFO_EACCES_NON_SIGNING \
        __einfo_uniqify ( EINFO_EACCES, 0x01, "Not a signing certificate" )
#define EACCES_NON_CODE_SIGNING \
        __einfo_error ( EINFO_EACCES_NON_CODE_SIGNING )
#define EINFO_EACCES_NON_CODE_SIGNING \
        __einfo_uniqify ( EINFO_EACCES, 0x02, "Not a code-signing certificate" )
#define EACCES_WRONG_NAME \
        __einfo_error ( EINFO_EACCES_WRONG_NAME )
#define EINFO_EACCES_WRONG_NAME \
        __einfo_uniqify ( EINFO_EACCES, 0x04, "Incorrect certificate name" )
#define EACCES_NO_SIGNATURES \
        __einfo_error ( EINFO_EACCES_NO_SIGNATURES )
#define EINFO_EACCES_NO_SIGNATURES \
        __einfo_uniqify ( EINFO_EACCES, 0x05, "No signatures present" )
#define EINVAL_DIGEST \
        __einfo_error ( EINFO_EINVAL_DIGEST )
#define EINFO_EINVAL_DIGEST \
        __einfo_uniqify ( EINFO_EINVAL, 0x01, "Not a digest algorithm" )
#define EINVAL_PUBKEY \
        __einfo_error ( EINFO_EINVAL_PUBKEY )
#define EINFO_EINVAL_PUBKEY \
        __einfo_uniqify ( EINFO_EINVAL, 0x02, "Not a public-key algorithm" )
#define ENOTSUP_SIGNEDDATA \
        __einfo_error ( EINFO_ENOTSUP_SIGNEDDATA )
#define EINFO_ENOTSUP_SIGNEDDATA \
        __einfo_uniqify ( EINFO_ENOTSUP, 0x01, "Not a digital signature" )

/** "pkcs7-signedData" object identifier */
static uint8_t oid_signeddata[] = { ASN1_OID_SIGNEDDATA };

/** "pkcs7-signedData" object identifier cursor */
static struct asn1_cursor oid_signeddata_cursor =
        ASN1_CURSOR ( oid_signeddata );

/**
 * Parse CMS signature content type
 *
 * @v sig               CMS signature
 * @v raw               ASN.1 cursor
 * @ret rc              Return status code
 */
static int cms_parse_content_type ( struct cms_signature *sig,
                                    const struct asn1_cursor *raw ) {
        struct asn1_cursor cursor;

        /* Enter contentType */
        memcpy ( &cursor, raw, sizeof ( cursor ) );
        asn1_enter ( &cursor, ASN1_OID );

        /* Check OID is pkcs7-signedData */
        if ( asn1_compare ( &cursor, &oid_signeddata_cursor ) != 0 ) {
                DBGC ( sig, "CMS %p does not contain signedData:\n", sig );
                DBGC_HDA ( sig, 0, raw->data, raw->len );
                return -ENOTSUP_SIGNEDDATA;
        }

        DBGC ( sig, "CMS %p contains signedData\n", sig );
        return 0;
}

/**
 * Parse CMS signature certificate list
 *
 * @v sig               CMS signature
 * @v raw               ASN.1 cursor
 * @ret rc              Return status code
 */
static int cms_parse_certificates ( struct cms_signature *sig,
                                    const struct asn1_cursor *raw ) {
        struct asn1_cursor cursor;
        struct x509_certificate *cert;
        int rc;

        /* Enter certificates */
        memcpy ( &cursor, raw, sizeof ( cursor ) );
        asn1_enter ( &cursor, ASN1_EXPLICIT_TAG ( 0 ) );

        /* Add each certificate */
        while ( cursor.len ) {

                /* Add certificate to chain */
                if ( ( rc = x509_append_raw ( sig->certificates, cursor.data,
                                              cursor.len ) ) != 0 ) {
                        DBGC ( sig, "CMS %p could not append certificate: %s\n",
                               sig, strerror ( rc) );
                        DBGC_HDA ( sig, 0, cursor.data, cursor.len );
                        return rc;
                }
                cert = x509_last ( sig->certificates );
                DBGC ( sig, "CMS %p found certificate %s\n",
                       sig, x509_name ( cert ) );

                /* Move to next certificate */
                asn1_skip_any ( &cursor );
        }

        return 0;
}

/**
 * Identify CMS signature certificate by issuer and serial number
 *
 * @v sig               CMS signature
 * @v issuer            Issuer
 * @v serial            Serial number
 * @ret cert            X.509 certificate, or NULL if not found
 */
static struct x509_certificate *
cms_find_issuer_serial ( struct cms_signature *sig,
                         const struct asn1_cursor *issuer,
                         const struct asn1_cursor *serial ) {
        struct x509_link *link;
        struct x509_certificate *cert;

        /* Scan through certificate list */
        list_for_each_entry ( link, &sig->certificates->links, list ) {

                /* Check issuer and serial number */
                cert = link->cert;
                if ( ( asn1_compare ( issuer, &cert->issuer.raw ) == 0 ) &&
                     ( asn1_compare ( serial, &cert->serial.raw ) == 0 ) )
                        return cert;
        }

        return NULL;
}

/**
 * Parse CMS signature signer identifier
 *
 * @v sig               CMS signature
 * @v info              Signer information to fill in
 * @v raw               ASN.1 cursor
 * @ret rc              Return status code
 */
static int cms_parse_signer_identifier ( struct cms_signature *sig,
                                         struct cms_signer_info *info,
                                         const struct asn1_cursor *raw ) {
        struct asn1_cursor cursor;
        struct asn1_cursor serial;
        struct asn1_cursor issuer;
        struct x509_certificate *cert;
        int rc;

        /* Enter issuerAndSerialNumber */
        memcpy ( &cursor, raw, sizeof ( cursor ) );
        asn1_enter ( &cursor, ASN1_SEQUENCE );

        /* Identify issuer */
        memcpy ( &issuer, &cursor, sizeof ( issuer ) );
        if ( ( rc = asn1_shrink ( &issuer, ASN1_SEQUENCE ) ) != 0 ) {
                DBGC ( sig, "CMS %p/%p could not locate issuer: %s\n",
                       sig, info, strerror ( rc ) );
                DBGC_HDA ( sig, 0, raw->data, raw->len );
                return rc;
        }
        DBGC ( sig, "CMS %p/%p issuer is:\n", sig, info );
        DBGC_HDA ( sig, 0, issuer.data, issuer.len );
        asn1_skip_any ( &cursor );

        /* Identify serialNumber */
        memcpy ( &serial, &cursor, sizeof ( serial ) );
        if ( ( rc = asn1_shrink ( &serial, ASN1_INTEGER ) ) != 0 ) {
                DBGC ( sig, "CMS %p/%p could not locate serialNumber: %s\n",
                       sig, info, strerror ( rc ) );
                DBGC_HDA ( sig, 0, raw->data, raw->len );
                return rc;
        }
        DBGC ( sig, "CMS %p/%p serial number is:\n", sig, info );
        DBGC_HDA ( sig, 0, serial.data, serial.len );

        /* Identify certificate */
        cert = cms_find_issuer_serial ( sig, &issuer, &serial );
        if ( ! cert ) {
                DBGC ( sig, "CMS %p/%p could not identify signer's "
                       "certificate\n", sig, info );
                return -ENOENT;
        }

        /* Append certificate to chain */
        if ( ( rc = x509_append ( info->chain, cert ) ) != 0 ) {
                DBGC ( sig, "CMS %p/%p could not append certificate: %s\n",
                       sig, info, strerror ( rc ) );
                return rc;
        }

        /* Append remaining certificates to chain */
        if ( ( rc = x509_auto_append ( info->chain,
                                       sig->certificates ) ) != 0 ) {
                DBGC ( sig, "CMS %p/%p could not append certificates: %s\n",
                       sig, info, strerror ( rc ) );
                return rc;
        }

        return 0;
}

/**
 * Parse CMS signature digest algorithm
 *
 * @v sig               CMS signature
 * @v info              Signer information to fill in
 * @v raw               ASN.1 cursor
 * @ret rc              Return status code
 */
static int cms_parse_digest_algorithm ( struct cms_signature *sig,
                                        struct cms_signer_info *info,
                                        const struct asn1_cursor *raw ) {
        struct asn1_algorithm *algorithm;
        int rc;

        /* Identify algorithm */
        if ( ( rc = asn1_digest_algorithm ( raw, &algorithm ) ) != 0 ) {
                DBGC ( sig, "CMS %p/%p could not identify digest algorithm: "
                       "%s\n", sig, info, strerror ( rc ) );
                DBGC_HDA ( sig, 0, raw->data, raw->len );
                return rc;
        }

        /* Record digest algorithm */
        info->digest = algorithm->digest;
        DBGC ( sig, "CMS %p/%p digest algorithm is %s\n",
               sig, info, algorithm->name );

        return 0;
}

/**
 * Parse CMS signature algorithm
 *
 * @v sig               CMS signature
 * @v info              Signer information to fill in
 * @v raw               ASN.1 cursor
 * @ret rc              Return status code
 */
static int cms_parse_signature_algorithm ( struct cms_signature *sig,
                                           struct cms_signer_info *info,
                                           const struct asn1_cursor *raw ) {
        struct asn1_algorithm *algorithm;
        int rc;

        /* Identify algorithm */
        if ( ( rc = asn1_pubkey_algorithm ( raw, &algorithm ) ) != 0 ) {
                DBGC ( sig, "CMS %p/%p could not identify public-key "
                       "algorithm: %s\n", sig, info, strerror ( rc ) );
                DBGC_HDA ( sig, 0, raw->data, raw->len );
                return rc;
        }

        /* Record signature algorithm */
        info->pubkey = algorithm->pubkey;
        DBGC ( sig, "CMS %p/%p public-key algorithm is %s\n",
               sig, info, algorithm->name );

        return 0;
}

/**
 * Parse CMS signature value
 *
 * @v sig               CMS signature
 * @v info              Signer information to fill in
 * @v raw               ASN.1 cursor
 * @ret rc              Return status code
 */
static int cms_parse_signature_value ( struct cms_signature *sig,
                                       struct cms_signer_info *info,
                                       const struct asn1_cursor *raw ) {
        struct asn1_cursor cursor;
        int rc;

        /* Enter signature */
        memcpy ( &cursor, raw, sizeof ( cursor ) );
        if ( ( rc = asn1_enter ( &cursor, ASN1_OCTET_STRING ) ) != 0 ) {
                DBGC ( sig, "CMS %p/%p could not locate signature:\n",
                       sig, info );
                DBGC_HDA ( sig, 0, raw->data, raw->len );
                return rc;
        }

        /* Record signature */
        info->signature_len = cursor.len;
        info->signature = malloc ( info->signature_len );
        if ( ! info->signature )
                return -ENOMEM;
        memcpy ( info->signature, cursor.data, info->signature_len );
        DBGC ( sig, "CMS %p/%p signature value is:\n", sig, info );
        DBGC_HDA ( sig, 0, info->signature, info->signature_len );

        return 0;
}

/**
 * Parse CMS signature signer information
 *
 * @v sig               CMS signature
 * @v info              Signer information to fill in
 * @v raw               ASN.1 cursor
 * @ret rc              Return status code
 */
static int cms_parse_signer_info ( struct cms_signature *sig,
                                   struct cms_signer_info *info,
                                   const struct asn1_cursor *raw ) {
        struct asn1_cursor cursor;
        int rc;

        /* Enter signerInfo */
        memcpy ( &cursor, raw, sizeof ( cursor ) );
        asn1_enter ( &cursor, ASN1_SEQUENCE );

        /* Skip version */
        asn1_skip ( &cursor, ASN1_INTEGER );

        /* Parse sid */
        if ( ( rc = cms_parse_signer_identifier ( sig, info, &cursor ) ) != 0 )
                return rc;
        asn1_skip_any ( &cursor );

        /* Parse digestAlgorithm */
        if ( ( rc = cms_parse_digest_algorithm ( sig, info, &cursor ) ) != 0 )
                return rc;
        asn1_skip_any ( &cursor );

        /* Skip signedAttrs, if present */
        asn1_skip_if_exists ( &cursor, ASN1_EXPLICIT_TAG ( 0 ) );

        /* Parse signatureAlgorithm */
        if ( ( rc = cms_parse_signature_algorithm ( sig, info, &cursor ) ) != 0)
                return rc;
        asn1_skip_any ( &cursor );

        /* Parse signature */
        if ( ( rc = cms_parse_signature_value ( sig, info, &cursor ) ) != 0 )
                return rc;

        return 0;
}

/**
 * Parse CMS signature from ASN.1 data
 *
 * @v sig               CMS signature
 * @v raw               ASN.1 cursor
 * @ret rc              Return status code
 */
static int cms_parse ( struct cms_signature *sig,
                       const struct asn1_cursor *raw ) {
        struct asn1_cursor cursor;
        struct cms_signer_info *info;
        int rc;

        /* Enter contentInfo */
        memcpy ( &cursor, raw, sizeof ( cursor ) );
        asn1_enter ( &cursor, ASN1_SEQUENCE );

        /* Parse contentType */

        if ( ( rc = cms_parse_content_type ( sig, &cursor ) ) != 0 )
                return rc;
        asn1_skip_any ( &cursor );

        /* Enter content */
        asn1_enter ( &cursor, ASN1_EXPLICIT_TAG ( 0 ) );

        /* Enter signedData */
        asn1_enter ( &cursor, ASN1_SEQUENCE );

        /* Skip version */
        asn1_skip ( &cursor, ASN1_INTEGER );

        /* Skip digestAlgorithms */
        asn1_skip ( &cursor, ASN1_SET );

        /* Skip encapContentInfo */
        asn1_skip ( &cursor, ASN1_SEQUENCE );

        /* Parse certificates */
        if ( ( rc = cms_parse_certificates ( sig, &cursor ) ) != 0 )
                return rc;
        asn1_skip_any ( &cursor );

        /* Skip crls, if present */
        asn1_skip_if_exists ( &cursor, ASN1_EXPLICIT_TAG ( 1 ) );

        /* Enter signerInfos */
        asn1_enter ( &cursor, ASN1_SET );

        /* Add each signerInfo.  Errors are handled by ensuring that
         * cms_put() will always be able to free any allocated memory.
         */
        while ( cursor.len ) {

                /* Allocate signer information block */
                info = zalloc ( sizeof ( *info ) );
                if ( ! info )
                        return -ENOMEM;
                list_add ( &info->list, &sig->info );

                /* Allocate certificate chain */
                info->chain = x509_alloc_chain();
                if ( ! info->chain )
                        return -ENOMEM;

                /* Parse signerInfo */
                if ( ( rc = cms_parse_signer_info ( sig, info,
                                                    &cursor ) ) != 0 )
                        return rc;
                asn1_skip_any ( &cursor );
        }

        return 0;
}

/**
 * Free CMS signature
 *
 * @v refcnt            Reference count
 */
static void cms_free ( struct refcnt *refcnt ) {
        struct cms_signature *sig =
                container_of ( refcnt, struct cms_signature, refcnt );
        struct cms_signer_info *info;
        struct cms_signer_info *tmp;

        list_for_each_entry_safe ( info, tmp, &sig->info, list ) {
                list_del ( &info->list );
                x509_chain_put ( info->chain );
                free ( info->signature );
                free ( info );
        }
        x509_chain_put ( sig->certificates );
        free ( sig );
}

/**
 * Create CMS signature
 *
 * @v data              Raw signature data
 * @v len               Length of raw data
 * @ret sig             CMS signature
 * @ret rc              Return status code
 *
 * On success, the caller holds a reference to the CMS signature, and
 * is responsible for ultimately calling cms_put().
 */
int cms_signature ( const void *data, size_t len, struct cms_signature **sig ) {
        struct asn1_cursor cursor;
        int rc;

        /* Allocate and initialise signature */
        *sig = zalloc ( sizeof ( **sig ) );
        if ( ! *sig ) {
                rc = -ENOMEM;
                goto err_alloc;
        }
        ref_init ( &(*sig)->refcnt, cms_free );
        INIT_LIST_HEAD ( &(*sig)->info );

        /* Allocate certificate list */
        (*sig)->certificates = x509_alloc_chain();
        if ( ! (*sig)->certificates ) {
                rc = -ENOMEM;
                goto err_alloc_chain;
        }

        /* Initialise cursor */
        cursor.data = data;
        cursor.len = len;
        asn1_shrink_any ( &cursor );

        /* Parse signature */
        if ( ( rc = cms_parse ( *sig, &cursor ) ) != 0 )
                goto err_parse;

        return 0;

 err_parse:
 err_alloc_chain:
        cms_put ( *sig );
 err_alloc:
        return rc;
}

/**
 * Calculate digest of CMS-signed data
 *
 * @v sig               CMS signature
 * @v info              Signer information
 * @v data              Signed data
 * @v len               Length of signed data
 * @v out               Digest output
 */
static void cms_digest ( struct cms_signature *sig,
                         struct cms_signer_info *info,
                         userptr_t data, size_t len, void *out ) {
        struct digest_algorithm *digest = info->digest;
        uint8_t ctx[ digest->ctxsize ];
        uint8_t block[ digest->blocksize ];
        size_t offset = 0;
        size_t frag_len;

        /* Initialise digest */
        digest_init ( digest, ctx );

        /* Process data one block at a time */
        while ( len ) {
                frag_len = len;
                if ( frag_len > sizeof ( block ) )
                        frag_len = sizeof ( block );
                copy_from_user ( block, data, offset, frag_len );
                digest_update ( digest, ctx, block, frag_len );
                offset += frag_len;
                len -= frag_len;
        }

        /* Finalise digest */
        digest_final ( digest, ctx, out );

        DBGC ( sig, "CMS %p/%p digest value:\n", sig, info );
        DBGC_HDA ( sig, 0, out, digest->digestsize );
}

/**
 * Verify digest of CMS-signed data
 *
 * @v sig               CMS signature
 * @v info              Signer information
 * @v cert              Corresponding certificate
 * @v data              Signed data
 * @v len               Length of signed data
 * @ret rc              Return status code
 */
static int cms_verify_digest ( struct cms_signature *sig,
                               struct cms_signer_info *info,
                               struct x509_certificate *cert,
                               userptr_t data, size_t len ) {
        struct digest_algorithm *digest = info->digest;
        struct pubkey_algorithm *pubkey = info->pubkey;
        struct x509_public_key *public_key = &cert->subject.public_key;
        uint8_t digest_out[ digest->digestsize ];
        uint8_t ctx[ pubkey->ctxsize ];
        int rc;

        /* Generate digest */
        cms_digest ( sig, info, data, len, digest_out );

        /* Initialise public-key algorithm */
        if ( ( rc = pubkey_init ( pubkey, ctx, public_key->raw.data,
                                  public_key->raw.len ) ) != 0 ) {
                DBGC ( sig, "CMS %p/%p could not initialise public key: %s\n",
                       sig, info, strerror ( rc ) );
                goto err_init;
        }

        /* Verify digest */
        if ( ( rc = pubkey_verify ( pubkey, ctx, digest, digest_out,
                                    info->signature,
                                    info->signature_len ) ) != 0 ) {
                DBGC ( sig, "CMS %p/%p signature verification failed: %s\n",
                       sig, info, strerror ( rc ) );
                goto err_verify;
        }

 err_verify:
        pubkey_final ( pubkey, ctx );
 err_init:
        return rc;
}

/**
 * Verify CMS signature signer information
 *
 * @v sig               CMS signature
 * @v info              Signer information
 * @v data              Signed data
 * @v len               Length of signed data
 * @v time              Time at which to validate certificates
 * @v store             Certificate store, or NULL to use default
 * @v root              Root certificate list, or NULL to use default
 * @ret rc              Return status code
 */
static int cms_verify_signer_info ( struct cms_signature *sig,
                                    struct cms_signer_info *info,
                                    userptr_t data, size_t len,
                                    time_t time, struct x509_chain *store,
                                    struct x509_root *root ) {
        struct x509_certificate *cert;
        int rc;

        /* Validate certificate chain */
        if ( ( rc = x509_validate_chain ( info->chain, time, store,
                                          root ) ) != 0 ) {
                DBGC ( sig, "CMS %p/%p could not validate chain: %s\n",
                       sig, info, strerror ( rc ) );
                return rc;
        }

        /* Extract code-signing certificate */
        cert = x509_first ( info->chain );
        assert ( cert != NULL );

        /* Check that certificate can create digital signatures */
        if ( ! ( cert->extensions.usage.bits & X509_DIGITAL_SIGNATURE ) ) {
                DBGC ( sig, "CMS %p/%p certificate cannot create signatures\n",
                       sig, info );
                return -EACCES_NON_SIGNING;
        }

        /* Check that certificate can sign code */
        if ( ! ( cert->extensions.ext_usage.bits & X509_CODE_SIGNING ) ) {
                DBGC ( sig, "CMS %p/%p certificate is not code-signing\n",
                       sig, info );
                return -EACCES_NON_CODE_SIGNING;
        }

        /* Verify digest */
        if ( ( rc = cms_verify_digest ( sig, info, cert, data, len ) ) != 0 )
                return rc;

        return 0;
}

/**
 * Verify CMS signature
 *
 * @v sig               CMS signature
 * @v data              Signed data
 * @v len               Length of signed data
 * @v name              Required common name, or NULL to check all signatures
 * @v time              Time at which to validate certificates
 * @v store             Certificate store, or NULL to use default
 * @v root              Root certificate list, or NULL to use default
 * @ret rc              Return status code
 */
int cms_verify ( struct cms_signature *sig, userptr_t data, size_t len,
                 const char *name, time_t time, struct x509_chain *store,
                 struct x509_root *root ) {
        struct cms_signer_info *info;
        struct x509_certificate *cert;
        int count = 0;
        int rc;

        /* Verify using all signerInfos */
        list_for_each_entry ( info, &sig->info, list ) {
                cert = x509_first ( info->chain );
                if ( name && ( x509_check_name ( cert, name ) != 0 ) )
                        continue;
                if ( ( rc = cms_verify_signer_info ( sig, info, data, len, time,
                                                     store, root ) ) != 0 )
                        return rc;
                count++;
        }

        /* Check that we have verified at least one signature */
        if ( count == 0 ) {
                if ( name ) {
                        DBGC ( sig, "CMS %p had no signatures matching name "
                               "%s\n", sig, name );
                        return -EACCES_WRONG_NAME;
                } else {
                        DBGC ( sig, "CMS %p had no signatures\n", sig );
                        return -EACCES_NO_SIGNATURES;
                }
        }

        return 0;
}