helpers.c

/*
 * osslsigncode support library
 *
 * Copyright (C) 2021-2023 Michał Trojnara <Michal.Trojnara@stunnel.org>
 * Author: Małgorzata Olszówka <Malgorzata.Olszowka@stunnel.org>
 */

#include "osslsigncode.h"
#include "helpers.h"

/* Prototypes */
static int pkcs7_set_content_blob(PKCS7 *sig, PKCS7 *cursig);
static SpcSpOpusInfo *spc_sp_opus_info_create(FILE_FORMAT_CTX *ctx);
static int spc_indirect_data_content_get(u_char **blob, int *len, FILE_FORMAT_CTX *ctx);
static int pkcs7_set_spc_indirect_data_content(PKCS7 *p7, BIO *hash, u_char *buf, int len);
static int pkcs7_signer_info_add_spc_sp_opus_info(PKCS7_SIGNER_INFO *si, FILE_FORMAT_CTX *ctx);
static int pkcs7_signer_info_add_purpose(PKCS7_SIGNER_INFO *si, FILE_FORMAT_CTX *ctx);

/*
 * Common functions
 */

/*
 * [in] infile
 * [returns] file size
 */
uint32_t get_file_size(const char *infile)
{
    int ret;
#ifdef _WIN32
    struct _stat64 st;
    ret = _stat64(infile, &st);
#else
    struct stat st;
    ret = stat(infile, &st);
#endif
    if (ret) {
        printf("Failed to open file: %s\n", infile);
        return 0;
    }

    if (st.st_size < 4) {
        printf("Unrecognized file type - file is too short: %s\n", infile);
        return 0;
    }
    if (st.st_size > UINT32_MAX) {
        printf("Unsupported file - too large: %s\n", infile);
        return 0;
    }
    return (uint32_t)st.st_size;
}

/*
 * [in] infile: starting address for the new mapping
 * [returns] pointer to the mapped area
 */
char *map_file(const char *infile, const size_t size)
{
    char *indata = NULL;
#ifdef WIN32
    HANDLE fhandle, fmap;
    (void)size;
    fhandle = CreateFile(infile, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_EXISTING, 0, NULL);
    if (fhandle == INVALID_HANDLE_VALUE) {
        return NULL;
    }
    fmap = CreateFileMapping(fhandle, NULL, PAGE_READONLY, 0, 0, NULL);
    CloseHandle(fhandle);
    if (fmap == NULL) {
        return NULL;
    }
    indata = (char *)MapViewOfFile(fmap, FILE_MAP_READ, 0, 0, 0);
    CloseHandle(fmap);
#else
#ifdef HAVE_SYS_MMAN_H
    int fd = open(infile, O_RDONLY);
    if (fd < 0) {
        return NULL;
    }
    indata = mmap(0, size, PROT_READ, MAP_PRIVATE, fd, 0);
    if (indata == MAP_FAILED) {
        close(fd);
        return NULL;
    }
    close(fd);
#else
    printf("No file mapping function\n");
    return NULL;
#endif /* HAVE_SYS_MMAN_H */
#endif /* WIN32 */
    return indata;
}

/*
 * [in] indata: starting address space
 * [in] size: mapped area length
 * [returns] none
 */
void unmap_file(char *indata, const size_t size)
{
    if (!indata)
        return;
#ifdef WIN32
    (void)size;
    UnmapViewOfFile(indata);
#else
    munmap(indata, size);
#endif /* WIN32 */
}

/*
 * [in, out] si: PKCS7_SIGNER_INFO structure
 * [in] ctx: FILE_FORMAT_CTX structure
 * [returns] 0 on error or 1 on success
 */
static int pkcs7_signer_info_add_spc_sp_opus_info(PKCS7_SIGNER_INFO *si, FILE_FORMAT_CTX *ctx)
{
    SpcSpOpusInfo *opus;
    ASN1_STRING *astr;
    int len;
    u_char *p = NULL;

    opus = spc_sp_opus_info_create(ctx);
    if ((len = i2d_SpcSpOpusInfo(opus, NULL)) <= 0
        || (p = OPENSSL_malloc((size_t)len)) == NULL) {
        SpcSpOpusInfo_free(opus);
        return 0; /* FAILED */
    }
    i2d_SpcSpOpusInfo(opus, &p);
    p -= len;
    astr = ASN1_STRING_new();
    ASN1_STRING_set(astr, p, len);
    OPENSSL_free(p);
    SpcSpOpusInfo_free(opus);
    return PKCS7_add_signed_attribute(si, OBJ_txt2nid(SPC_SP_OPUS_INFO_OBJID),
            V_ASN1_SEQUENCE, astr);
}

/*
 * [in, out] si: PKCS7_SIGNER_INFO structure
 * [in] ctx: structure holds input and output data
 * [returns] 0 on error or 1 on success
 */
static int pkcs7_signer_info_add_purpose(PKCS7_SIGNER_INFO *si, FILE_FORMAT_CTX *ctx)
{
    static const u_char purpose_ind[] = {
        0x30, 0x0c, 0x06, 0x0a, 0x2b, 0x06, 0x01, 0x04,
        0x01, 0x82, 0x37, 0x02, 0x01, 0x15
    };
    static const u_char purpose_comm[] = {
        0x30, 0x0c, 0x06, 0x0a, 0x2b, 0x06, 0x01, 0x04,
        0x01, 0x82, 0x37, 0x02, 0x01, 0x16
    };
    ASN1_STRING *purpose = ASN1_STRING_new();

    if (ctx->options->comm) {
        ASN1_STRING_set(purpose, purpose_comm, sizeof purpose_comm);
    } else {
        ASN1_STRING_set(purpose, purpose_ind, sizeof purpose_ind);
    }
    return PKCS7_add_signed_attribute(si, OBJ_txt2nid(SPC_STATEMENT_TYPE_OBJID),
            V_ASN1_SEQUENCE, purpose);
}

/*
 * Add a custom, non-trusted time to the PKCS7 structure to prevent OpenSSL
 * adding the _current_ time. This allows to create a deterministic signature
 * when no trusted timestamp server was specified, making osslsigncode
 * behaviour closer to signtool.exe (which doesn't include any non-trusted
 * time in this case.)
 * [in, out] si: PKCS7_SIGNER_INFO structure
 * [in] ctx: structure holds input and output data
 * [returns] 0 on error or 1 on success
 */
int pkcs7_signer_info_add_signing_time(PKCS7_SIGNER_INFO *si, FILE_FORMAT_CTX *ctx)
{
    if (ctx->options->time == INVALID_TIME) /* -time option was not specified */
        return 1; /* SUCCESS */
    return PKCS7_add_signed_attribute(si, NID_pkcs9_signingTime, V_ASN1_UTCTIME,
        ASN1_TIME_adj(NULL, ctx->options->time, 0, 0));
}

/*
 * Retrieve a decoded PKCS#7 structure corresponding to the signature
 * stored in the "sigin" file
 * CMD_ATTACH command specific
 * [in] ctx: structure holds input and output data
 * [returns] pointer to PKCS#7 structure
 */
PKCS7 *pkcs7_get_sigfile(FILE_FORMAT_CTX *ctx)
{
    PKCS7 *p7 = NULL;
    uint32_t filesize;
    char *indata;
    BIO *bio;
    const char pemhdr[] = "-----BEGIN PKCS7-----";

    filesize = get_file_size(ctx->options->sigfile);
    if (!filesize) {
        return NULL; /* FAILED */
    }
    indata = map_file(ctx->options->sigfile, filesize);
    if (!indata) {
        printf("Failed to open file: %s\n", ctx->options->sigfile);
        return NULL; /* FAILED */
    }
    bio = BIO_new_mem_buf(indata, (int)filesize);
    if (filesize >= sizeof pemhdr && !memcmp(indata, pemhdr, sizeof pemhdr - 1)) {
        /* PEM format */
        p7 = PEM_read_bio_PKCS7(bio, NULL, NULL, NULL);
    } else { /* DER format */
        p7 = d2i_PKCS7_bio(bio, NULL);
    }
    BIO_free_all(bio);
    unmap_file(indata, filesize);
    return p7;
}

/*
 * Allocate, set type, add content and return a new PKCS#7 signature
 * [in] ctx: structure holds input and output data
 * [returns] pointer to PKCS#7 structure
 */
PKCS7 *pkcs7_create(FILE_FORMAT_CTX *ctx)
{
    int i, signer = -1;
    PKCS7 *p7;
    PKCS7_SIGNER_INFO *si = NULL;

    p7 = PKCS7_new();
    PKCS7_set_type(p7, NID_pkcs7_signed);

    if (ctx->options->cert != NULL) {
        /*
         * the private key and corresponding certificate are parsed from the PKCS12
         * structure or loaded from the security token, so we may omit to check
         * the consistency of a private key with the public key in an X509 certificate
         */
        si = PKCS7_add_signature(p7, ctx->options->cert, ctx->options->pkey,
            ctx->options->md);
        if (si == NULL)
            return NULL; /* FAILED */
    } else {
        /* find the signer's certificate located somewhere in the whole certificate chain */
        for (i=0; i<sk_X509_num(ctx->options->certs); i++) {
            X509 *signcert = sk_X509_value(ctx->options->certs, i);
            if (X509_check_private_key(signcert, ctx->options->pkey)) {
                si = PKCS7_add_signature(p7, signcert, ctx->options->pkey, ctx->options->md);
                signer = i;
                break;
            }
        }
        if (si == NULL) {
            printf("Failed to checking the consistency of a private key: %s\n",
                ctx->options->keyfile);
            printf("          with a public key in any X509 certificate: %s\n\n",
                ctx->options->certfile);
            return NULL; /* FAILED */
        }
    }
    pkcs7_signer_info_add_signing_time(si, ctx);

    if (!pkcs7_signer_info_add_purpose(si, ctx))
        return NULL; /* FAILED */

    if ((ctx->options->desc || ctx->options->url) &&
            !pkcs7_signer_info_add_spc_sp_opus_info(si, ctx)) {
        printf("Couldn't allocate memory for opus info\n");
        return NULL; /* FAILED */
    }
    PKCS7_content_new(p7, NID_pkcs7_data);

    /* add the signer's certificate */
    if (ctx->options->cert != NULL)
        PKCS7_add_certificate(p7, ctx->options->cert);
    if (signer != -1)
        PKCS7_add_certificate(p7, sk_X509_value(ctx->options->certs, signer));

    /* add the certificate chain */
    for (i=0; i<sk_X509_num(ctx->options->certs); i++) {
        if (i == signer)
            continue;
        PKCS7_add_certificate(p7, sk_X509_value(ctx->options->certs, i));
    }
    /* add all cross certificates */
    if (ctx->options->xcerts) {
        for (i=0; i<sk_X509_num(ctx->options->xcerts); i++)
            PKCS7_add_certificate(p7, sk_X509_value(ctx->options->xcerts, i));
    }
    /* add crls */
    if (ctx->options->crls) {
        for (i=0; i<sk_X509_CRL_num(ctx->options->crls); i++)
            PKCS7_add_crl(p7, sk_X509_CRL_value(ctx->options->crls, i));
    }
    return p7; /* OK */
}

/*
 * [in, out] p7: new PKCS#7 signature
 * [in] hash: message digest BIO
 * [returns] 0 on error or 1 on success
 */
int add_indirect_data_object(PKCS7 *p7, BIO *hash, FILE_FORMAT_CTX *ctx)
{
    STACK_OF(PKCS7_SIGNER_INFO) *signer_info;
    PKCS7_SIGNER_INFO *si;

    signer_info = PKCS7_get_signer_info(p7);
    if (!signer_info)
        return 0; /* FAILED */
    si = sk_PKCS7_SIGNER_INFO_value(signer_info, 0);
    if (!si)
        return 0; /* FAILED */
    if (!PKCS7_add_signed_attribute(si, NID_pkcs9_contentType,
        V_ASN1_OBJECT, OBJ_txt2obj(SPC_INDIRECT_DATA_OBJID, 1)))
        return 0; /* FAILED */
    if (!pkcs7_set_data_content(p7, hash, ctx)) {
        printf("Signing failed\n");
        return 0; /* FAILED */
    }
    return 1; /* OK */
}

/*
 * [in, out] p7: new PKCS#7 signature
 * [in] cursig: current PKCS#7 signature
 * [returns] 0 on error or 1 on success
 */
int add_ms_ctl_object(PKCS7 *p7, PKCS7 *cursig)
{
    STACK_OF(PKCS7_SIGNER_INFO) *signer_info;
    PKCS7_SIGNER_INFO *si;

    signer_info = PKCS7_get_signer_info(p7);
    if (!signer_info)
        return 0; /* FAILED */
    si = sk_PKCS7_SIGNER_INFO_value(signer_info, 0);
    if (!si)
        return 0; /* FAILED */
    if (!PKCS7_add_signed_attribute(si, NID_pkcs9_contentType,
        V_ASN1_OBJECT, OBJ_txt2obj(MS_CTL_OBJID, 1)))
        return 0; /* FAILED */
    if (!pkcs7_set_content_blob(p7, cursig)) {
        printf("Signing failed\n");
        return 0; /* FAILED */
    }
    return 1; /* OK */
}

static int pkcs7_set_content_blob(PKCS7 *sig, PKCS7 *cursig)
{
    PKCS7 *contents;
    u_char *content;
    int seqhdrlen, content_length;
    BIO *sigbio;

    contents = cursig->d.sign->contents;
    seqhdrlen = asn1_simple_hdr_len(contents->d.other->value.sequence->data,
        contents->d.other->value.sequence->length);
    content = contents->d.other->value.sequence->data + seqhdrlen;
    content_length = contents->d.other->value.sequence->length - seqhdrlen;

    if ((sigbio = PKCS7_dataInit(sig, NULL)) == NULL) {
        printf("PKCS7_dataInit failed\n");
        return 0; /* FAILED */
    }
    BIO_write(sigbio, content, content_length);
    (void)BIO_flush(sigbio);
    if (!PKCS7_dataFinal(sig, sigbio)) {
        printf("PKCS7_dataFinal failed\n");
        return 0; /* FAILED */
    }
    BIO_free_all(sigbio);
    if (!PKCS7_set_content(sig, PKCS7_dup(contents))) {
        printf("PKCS7_set_content failed\n");
        return 0; /* FAILED */
    }
    return 1; /* OK */
}

/* Return the header length (tag and length octets) of the ASN.1 type
 * [in] p: ASN.1 data
 * [in] len: ASN.1 data length
 * [returns] header length
 */
int asn1_simple_hdr_len(const u_char *p, int len)
{
    if (len <= 2 || p[0] > 0x31)
        return 0;
    return (p[1]&0x80) ? (2 + (p[1]&0x7f)) : 2;
}

/*
 * [in, out] hash: BIO with message digest method
 * [in] indata: starting address space
 * [in] idx: offset
 * [in] fileend: the length of the hashed area
 * [returns] 0 on error or 1 on success
 */
int bio_hash_data(BIO *hash, char *indata, size_t idx, size_t fileend)
{
    while (idx < fileend) {
        size_t want, written;
        want = fileend - idx;
        if (want > SIZE_64K)
            want = SIZE_64K;
        if (!BIO_write_ex(hash, indata + idx, want, &written))
            return 0; /* FAILED */
        idx += written;
    }
    return 1; /* OK */
}

/*
 * [in] descript1, descript2: descriptions
 * [in] mdbuf: message digest
 * [in] len: message digest length
 * [returns] none
 */
void print_hash(const char *descript1, const char *descript2, const u_char *mdbuf, int len)
{
    char *hexbuf = NULL;
    int size, i, j = 0;

    size = 2 * len + 1;
    hexbuf = OPENSSL_malloc((size_t)size);
    for (i = 0; i < len; i++) {
#ifdef WIN32
        j += sprintf_s(hexbuf + j, size - j, "%02X", mdbuf[i]);
#else
        j += sprintf(hexbuf + j, "%02X", mdbuf[i]);
#endif /* WIN32 */
    }
    printf("%s: %s %s\n", descript1, hexbuf, descript2);
    OPENSSL_free(hexbuf);
}

/*
 * [in] p7: new PKCS#7 signature
 * [in] objid: Microsoft OID Authenticode
 * [returns] 0 on error or 1 on success
 */
int is_content_type(PKCS7 *p7, const char *objid)
{
    ASN1_OBJECT *indir_objid;
    int ret;

    indir_objid = OBJ_txt2obj(objid, 1);
    ret = p7 && PKCS7_type_is_signed(p7) &&
        !OBJ_cmp(p7->d.sign->contents->type, indir_objid) &&
        (p7->d.sign->contents->d.other->type == V_ASN1_SEQUENCE ||
        p7->d.sign->contents->d.other->type == V_ASN1_OCTET_STRING);
    ASN1_OBJECT_free(indir_objid);
    return ret;
}

/*
 * [out] p7: new PKCS#7 signature
 * [in] hash: message digest BIO
 * [in] ctx: structure holds input and output data
 * [returns] 0 on error or 1 on success
 */
int pkcs7_set_data_content(PKCS7 *p7, BIO *hash, FILE_FORMAT_CTX *ctx)
{
    u_char *p = NULL;
    int len = 0;
    u_char *buf;

    if (!spc_indirect_data_content_get(&p, &len, ctx))
        return 0; /* FAILED */
    buf = OPENSSL_malloc(SIZE_64K);
    memcpy(buf, p, (size_t)len);
    OPENSSL_free(p);
    if (!pkcs7_set_spc_indirect_data_content(p7, hash, buf, len)) {
        OPENSSL_free(buf);
        return 0; /* FAILED */
    }
    OPENSSL_free(buf);

    return 1; /* OK */
}

/*
 * PE and CAB format specific
 * [in] none
 * [returns] pointer to SpcLink
 */
SpcLink *spc_link_obsolete_get(void)
{
    const u_char obsolete[] = {
        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
    };
    SpcLink *link = SpcLink_new();
    link->type = 2;
    link->value.file = SpcString_new();
    link->value.file->type = 0;
    link->value.file->value.unicode = ASN1_BMPSTRING_new();
    ASN1_STRING_set(link->value.file->value.unicode, obsolete, sizeof obsolete);
    return link;
}

/*
 * Retrieve a decoded PKCS#7 structure
 * [in] indata: mapped file
 * [in] sigpos: signature data offset
 * [in] siglen: signature data size
 * [returns] pointer to PKCS#7 structure
 */
PKCS7 *pkcs7_get(char *indata, uint32_t sigpos, uint32_t siglen)
{
    PKCS7 *p7 = NULL;
    const u_char *blob;

    blob = (u_char *)indata + sigpos;
    p7 = d2i_PKCS7(NULL, &blob, siglen);
    return p7;
}

/*
 * [in] mdbuf, cmdbuf: message digests
 * [in] mdtype: message digest algorithm type
 * [returns] 0 on error or 1 on success
 */
int compare_digests(u_char *mdbuf, u_char *cmdbuf, int mdtype)
{
    int mdlen = EVP_MD_size(EVP_get_digestbynid(mdtype));
    int mdok = !memcmp(mdbuf, cmdbuf, (size_t)mdlen);
    printf("Message digest algorithm  : %s\n", OBJ_nid2sn(mdtype));
    print_hash("Current message digest    ", "", mdbuf, mdlen);
    print_hash("Calculated message digest ", mdok ? "\n" : "    MISMATCH!!!\n", cmdbuf, mdlen);
    return mdok;
}

/*
 * Helper functions
 */

/*
 * [in] ctx: FILE_FORMAT_CTX structure
 * [returns] pointer to SpcSpOpusInfo structure
 */
static SpcSpOpusInfo *spc_sp_opus_info_create(FILE_FORMAT_CTX *ctx)
{
    SpcSpOpusInfo *info = SpcSpOpusInfo_new();

    if (ctx->options->desc) {
        info->programName = SpcString_new();
        info->programName->type = 1;
        info->programName->value.ascii = ASN1_IA5STRING_new();
        ASN1_STRING_set((ASN1_STRING *)info->programName->value.ascii,
                ctx->options->desc, (int)strlen(ctx->options->desc));
    }
    if (ctx->options->url) {
        info->moreInfo = SpcLink_new();
        info->moreInfo->type = 0;
        info->moreInfo->value.url = ASN1_IA5STRING_new();
        ASN1_STRING_set((ASN1_STRING *)info->moreInfo->value.url,
                ctx->options->url, (int)strlen(ctx->options->url));
    }
    return info;
}

/*
 * [out] blob: SpcIndirectDataContent data
 * [out] len: SpcIndirectDataContent data length
 * [in] ctx: FILE_FORMAT_CTX structure
 * [returns] 0 on error or 1 on success
 */
static int spc_indirect_data_content_get(u_char **blob, int *len, FILE_FORMAT_CTX *ctx)
{
    u_char *p = NULL;
    int hashlen, l = 0;
    void *hash;
    SpcIndirectDataContent *idc = SpcIndirectDataContent_new();

    idc->data->value = ASN1_TYPE_new();
    idc->data->value->type = V_ASN1_SEQUENCE;
    idc->data->value->value.sequence = ASN1_STRING_new();
    idc->data->type = ctx->format->data_blob_get(&p, &l, ctx);
    idc->data->value->value.sequence->data = p;
    idc->data->value->value.sequence->length = l;
    idc->messageDigest->digestAlgorithm->algorithm = OBJ_nid2obj(EVP_MD_nid(ctx->options->md));
    idc->messageDigest->digestAlgorithm->parameters = ASN1_TYPE_new();
    idc->messageDigest->digestAlgorithm->parameters->type = V_ASN1_NULL;

    hashlen = EVP_MD_size(ctx->options->md);
    hash = OPENSSL_malloc((size_t)hashlen);
    memset(hash, 0, (size_t)hashlen);
    ASN1_OCTET_STRING_set(idc->messageDigest->digest, hash, hashlen);
    OPENSSL_free(hash);

    *len  = i2d_SpcIndirectDataContent(idc, NULL);
    *blob = OPENSSL_malloc((size_t)*len);
    p = *blob;
    i2d_SpcIndirectDataContent(idc, &p);
    SpcIndirectDataContent_free(idc);
    *len -= EVP_MD_size(ctx->options->md);
    return 1; /* OK */
}

/*
 * Replace the data part with the MS Authenticode spcIndirectDataContent blob
 * [out] p7: new PKCS#7 signature
 * [in] hash: message digest BIO
 * [in] blob: SpcIndirectDataContent data
 * [in] len: SpcIndirectDataContent data length
 * [returns] 0 on error or 1 on success
 */
static int pkcs7_set_spc_indirect_data_content(PKCS7 *p7, BIO *hash, u_char *buf, int len)
{
    u_char mdbuf[EVP_MAX_MD_SIZE];
    int mdlen, seqhdrlen;
    BIO *bio;
    PKCS7 *td7;

    mdlen = BIO_gets(hash, (char*)mdbuf, EVP_MAX_MD_SIZE);
    memcpy(buf+len, mdbuf, (size_t)mdlen);
    seqhdrlen = asn1_simple_hdr_len(buf, len);

    if ((bio = PKCS7_dataInit(p7, NULL)) == NULL) {
        printf("PKCS7_dataInit failed\n");
        return 0; /* FAILED */
    }
    BIO_write(bio, buf + seqhdrlen, len - seqhdrlen + mdlen);
    (void)BIO_flush(bio);

    if (!PKCS7_dataFinal(p7, bio)) {
        printf("PKCS7_dataFinal failed\n");
        return 0; /* FAILED */
    }
    BIO_free_all(bio);

    td7 = PKCS7_new();
    td7->type = OBJ_txt2obj(SPC_INDIRECT_DATA_OBJID, 1);
    td7->d.other = ASN1_TYPE_new();
    td7->d.other->type = V_ASN1_SEQUENCE;
    td7->d.other->value.sequence = ASN1_STRING_new();
    ASN1_STRING_set(td7->d.other->value.sequence, buf, len+mdlen);
    if (!PKCS7_set_content(p7, td7)) {
        PKCS7_free(td7);
        printf("PKCS7_set_content failed\n");
        return 0; /* FAILED */
    }
    return 1; /* OK */
}

/*
Local Variables:
   c-basic-offset: 4
   tab-width: 4
   indent-tabs-mode: nil
End:

  vim: set ts=4 expandtab:
*/