// The functions here are derrived from BearSSL/tools/*.c
// When that is refactored suitably we can use them directly.
/*
 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */
#include <sys/cdefs.h>
#define NEED_BRSSL_H
#include "libsecureboot-priv.h"
#include <brssl.h>


static int
is_ign(int c)
{
        if (c == 0) {
                return (0);
        }
        if (c <= 32 || c == '-' || c == '_' || c == '.'
                || c == '/' || c == '+' || c == ':')
        {
                return (1);
        }
        return (0);
}

/*
 * Get next non-ignored character, normalised:
 *    ASCII letters are converted to lowercase
 *    control characters, space, '-', '_', '.', '/', '+' and ':' are ignored
 * A terminating zero is returned as 0.
 */
static int
next_char(const char **ps, const char *limit)
{
        for (;;) {
                int c;

                if (*ps == limit) {
                        return (0);
                }
                c = *(*ps) ++;
                if (c == 0) {
                        return (0);
                }
                if (c >= 'A' && c <= 'Z') {
                        c += 'a' - 'A';
                }
                if (!is_ign(c)) {
                        return (c);
                }
        }
}

/*
 * Partial string equality comparison, with normalisation.
 */
static int
eqstr_chunk(const char *s1, size_t s1_len, const char *s2, size_t s2_len)
{
        const char *lim1, *lim2;

        lim1 = s1 + s1_len;
        lim2 = s2 + s2_len;
        for (;;) {
                int c1, c2;

                c1 = next_char(&s1, lim1);
                c2 = next_char(&s2, lim2);
                if (c1 != c2) {
                        return (0);
                }
                if (c1 == 0) {
                        return (1);
                }
        }
}

/* see brssl.h */
int
eqstr(const char *s1, const char *s2)
{
        return (eqstr_chunk(s1, strlen(s1), s2, strlen(s2)));
}

int
looks_like_DER(const unsigned char *buf, size_t len)
{
        int fb;
        size_t dlen;

        if (len < 2) {
                return (0);
        }
        if (*buf ++ != 0x30) {
                return (0);
        }
        fb = *buf ++;
        len -= 2;
        if (fb < 0x80) {
                return ((size_t)fb == len);
        } else if (fb == 0x80) {
                return (0);
        } else {
                fb -= 0x80;
                if (len < (size_t)fb + 2) {
                        return (0);
                }
                len -= (size_t)fb;
                dlen = 0;
                while (fb -- > 0) {
                        if (dlen > (len >> 8)) {
                                return (0);
                        }
                        dlen = (dlen << 8) + (size_t)*buf ++;
                }
                return (dlen == len);
        }
}

static void
vblob_append(void *cc, const void *data, size_t len)
{
        bvector *bv;

        bv = cc;
        VEC_ADDMANY(*bv, data, len);
}

void
free_pem_object_contents(pem_object *po)
{
        if (po != NULL) {
                xfree(po->name);
                xfree(po->data);
        }
}

pem_object *
decode_pem(const void *src, size_t len, size_t *num)
{
        VECTOR(pem_object) pem_list = VEC_INIT;
        br_pem_decoder_context pc;
        pem_object po, *pos;
        const unsigned char *buf;
        bvector bv = VEC_INIT;
        int inobj;
        int extra_nl;

        *num = 0;
        br_pem_decoder_init(&pc);
        buf = src;
        inobj = 0;
        po.name = NULL;
        po.data = NULL;
        po.data_len = 0;
        extra_nl = 1;
        while (len > 0) {
                size_t tlen;

                tlen = br_pem_decoder_push(&pc, buf, len);
                buf += tlen;
                len -= tlen;
                switch (br_pem_decoder_event(&pc)) {

                case BR_PEM_BEGIN_OBJ:
                        po.name = xstrdup(br_pem_decoder_name(&pc));
                        br_pem_decoder_setdest(&pc, vblob_append, &bv);
                        inobj = 1;
                        break;

                case BR_PEM_END_OBJ:
                        if (inobj) {
                                po.data = VEC_TOARRAY(bv);
                                po.data_len = VEC_LEN(bv);
                                VEC_ADD(pem_list, po);
                                VEC_CLEAR(bv);
                                po.name = NULL;
                                po.data = NULL;
                                po.data_len = 0;
                                inobj = 0;
                        }
                        break;

                case BR_PEM_ERROR:
                        xfree(po.name);
                        VEC_CLEAR(bv);
                        ve_error_set("ERROR: invalid PEM encoding");
                        VEC_CLEAREXT(pem_list, &free_pem_object_contents);
                        return (NULL);
                }

                /*
                 * We add an extra newline at the end, in order to
                 * support PEM files that lack the newline on their last
                 * line (this is somwehat invalid, but PEM format is not
                 * standardised and such files do exist in the wild, so
                 * we'd better accept them).
                 */
                if (len == 0 && extra_nl) {
                        extra_nl = 0;
                        buf = (const unsigned char *)"\n";
                        len = 1;
                }
        }
        if (inobj) {
            ve_error_set("ERROR: unfinished PEM object");
                xfree(po.name);
                VEC_CLEAR(bv);
                VEC_CLEAREXT(pem_list, &free_pem_object_contents);
                return (NULL);
        }

        *num = VEC_LEN(pem_list);
        VEC_ADD(pem_list, po);
        pos = VEC_TOARRAY(pem_list);
        VEC_CLEAR(pem_list);
        return (pos);
}

br_x509_certificate *
parse_certificates(unsigned char *buf, size_t len, size_t *num)
{
        VECTOR(br_x509_certificate) cert_list = VEC_INIT;
        pem_object *pos;
        size_t u, num_pos;
        br_x509_certificate *xcs;
        br_x509_certificate dummy;

        *num = 0;

        /*
         * Check for a DER-encoded certificate.
         */
        if (looks_like_DER(buf, len)) {
                xcs = xmalloc(2 * sizeof *xcs);
                xcs[0].data = buf;
                xcs[0].data_len = len;
                xcs[1].data = NULL;
                xcs[1].data_len = 0;
                *num = 1;
                return (xcs);
        }

        pos = decode_pem(buf, len, &num_pos);
        if (pos == NULL) {
                return (NULL);
        }
        for (u = 0; u < num_pos; u ++) {
                if (eqstr(pos[u].name, "CERTIFICATE")
                        || eqstr(pos[u].name, "X509 CERTIFICATE"))
                {
                        br_x509_certificate xc;

                        xc.data = pos[u].data;
                        xc.data_len = pos[u].data_len;
                        pos[u].data = NULL;
                        VEC_ADD(cert_list, xc);
                }
        }
        for (u = 0; u < num_pos; u ++) {
                free_pem_object_contents(&pos[u]);
        }
        xfree(pos);

        if (VEC_LEN(cert_list) == 0) {
                return (NULL);
        }
        *num = VEC_LEN(cert_list);
        dummy.data = NULL;
        dummy.data_len = 0;
        VEC_ADD(cert_list, dummy);
        xcs = VEC_TOARRAY(cert_list);
        VEC_CLEAR(cert_list);
        return (xcs);
}

br_x509_certificate *
read_certificates(const char *fname, size_t *num)
{
        br_x509_certificate *xcs;
        unsigned char *buf;
        size_t len;

        *num = 0;

        /*
         * TODO: reading the whole file is crude; we could parse them
         * in a streamed fashion. But it does not matter much in practice.
         */
        buf = read_file(fname, &len);
        if (buf == NULL) {
                return (NULL);
        }
        xcs = parse_certificates(buf, len, num);
        if (xcs == NULL) {
            ve_error_set("ERROR: no certificate in file '%s'\n", fname);
        }
        xfree(buf);
        return (xcs);
}

/* see brssl.h */
void
free_certificates(br_x509_certificate *certs, size_t num)
{
        size_t u;

        for (u = 0; u < num; u ++) {
                xfree(certs[u].data);
        }
        xfree(certs);
}


static void
dn_append(void *ctx, const void *buf, size_t len)
{
        VEC_ADDMANY(*(bvector *)ctx, buf, len);
}

int
certificate_to_trust_anchor_inner(br_x509_trust_anchor *ta,
        br_x509_certificate *xc)
{
        br_x509_decoder_context dc;
        bvector vdn = VEC_INIT;
        br_x509_pkey *pk;

        br_x509_decoder_init(&dc, dn_append, &vdn);
        br_x509_decoder_push(&dc, xc->data, xc->data_len);
        pk = br_x509_decoder_get_pkey(&dc);
        if (pk == NULL) {
            ve_error_set("ERROR: CA decoding failed with error %d\n",
                      br_x509_decoder_last_error(&dc));
            VEC_CLEAR(vdn);
            return (-1);
        }
        ta->dn.data = VEC_TOARRAY(vdn);
        ta->dn.len = VEC_LEN(vdn);
        VEC_CLEAR(vdn);
        ta->flags = 0;
        if (br_x509_decoder_isCA(&dc)) {
                ta->flags |= BR_X509_TA_CA;
        }
        switch (pk->key_type) {
        case BR_KEYTYPE_RSA:
                ta->pkey.key_type = BR_KEYTYPE_RSA;
                ta->pkey.key.rsa.n = xblobdup(pk->key.rsa.n, pk->key.rsa.nlen);
                ta->pkey.key.rsa.nlen = pk->key.rsa.nlen;
                ta->pkey.key.rsa.e = xblobdup(pk->key.rsa.e, pk->key.rsa.elen);
                ta->pkey.key.rsa.elen = pk->key.rsa.elen;
                break;
        case BR_KEYTYPE_EC:
                ta->pkey.key_type = BR_KEYTYPE_EC;
                ta->pkey.key.ec.curve = pk->key.ec.curve;
                ta->pkey.key.ec.q = xblobdup(pk->key.ec.q, pk->key.ec.qlen);
                ta->pkey.key.ec.qlen = pk->key.ec.qlen;
                break;
        default:
            ve_error_set("ERROR: unsupported public key type in CA\n");
                xfree(ta->dn.data);
                return (-1);
        }
        return (0);
}

/* see brssl.h */
void
free_ta_contents(br_x509_trust_anchor *ta)
{
        xfree(ta->dn.data);
        switch (ta->pkey.key_type) {
        case BR_KEYTYPE_RSA:
                xfree(ta->pkey.key.rsa.n);
                xfree(ta->pkey.key.rsa.e);
                break;
        case BR_KEYTYPE_EC:
                xfree(ta->pkey.key.ec.q);
                break;
        }
}