/*
 * Copyright 2020-2021 The OpenSSL Project Authors. All Rights Reserved.
 *
 * Licensed under the Apache License 2.0 (the "License").  You may not use
 * this file except in compliance with the License.  You can obtain a copy
 * in the file LICENSE in the source distribution or at
 * https://www.openssl.org/source/license.html
 */

/*
 * RSA low level APIs are deprecated for public use, but still ok for
 * internal use.
 */
#include "internal/deprecated.h"

#include <string.h>

#include <openssl/core_dispatch.h>
#include <openssl/core_names.h>
#include <openssl/core_object.h>
#include <openssl/crypto.h>
#include <openssl/err.h>
#include <openssl/params.h>
#include <openssl/pem.h>
#include <openssl/proverr.h>
#include "internal/nelem.h"
#include "prov/bio.h"
#include "prov/implementations.h"
#include "endecoder_local.h"

static int read_pem(PROV_CTX *provctx, OSSL_CORE_BIO *cin,
                    char **pem_name, char **pem_header,
                    unsigned char **data, long *len)
{
    BIO *in = ossl_bio_new_from_core_bio(provctx, cin);
    int ok = (PEM_read_bio(in, pem_name, pem_header, data, len) > 0);

    BIO_free(in);
    return ok;
}

static OSSL_FUNC_decoder_newctx_fn pem2der_newctx;
static OSSL_FUNC_decoder_freectx_fn pem2der_freectx;
static OSSL_FUNC_decoder_gettable_params_fn pem2der_gettable_params;
static OSSL_FUNC_decoder_get_params_fn pem2der_get_params;
static OSSL_FUNC_decoder_decode_fn pem2der_decode;

/*
 * Context used for PEM to DER decoding.
 */
struct pem2der_ctx_st {
    PROV_CTX *provctx;
};

static void *pem2der_newctx(void *provctx)
{
    struct pem2der_ctx_st *ctx = OPENSSL_zalloc(sizeof(*ctx));

    if (ctx != NULL)
        ctx->provctx = provctx;
    return ctx;
}

static void pem2der_freectx(void *vctx)
{
    struct pem2der_ctx_st *ctx = vctx;

    OPENSSL_free(ctx);
}

static const OSSL_PARAM *pem2der_gettable_params(void *provctx)
{
    static const OSSL_PARAM gettables[] = {
        { OSSL_DECODER_PARAM_INPUT_TYPE, OSSL_PARAM_UTF8_PTR, NULL, 0, 0 },
        OSSL_PARAM_END,
    };

    return gettables;
}

static int pem2der_get_params(OSSL_PARAM params[])
{
    OSSL_PARAM *p;

    p = OSSL_PARAM_locate(params, OSSL_DECODER_PARAM_INPUT_TYPE);
    if (p != NULL && !OSSL_PARAM_set_utf8_ptr(p, "PEM"))
        return 0;

    return 1;
}

/* pem_password_cb compatible function */
struct pem2der_pass_data_st {
    OSSL_PASSPHRASE_CALLBACK *cb;
    void *cbarg;
};

static int pem2der_pass_helper(char *buf, int num, int w, void *data)
{
    struct pem2der_pass_data_st *pass_data = data;
    size_t plen;

    if (pass_data == NULL
        || pass_data->cb == NULL
        || !pass_data->cb(buf, num, &plen, NULL, pass_data->cbarg))
        return -1;
    return (int)plen;
}

/*
 * The selection parameter in pem2der_decode() is not used by this function
 * because it's not relevant just to decode PEM to DER.
 */
static int pem2der_decode(void *vctx, OSSL_CORE_BIO *cin, int selection,
                          OSSL_CALLBACK *data_cb, void *data_cbarg,
                          OSSL_PASSPHRASE_CALLBACK *pw_cb, void *pw_cbarg)
{
    /* Strings to peel off the pem name */
    static struct peelablee_pem_name_endings_st {
        const char *ending;
        const char *data_structure;
    } peelable_pem_name_endings[] = {
        /*
         * These entries should be in longest to shortest order to avoid
         * mixups.
         */
        { "ENCRYPTED PRIVATE KEY", "pkcs8" },
        { "PRIVATE KEY", "pkcs8" },
        { "PUBLIC KEY", "SubjectPublicKeyInfo" },
        { "PARAMETERS", NULL }

        /*
         * Libcrypto currently only supports decoding keys with provider side
         * decoders, so we don't try to peel any other PEM name.  That's an
         * exercise for when libcrypto starts to treat other types of objects
         * via providers.
         */
    };
    struct pem2der_ctx_st *ctx = vctx;
    char *pem_name = NULL, *pem_header = NULL;
    size_t pem_name_len, i;
    unsigned char *der = NULL;
    long der_len = 0;
    int ok = 0;
    int objtype = OSSL_OBJECT_UNKNOWN;
    const char *data_structure = NULL;

    if (read_pem(ctx->provctx, cin, &pem_name, &pem_header,
                 &der, &der_len) <= 0)
        return 0;

    /*
     * 10 is the number of characters in "Proc-Type:", which
     * PEM_get_EVP_CIPHER_INFO() requires to be present.
     * If the PEM header has less characters than that, it's
     * not worth spending cycles on it.
     */
    if (strlen(pem_header) > 10) {
        EVP_CIPHER_INFO cipher;
        struct pem2der_pass_data_st pass_data;

        pass_data.cb = pw_cb;
        pass_data.cbarg = pw_cbarg;
        if (!PEM_get_EVP_CIPHER_INFO(pem_header, &cipher)
            || !PEM_do_header(&cipher, der, &der_len,
                              pem2der_pass_helper, &pass_data))
            goto end;
    }

    /*
     * Peal off certain strings from the end of |pem_name|, as they serve
     * no further purpose.
     */
    for (i = 0, pem_name_len = strlen(pem_name);
         i < OSSL_NELEM(peelable_pem_name_endings);
         i++) {
        size_t peel_len = strlen(peelable_pem_name_endings[i].ending);
        size_t pem_name_offset;

        if (peel_len <= pem_name_len) {
            pem_name_offset = pem_name_len - peel_len;
            if (strcmp(pem_name + pem_name_offset,
                       peelable_pem_name_endings[i].ending) == 0) {

                do {
                    pem_name[pem_name_offset] = '\0';
                } while (pem_name_offset > 0
                         && pem_name[--pem_name_offset] == ' ');

                if (pem_name[0] == '\0') {
                    OPENSSL_free(pem_name);
                    pem_name = NULL;
                }
                /* All of these peelable endings are for EVP_PKEYs */
                objtype = OSSL_OBJECT_PKEY;
                if (pem_name == NULL) {
                    data_structure = peelable_pem_name_endings[i].data_structure;
                    if (data_structure == NULL)
                        goto end;
                } else {
                    /*
                     * If there is an algorithm name prefix then it is a
                     * type-specific data structure
                     */
                    data_structure = "type-specific";
                }
                break;
            }
        }
    }

    /* If we don't know the object type yet check if it's one we know about */
    if (objtype == OSSL_OBJECT_UNKNOWN) {
        if (strcmp(pem_name, PEM_STRING_X509) == 0
                || strcmp(pem_name, PEM_STRING_X509_TRUSTED) == 0
                || strcmp(pem_name, PEM_STRING_X509_OLD) == 0)
            objtype = OSSL_OBJECT_CERT;
        else if (strcmp(pem_name, PEM_STRING_X509_CRL) == 0)
            objtype = OSSL_OBJECT_CRL;
    }

    {
        OSSL_PARAM params[5], *p = params;

        if (pem_name != NULL)
            *p++ =
                OSSL_PARAM_construct_utf8_string(OSSL_OBJECT_PARAM_DATA_TYPE,
                                                 pem_name, 0);

        /* We expect this to be read only so casting away the const is ok */
        if (data_structure != NULL)
            *p++ =
                OSSL_PARAM_construct_utf8_string(OSSL_OBJECT_PARAM_DATA_STRUCTURE,
                                                 (char *)data_structure, 0);
        *p++ =
            OSSL_PARAM_construct_octet_string(OSSL_OBJECT_PARAM_DATA,
                                              der, der_len);
        *p++ =
            OSSL_PARAM_construct_int(OSSL_OBJECT_PARAM_TYPE, &objtype);

        *p = OSSL_PARAM_construct_end();

        ok = data_cb(params, data_cbarg);
    }

 end:
    OPENSSL_free(pem_name);
    OPENSSL_free(pem_header);
    OPENSSL_free(der);
    return ok;
}

const OSSL_DISPATCH ossl_pem_to_der_decoder_functions[] = {
    { OSSL_FUNC_DECODER_NEWCTX, (void (*)(void))pem2der_newctx },
    { OSSL_FUNC_DECODER_FREECTX, (void (*)(void))pem2der_freectx },
    { OSSL_FUNC_DECODER_GETTABLE_PARAMS,
      (void (*)(void))pem2der_gettable_params },
    { OSSL_FUNC_DECODER_GET_PARAMS,
      (void (*)(void))pem2der_get_params },
    { OSSL_FUNC_DECODER_DECODE, (void (*)(void))pem2der_decode },
    { 0, NULL }
};
