/*

 * Copyright 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

 */

/*

 * This is a read only BIO filter that can be used to add BIO_tell() and

 * BIO_seek() support to source/sink BIO's (such as a file BIO that uses stdin).

 * It does this by caching ALL data read from the BIO source/sink into a

 * resizable memory buffer.

 */

#include <stdio.h>

#include <errno.h>

#include "bio_local.h"

#include "internal/cryptlib.h"

#define DEFAULT_BUFFER_SIZE     4096

static int readbuffer_write(BIO *h, const char *buf, int num);

static int readbuffer_read(BIO *h, char *buf, int size);

static int readbuffer_puts(BIO *h, const char *str);

static int readbuffer_gets(BIO *h, char *str, int size);

static long readbuffer_ctrl(BIO *h, int cmd, long arg1, void *arg2);

static int readbuffer_new(BIO *h);

static int readbuffer_free(BIO *data);

static long readbuffer_callback_ctrl(BIO *h, int cmd, BIO_info_cb *fp);

static const BIO_METHOD methods_readbuffer = {

    BIO_TYPE_BUFFER,

    "readbuffer",

    bwrite_conv,

    readbuffer_write,

    bread_conv,

    readbuffer_read,

    readbuffer_puts,

    readbuffer_gets,

    readbuffer_ctrl,

    readbuffer_new,

    readbuffer_free,

    readbuffer_callback_ctrl,

};

const BIO_METHOD *BIO_f_readbuffer(void)

{

    return &methods_readbuffer;

}

static int readbuffer_new(BIO *bi)

{

    BIO_F_BUFFER_CTX *ctx = OPENSSL_zalloc(sizeof(*ctx));

    if (ctx == NULL)

        return 0;

    ctx->ibuf_size = DEFAULT_BUFFER_SIZE;

    ctx->ibuf = OPENSSL_zalloc(DEFAULT_BUFFER_SIZE);

    if (ctx->ibuf == NULL) {

        OPENSSL_free(ctx);

        return 0;

    }

    bi->init = 1;

    bi->ptr = (char *)ctx;

    bi->flags = 0;

    return 1;

}

static int readbuffer_free(BIO *a)

{

    BIO_F_BUFFER_CTX *b;

    if (a == NULL)

        return 0;

    b = (BIO_F_BUFFER_CTX *)a->ptr;

    OPENSSL_free(b->ibuf);

    OPENSSL_free(a->ptr);

    a->ptr = NULL;

    a->init = 0;

    a->flags = 0;

    return 1;

}

static int readbuffer_resize(BIO_F_BUFFER_CTX *ctx, int sz)

{

    char *tmp;

    /* Figure out how many blocks are required */

    sz += (ctx->ibuf_off + DEFAULT_BUFFER_SIZE - 1);

    sz = DEFAULT_BUFFER_SIZE * (sz / DEFAULT_BUFFER_SIZE);

    /* Resize if the buffer is not big enough */

    if (sz > ctx->ibuf_size) {

        tmp = OPENSSL_realloc(ctx->ibuf, sz);

        if (tmp == NULL)

            return 0;

        ctx->ibuf = tmp;

        ctx->ibuf_size = sz;

    }

    return 1;

}

static int readbuffer_read(BIO *b, char *out, int outl)

{

    int i, num = 0;

    BIO_F_BUFFER_CTX *ctx;

    if (out == NULL || outl == 0)

        return 0;

    ctx = (BIO_F_BUFFER_CTX *)b->ptr;

    if ((ctx == NULL) || (b->next_bio == NULL))

        return 0;

    BIO_clear_retry_flags(b);

    for (;;) {

        i = ctx->ibuf_len;

        /* If there is something in the buffer just read it. */

        if (i != 0) {

            if (i > outl)

                i = outl;

            memcpy(out, &(ctx->ibuf[ctx->ibuf_off]), i);

            ctx->ibuf_off += i;

            ctx->ibuf_len -= i;

            num += i;

            /* Exit if we have read the bytes required out of the buffer */

            if (outl == i)

                return num;

            outl -= i;

            out += i;

        }

        /* Only gets here if the buffer has been consumed */

        if (!readbuffer_resize(ctx, outl))

            return 0;

        /* Do some buffering by reading from the next bio */

        i = BIO_read(b->next_bio, ctx->ibuf + ctx->ibuf_off, outl);

        if (i <= 0) {

            BIO_copy_next_retry(b);

            if (i < 0)

                return ((num > 0) ? num : i);

            else

                return num; /* i == 0 */

        }

        ctx->ibuf_len = i;

    }

}

static int readbuffer_write(BIO *b, const char *in, int inl)

{

    return 0;

}

static int readbuffer_puts(BIO *b, const char *str)

{

    return 0;

}

static long readbuffer_ctrl(BIO *b, int cmd, long num, void *ptr)

{

    BIO_F_BUFFER_CTX *ctx;

    long ret = 1, sz;

    ctx = (BIO_F_BUFFER_CTX *)b->ptr;

    switch (cmd) {

    case BIO_CTRL_EOF:

        if (ctx->ibuf_len > 0)

            return 0;

        if (b->next_bio == NULL)

            return 1;

        ret = BIO_ctrl(b->next_bio, cmd, num, ptr);

        break;

    case BIO_C_FILE_SEEK:

    case BIO_CTRL_RESET:

        sz = ctx->ibuf_off + ctx->ibuf_len;

        /* Assume it can only seek backwards */

        if (num < 0 || num > sz)

            return 0;

        ctx->ibuf_off = num;

        ctx->ibuf_len = sz - num;

        break;

    case BIO_C_FILE_TELL:

    case BIO_CTRL_INFO:

        ret = (long)ctx->ibuf_off;

        break;

    case BIO_CTRL_PENDING:

        ret = (long)ctx->ibuf_len;

        if (ret == 0) {

            if (b->next_bio == NULL)

                return 0;

            ret = BIO_ctrl(b->next_bio, cmd, num, ptr);

        }

        break;

    case BIO_CTRL_DUP:

    case BIO_CTRL_FLUSH:

        ret = 1;

        break;

    default:

        ret = 0;

        break;

    }

    return ret;

}

static long readbuffer_callback_ctrl(BIO *b, int cmd, BIO_info_cb *fp)

{

    if (b->next_bio == NULL)

        return 0;

    return BIO_callback_ctrl(b->next_bio, cmd, fp);

}

static int readbuffer_gets(BIO *b, char *buf, int size)

{

    BIO_F_BUFFER_CTX *ctx;

    int num = 0, num_chars, found_newline;

    char *p;

    int i, j;

    if (size == 0)

        return 0;

    --size; /* the passed in size includes the terminator - so remove it here */

    ctx = (BIO_F_BUFFER_CTX *)b->ptr;

    BIO_clear_retry_flags(b);

    /* If data is already buffered then use this first */

    if (ctx->ibuf_len > 0) {

        p = ctx->ibuf + ctx->ibuf_off;

        found_newline = 0;

        for (num_chars = 0;

             (num_chars < ctx->ibuf_len) && (num_chars < size);

             num_chars++) {

            *buf++ = p[num_chars];

            if (p[num_chars] == '\n') {

                found_newline = 1;

                num_chars++;

                break;

            }

        }

        num += num_chars;

        size -= num_chars;

        ctx->ibuf_len -= num_chars;

        ctx->ibuf_off += num_chars;

        if (found_newline || size == 0) {

            *buf = '\0';

            return num;

        }

    }

    /*

     * If there is no buffered data left then read any remaining data from the

     * next bio.

     */

     /* Resize if we have to */

     if (!readbuffer_resize(ctx, 1 + size))

         return 0;

     /*

      * Read more data from the next bio using BIO_read_ex:

      * Note we cannot use BIO_gets() here as it does not work on a

      * binary stream that contains 0x00. (Since strlen() will stop at

      * any 0x00 not at the last read '\n' in a FILE bio).

      * Also note that some applications open and close the file bio

      * multiple times and need to read the next available block when using

      * stdin - so we need to READ one byte at a time!

      */

     p = ctx->ibuf + ctx->ibuf_off;

     for (i = 0; i < size; ++i) {

         j = BIO_read(b->next_bio, p, 1);

         if (j <= 0) {

             BIO_copy_next_retry(b);

             *buf = '\0';

             return num > 0 ? num : j;

         }

         *buf++ = *p;

         num++;

         ctx->ibuf_off++;

         if (*p == '\n')

             break;

         ++p;

     }

     *buf = '\0';

     return num;

}