/* crypto/bio/bss_bio.c  -*- Mode: C; c-file-style: "eay" -*- */

/* Special method for a BIO where the other endpoint is also a BIO
 * of this kind, handled by the same thread (i.e. the "peer" is actually
 * ourselves, wearing a different hat).
 * Such "BIO pairs" are mainly for using the SSL library with I/O interfaces
 * for which no specific BIO method is available.
 * See ssl/ssltest.c for some hints on how this can be used. */

#ifndef BIO_PAIR_DEBUG
# undef NDEBUG /* avoid conflicting definitions */
# define NDEBUG
#endif

#include <assert.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>

#include <openssl/bio.h>
#include <openssl/err.h>
#include <openssl/crypto.h>

static int bio_new(BIO *bio);
static int bio_free(BIO *bio);
static int bio_read(BIO *bio, char *buf, int size);
static int bio_write(BIO *bio, char *buf, int num);
static long bio_ctrl(BIO *bio, int cmd, long num, void *ptr);
static int bio_puts(BIO *bio, char *str);

static int bio_make_pair(BIO *bio1, BIO *bio2);
static void bio_destroy_pair(BIO *bio);

static BIO_METHOD methods_biop =
{
	BIO_TYPE_BIO,
	"BIO pair",
	bio_write,
	bio_read,
	bio_puts,
	NULL /* no bio_gets */,
	bio_ctrl,
	bio_new,
	bio_free
};

BIO_METHOD *BIO_s_bio(void)
	{
	return &methods_biop;
	}

struct bio_bio_st
{
	BIO *peer;     /* NULL if buf == NULL.
	                * If peer != NULL, then peer->ptr is also a bio_bio_st,
	                * and its "peer" member points back to us.
	                * peer != NULL iff init != 0 in the BIO. */
	
	/* This is for what we write (i.e. reading uses peer's struct): */
	int closed;     /* valid iff peer != NULL */
	size_t len;     /* valid iff buf != NULL; 0 if peer == NULL */
	size_t offset;  /* valid iff buf != NULL; 0 if len == 0 */
	size_t size;
	char *buf;      /* "size" elements (if != NULL) */

	size_t request; /* valid iff peer != NULL; 0 if len != 0,
	                 * otherwise set by peer to number of bytes
	                 * it (unsuccesfully) tried to read,
	                 * never more than buffer space (size-len) warrants. */
};

static int bio_new(BIO *bio)
	{
	struct bio_bio_st *b;
	
	b = Malloc(sizeof *b);
	if (b == NULL)
		return 0;

	b->peer = NULL;
	b->size = 17*1024; /* enough for one TLS record (just a default) */
	b->buf = NULL;

	bio->ptr = b;
	return 1;
	}


static int bio_free(BIO *bio)
	{
	struct bio_bio_st *b;

	if (bio == NULL)
		return 0;
	b = bio->ptr;

	assert(b != NULL);

	if (b->peer)
		bio_destroy_pair(bio);
	
	if (b->buf != NULL)
		{
		Free(b->buf);
		}

	Free(b);

	return 1;
	}



static int bio_read(BIO *bio, char *buf, int size_)
	{
	size_t size = size_;
	size_t rest;
	struct bio_bio_st *b, *peer_b;

	BIO_clear_retry_flags(bio);

	if (!bio->init)
		return 0;

	b = bio->ptr;
	assert(b != NULL);
	assert(b->peer != NULL);
	peer_b = b->peer->ptr;
	assert(peer_b != NULL);
	assert(peer_b->buf != NULL);

	peer_b->request = 0; /* will be set in "retry_read" situation */

	if (buf == NULL || size == 0)
		return 0;

	if (peer_b->len == 0)
		{
		if (peer_b->closed)
			return 0; /* writer has closed, and no data is left */
		else
			{
			BIO_set_retry_read(bio); /* buffer is empty */
			if (size <= peer_b->size)
				peer_b->request = size;
			else
				/* don't ask for more than the peer can
				 * deliver in one write */
				peer_b->request = peer_b->size;
			return -1;
			}
		}

	/* we can read */
	if (peer_b->len < size)
		size = peer_b->len;

	/* now read "size" bytes */
	
	rest = size;
	
	assert(rest > 0);
	do /* one or two iterations */
		{
		size_t chunk;
		
		assert(rest <= peer_b->len);
		if (peer_b->offset + rest <= peer_b->size)
			chunk = rest;
		else
			/* wrap around ring buffer */
			chunk = peer_b->size - peer_b->offset;
		assert(peer_b->offset + chunk <= peer_b->size);
		
		memcpy(buf, peer_b->buf + peer_b->offset, chunk);
		
		peer_b->len -= chunk;
		if (peer_b->len)
			{
			peer_b->offset += chunk;
			assert(peer_b->offset <= peer_b->size);
			if (peer_b->offset == peer_b->size)
				peer_b->offset = 0;
			buf += chunk;
			}
		else
			{
			/* buffer now empty, no need to advance "buf" */
			assert(chunk == rest);
			peer_b->offset = 0;
			}
		rest -= chunk;
		}
	while (rest);
	
	return size;
	}

/* non-copying interface: provide pointer to available data in buffer
 *    bio_nread0:  return number of available bytes
 *    bio_nread:   also advance index
 * (example usage:  bio_nread0(), read from buffer, bio_nread()
 *  or just         bio_nread(), read from buffer)
 */
/* WARNING: The non-copying interface is largely untested as of yet
 * and may contain bugs. */
static size_t bio_nread0(BIO *bio, char **buf)
	{
	struct bio_bio_st *b, *peer_b;
	size_t num;
	
	BIO_clear_retry_flags(bio);

	if (!bio->init)
		return 0;
	
	b = bio->ptr;
	assert(b != NULL);
	assert(b->peer != NULL);
	peer_b = b->peer->ptr;
	assert(peer_b != NULL);
	assert(peer_b->buf != NULL);
	
	peer_b->request = 0;
	
	if (peer_b->len == 0)
		{
		char dummy;
		
		/* avoid code duplication -- nothing available for reading */
		return bio_read(bio, &dummy, 1); /* returns 0 or -1 */
		}

	num = peer_b->len;
	if (peer_b->size < peer_b->offset + num)
		/* no ring buffer wrap-around for non-copying interface */
		num = peer_b->size - peer_b->offset;
	assert(num > 0);

	if (buf != NULL)
		*buf = peer_b->buf + peer_b->offset;
	return num;
	}

static size_t bio_nread(BIO *bio, char **buf, size_t num)
	{
	struct bio_bio_st *b, *peer_b;
	size_t available;

	available = bio_nread0(bio, buf);
	if (num > available)
		num = available;
	if (num <= 0)
		return num;

	b = bio->ptr;
	peer_b = b->peer->ptr;

	peer_b->len -= num;
	if (peer_b->len) 
		{
		peer_b->offset += num;
		assert(peer_b->offset <= peer_b->size);
		if (peer_b->offset == peer_b->size)
			peer_b->offset = 0;
		}
	else
		peer_b->offset = 0;

	return num;
	}


static int bio_write(BIO *bio, char *buf, int num_)
	{
	size_t num = num_;
	size_t rest;
	struct bio_bio_st *b;

	BIO_clear_retry_flags(bio);

	if (!bio->init || buf == NULL || num == 0)
		return 0;

	b = bio->ptr;		
	assert(b != NULL);
	assert(b->peer != NULL);
	assert(b->buf != NULL);

	b->request = 0;
	if (b->closed)
		{
		/* we already closed */
		BIOerr(BIO_F_BIO_WRITE, BIO_R_BROKEN_PIPE);
		return -1;
		}

	assert(b->len <= b->size);

	if (b->len == b->size)
		{
		BIO_set_retry_write(bio); /* buffer is full */
		return -1;
		}

	/* we can write */
	if (num > b->size - b->len)
		num = b->size - b->len;
	
	/* now write "num" bytes */

	rest = num;
	
	assert(rest > 0);
	do /* one or two iterations */
		{
		size_t write_offset;
		size_t chunk;

		assert(b->len + rest <= b->size);

		write_offset = b->offset + b->len;
		if (write_offset >= b->size)
			write_offset -= b->size;
		/* b->buf[write_offset] is the first byte we can write to. */

		if (write_offset + rest <= b->size)
			chunk = rest;
		else
			/* wrap around ring buffer */
			chunk = b->size - write_offset;
		
		memcpy(b->buf + write_offset, buf, chunk);
		
		b->len += chunk;

		assert(b->len <= b->size);
		
		rest -= chunk;
		buf += chunk;
		}
	while (rest);

	return num;
	}

/* non-copying interface: provide pointer to region to write to
 *   bio_nwrite0:  check how much space is available
 *   bio_nwrite:   also increase length
 * (example usage:  bio_nwrite0(), write to buffer, bio_nwrite()
 *  or just         bio_nwrite(), write to buffer)
 */
static size_t bio_nwrite0(BIO *bio, char **buf)
	{
	struct bio_bio_st *b;
	size_t num;
	size_t write_offset;

	BIO_clear_retry_flags(bio);

	if (!bio->init)
		return 0;

	b = bio->ptr;		
	assert(b != NULL);
	assert(b->peer != NULL);
	assert(b->buf != NULL);

	b->request = 0;
	if (b->closed)
		{
		BIOerr(BIO_F_BIO_NWRITE0, BIO_R_BROKEN_PIPE);
		return -1;
		}

	assert(b->len <= b->size);

	if (b->len == b->size)
		{
		BIO_set_retry_write(bio);
		return -1;
		}

	num = b->size - b->len;
	write_offset = b->offset + b->len;
	if (write_offset >= b->size)
		write_offset -= b->size;
	if (write_offset + num > b->size)
		/* no ring buffer wrap-around for non-copying interface
		 * (to fulfil the promise by BIO_ctrl_get_write_guarantee,
		 * BIO_nwrite may have to be called twice) */
		num = b->size - write_offset;

	if (buf != NULL)
		*buf = b->buf + write_offset;
	assert(write_offset + num <= b->size);

	return num;
	}

static size_t bio_nwrite(BIO *bio, char **buf, size_t num)
	{
	struct bio_bio_st *b;
	size_t space;

	space = bio_nwrite0(bio, buf);
	if (num > space)
		num = space;
	if (num <= 0)
		return num;
	b = bio->ptr;
	assert(b != NULL);
	b->len += num;
	assert(b->len <= b->size);

	return num;
	}


static long bio_ctrl(BIO *bio, int cmd, long num, void *ptr)
	{
	long ret;
	struct bio_bio_st *b = bio->ptr;
	
	assert(b != NULL);

	switch (cmd)
		{
	/* specific CTRL codes */

	case BIO_C_SET_WRITE_BUF_SIZE:
		if (b->peer)
			{
			BIOerr(BIO_F_BIO_CTRL, BIO_R_IN_USE);
			ret = 0;
			}
		else if (num == 0)
			{
			BIOerr(BIO_F_BIO_CTRL, BIO_R_INVALID_ARGUMENT);
			ret = 0;
			}
		else
			{
			size_t new_size = num;

			if (b->size != new_size)
				{
				if (b->buf) 
					{
					Free(b->buf);
					b->buf = NULL;
					}
				b->size = new_size;
				}
			ret = 1;
			}
		break;

	case BIO_C_GET_WRITE_BUF_SIZE:
		num = (long) b->size;

	case BIO_C_MAKE_BIO_PAIR:
		{
		BIO *other_bio = ptr;
		
		if (bio_make_pair(bio, other_bio))
			ret = 1;
		else
			ret = 0;
		}
		break;
		
	case BIO_C_DESTROY_BIO_PAIR:
		/* Effects both BIOs in the pair -- call just once!
		 * Or let BIO_free(bio1); BIO_free(bio2); do the job. */
		bio_destroy_pair(bio);
		ret = 1;
		break;

	case BIO_C_GET_WRITE_GUARANTEE:
		/* How many bytes can the caller feed to the next write
		 * withouth having to keep any? */
		if (b->peer == NULL || b->closed)
			ret = 0;
		else
			ret = (long) b->size - b->len;
		break;

	case BIO_C_GET_READ_REQUEST:
		/* If the peer unsuccesfully tried to read, how many bytes
		 * were requested?  (As with BIO_CTRL_PENDING, that number
		 * can usually be treated as boolean.) */
		ret = (long) b->request;
		break;

	case BIO_C_RESET_READ_REQUEST:
		/* Reset request.  (Can be useful after read attempts
		 * at the other side that are meant to be non-blocking,
		 * e.g. when probing SSL_read to see if any data is
		 * available.) */
		b->request = 0;
		ret = 1;
		break;

	case BIO_C_SHUTDOWN_WR:
		/* similar to shutdown(..., SHUT_WR) */
		b->closed = 1;
		ret = 1;
		break;

	case BIO_C_NREAD:
		/* non-copying read */
		ret = (long) bio_nread(bio, ptr, (size_t) num);
		break;
		
	case BIO_C_NWRITE0:
		/* prepare for non-copying write */
		ret = (long) bio_nwrite0(bio, ptr);
		break;

	case BIO_C_NWRITE:
		/* non-copying write */
		ret = (long) bio_nwrite(bio, ptr, (size_t) num);
		break;
		

	/* standard CTRL codes follow */

	case BIO_CTRL_RESET:
		if (b->buf != NULL)
			{
			b->len = 0;
			b->offset = 0;
			}
		ret = 0;
		break;		

	case BIO_CTRL_GET_CLOSE:
		ret = bio->shutdown;
		break;

	case BIO_CTRL_SET_CLOSE:
		bio->shutdown = (int) num;
		ret = 1;
		break;

	case BIO_CTRL_PENDING:
		if (b->peer != NULL)
			{
			struct bio_bio_st *peer_b = b->peer->ptr;
			
			ret = (long) peer_b->len;
			}
		else
			ret = 0;
		break;

	case BIO_CTRL_WPENDING:
		if (b->buf != NULL)
			ret = (long) b->len;
		else
			ret = 0;
		break;

	case BIO_CTRL_DUP:
		/* See BIO_dup_chain for circumstances we have to expect. */
		{
		BIO *other_bio = ptr;
		struct bio_bio_st *other_b;
		
		assert(other_bio != NULL);
		other_b = other_bio->ptr;
		assert(other_b != NULL);
		
		assert(other_b->buf == NULL); /* other_bio is always fresh */

		other_b->size = b->size;
		}

		ret = 1;
		break;

	case BIO_CTRL_FLUSH:
		ret = 1;
		break;

	case BIO_CTRL_EOF:
		{
		BIO *other_bio = ptr;
		
		if (other_bio)
			{
			struct bio_bio_st *other_b = other_bio->ptr;
			
			assert(other_b != NULL);
			ret = other_b->len == 0 && other_b->closed;
			}
		else
			ret = 1;
		}
		break;

	default:
		ret = 0;
		}
	return ret;
	}

static int bio_puts(BIO *bio, char *str)
	{
	return bio_write(bio, str, strlen(str));
	}


static int bio_make_pair(BIO *bio1, BIO *bio2)
	{
	struct bio_bio_st *b1, *b2;

	assert(bio1 != NULL);
	assert(bio2 != NULL);

	b1 = bio1->ptr;
	b2 = bio2->ptr;
	
	if (b1->peer != NULL || b2->peer != NULL)
		{
		BIOerr(BIO_F_BIO_MAKE_PAIR, BIO_R_IN_USE);
		return 0;
		}
	
	if (b1->buf == NULL)
		{
		b1->buf = Malloc(b1->size);
		if (b1->buf == NULL)
			{
			BIOerr(BIO_F_BIO_MAKE_PAIR, ERR_R_MALLOC_FAILURE);
			return 0;
			}
		b1->len = 0;
		b1->offset = 0;
		}
	
	if (b2->buf == NULL)
		{
		b2->buf = Malloc(b2->size);
		if (b2->buf == NULL)
			{
			BIOerr(BIO_F_BIO_MAKE_PAIR, ERR_R_MALLOC_FAILURE);
			return 0;
			}
		b2->len = 0;
		b2->offset = 0;
		}
	
	b1->peer = bio2;
	b1->closed = 0;
	b1->request = 0;
	b2->peer = bio1;
	b2->closed = 0;
	b2->request = 0;

	bio1->init = 1;
	bio2->init = 1;

	return 1;
	}

static void bio_destroy_pair(BIO *bio)
	{
	struct bio_bio_st *b = bio->ptr;

	if (b != NULL)
		{
		BIO *peer_bio = b->peer;

		if (peer_bio != NULL)
			{
			struct bio_bio_st *peer_b = peer_bio->ptr;

			assert(peer_b != NULL);
			assert(peer_b->peer == bio);

			peer_b->peer = NULL;
			peer_bio->init = 0;
			assert(peer_b->buf != NULL);
			peer_b->len = 0;
			peer_b->offset = 0;
			
			b->peer = NULL;
			bio->init = 0;
			assert(b->buf != NULL);
			b->len = 0;
			b->offset = 0;
			}
		}
	}
 

/* Exported convenience functions */
int BIO_new_bio_pair(BIO **bio1_p, size_t writebuf1,
	BIO **bio2_p, size_t writebuf2)
	 {
	 BIO *bio1 = NULL, *bio2 = NULL;
	 long r;
	 int ret = 0;

	 bio1 = BIO_new(BIO_s_bio());
	 if (bio1 == NULL)
		 goto err;
	 bio2 = BIO_new(BIO_s_bio());
	 if (bio2 == NULL)
		 goto err;

	 if (writebuf1)
		 {
		 r = BIO_set_write_buf_size(bio1, writebuf1);
		 if (!r)
			 goto err;
		 }
	 if (writebuf2)
		 {
		 r = BIO_set_write_buf_size(bio2, writebuf2);
		 if (!r)
			 goto err;
		 }

	 r = BIO_make_bio_pair(bio1, bio2);
	 if (!r)
		 goto err;
	 ret = 1;

 err:
	 if (ret == 0)
		 {
		 if (bio1)
			 {
			 BIO_free(bio1);
			 bio1 = NULL;
			 }
		 if (bio2)
			 {
			 BIO_free(bio2);
			 bio2 = NULL;
			 }
		 }

	 *bio1_p = bio1;
	 *bio2_p = bio2;
	 return ret;
	 }

size_t BIO_ctrl_get_write_guarantee(BIO *bio)
	{
	return BIO_ctrl(bio, BIO_C_GET_WRITE_GUARANTEE, 0, NULL);
	}

size_t BIO_ctrl_get_read_request(BIO *bio)
	{
	return BIO_ctrl(bio, BIO_C_GET_READ_REQUEST, 0, NULL);
	}

int BIO_ctrl_reset_read_request(BIO *bio)
	{
	return (BIO_ctrl(bio, BIO_C_RESET_READ_REQUEST, 0, NULL) != 0);
	}


/* BIO_nread0/nread/nwrite0/nwrite are availabe only for BIO pairs for now
 * (conceivably some other BIOs could allow non-copying reads and writes too.)
 */
int BIO_nread0(BIO *bio, char **buf)
	{
	long ret;

	if (!bio->init)
		{
		BIOerr(BIO_F_BIO_NREAD0, BIO_R_UNINITIALIZED);
		return -2;
		}

	ret = BIO_ctrl(bio, BIO_C_NREAD0, 0, buf);
	if (ret > INT_MAX)
		return INT_MAX;
	else
		return (int) ret;
	}

int BIO_nread(BIO *bio, char **buf, int num)
	{
	int ret;

	if (!bio->init)
		{
		BIOerr(BIO_F_BIO_NREAD, BIO_R_UNINITIALIZED);
		return -2;
		}

	ret = (int) BIO_ctrl(bio, BIO_C_NREAD, num, buf);
	if (ret > 0)
		bio->num_read += ret;
	return ret;
	}

int BIO_nwrite0(BIO *bio, char **buf)
	{
	long ret;

	if (!bio->init)
		{
		BIOerr(BIO_F_BIO_NWRITE0, BIO_R_UNINITIALIZED);
		return -2;
		}

	ret = BIO_ctrl(bio, BIO_C_NWRITE0, 0, buf);
	if (ret > INT_MAX)
		return INT_MAX;
	else
		return (int) ret;
	}

int BIO_nwrite(BIO *bio, char **buf, int num)
	{
	int ret;

	if (!bio->init)
		{
		BIOerr(BIO_F_BIO_NWRITE, BIO_R_UNINITIALIZED);
		return -2;
		}

	ret = BIO_ctrl(bio, BIO_C_NWRITE, num, buf);
	if (ret > 0)
		bio->num_read += ret;
	return ret;
	}