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refactor channels.c

Move static state to a "struct ssh_channels" that is allocated at
runtime and tracked as a member of struct ssh.

Explicitly pass "struct ssh" to all channels functions.

Replace use of the legacy packet APIs in channels.c.

Rework sshd_config PermitOpen handling: previously the configuration
parser would call directly into the channels layer. After the refactor
this is not possible, as the channels structures are allocated at
connection time and aren't available when the configuration is parsed.
The server config parser now tracks PermitOpen itself and explicitly
configures the channels code later.

ok markus@

/*	$OpenBSD: sshbuf.h,v 1.9 2017/09/12 06:32:07 djm Exp $	*/
/*
 * Copyright (c) 2011 Damien Miller
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#ifndef _SSHBUF_H
#define _SSHBUF_H

#include <sys/types.h>
#include <stdarg.h>
#include <stdio.h>
#include <openssl/bn.h>
#include <openssl/ec.h>

#define SSHBUF_SIZE_MAX		0x8000000	/* Hard maximum size */
#define SSHBUF_REFS_MAX		0x100000	/* Max child buffers */
#define SSHBUF_MAX_BIGNUM	(16384 / 8)	/* Max bignum *bytes* */
#define SSHBUF_MAX_ECPOINT	((528 * 2 / 8) + 1) /* Max EC point *bytes* */

/*
 * NB. do not depend on the internals of this. It will be made opaque
 * one day.
 */
struct sshbuf {
	u_char *d;		/* Data */
	const u_char *cd;	/* Const data */
	size_t off;		/* First available byte is buf->d + buf->off */
	size_t size;		/* Last byte is buf->d + buf->size - 1 */
	size_t max_size;	/* Maximum size of buffer */
	size_t alloc;		/* Total bytes allocated to buf->d */
	int readonly;		/* Refers to external, const data */
	int dont_free;		/* Kludge to support sshbuf_init */
	u_int refcount;		/* Tracks self and number of child buffers */
	struct sshbuf *parent;	/* If child, pointer to parent */
};

#ifndef SSHBUF_NO_DEPREACTED
/*
 * NB. Please do not use sshbuf_init() in new code. Please use sshbuf_new()
 * instead. sshbuf_init() is deprectated and will go away soon (it is
 * only included to allow compat with buffer_* in OpenSSH)
 */
void sshbuf_init(struct sshbuf *buf);
#endif

/*
 * Create a new sshbuf buffer.
 * Returns pointer to buffer on success, or NULL on allocation failure.
 */
struct sshbuf *sshbuf_new(void);

/*
 * Create a new, read-only sshbuf buffer from existing data.
 * Returns pointer to buffer on success, or NULL on allocation failure.
 */
struct sshbuf *sshbuf_from(const void *blob, size_t len);

/*
 * Create a new, read-only sshbuf buffer from the contents of an existing
 * buffer. The contents of "buf" must not change in the lifetime of the
 * resultant buffer.
 * Returns pointer to buffer on success, or NULL on allocation failure.
 */
struct sshbuf *sshbuf_fromb(struct sshbuf *buf);

/*
 * Create a new, read-only sshbuf buffer from the contents of a string in
 * an existing buffer (the string is consumed in the process).
 * The contents of "buf" must not change in the lifetime of the resultant
 * buffer.
 * Returns pointer to buffer on success, or NULL on allocation failure.
 */
int	sshbuf_froms(struct sshbuf *buf, struct sshbuf **bufp);

/*
 * Clear and free buf
 */
void	sshbuf_free(struct sshbuf *buf);

/*
 * Reset buf, clearing its contents. NB. max_size is preserved.
 */
void	sshbuf_reset(struct sshbuf *buf);

/*
 * Return the maximum size of buf
 */
size_t	sshbuf_max_size(const struct sshbuf *buf);

/*
 * Set the maximum size of buf
 * Returns 0 on success, or a negative SSH_ERR_* error code on failure.
 */
int	sshbuf_set_max_size(struct sshbuf *buf, size_t max_size);

/*
 * Returns the length of data in buf
 */
size_t	sshbuf_len(const struct sshbuf *buf);

/*
 * Returns number of bytes left in buffer before hitting max_size.
 */
size_t	sshbuf_avail(const struct sshbuf *buf);

/*
 * Returns a read-only pointer to the start of the data in buf
 */
const u_char *sshbuf_ptr(const struct sshbuf *buf);

/*
 * Returns a mutable pointer to the start of the data in buf, or
 * NULL if the buffer is read-only.
 */
u_char *sshbuf_mutable_ptr(const struct sshbuf *buf);

/*
 * Check whether a reservation of size len will succeed in buf
 * Safer to use than direct comparisons again sshbuf_avail as it copes
 * with unsigned overflows correctly.
 * Returns 0 on success, or a negative SSH_ERR_* error code on failure.
 */
int	sshbuf_check_reserve(const struct sshbuf *buf, size_t len);

/*
 * Preallocates len additional bytes in buf.
 * Useful for cases where the caller knows how many bytes will ultimately be
 * required to avoid realloc in the buffer code.
 * Returns 0 on success, or a negative SSH_ERR_* error code on failure.
 */
int	sshbuf_allocate(struct sshbuf *buf, size_t len);

/*
 * Reserve len bytes in buf.
 * Returns 0 on success and a pointer to the first reserved byte via the
 * optional dpp parameter or a negative * SSH_ERR_* error code on failure.
 */
int	sshbuf_reserve(struct sshbuf *buf, size_t len, u_char **dpp);

/*
 * Consume len bytes from the start of buf
 * Returns 0 on success, or a negative SSH_ERR_* error code on failure.
 */
int	sshbuf_consume(struct sshbuf *buf, size_t len);

/*
 * Consume len bytes from the end of buf
 * Returns 0 on success, or a negative SSH_ERR_* error code on failure.
 */
int	sshbuf_consume_end(struct sshbuf *buf, size_t len);

/* Extract or deposit some bytes */
int	sshbuf_get(struct sshbuf *buf, void *v, size_t len);
int	sshbuf_put(struct sshbuf *buf, const void *v, size_t len);
int	sshbuf_putb(struct sshbuf *buf, const struct sshbuf *v);

/* Append using a printf(3) format */
int	sshbuf_putf(struct sshbuf *buf, const char *fmt, ...)
	    __attribute__((format(printf, 2, 3)));
int	sshbuf_putfv(struct sshbuf *buf, const char *fmt, va_list ap);

/* Functions to extract or store big-endian words of various sizes */
int	sshbuf_get_u64(struct sshbuf *buf, u_int64_t *valp);
int	sshbuf_get_u32(struct sshbuf *buf, u_int32_t *valp);
int	sshbuf_get_u16(struct sshbuf *buf, u_int16_t *valp);
int	sshbuf_get_u8(struct sshbuf *buf, u_char *valp);
int	sshbuf_put_u64(struct sshbuf *buf, u_int64_t val);
int	sshbuf_put_u32(struct sshbuf *buf, u_int32_t val);
int	sshbuf_put_u16(struct sshbuf *buf, u_int16_t val);
int	sshbuf_put_u8(struct sshbuf *buf, u_char val);

/*
 * Functions to extract or store SSH wire encoded strings (u32 len || data)
 * The "cstring" variants admit no \0 characters in the string contents.
 * Caller must free *valp.
 */
int	sshbuf_get_string(struct sshbuf *buf, u_char **valp, size_t *lenp);
int	sshbuf_get_cstring(struct sshbuf *buf, char **valp, size_t *lenp);
int	sshbuf_get_stringb(struct sshbuf *buf, struct sshbuf *v);
int	sshbuf_put_string(struct sshbuf *buf, const void *v, size_t len);
int	sshbuf_put_cstring(struct sshbuf *buf, const char *v);
int	sshbuf_put_stringb(struct sshbuf *buf, const struct sshbuf *v);

/*
 * "Direct" variant of sshbuf_get_string, returns pointer into the sshbuf to
 * avoid an malloc+memcpy. The pointer is guaranteed to be valid until the
 * next sshbuf-modifying function call. Caller does not free.
 */
int	sshbuf_get_string_direct(struct sshbuf *buf, const u_char **valp,
	    size_t *lenp);

/* Skip past a string */
#define sshbuf_skip_string(buf) sshbuf_get_string_direct(buf, NULL, NULL)

/* Another variant: "peeks" into the buffer without modifying it */
int	sshbuf_peek_string_direct(const struct sshbuf *buf, const u_char **valp,
	    size_t *lenp);
/* XXX peek_u8 / peek_u32 */

/*
 * Functions to extract or store SSH wire encoded bignums and elliptic
 * curve points.
 */
int	sshbuf_get_bignum2(struct sshbuf *buf, BIGNUM *v);
int	sshbuf_get_bignum1(struct sshbuf *buf, BIGNUM *v);
int	sshbuf_get_bignum2_bytes_direct(struct sshbuf *buf,
	    const u_char **valp, size_t *lenp);
int	sshbuf_put_bignum2(struct sshbuf *buf, const BIGNUM *v);
int	sshbuf_put_bignum1(struct sshbuf *buf, const BIGNUM *v);
int	sshbuf_put_bignum2_bytes(struct sshbuf *buf, const void *v, size_t len);
int	sshbuf_get_ec(struct sshbuf *buf, EC_POINT *v, const EC_GROUP *g);
int	sshbuf_get_eckey(struct sshbuf *buf, EC_KEY *v);
int	sshbuf_put_ec(struct sshbuf *buf, const EC_POINT *v, const EC_GROUP *g);
int	sshbuf_put_eckey(struct sshbuf *buf, const EC_KEY *v);

/* Dump the contents of the buffer in a human-readable format */
void	sshbuf_dump(struct sshbuf *buf, FILE *f);

/* Dump specified memory in a human-readable format */
void	sshbuf_dump_data(const void *s, size_t len, FILE *f);

/* Return the hexadecimal representation of the contents of the buffer */
char	*sshbuf_dtob16(struct sshbuf *buf);

/* Encode the contents of the buffer as base64 */
char	*sshbuf_dtob64(struct sshbuf *buf);

/* Decode base64 data and append it to the buffer */
int	sshbuf_b64tod(struct sshbuf *buf, const char *b64);

/*
 * Duplicate the contents of a buffer to a string (caller to free).
 * Returns NULL on buffer error, or if the buffer contains a premature
 * nul character.
 */
char *sshbuf_dup_string(struct sshbuf *buf);

/* Macros for decoding/encoding integers */
#define PEEK_U64(p) \
	(((u_int64_t)(((const u_char *)(p))[0]) << 56) | \
	 ((u_int64_t)(((const u_char *)(p))[1]) << 48) | \
	 ((u_int64_t)(((const u_char *)(p))[2]) << 40) | \
	 ((u_int64_t)(((const u_char *)(p))[3]) << 32) | \
	 ((u_int64_t)(((const u_char *)(p))[4]) << 24) | \
	 ((u_int64_t)(((const u_char *)(p))[5]) << 16) | \
	 ((u_int64_t)(((const u_char *)(p))[6]) << 8) | \
	  (u_int64_t)(((const u_char *)(p))[7]))
#define PEEK_U32(p) \
	(((u_int32_t)(((const u_char *)(p))[0]) << 24) | \
	 ((u_int32_t)(((const u_char *)(p))[1]) << 16) | \
	 ((u_int32_t)(((const u_char *)(p))[2]) << 8) | \
	  (u_int32_t)(((const u_char *)(p))[3]))
#define PEEK_U16(p) \
	(((u_int16_t)(((const u_char *)(p))[0]) << 8) | \
	  (u_int16_t)(((const u_char *)(p))[1]))

#define POKE_U64(p, v) \
	do { \
		const u_int64_t __v = (v); \
		((u_char *)(p))[0] = (__v >> 56) & 0xff; \
		((u_char *)(p))[1] = (__v >> 48) & 0xff; \
		((u_char *)(p))[2] = (__v >> 40) & 0xff; \
		((u_char *)(p))[3] = (__v >> 32) & 0xff; \
		((u_char *)(p))[4] = (__v >> 24) & 0xff; \
		((u_char *)(p))[5] = (__v >> 16) & 0xff; \
		((u_char *)(p))[6] = (__v >> 8) & 0xff; \
		((u_char *)(p))[7] = __v & 0xff; \
	} while (0)
#define POKE_U32(p, v) \
	do { \
		const u_int32_t __v = (v); \
		((u_char *)(p))[0] = (__v >> 24) & 0xff; \
		((u_char *)(p))[1] = (__v >> 16) & 0xff; \
		((u_char *)(p))[2] = (__v >> 8) & 0xff; \
		((u_char *)(p))[3] = __v & 0xff; \
	} while (0)
#define POKE_U16(p, v) \
	do { \
		const u_int16_t __v = (v); \
		((u_char *)(p))[0] = (__v >> 8) & 0xff; \
		((u_char *)(p))[1] = __v & 0xff; \
	} while (0)

/* Internal definitions follow. Exposed for regress tests */
#ifdef SSHBUF_INTERNAL

/*
 * Return the allocation size of buf
 */
size_t	sshbuf_alloc(const struct sshbuf *buf);

/*
 * Increment the reference count of buf.
 */
int	sshbuf_set_parent(struct sshbuf *child, struct sshbuf *parent);

/*
 * Return the parent buffer of buf, or NULL if it has no parent.
 */
const struct sshbuf *sshbuf_parent(const struct sshbuf *buf);

/*
 * Return the reference count of buf
 */
u_int	sshbuf_refcount(const struct sshbuf *buf);

# define SSHBUF_SIZE_INIT	256		/* Initial allocation */
# define SSHBUF_SIZE_INC	256		/* Preferred increment length */
# define SSHBUF_PACK_MIN	8192		/* Minimim packable offset */

/* # define SSHBUF_ABORT abort */
/* # define SSHBUF_DEBUG */

# ifndef SSHBUF_ABORT
#  define SSHBUF_ABORT()
# endif

# ifdef SSHBUF_DEBUG
#  define SSHBUF_TELL(what) do { \
		printf("%s:%d %s: %s size %zu alloc %zu off %zu max %zu\n", \
		    __FILE__, __LINE__, __func__, what, \
		    buf->size, buf->alloc, buf->off, buf->max_size); \
		fflush(stdout); \
	} while (0)
#  define SSHBUF_DBG(x) do { \
		printf("%s:%d %s: ", __FILE__, __LINE__, __func__); \
		printf x; \
		printf("\n"); \
		fflush(stdout); \
	} while (0)
# else
#  define SSHBUF_TELL(what)
#  define SSHBUF_DBG(x)
# endif
#endif /* SSHBUF_INTERNAL */

#endif /* _SSHBUF_H */