path: root/src/util/attr_scan0.c

/*++
/* NAME
/*	attr_scan0 3
/* SUMMARY
/*	recover attributes from byte stream
/* SYNOPSIS
/*	#include <attr.h>
/*
/*	int	attr_scan0(fp, flags, type, name, ..., ATTR_TYPE_END)
/*	VSTREAM	*fp;
/*	int	flags;
/*	int	type;
/*	char	*name;
/*
/*	int	attr_vscan0(fp, flags, ap)
/*	VSTREAM	*fp;
/*	int	flags;
/*	va_list	ap;
/*
/*	int	attr_scan_more0(fp)
/*	VSTREAM	*fp;
/* DESCRIPTION
/*	attr_scan0() takes zero or more (name, value) request attributes
/*	and recovers the attribute values from the byte stream that was
/*	possibly generated by attr_print0().
/*
/*	attr_vscan0() provides an alternative interface that is convenient
/*	for calling from within a variadic function.
/*
/*	attr_scan_more0() returns 0 when a terminator is found (and
/*	consumes that terminator), returns 1 when more input is
/*	expected (without consuming input), and returns -1 otherwise
/*	(error).
/*
/*	The input stream is formatted as follows, where (item)* stands
/*	for zero or more instances of the specified item, and where
/*	(item1 | item2) stands for choice:
/*
/* .in +5
/*	attr-list :== (simple-attr | multi-attr)* null
/* .br
/*	multi-attr :== "{" null simple-attr* "}" null
/* .br
/*	simple-attr :== attr-name null attr-value null
/* .br
/*	attr-name :== any string not containing null
/* .br
/*	attr-value :== any string not containing null
/* .br
/*	null :== the ASCII null character
/* .in
/*
/*	All attribute names and attribute values are sent as null terminated
/*	strings. Each string must be no longer than 4*var_line_limit
/*	characters including the terminator.
/*	These formatting rules favor implementations in C.
/*
/*	Normally, attributes must be received in the sequence as specified with
/*	the attr_scan0() argument list.  The input stream may contain additional
/*	attributes at any point in the input stream, including additional
/*	instances of requested attributes.
/*
/*	Additional input attributes or input attribute instances are silently
/*	skipped over, unless the ATTR_FLAG_EXTRA processing flag is specified
/*	(see below). This allows for some flexibility in the evolution of
/*	protocols while still providing the option of being strict where
/*	this is desirable.
/*
/*	Arguments:
/* .IP fp
/*	Stream to recover the input attributes from.
/* .IP flags
/*	The bit-wise OR of zero or more of the following.
/* .RS
/* .IP ATTR_FLAG_MISSING
/*	Log a warning when the input attribute list terminates before all
/*	requested attributes are recovered. It is always an error when the
/*	input stream ends without the newline attribute list terminator.
/* .IP ATTR_FLAG_EXTRA
/*	Log a warning and stop attribute recovery when the input stream
/*	contains an attribute that was not requested. This includes the
/*	case of additional instances of a requested attribute.
/* .IP ATTR_FLAG_MORE
/*	After recovering the requested attributes, leave the input stream
/*	in a state that is usable for more attr_scan0() operations from the
/*	same input attribute list.
/*	By default, attr_scan0() skips forward past the input attribute list
/*	terminator.
/* .IP ATTR_FLAG_STRICT
/*	For convenience, this value combines both ATTR_FLAG_MISSING and
/*	ATTR_FLAG_EXTRA.
/* .IP ATTR_FLAG_NONE
/*	For convenience, this value requests none of the above.
/* .RE
/* .IP List of attributes followed by terminator:
/* .RS
/* .IP "RECV_ATTR_INT(const char *name, int *ptr)"
/*	This argument is followed by an attribute name and an integer pointer.
/* .IP "RECV_ATTR_LONG(const char *name, long *ptr)"
/*	This argument is followed by an attribute name and a long pointer.
/* .IP "RECV_ATTR_STR(const char *name, VSTRING *vp)"
/*	This argument is followed by an attribute name and a VSTRING pointer.
/* .IP "RECV_ATTR_DATA(const char *name, VSTRING *vp)"
/*	This argument is followed by an attribute name and a VSTRING pointer.
/* .IP "RECV_ATTR_FUNC(ATTR_SCAN_SLAVE_FN, void *data)"
/*	This argument is followed by a function pointer and a generic data
/*	pointer. The caller-specified function returns < 0 in case of
/*	error.
/* .IP "RECV_ATTR_HASH(HTABLE *table)"
/* .IP "RECV_ATTR_NAMEVAL(NVTABLE *table)"
/*	Receive a sequence of attribute names and string values.
/*	There can be no more than 1024 attributes in a hash table.
/* .sp
/*	The attribute string values are stored in the hash table under
/*	keys equal to the attribute name (obtained from the input stream).
/*	Values from the input stream are added to the hash table. Existing
/*	hash table entries are not replaced.
/* .sp
/*	Note: the SEND_ATTR_HASH or SEND_ATTR_NAMEVAL requests
/*	format their payload as a multi-attr sequence (see syntax
/*	above). When the receiver's input does not start with a
/*	multi-attr delimiter (i.e. the sender did not request
/*	SEND_ATTR_HASH or SEND_ATTR_NAMEVAL), the receiver will
/*	store all attribute names and values up to the attribute
/*	list terminator. In terms of code, this means that the
/*	RECV_ATTR_HASH or RECV_ATTR_NAMEVAL request must be followed
/*	by ATTR_TYPE_END.
/* .IP ATTR_TYPE_END
/*	This argument terminates the requested attribute list.
/* .RE
/* BUGS
/*	RECV_ATTR_HASH (RECV_ATTR_NAMEVAL) accepts attributes with arbitrary
/*	names from possibly untrusted sources.
/*	This is unsafe, unless the resulting table is queried only with
/*	known to be good attribute names.
/* DIAGNOSTICS
/*	attr_scan0() and attr_vscan0() return -1 when malformed input is
/*	detected (string too long, incomplete line, missing end marker).
/*	Otherwise, the result value is the number of attributes that were
/*	successfully recovered from the input stream (a hash table counts
/*	as the number of entries stored into the table).
/*
/*	Panic: interface violation. All system call errors are fatal.
/* SEE ALSO
/*	attr_print0(3) send attributes over byte stream.
/* LICENSE
/* .ad
/* .fi
/*	The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/*	Wietse Venema
/*	IBM T.J. Watson Research
/*	P.O. Box 704
/*	Yorktown Heights, NY 10598, USA
/*
/*	Wietse Venema
/*	Google, Inc.
/*	111 8th Avenue
/*	New York, NY 10011, USA
/*--*/

/* System library. */

#include <sys_defs.h>
#include <stdarg.h>
#include <string.h>
#include <stdio.h>

/* Utility library. */

#include <msg.h>
#include <mymalloc.h>
#include <vstream.h>
#include <vstring.h>
#include <vstring_vstream.h>
#include <htable.h>
#include <base64_code.h>
#include <attr.h>

/* Application specific. */

#define STR(x)	vstring_str(x)
#define LEN(x)	VSTRING_LEN(x)

/* attr_scan0_string - pull a string from the input stream */

static int attr_scan0_string(VSTREAM *fp, VSTRING *plain_buf, const char *context)
{
    int     ch;

    if ((ch = vstring_get_null(plain_buf, fp)) == VSTREAM_EOF) {
	msg_warn("%s on %s while reading %s",
		 vstream_ftimeout(fp) ? "timeout" : "premature end-of-input",
		 VSTREAM_PATH(fp), context);
	return (-1);
    }
    if (ch != 0) {
	msg_warn("unexpected end-of-input from %s while reading %s",
		 VSTREAM_PATH(fp), context);
	return (-1);
    }
    if (msg_verbose)
	msg_info("%s: %s", context, *STR(plain_buf) ? STR(plain_buf) : "(end)");
    return (ch);
}

/* attr_scan0_data - pull a data blob from the input stream */

static int attr_scan0_data(VSTREAM *fp, VSTRING *str_buf,
			           const char *context)
{
    static VSTRING *base64_buf = 0;
    int     ch;

    if (base64_buf == 0)
	base64_buf = vstring_alloc(10);
    if ((ch = attr_scan0_string(fp, base64_buf, context)) < 0)
	return (-1);
    if (base64_decode(str_buf, STR(base64_buf), LEN(base64_buf)) == 0) {
	msg_warn("malformed base64 data from %s while reading %s: %.100s",
		 VSTREAM_PATH(fp), context, STR(base64_buf));
	return (-1);
    }
    return (ch);
}

/* attr_scan0_number - pull a number from the input stream */

static int attr_scan0_number(VSTREAM *fp, unsigned *ptr, VSTRING *str_buf,
			             const char *context)
{
    char    junk = 0;
    int     ch;

    if ((ch = attr_scan0_string(fp, str_buf, context)) < 0)
	return (-1);
    if (sscanf(STR(str_buf), "%u%c", ptr, &junk) != 1 || junk != 0) {
	msg_warn("malformed numerical data from %s while reading %s: %.100s",
		 VSTREAM_PATH(fp), context, STR(str_buf));
	return (-1);
    }
    return (ch);
}

/* attr_scan0_long_number - pull a number from the input stream */

static int attr_scan0_long_number(VSTREAM *fp, unsigned long *ptr,
				          VSTRING *str_buf,
				          const char *context)
{
    char    junk = 0;
    int     ch;

    if ((ch = attr_scan0_string(fp, str_buf, context)) < 0)
	return (-1);
    if (sscanf(STR(str_buf), "%lu%c", ptr, &junk) != 1 || junk != 0) {
	msg_warn("malformed numerical data from %s while reading %s: %.100s",
		 VSTREAM_PATH(fp), context, STR(str_buf));
	return (-1);
    }
    return (ch);
}

/* attr_vscan0 - receive attribute list from stream */

int     attr_vscan0(VSTREAM *fp, int flags, va_list ap)
{
    const char *myname = "attr_scan0";
    static VSTRING *str_buf = 0;
    static VSTRING *name_buf = 0;
    int     wanted_type = -1;
    char   *wanted_name;
    unsigned int *number;
    unsigned long *long_number;
    VSTRING *string;
    HTABLE *hash_table;
    int     ch;
    int     conversions;
    ATTR_SCAN_SLAVE_FN scan_fn;
    void   *scan_arg;

    /*
     * Sanity check.
     */
    if (flags & ~ATTR_FLAG_ALL)
	msg_panic("%s: bad flags: 0x%x", myname, flags);

    /*
     * EOF check.
     */
    if ((ch = VSTREAM_GETC(fp)) == VSTREAM_EOF)
	return (0);
    vstream_ungetc(fp, ch);

    /*
     * Initialize.
     */
    if (str_buf == 0) {
	str_buf = vstring_alloc(10);
	name_buf = vstring_alloc(10);
    }

    /*
     * Iterate over all (type, name, value) triples.
     */
    for (conversions = 0; /* void */ ; conversions++) {

	/*
	 * Determine the next attribute type and attribute name on the
	 * caller's wish list.
	 * 
	 * If we're reading into a hash table, we already know that the
	 * attribute value is string-valued, and we get the attribute name
	 * from the input stream instead. This is secure only when the
	 * resulting table is queried with known to be good attribute names.
	 */
	if (wanted_type != ATTR_TYPE_HASH
	    && wanted_type != ATTR_TYPE_CLOSE) {
	    wanted_type = va_arg(ap, int);
	    if (wanted_type == ATTR_TYPE_END) {
		if ((flags & ATTR_FLAG_MORE) != 0)
		    return (conversions);
		wanted_name = "(list terminator)";
	    } else if (wanted_type == ATTR_TYPE_HASH) {
		wanted_name = "(any attribute name or list terminator)";
		hash_table = va_arg(ap, HTABLE *);
	    } else if (wanted_type != ATTR_TYPE_FUNC) {
		wanted_name = va_arg(ap, char *);
	    }
	}

	/*
	 * Locate the next attribute of interest in the input stream.
	 */
	while (wanted_type != ATTR_TYPE_FUNC) {

	    /*
	     * Get the name of the next attribute. Hitting EOF is always bad.
	     * Hitting the end-of-input early is OK if the caller is prepared
	     * to deal with missing inputs.
	     */
	    if (msg_verbose)
		msg_info("%s: wanted attribute: %s",
			 VSTREAM_PATH(fp), wanted_name);
	    if ((ch = attr_scan0_string(fp, name_buf,
				    "input attribute name")) == VSTREAM_EOF)
		return (-1);
	    if (LEN(name_buf) == 0) {
		if (wanted_type == ATTR_TYPE_END
		    || wanted_type == ATTR_TYPE_HASH)
		    return (conversions);
		if ((flags & ATTR_FLAG_MISSING) != 0)
		    msg_warn("missing attribute %s in input from %s",
			     wanted_name, VSTREAM_PATH(fp));
		return (conversions);
	    }

	    /*
	     * See if the caller asks for this attribute.
	     */
	    if (wanted_type == ATTR_TYPE_HASH
		&& strcmp(ATTR_NAME_OPEN, STR(name_buf)) == 0) {
		wanted_type = ATTR_TYPE_CLOSE;
		wanted_name = "(any attribute name or '}')";
		/* Advance in the input stream. */
		continue;
	    } else if (wanted_type == ATTR_TYPE_CLOSE
		       && strcmp(ATTR_NAME_CLOSE, STR(name_buf)) == 0) {
		/* Advance in the argument list. */
		wanted_type = -1;
		break;
	    }
	    if (wanted_type == ATTR_TYPE_HASH
		|| wanted_type == ATTR_TYPE_CLOSE
		|| (wanted_type != ATTR_TYPE_END
		    && strcmp(wanted_name, STR(name_buf)) == 0))
		break;
	    if ((flags & ATTR_FLAG_EXTRA) != 0) {
		msg_warn("unexpected attribute %s from %s (expecting: %s)",
			 STR(name_buf), VSTREAM_PATH(fp), wanted_name);
		return (conversions);
	    }

	    /*
	     * Skip over this attribute. The caller does not ask for it.
	     */
	    (void) attr_scan0_string(fp, str_buf, "input attribute value");
	}

	/*
	 * Do the requested conversion.
	 */
	switch (wanted_type) {
	case ATTR_TYPE_INT:
	    number = va_arg(ap, unsigned int *);
	    if ((ch = attr_scan0_number(fp, number, str_buf,
					"input attribute value")) < 0)
		return (-1);
	    break;
	case ATTR_TYPE_LONG:
	    long_number = va_arg(ap, unsigned long *);
	    if ((ch = attr_scan0_long_number(fp, long_number, str_buf,
					     "input attribute value")) < 0)
		return (-1);
	    break;
	case ATTR_TYPE_STR:
	    string = va_arg(ap, VSTRING *);
	    if ((ch = attr_scan0_string(fp, string,
					"input attribute value")) < 0)
		return (-1);
	    break;
	case ATTR_TYPE_DATA:
	    string = va_arg(ap, VSTRING *);
	    if ((ch = attr_scan0_data(fp, string,
				      "input attribute value")) < 0)
		return (-1);
	    break;
	case ATTR_TYPE_FUNC:
	    scan_fn = va_arg(ap, ATTR_SCAN_SLAVE_FN);
	    scan_arg = va_arg(ap, void *);
	    if (scan_fn(attr_scan0, fp, flags | ATTR_FLAG_MORE, scan_arg) < 0)
		return (-1);
	    break;
	case ATTR_TYPE_HASH:
	case ATTR_TYPE_CLOSE:
	    if ((ch = attr_scan0_string(fp, str_buf,
					"input attribute value")) < 0)
		return (-1);
	    if (htable_locate(hash_table, STR(name_buf)) != 0) {
		if ((flags & ATTR_FLAG_EXTRA) != 0) {
		    msg_warn("duplicate attribute %s in input from %s",
			     STR(name_buf), VSTREAM_PATH(fp));
		    return (conversions);
		}
	    } else if (hash_table->used >= ATTR_HASH_LIMIT) {
		msg_warn("attribute count exceeds limit %d in input from %s",
			 ATTR_HASH_LIMIT, VSTREAM_PATH(fp));
		return (conversions);
	    } else {
		htable_enter(hash_table, STR(name_buf),
			     mystrdup(STR(str_buf)));
	    }
	    break;
	case -1:
	    conversions -= 1;
	    break;
	default:
	    msg_panic("%s: unknown type code: %d", myname, wanted_type);
	}
    }
}

/* attr_scan0 - read attribute list from stream */

int     attr_scan0(VSTREAM *fp, int flags,...)
{
    va_list ap;
    int     ret;

    va_start(ap, flags);
    ret = attr_vscan0(fp, flags, ap);
    va_end(ap);
    return (ret);
}

/* attr_scan_more0 - look ahead for more */

int     attr_scan_more0(VSTREAM *fp)
{
    int     ch;

    switch (ch = VSTREAM_GETC(fp)) {
    case 0:
	if (msg_verbose)
	    msg_info("%s: terminator (consumed)", VSTREAM_PATH(fp));
	return (0);
    case VSTREAM_EOF:
	if (msg_verbose)
	    msg_info("%s: EOF", VSTREAM_PATH(fp));
	return (-1);
    default:
	if (msg_verbose)
	    msg_info("%s: non-terminator '%c' (lookahead)",
		     VSTREAM_PATH(fp), ch);
	(void) vstream_ungetc(fp, ch);
	return (1);
    }
}

#ifdef TEST

 /*
  * Proof of concept test program.  Mirror image of the attr_scan0 test
  * program.
  */
#include <msg_vstream.h>

int     var_line_limit = 2048;

int     main(int unused_argc, char **used_argv)
{
    VSTRING *data_val = vstring_alloc(1);
    VSTRING *str_val = vstring_alloc(1);
    HTABLE *table = htable_create(1);
    HTABLE_INFO **ht_info_list;
    HTABLE_INFO **ht;
    int     int_val;
    long    long_val;
    long    long_val2;
    int     ret;

    msg_verbose = 1;
    msg_vstream_init(used_argv[0], VSTREAM_ERR);
    if ((ret = attr_scan0(VSTREAM_IN,
			  ATTR_FLAG_STRICT,
			  RECV_ATTR_INT(ATTR_NAME_INT, &int_val),
			  RECV_ATTR_LONG(ATTR_NAME_LONG, &long_val),
			  RECV_ATTR_STR(ATTR_NAME_STR, str_val),
			  RECV_ATTR_DATA(ATTR_NAME_DATA, data_val),
			  RECV_ATTR_HASH(table),
			  RECV_ATTR_LONG(ATTR_NAME_LONG, &long_val2),
			  ATTR_TYPE_END)) > 4) {
	vstream_printf("%s %d\n", ATTR_NAME_INT, int_val);
	vstream_printf("%s %ld\n", ATTR_NAME_LONG, long_val);
	vstream_printf("%s %s\n", ATTR_NAME_STR, STR(str_val));
	vstream_printf("%s %s\n", ATTR_NAME_DATA, STR(str_val));
	ht_info_list = htable_list(table);
	for (ht = ht_info_list; *ht; ht++)
	    vstream_printf("(hash) %s %s\n", ht[0]->key, (char *) ht[0]->value);
	myfree((void *) ht_info_list);
	vstream_printf("%s %ld\n", ATTR_NAME_LONG, long_val2);
    } else {
	vstream_printf("return: %d\n", ret);
    }
    if ((ret = attr_scan0(VSTREAM_IN,
			  ATTR_FLAG_STRICT,
			  RECV_ATTR_INT(ATTR_NAME_INT, &int_val),
			  RECV_ATTR_LONG(ATTR_NAME_LONG, &long_val),
			  RECV_ATTR_STR(ATTR_NAME_STR, str_val),
			  RECV_ATTR_DATA(ATTR_NAME_DATA, data_val),
			  ATTR_TYPE_END)) == 4) {
	vstream_printf("%s %d\n", ATTR_NAME_INT, int_val);
	vstream_printf("%s %ld\n", ATTR_NAME_LONG, long_val);
	vstream_printf("%s %s\n", ATTR_NAME_STR, STR(str_val));
	vstream_printf("%s %s\n", ATTR_NAME_DATA, STR(data_val));
	ht_info_list = htable_list(table);
	for (ht = ht_info_list; *ht; ht++)
	    vstream_printf("(hash) %s %s\n", ht[0]->key, (char *) ht[0]->value);
	myfree((void *) ht_info_list);
    } else {
	vstream_printf("return: %d\n", ret);
    }
    if (vstream_fflush(VSTREAM_OUT) != 0)
	msg_fatal("write error: %m");

    vstring_free(data_val);
    vstring_free(str_val);
    htable_free(table, myfree);

    return (0);
}

#endif