attr_scan64.c

[詳解]

/*++
/* NAME
/*  attr_scan64 3
/* SUMMARY
/*  recover attributes from byte stream
/* SYNOPSIS
/*  #include <attr.h>
/*
/*  int attr_scan64(fp, flags, type, name, ..., ATTR_TYPE_END)
/*  VSTREAM *fp;
/*  int flags;
/*  int type;
/*  char    *name;
/*
/*  int attr_vscan64(fp, flags, ap)
/*  VSTREAM *fp;
/*  int flags;
/*  va_list ap;
/*
/*  int attr_scan_more64(fp)
/*  VSTREAM *fp;
/* DESCRIPTION
/*  attr_scan64() takes zero or more (name, value) request attributes
/*  and recovers the attribute values from the byte stream that was
/*  possibly generated by attr_print64().
/*
/*  attr_vscan64() provides an alternative interface that is convenient
/*  for calling from within a variadic function.
/*
/*  attr_scan_more64() 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)* newline
/* .br
/*  multi-attr :== "{" newline simple-attr* "}" newline
/* .br
/*  simple-attr :== attr-name colon attr-value newline
/* .br
/*  attr-name :== any base64 encoded string
/* .br
/*  attr-value :== any base64 encoded string
/* .br
/*  colon :== the ASCII colon character
/* .br
/*  newline :== the ASCII newline character
/* .in
/*
/*  All attribute names and attribute values are sent as base64-encoded
/*  strings. Each base64 encoding must be no longer than 4*var_line_limit
/*  characters. The formatting rules aim to make implementations in PERL
/*  and other languages easy.
/*
/*  Normally, attributes must be received in the sequence as specified with
/*  the attr_scan64() 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_scan64() operations from the
/*  same input attribute list.
/*  By default, attr_scan64() 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_scan64() and attr_vscan64() 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_print64(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 <htable.h>
#include <base64_code.h>
#include <attr.h>

/* Application specific. */

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

/* attr_scan64_string - pull a string from the input stream */

static int attr_scan64_string(VSTREAM *fp, VSTRING *plain_buf, const char *context)
{
    static VSTRING *base64_buf = 0;

#if 0
    extern int var_line_limit;      /* XXX */
    int     limit = var_line_limit * 4;

#endif
    int     ch;

    if (base64_buf == 0)
    base64_buf = vstring_alloc(10);

    VSTRING_RESET(base64_buf);
    while ((ch = VSTREAM_GETC(fp)) != ':' && ch != '\n') {
    if (ch == VSTREAM_EOF) {
        msg_warn("%s on %s while reading %s",
        vstream_ftimeout(fp) ? "timeout" : "premature end-of-input",
             VSTREAM_PATH(fp), context);
        return (-1);
    }
    VSTRING_ADDCH(base64_buf, ch);
#if 0
    if (LEN(base64_buf) > limit) {
        msg_warn("string length > %d characters from %s while reading %s",
             limit, VSTREAM_PATH(fp), context);
        return (-1);
    }
#endif
    }
    VSTRING_TERMINATE(base64_buf);
    if (base64_decode(plain_buf, STR(base64_buf), LEN(base64_buf)) == 0) {
    msg_warn("malformed base64 data from %s: %.100s",
         VSTREAM_PATH(fp), STR(base64_buf));
    return (-1);
    }
    if (msg_verbose)
    msg_info("%s: %s", context, *STR(plain_buf) ? STR(plain_buf) : "(end)");
    return (ch);
}

/* attr_scan64_number - pull a number from the input stream */

static int attr_scan64_number(VSTREAM *fp, unsigned *ptr, VSTRING *str_buf,
                          const char *context)
{
    char    junk = 0;
    int     ch;

    if ((ch = attr_scan64_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_scan64_long_number - pull a number from the input stream */

static int attr_scan64_long_number(VSTREAM *fp, unsigned long *ptr,
                           VSTRING *str_buf,
                           const char *context)
{
    char    junk = 0;
    int     ch;

    if ((ch = attr_scan64_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_vscan64 - receive attribute list from stream */

int     attr_vscan64(VSTREAM *fp, int flags, va_list ap)
{
    const char *myname = "attr_scan64";
    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_scan64_string(fp, name_buf,
                    "input attribute name")) == VSTREAM_EOF)
        return (-1);
        if (ch == '\n' && 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
          && ch == '\n' && 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
         && ch == '\n' && 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.
         */
        while (ch != '\n' && (ch = VSTREAM_GETC(fp)) != VSTREAM_EOF)
         /* void */ ;
    }

    /*
     * Do the requested conversion. If the target attribute is a
     * non-array type, disallow sending a multi-valued attribute, and
     * disallow sending no value. If the target attribute is an array
     * type, allow the sender to send a zero-element array (i.e. no value
     * at all). XXX Need to impose a bound on the number of array
     * elements.
     */
    switch (wanted_type) {
    case ATTR_TYPE_INT:
        if (ch != ':') {
        msg_warn("missing value for number attribute %s from %s",
             STR(name_buf), VSTREAM_PATH(fp));
        return (-1);
        }
        number = va_arg(ap, unsigned int *);
        if ((ch = attr_scan64_number(fp, number, str_buf,
                     "input attribute value")) < 0)
        return (-1);
        if (ch != '\n') {
        msg_warn("multiple values for attribute %s from %s",
             STR(name_buf), VSTREAM_PATH(fp));
        return (-1);
        }
        break;
    case ATTR_TYPE_LONG:
        if (ch != ':') {
        msg_warn("missing value for number attribute %s from %s",
             STR(name_buf), VSTREAM_PATH(fp));
        return (-1);
        }
        long_number = va_arg(ap, unsigned long *);
        if ((ch = attr_scan64_long_number(fp, long_number, str_buf,
                          "input attribute value")) < 0)
        return (-1);
        if (ch != '\n') {
        msg_warn("multiple values for attribute %s from %s",
             STR(name_buf), VSTREAM_PATH(fp));
        return (-1);
        }
        break;
    case ATTR_TYPE_STR:
        if (ch != ':') {
        msg_warn("missing value for string attribute %s from %s",
             STR(name_buf), VSTREAM_PATH(fp));
        return (-1);
        }
        string = va_arg(ap, VSTRING *);
        if ((ch = attr_scan64_string(fp, string,
                     "input attribute value")) < 0)
        return (-1);
        if (ch != '\n') {
        msg_warn("multiple values for attribute %s from %s",
             STR(name_buf), VSTREAM_PATH(fp));
        return (-1);
        }
        break;
    case ATTR_TYPE_DATA:
        if (ch != ':') {
        msg_warn("missing value for data attribute %s from %s",
             STR(name_buf), VSTREAM_PATH(fp));
        return (-1);
        }
        string = va_arg(ap, VSTRING *);
        if ((ch = attr_scan64_string(fp, string,
                     "input attribute value")) < 0)
        return (-1);
        if (ch != '\n') {
        msg_warn("multiple values for attribute %s from %s",
             STR(name_buf), VSTREAM_PATH(fp));
        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_scan64, fp, flags | ATTR_FLAG_MORE, scan_arg) < 0)
        return (-1);
        break;
    case ATTR_TYPE_HASH:
    case ATTR_TYPE_CLOSE:
        if (ch != ':') {
        msg_warn("missing value for string attribute %s from %s",
             STR(name_buf), VSTREAM_PATH(fp));
        return (-1);
        }
        if ((ch = attr_scan64_string(fp, str_buf,
                     "input attribute value")) < 0)
        return (-1);
        if (ch != '\n') {
        msg_warn("multiple values for attribute %s from %s",
             STR(name_buf), VSTREAM_PATH(fp));
        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_scan64 - read attribute list from stream */

int     attr_scan64(VSTREAM *fp, int flags,...)
{
    va_list ap;
    int     ret;

    va_start(ap, flags);
    ret = attr_vscan64(fp, flags, ap);
    va_end(ap);
    return (ret);
}

/* attr_scan_more64 - look ahead for more */

int     attr_scan_more64(VSTREAM *fp)
{
    int     ch;

    switch (ch = VSTREAM_GETC(fp)) {
    case '\n':
    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_scan64 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_scan64(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(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);
    vstream_printf("%s %ld\n", ATTR_NAME_LONG, long_val2);
    } else {
    vstream_printf("return: %d\n", ret);
    }
    if ((ret = attr_scan64(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