Adding upstream version 3.8.5.upstream/3.8.5

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 848 insertions, 0 deletions

diff --git a/src/util/mac_expand.c b/src/util/mac_expand.c
new file mode 100644
index 0000000..f40819e
--- /dev/null
+++ b/src/util/mac_expand.c
@@ -0,0 +1,848 @@
+/*++
+/* NAME
+/*	mac_expand 3
+/* SUMMARY
+/*	attribute expansion
+/* SYNOPSIS
+/*	#include <mac_expand.h>
+/*
+/*	int	mac_expand(result, pattern, flags, filter, lookup, context)
+/*	VSTRING *result;
+/*	const char *pattern;
+/*	int	flags;
+/*	const char *filter;
+/*	const char *lookup(const char *key, int mode, void *context)
+/*	void *context;
+/* AUXILIARY FUNCTIONS
+/*	typedef	MAC_EXP_OP_RES (*MAC_EXPAND_RELOP_FN) (
+/*	const char *left,
+/*	int	tok_val,
+/*	const char *rite)
+/*
+/*	void	mac_expand_add_relop(
+/*	int	*tok_list,
+/*	const char *suffix,
+/*	MAC_EXPAND_RELOP_FN relop_eval)
+/*
+/*	MAC_EXP_OP_RES mac_exp_op_res_bool[2];
+/* DESCRIPTION
+/*	This module implements parameter-less named attribute
+/*	expansions, both conditional and unconditional. As of Postfix
+/*	3.0 this code supports relational expression evaluation.
+/*
+/*	In this text, an attribute is considered "undefined" when its value
+/*	is a null pointer.  Otherwise, the attribute is considered "defined"
+/*	and is expected to have as value a null-terminated string.
+/*
+/*	In the text below, the legacy form $(...) is equivalent to
+/*	${...}. The legacy form $(...) may eventually disappear
+/*	from documentation. In the text below, the name in $name
+/*	and ${name...} must contain only characters from the set
+/*	[a-zA-Z0-9_].
+/*
+/*	The following substitutions are supported:
+/* .IP "$name, ${name}"
+/*	Unconditional attribute-based substitution. The result is the
+/*	named attribute value (empty if the attribute is not defined)
+/*	after optional further named attribute substitution.
+/* .IP "${name?text}, ${name?{text}}"
+/*	Conditional attribute-based substitution. If the named attribute
+/*	value is non-empty, the result is the given text, after
+/*	named attribute expansion and relational expression evaluation.
+/*	Otherwise, the result is empty.  Whitespace before or after
+/*	{text} is ignored.
+/* .IP "${name:text}, ${name:{text}}"
+/*	Conditional attribute-based substitution. If the attribute
+/*	value is empty or undefined, the expansion is the given
+/*	text, after named attribute expansion and relational expression
+/*	evaluation.  Otherwise, the result is empty.  Whitespace
+/*	before or after {text} is ignored.
+/* .IP "${name?{text1}:{text2}}, ${name?{text1}:text2}"
+/*	Conditional attribute-based substitution. If the named attribute
+/*	value is non-empty, the result is text1.  Otherwise, the
+/*	result is text2. In both cases the result is subject to
+/*	named attribute expansion and relational expression evaluation.
+/*	Whitespace before or after {text1} or {text2} is ignored.
+/* .IP "${{text1} == ${text2} ? {text3} : {text4}}"
+/*	Relational expression-based substitution.  First, the content
+/*	of {text1} and ${text2} is subjected to named attribute and
+/*	relational expression-based substitution.  Next, the relational
+/*	expression is evaluated. If it evaluates to "true", the
+/*	result is the content of {text3}, otherwise it is the content
+/*	of {text4}, after named attribute and relational expression-based
+/*	substitution. In addition to ==, this supports !=, <, <=,
+/*	>=, and >. Comparisons are numerical when both operands are
+/*	all digits, otherwise the comparisons are lexicographical.
+/*
+/*	Arguments:
+/* .IP result
+/*	Storage for the result of expansion. By default, the result
+/*	is truncated upon entry.
+/* .IP pattern
+/*	The string to be expanded.
+/* .IP flags
+/*	Bit-wise OR of zero or more of the following:
+/* .RS
+/* .IP MAC_EXP_FLAG_RECURSE
+/*	Expand attributes in lookup results. This should never be
+/*	done with data whose origin is untrusted.
+/* .IP MAC_EXP_FLAG_APPEND
+/*	Append text to the result buffer without truncating it.
+/* .IP MAC_EXP_FLAG_SCAN
+/*	Scan the input for named attributes, including named
+/*	attributes in all conditional result values.  Do not expand
+/*	named attributes, and do not truncate or write to the result
+/*	argument.
+/* .IP MAC_EXP_FLAG_PRINTABLE
+/*	Use the printable() function instead of \fIfilter\fR.
+/* .PP
+/*	The constant MAC_EXP_FLAG_NONE specifies a manifest null value.
+/* .RE
+/* .IP filter
+/*	A null pointer, or a null-terminated array of characters that
+/*	are allowed to appear in an expansion. Illegal characters are
+/*	replaced by underscores.
+/* .IP lookup
+/*	The attribute lookup routine. Arguments are: the attribute name,
+/*	MAC_EXP_MODE_TEST to test the existence of the named attribute
+/*	or MAC_EXP_MODE_USE to use the value of the named attribute,
+/*	and the caller context that was given to mac_expand(). A null
+/*	result value means that the requested attribute was not defined.
+/* .IP context
+/*	Caller context that is passed on to the attribute lookup routine.
+/* .PP
+/*	mac_expand_add_relop() registers a function that implements
+/*	support for custom relational operators. Custom operator names
+/*	such as "==xxx" have two parts: a prefix that is identical to
+/*	a built-in operator such as "==", and an application-specified
+/*	suffix such as "xxx".
+/*
+/*	Arguments:
+/* .IP tok_list
+/*	A null-terminated list of MAC_EXP_OP_TOK_* values that support
+/*	the custom operator suffix.
+/* .IP suffix
+/*	A null-terminated alphanumeric string that specifies the custom
+/*	operator suffix.
+/* .IP relop_eval
+/*	A function that compares two strings according to the
+/*	MAC_EXP_OP_TOK_* value specified with the tok_val argument,
+/*	and that returns non-zero if the custom operator evaluates to
+/*	true, zero otherwise.
+/*
+/*	mac_exp_op_res_bool provides an array that converts a boolean
+/*	value (0 or 1) to the corresponding MAX_EXP_OP_RES_TRUE or
+/*	MAX_EXP_OP_RES_FALSE value.
+/* DIAGNOSTICS
+/*	Fatal errors: out of memory.  Warnings: syntax errors, unreasonable
+/*	recursion depth.
+/*
+/*	The result value is the binary OR of zero or more of the following:
+/* .IP MAC_PARSE_ERROR
+/*	A syntax error was found in \fBpattern\fR, or some attribute had
+/*	an unreasonable nesting depth.
+/* .IP MAC_PARSE_UNDEF
+/*	An attribute was expanded but its value was not defined.
+/* SEE ALSO
+/*	mac_parse(3) locate macro references in string.
+/* 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 <ctype.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+
+/* Utility library. */
+
+#include <msg.h>
+#include <htable.h>
+#include <vstring.h>
+#include <mymalloc.h>
+#include <stringops.h>
+#include <name_code.h>
+#include <sane_strtol.h>
+#include <mac_parse.h>
+#include <mac_expand.h>
+
+ /*
+  * Simplifies the return of common relational operator results.
+  */
+MAC_EXP_OP_RES mac_exp_op_res_bool[2] = {
+    MAC_EXP_OP_RES_FALSE,
+    MAC_EXP_OP_RES_TRUE
+};
+
+ /*
+  * Little helper structure.
+  */
+typedef struct {
+    VSTRING *result;			/* result buffer */
+    int     flags;			/* features */
+    const char *filter;			/* character filter */
+    MAC_EXP_LOOKUP_FN lookup;		/* lookup routine */
+    void   *context;			/* caller context */
+    int     status;			/* findings */
+    int     level;			/* nesting level */
+} MAC_EXP_CONTEXT;
+
+ /*
+  * Support for relational expressions.
+  * 
+  * As of Postfix 2.2, ${attr-name?result} or ${attr-name:result} return the
+  * result respectively when the parameter value is non-empty, or when the
+  * parameter value is undefined or empty; support for the ternary ?:
+  * operator was anticipated, but not implemented for 10 years.
+  * 
+  * To make ${relational-expr?result} and ${relational-expr:result} work as
+  * expected without breaking the way that ? and : work, relational
+  * expressions evaluate to a non-empty or empty value. It does not matter
+  * what non-empty value we use for TRUE. However we must not use the
+  * undefined (null pointer) value for FALSE - that would raise the
+  * MAC_PARSE_UNDEF flag.
+  * 
+  * The value of a relational expression can be exposed with ${relational-expr},
+  * i.e. a relational expression that is not followed by ? or : conditional
+  * expansion.
+  */
+#define MAC_EXP_BVAL_TRUE	"true"
+#define MAC_EXP_BVAL_FALSE	""
+
+ /*
+  * Relational operators. The MAC_EXP_OP_TOK_* are defined in the header
+  * file.
+  */
+#define MAC_EXP_OP_STR_EQ	"=="
+#define MAC_EXP_OP_STR_NE	"!="
+#define MAC_EXP_OP_STR_LT	"<"
+#define MAC_EXP_OP_STR_LE	"<="
+#define MAC_EXP_OP_STR_GE	">="
+#define MAC_EXP_OP_STR_GT	">"
+#define MAC_EXP_OP_STR_ANY	"\"" MAC_EXP_OP_STR_EQ \
+				"\" or \"" MAC_EXP_OP_STR_NE "\"" \
+				"\" or \"" MAC_EXP_OP_STR_LT "\"" \
+				"\" or \"" MAC_EXP_OP_STR_LE "\"" \
+				"\" or \"" MAC_EXP_OP_STR_GE "\"" \
+				"\" or \"" MAC_EXP_OP_STR_GT "\""
+
+static const NAME_CODE mac_exp_op_table[] =
+{
+    MAC_EXP_OP_STR_EQ, MAC_EXP_OP_TOK_EQ,
+    MAC_EXP_OP_STR_NE, MAC_EXP_OP_TOK_NE,
+    MAC_EXP_OP_STR_LT, MAC_EXP_OP_TOK_LT,
+    MAC_EXP_OP_STR_LE, MAC_EXP_OP_TOK_LE,
+    MAC_EXP_OP_STR_GE, MAC_EXP_OP_TOK_GE,
+    MAC_EXP_OP_STR_GT, MAC_EXP_OP_TOK_GT,
+    0, MAC_EXP_OP_TOK_NONE,
+};
+
+ /*
+  * The whitespace separator set.
+  */
+#define MAC_EXP_WHITESPACE	CHARS_SPACE
+
+ /*
+  * Support for operator extensions.
+  */
+static HTABLE *mac_exp_ext_table;
+static VSTRING *mac_exp_ext_key;
+
+ /*
+  * SLMs.
+  */
+#define STR(x)	vstring_str(x)
+
+/* atol_or_die - convert or die */
+
+static long atol_or_die(const char *strval)
+{
+    long    result;
+    char   *remainder;
+
+    result = sane_strtol(strval, &remainder, 10);
+    if (*strval == 0 /* can't happen */ || *remainder != 0 || errno == ERANGE)
+	msg_fatal("mac_exp_eval: bad conversion: %s", strval);
+    return (result);
+}
+
+/* mac_exp_eval - evaluate binary expression */
+
+static MAC_EXP_OP_RES mac_exp_eval(const char *left, int tok_val,
+				           const char *rite)
+{
+    static const char myname[] = "mac_exp_eval";
+    long    delta;
+
+    /*
+     * Numerical or string comparison.
+     */
+    if (alldig(left) && alldig(rite)) {
+	delta = atol_or_die(left) - atol_or_die(rite);
+    } else {
+	delta = strcmp(left, rite);
+    }
+    switch (tok_val) {
+    case MAC_EXP_OP_TOK_EQ:
+	return (mac_exp_op_res_bool[delta == 0]);
+    case MAC_EXP_OP_TOK_NE:
+	return (mac_exp_op_res_bool[delta != 0]);
+    case MAC_EXP_OP_TOK_LT:
+	return (mac_exp_op_res_bool[delta < 0]);
+    case MAC_EXP_OP_TOK_LE:
+	return (mac_exp_op_res_bool[delta <= 0]);
+    case MAC_EXP_OP_TOK_GE:
+	return (mac_exp_op_res_bool[delta >= 0]);
+    case MAC_EXP_OP_TOK_GT:
+	return (mac_exp_op_res_bool[delta > 0]);
+    default:
+	msg_panic("%s: unknown operator: %d",
+		  myname, tok_val);
+    }
+}
+
+/* mac_exp_parse_error - report parse error, set error flag, return status */
+
+static int PRINTFLIKE(2, 3) mac_exp_parse_error(MAC_EXP_CONTEXT *mc,
+						        const char *fmt,...)
+{
+    va_list ap;
+
+    va_start(ap, fmt);
+    vmsg_warn(fmt, ap);
+    va_end(ap);
+    return (mc->status |= MAC_PARSE_ERROR);
+};
+
+/* MAC_EXP_ERR_RETURN - report parse error, set error flag, return status */
+
+#define MAC_EXP_ERR_RETURN(mc, fmt, ...) do { \
+	return (mac_exp_parse_error(mc, fmt, __VA_ARGS__)); \
+    } while (0)
+
+ /*
+  * Postfix 3.0 introduces support for {text} operands. Only with these do we
+  * support the ternary ?: operator and relational operators.
+  * 
+  * We cannot support operators in random text, because that would break Postfix
+  * 2.11 compatibility. For example, with the expression "${name?value}", the
+  * value is random text that may contain ':', '?', '{' and '}' characters.
+  * In particular, with Postfix 2.2 .. 2.11, "${name??foo:{b}ar}" evaluates
+  * to "?foo:{b}ar" or empty. There are explicit tests in this directory and
+  * the postconf directory to ensure that Postfix 2.11 compatibility is
+  * maintained.
+  * 
+  * Ideally, future Postfix configurations enclose random text operands inside
+  * {} braces. These allow whitespace around operands, which improves
+  * readability.
+  */
+
+/* MAC_EXP_FIND_LEFT_CURLY - skip over whitespace to '{', advance read ptr */
+
+#define MAC_EXP_FIND_LEFT_CURLY(len, cp) \
+	((cp[len = strspn(cp, MAC_EXP_WHITESPACE)] == '{') ? \
+	 (cp += len) : 0)
+
+/* mac_exp_extract_curly_payload - balance {}, skip whitespace, return payload */
+
+static char *mac_exp_extract_curly_payload(MAC_EXP_CONTEXT *mc, char **bp)
+{
+    char   *payload;
+    char   *cp;
+    int     level;
+    int     ch;
+
+    /*
+     * Extract the payload and balance the {}. The caller is expected to skip
+     * leading whitespace before the {. See MAC_EXP_FIND_LEFT_CURLY().
+     */
+    for (level = 1, cp = *bp, payload = ++cp; /* see below */ ; cp++) {
+	if ((ch = *cp) == 0) {
+	    mac_exp_parse_error(mc, "unbalanced {} in attribute expression: "
+				"\"%s\"",
+				*bp);
+	    return (0);
+	} else if (ch == '{') {
+	    level++;
+	} else if (ch == '}') {
+	    if (--level <= 0)
+		break;
+	}
+    }
+    *cp++ = 0;
+
+    /*
+     * Skip trailing whitespace after }.
+     */
+    *bp = cp + strspn(cp, MAC_EXP_WHITESPACE);
+    return (payload);
+}
+
+/* mac_exp_parse_relational - parse relational expression, advance read ptr */
+
+static int mac_exp_parse_relational(MAC_EXP_CONTEXT *mc, const char **lookup,
+				            char **bp)
+{
+    char   *cp = *bp;
+    VSTRING *left_op_buf;
+    VSTRING *rite_op_buf;
+    const char *left_op_strval;
+    const char *rite_op_strval;
+    char   *op_pos;
+    char   *op_strval;
+    size_t  op_len;
+    int     op_tokval;
+    int     op_result;
+    size_t  tmp_len;
+    char   *type_pos;
+    size_t  type_len;
+    MAC_EXPAND_RELOP_FN relop_eval;
+
+    /*
+     * Left operand. The caller is expected to skip leading whitespace before
+     * the {. See MAC_EXP_FIND_LEFT_CURLY().
+     */
+    if ((left_op_strval = mac_exp_extract_curly_payload(mc, &cp)) == 0)
+	return (mc->status);
+
+    /*
+     * Operator. Todo: regexp operator.
+     */
+    op_pos = cp;
+    op_len = strspn(cp, "<>!=?+-*/~&|%");	/* for better diagnostics. */
+    op_strval = mystrndup(cp, op_len);
+    op_tokval = name_code(mac_exp_op_table, NAME_CODE_FLAG_NONE, op_strval);
+    myfree(op_strval);
+    if (op_tokval == MAC_EXP_OP_TOK_NONE)
+	MAC_EXP_ERR_RETURN(mc, "%s expected at: \"...%s}>>>%.20s\"",
+			   MAC_EXP_OP_STR_ANY, left_op_strval, cp);
+    cp += op_len;
+
+    /*
+     * Custom operator suffix.
+     */
+    if (mac_exp_ext_table && ISALNUM(*cp)) {
+	type_pos = cp;
+	for (type_len = 1; ISALNUM(cp[type_len]); type_len++)
+	     /* void */ ;
+	cp += type_len;
+	vstring_sprintf(mac_exp_ext_key, "%.*s",
+			(int) (op_len + type_len), op_pos);
+	if ((relop_eval = (MAC_EXPAND_RELOP_FN) htable_find(mac_exp_ext_table,
+						STR(mac_exp_ext_key))) == 0)
+	    MAC_EXP_ERR_RETURN(mc, "bad operator suffix at: \"...%.*s>>>%.*s\"",
+			    (int) op_len, op_pos, (int) type_len, type_pos);
+    } else {
+	relop_eval = mac_exp_eval;
+    }
+
+    /*
+     * Right operand. Todo: syntax may depend on operator.
+     */
+    if (MAC_EXP_FIND_LEFT_CURLY(tmp_len, cp) == 0)
+	MAC_EXP_ERR_RETURN(mc, "\"{expression}\" expected at: "
+			   "\"...{%s} %.*s>>>%.20s\"",
+			   left_op_strval, (int) op_len, op_pos, cp);
+    if ((rite_op_strval = mac_exp_extract_curly_payload(mc, &cp)) == 0)
+	return (mc->status);
+
+    /*
+     * Evaluate the relational expression. Todo: regexp support.
+     */
+    mc->status |=
+	mac_expand(left_op_buf = vstring_alloc(100), left_op_strval,
+		   mc->flags, mc->filter, mc->lookup, mc->context);
+    mc->status |=
+	mac_expand(rite_op_buf = vstring_alloc(100), rite_op_strval,
+		   mc->flags, mc->filter, mc->lookup, mc->context);
+    if ((mc->flags & MAC_EXP_FLAG_SCAN) == 0
+	&& (op_result = relop_eval(vstring_str(left_op_buf), op_tokval,
+			 vstring_str(rite_op_buf))) == MAC_EXP_OP_RES_ERROR)
+	mc->status |= MAC_PARSE_ERROR;
+    vstring_free(left_op_buf);
+    vstring_free(rite_op_buf);
+    if (mc->status & MAC_PARSE_ERROR)
+	return (mc->status);
+
+    /*
+     * Here, we fake up a non-empty or empty parameter value lookup result,
+     * for compatibility with the historical code that looks named parameter
+     * values.
+     */
+    if (mc->flags & MAC_EXP_FLAG_SCAN) {
+	*lookup = 0;
+    } else {
+	switch (op_result) {
+	case MAC_EXP_OP_RES_TRUE:
+	    *lookup = MAC_EXP_BVAL_TRUE;
+	    break;
+	case MAC_EXP_OP_RES_FALSE:
+	    *lookup = MAC_EXP_BVAL_FALSE;
+	    break;
+	default:
+	    msg_panic("mac_expand: unexpected operator result: %d", op_result);
+	}
+    }
+    *bp = cp;
+    return (0);
+}
+
+/* mac_expand_add_relop - register operator extensions */
+
+void    mac_expand_add_relop(int *tok_list, const char *suffix,
+			             MAC_EXPAND_RELOP_FN relop_eval)
+{
+    const char myname[] = "mac_expand_add_relop";
+    const char *tok_name;
+    int    *tp;
+
+    /*
+     * Sanity checks.
+     */
+    if (!allalnum(suffix))
+	msg_panic("%s: bad operator suffix: %s", myname, suffix);
+
+    /*
+     * One-time initialization.
+     */
+    if (mac_exp_ext_table == 0) {
+	mac_exp_ext_table = htable_create(10);
+	mac_exp_ext_key = vstring_alloc(10);
+    }
+    for (tp = tok_list; *tp; tp++) {
+	if ((tok_name = str_name_code(mac_exp_op_table, *tp)) == 0)
+	    msg_panic("%s: unknown token code: %d", myname, *tp);
+	vstring_sprintf(mac_exp_ext_key, "%s%s", tok_name, suffix);
+	if (htable_locate(mac_exp_ext_table, STR(mac_exp_ext_key)) != 0)
+	    msg_panic("%s: duplicate key: %s", myname, STR(mac_exp_ext_key));
+	(void) htable_enter(mac_exp_ext_table,
+			    STR(mac_exp_ext_key), (void *) relop_eval);
+    }
+}
+
+/* mac_expand_callback - callback for mac_parse */
+
+static int mac_expand_callback(int type, VSTRING *buf, void *ptr)
+{
+    static const char myname[] = "mac_expand_callback";
+    MAC_EXP_CONTEXT *mc = (MAC_EXP_CONTEXT *) ptr;
+    int     lookup_mode;
+    const char *lookup;
+    char   *cp;
+    int     ch;
+    ssize_t res_len;
+    ssize_t tmp_len;
+    const char *res_iftrue;
+    const char *res_iffalse;
+
+    /*
+     * Sanity check.
+     */
+    if (mc->level++ > 100)
+	mac_exp_parse_error(mc, "unreasonable macro call nesting: \"%s\"",
+			    vstring_str(buf));
+    if (mc->status & MAC_PARSE_ERROR)
+	return (mc->status);
+
+    /*
+     * Named parameter or relational expression. In case of a syntax error,
+     * return without doing damage, and issue a warning instead.
+     */
+    if (type == MAC_PARSE_EXPR) {
+
+	cp = vstring_str(buf);
+
+	/*
+	 * Relational expression. If recursion is disabled, perform only one
+	 * level of $name expansion.
+	 */
+	if (MAC_EXP_FIND_LEFT_CURLY(tmp_len, cp)) {
+	    if (mac_exp_parse_relational(mc, &lookup, &cp) != 0)
+		return (mc->status);
+
+	    /*
+	     * Look for the ? or : operator.
+	     */
+	    if ((ch = *cp) != 0) {
+		if (ch != '?' && ch != ':')
+		    MAC_EXP_ERR_RETURN(mc, "\"?\" or \":\" expected at: "
+				       "\"...}>>>%.20s\"", cp);
+		cp++;
+	    }
+	}
+
+	/*
+	 * Named parameter.
+	 */
+	else {
+	    char   *start;
+
+	    /*
+	     * Look for the ? or : operator. In case of a syntax error,
+	     * return without doing damage, and issue a warning instead.
+	     */
+	    start = (cp += strspn(cp, MAC_EXP_WHITESPACE));
+	    for ( /* void */ ; /* void */ ; cp++) {
+		if ((ch = cp[tmp_len = strspn(cp, MAC_EXP_WHITESPACE)]) == 0) {
+		    *cp = 0;
+		    lookup_mode = MAC_EXP_MODE_USE;
+		    break;
+		}
+		if (ch == '?' || ch == ':') {
+		    *cp++ = 0;
+		    cp += tmp_len;
+		    lookup_mode = MAC_EXP_MODE_TEST;
+		    break;
+		}
+		ch = *cp;
+		if (!ISALNUM(ch) && ch != '_') {
+		    MAC_EXP_ERR_RETURN(mc, "attribute name syntax error at: "
+				       "\"...%.*s>>>%.20s\"",
+				       (int) (cp - vstring_str(buf)),
+				       vstring_str(buf), cp);
+		}
+	    }
+
+	    /*
+	     * Look up the named parameter. Todo: allow the lookup function
+	     * to specify if the result is safe for $name expansion.
+	     */
+	    lookup = mc->lookup(start, lookup_mode, mc->context);
+	}
+
+	/*
+	 * Return the requested result. After parsing the result operand
+	 * following ?, we fall through to parse the result operand following
+	 * :. This is necessary with the ternary ?: operator: first, with
+	 * MAC_EXP_FLAG_SCAN to parse both result operands with mac_parse(),
+	 * and second, to find garbage after any result operand. Without
+	 * MAC_EXP_FLAG_SCAN the content of only one of the ?: result
+	 * operands will be parsed with mac_parse(); syntax errors in the
+	 * other operand will be missed.
+	 */
+	switch (ch) {
+	case '?':
+	    if (MAC_EXP_FIND_LEFT_CURLY(tmp_len, cp)) {
+		if ((res_iftrue = mac_exp_extract_curly_payload(mc, &cp)) == 0)
+		    return (mc->status);
+	    } else {
+		res_iftrue = cp;
+		cp = "";			/* no left-over text */
+	    }
+	    if ((lookup != 0 && *lookup != 0) || (mc->flags & MAC_EXP_FLAG_SCAN))
+		mc->status |= mac_parse(res_iftrue, mac_expand_callback,
+					(void *) mc);
+	    if (*cp == 0)			/* end of input, OK */
+		break;
+	    if (*cp != ':')			/* garbage */
+		MAC_EXP_ERR_RETURN(mc, "\":\" expected at: "
+				   "\"...%s}>>>%.20s\"", res_iftrue, cp);
+	    cp += 1;
+	    /* FALLTHROUGH: do not remove, see comment above. */
+	case ':':
+	    if (MAC_EXP_FIND_LEFT_CURLY(tmp_len, cp)) {
+		if ((res_iffalse = mac_exp_extract_curly_payload(mc, &cp)) == 0)
+		    return (mc->status);
+	    } else {
+		res_iffalse = cp;
+		cp = "";			/* no left-over text */
+	    }
+	    if (lookup == 0 || *lookup == 0 || (mc->flags & MAC_EXP_FLAG_SCAN))
+		mc->status |= mac_parse(res_iffalse, mac_expand_callback,
+					(void *) mc);
+	    if (*cp != 0)			/* garbage */
+		MAC_EXP_ERR_RETURN(mc, "unexpected input at: "
+				   "\"...%s}>>>%.20s\"", res_iffalse, cp);
+	    break;
+	case 0:
+	    if (lookup == 0) {
+		mc->status |= MAC_PARSE_UNDEF;
+	    } else if (*lookup == 0 || (mc->flags & MAC_EXP_FLAG_SCAN)) {
+		 /* void */ ;
+	    } else if (mc->flags & MAC_EXP_FLAG_RECURSE) {
+		vstring_strcpy(buf, lookup);
+		mc->status |= mac_parse(vstring_str(buf), mac_expand_callback,
+					(void *) mc);
+	    } else {
+		res_len = VSTRING_LEN(mc->result);
+		vstring_strcat(mc->result, lookup);
+		if (mc->flags & MAC_EXP_FLAG_PRINTABLE) {
+		    printable(vstring_str(mc->result) + res_len, '_');
+		} else if (mc->filter) {
+		    cp = vstring_str(mc->result) + res_len;
+		    while (*(cp += strspn(cp, mc->filter)))
+			*cp++ = '_';
+		}
+	    }
+	    break;
+	default:
+	    msg_panic("%s: unknown operator code %d", myname, ch);
+	}
+    }
+
+    /*
+     * Literal text.
+     */
+    else if ((mc->flags & MAC_EXP_FLAG_SCAN) == 0) {
+	vstring_strcat(mc->result, vstring_str(buf));
+    }
+    mc->level--;
+
+    return (mc->status);
+}
+
+/* mac_expand - expand $name instances */
+
+int     mac_expand(VSTRING *result, const char *pattern, int flags,
+		           const char *filter,
+		           MAC_EXP_LOOKUP_FN lookup, void *context)
+{
+    MAC_EXP_CONTEXT mc;
+    int     status;
+
+    /*
+     * Bundle up the request and do the substitutions.
+     */
+    mc.result = result;
+    mc.flags = flags;
+    mc.filter = filter;
+    mc.lookup = lookup;
+    mc.context = context;
+    mc.status = 0;
+    mc.level = 0;
+    if ((flags & (MAC_EXP_FLAG_APPEND | MAC_EXP_FLAG_SCAN)) == 0)
+	VSTRING_RESET(result);
+    status = mac_parse(pattern, mac_expand_callback, (void *) &mc);
+    if ((flags & MAC_EXP_FLAG_SCAN) == 0)
+	VSTRING_TERMINATE(result);
+
+    return (status);
+}
+
+#ifdef TEST
+
+ /*
+  * This code certainly deserves a stand-alone test program.
+  */
+#include <stringops.h>
+#include <htable.h>
+#include <vstream.h>
+#include <vstring_vstream.h>
+
+static const char *lookup(const char *name, int unused_mode, void *context)
+{
+    HTABLE *table = (HTABLE *) context;
+
+    return (htable_find(table, name));
+}
+
+static MAC_EXP_OP_RES length_relop_eval(const char *left, int relop,
+					        const char *rite)
+{
+    const char myname[] = "length_relop_eval";
+    ssize_t delta = strlen(left) - strlen(rite);
+
+    switch (relop) {
+    case MAC_EXP_OP_TOK_EQ:
+	return (mac_exp_op_res_bool[delta == 0]);
+    case MAC_EXP_OP_TOK_NE:
+	return (mac_exp_op_res_bool[delta != 0]);
+    case MAC_EXP_OP_TOK_LT:
+	return (mac_exp_op_res_bool[delta < 0]);
+    case MAC_EXP_OP_TOK_LE:
+	return (mac_exp_op_res_bool[delta <= 0]);
+    case MAC_EXP_OP_TOK_GE:
+	return (mac_exp_op_res_bool[delta >= 0]);
+    case MAC_EXP_OP_TOK_GT:
+	return (mac_exp_op_res_bool[delta > 0]);
+    default:
+	msg_panic("%s: unknown operator: %d",
+		  myname, relop);
+    }
+}
+
+int     main(int unused_argc, char **argv)
+{
+    VSTRING *buf = vstring_alloc(100);
+    VSTRING *result = vstring_alloc(100);
+    char   *cp;
+    char   *name;
+    char   *value;
+    HTABLE *table;
+    int     stat;
+    int     length_relops[] = {
+	MAC_EXP_OP_TOK_EQ, MAC_EXP_OP_TOK_NE,
+	MAC_EXP_OP_TOK_GT, MAC_EXP_OP_TOK_GE,
+	MAC_EXP_OP_TOK_LT, MAC_EXP_OP_TOK_LE,
+	0,
+    };
+
+    /*
+     * Add relops that compare string lengths instead of content.
+     */
+    mac_expand_add_relop(length_relops, "length", length_relop_eval);
+
+    /*
+     * Loop over the inputs.
+     */
+    while (!vstream_feof(VSTREAM_IN)) {
+
+	table = htable_create(0);
+
+	/*
+	 * Read a block of definitions, terminated with an empty line.
+	 */
+	while (vstring_get_nonl(buf, VSTREAM_IN) != VSTREAM_EOF) {
+	    vstream_printf("<< %s\n", vstring_str(buf));
+	    vstream_fflush(VSTREAM_OUT);
+	    if (VSTRING_LEN(buf) == 0)
+		break;
+	    cp = vstring_str(buf);
+	    name = mystrtok(&cp, CHARS_SPACE "=");
+	    value = mystrtok(&cp, CHARS_SPACE "=");
+	    htable_enter(table, name, value ? mystrdup(value) : 0);
+	}
+
+	/*
+	 * Read a block of patterns, terminated with an empty line or EOF.
+	 */
+	while (vstring_get_nonl(buf, VSTREAM_IN) != VSTREAM_EOF) {
+	    vstream_printf("<< %s\n", vstring_str(buf));
+	    vstream_fflush(VSTREAM_OUT);
+	    if (VSTRING_LEN(buf) == 0)
+		break;
+	    cp = vstring_str(buf);
+	    VSTRING_RESET(result);
+	    stat = mac_expand(result, vstring_str(buf), MAC_EXP_FLAG_NONE,
+			      (char *) 0, lookup, (void *) table);
+	    vstream_printf("stat=%d result=%s\n", stat, vstring_str(result));
+	    vstream_fflush(VSTREAM_OUT);
+	}
+	htable_free(table, myfree);
+	vstream_printf("\n");
+    }
+
+    /*
+     * Clean up.
+     */
+    vstring_free(buf);
+    vstring_free(result);
+    exit(0);
+}
+
+#endif