var-expand.c

/* Copyright (c) 2003-2016 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "array.h"
#include "md5.h"
#include "hash.h"
#include "hex-binary.h"
#include "hostpid.h"
#include "str.h"
#include "strescape.h"
#include "var-expand.h"

#include <unistd.h>
#include <ctype.h>

#define TABLE_LAST(t) \
	((t)->key == '\0' && (t)->long_key == NULL)

struct var_expand_context {
	int offset;
	int width;
	bool zero_padding;
};

struct var_expand_modifier {
	char key;
	const char *(*func)(const char *, struct var_expand_context *);
};

static const char *
m_str_lcase(const char *str, struct var_expand_context *ctx ATTR_UNUSED)
{
	return t_str_lcase(str);
}

static const char *
m_str_ucase(const char *str, struct var_expand_context *ctx ATTR_UNUSED)
{
	return t_str_ucase(str);
}

static const char *
m_str_escape(const char *str, struct var_expand_context *ctx ATTR_UNUSED)
{
	return str_escape(str);
}

static const char *
m_str_hex(const char *str, struct var_expand_context *ctx ATTR_UNUSED)
{
	unsigned long long l;

	if (str_to_ullong(str, &l) < 0)
		l = 0;
	return t_strdup_printf("%llx", l);
}

static const char *
m_str_reverse(const char *str, struct var_expand_context *ctx ATTR_UNUSED)
{
	size_t len = strlen(str);
	char *p, *rev;

	rev = t_malloc(len + 1);
	rev[len] = '\0';

	for (p = rev + len - 1; *str != '\0'; str++)
		*p-- = *str;
	return rev;
}

static const char *m_str_hash(const char *str, struct var_expand_context *ctx)
{
	unsigned int value = str_hash(str);
	string_t *hash = t_str_new(20);

	if (ctx->width != 0) {
		value %= ctx->width;
		ctx->width = 0;
	}

	str_printfa(hash, "%x", value);
	while ((int)str_len(hash) < ctx->offset)
		str_insert(hash, 0, "0");
        ctx->offset = 0;

	return str_c(hash);
}

static const char *
m_str_newhash(const char *str, struct var_expand_context *ctx)
{
	string_t *hash = t_str_new(20);
	unsigned char result[MD5_RESULTLEN];
	unsigned int i;
	uint64_t value = 0;

	md5_get_digest(str, strlen(str), result);
	for (i = 0; i < sizeof(value); i++) {
		value <<= 8;
		value |= result[i];
	}

	if (ctx->width != 0) {
		value %= ctx->width;
		ctx->width = 0;
	}

	str_printfa(hash, "%x", (unsigned int)value);
	while ((int)str_len(hash) < ctx->offset)
		str_insert(hash, 0, "0");
        ctx->offset = 0;

	return str_c(hash);
}

static const char *
m_str_md5(const char *str, struct var_expand_context *ctx ATTR_UNUSED)
{
	unsigned char digest[16];

	md5_get_digest(str, strlen(str), digest);

	return binary_to_hex(digest, sizeof(digest));
}

static const char *
m_str_ldap_dn(const char *str, struct var_expand_context *ctx ATTR_UNUSED)
{
	string_t *ret = t_str_new(256);

	while (*str) {
		if (*str == '.')
			str_append(ret, ",dc=");
		else
			str_append_c(ret, *str);
		str++;
	}

	return str_free_without_data(&ret);
}

static const char *
m_str_trim(const char *str, struct var_expand_context *ctx ATTR_UNUSED)
{
	unsigned int len;

	len = strlen(str);
	while (len > 0 && i_isspace(str[len-1]))
		len--;
	return t_strndup(str, len);
}

#define MAX_MODIFIER_COUNT 10
static const struct var_expand_modifier modifiers[] = {
	{ 'L', m_str_lcase },
	{ 'U', m_str_ucase },
	{ 'E', m_str_escape },
	{ 'X', m_str_hex },
	{ 'R', m_str_reverse },
	{ 'H', m_str_hash },
	{ 'N', m_str_newhash },
	{ 'M', m_str_md5 },
	{ 'D', m_str_ldap_dn },
	{ 'T', m_str_trim },
	{ '\0', NULL }
};

static const char *
var_expand_func(const struct var_expand_func_table *func_table,
		const char *key, const char *data, void *context)
{
	const char *value;

	if (strcmp(key, "env") == 0) {
		value = getenv(data);
		return value != NULL ? value : "";
	}
	if (func_table == NULL)
		return NULL;

	for (; func_table->key != NULL; func_table++) {
		if (strcmp(func_table->key, key) == 0) {
			value = func_table->func(data, context);
			return value != NULL ? value : "";
		}
	}
	return NULL;
}

static const char *
var_expand_long(const struct var_expand_table *table,
		const struct var_expand_func_table *func_table,
		const void *key_start, unsigned int key_len, void *context)
{
        const struct var_expand_table *t;
	const char *key, *value = NULL;

	if (table != NULL) {
		for (t = table; !TABLE_LAST(t); t++) {
			if (t->long_key != NULL &&
			    strncmp(t->long_key, key_start, key_len) == 0 &&
			    t->long_key[key_len] == '\0') {
				return t->value != NULL ? t->value : "";
			}
		}
	}
	key = t_strndup(key_start, key_len);

	/* built-in variables: */
	switch (key_len) {
	case 3:
		if (strcmp(key, "pid") == 0)
			value = my_pid;
		else if (strcmp(key, "uid") == 0)
			value = dec2str(geteuid());
		else if (strcmp(key, "gid") == 0)
			value = dec2str(getegid());
		break;
	case 8:
		if (strcmp(key, "hostname") == 0)
			value = my_hostname;
		break;
	}

	if (value == NULL) {
		const char *data = strchr(key, ':');

		if (data != NULL)
			key = t_strdup_until(key, data++);
		else
			data = "";
		value = var_expand_func(func_table, key, data, context);
	}
	if (value == NULL)
		return t_strdup_printf("UNSUPPORTED_VARIABLE_%s", key);
	return value;
}

void var_expand_with_funcs(string_t *dest, const char *str,
			   const struct var_expand_table *table,
			   const struct var_expand_func_table *func_table,
			   void *context)
{
        const struct var_expand_modifier *m;
        const struct var_expand_table *t;
	const char *var;
        struct var_expand_context ctx;
	const char *(*modifier[MAX_MODIFIER_COUNT])
		(const char *, struct var_expand_context *);
	const char *end;
	unsigned int i, len, modifier_count;

	memset(&ctx, 0, sizeof(ctx));
	for (; *str != '\0'; str++) {
		if (*str != '%')
			str_append_c(dest, *str);
		else {
			int sign = 1;

			str++;
			memset(&ctx, 0, sizeof(ctx));

			/* [<offset>.]<width>[<modifiers>]<variable> */
			if (*str == '-') {
				sign = -1;
				str++;
			}
			if (*str == '0') {
				ctx.zero_padding = TRUE;
				str++;
			}
			while (*str >= '0' && *str <= '9') {
				ctx.width = ctx.width*10 + (*str - '0');
				str++;
			}

			if (*str == '.') {
				ctx.offset = sign * ctx.width;
				sign = 1;
				ctx.width = 0;
				str++;

				/* if offset was prefixed with zero (or it was
				   plain zero), just ignore that. zero padding
				   is done with the width. */
				ctx.zero_padding = FALSE;
				if (*str == '0') {
					ctx.zero_padding = TRUE;
					str++;
				}
				if (*str == '-') {
					sign = -1;
					str++;
				}

				while (*str >= '0' && *str <= '9') {
					ctx.width = ctx.width*10 + (*str - '0');
					str++;
				}
				ctx.width = sign * ctx.width;
			}

                        modifier_count = 0;
			while (modifier_count < MAX_MODIFIER_COUNT) {
				modifier[modifier_count] = NULL;
				for (m = modifiers; m->key != '\0'; m++) {
					if (m->key == *str) {
						/* @UNSAFE */
						modifier[modifier_count] =
							m->func;
						str++;
						break;
					}
				}
				if (modifier[modifier_count] == NULL)
					break;
				modifier_count++;
			}

			if (*str == '\0')
				break;

			var = NULL;
			if (*str == '{' && (end = strchr(str, '}')) != NULL) {
				/* %{long_key} */
				len = end - (str + 1);
				var = var_expand_long(table, func_table,
						      str+1, len, context);
				i_assert(var != NULL);
				str = end;
			} else if (table != NULL) {
				for (t = table; !TABLE_LAST(t); t++) {
					if (t->key == *str) {
						var = t->value != NULL ?
							t->value : "";
						break;
					}
				}
			}

			if (var == NULL) {
				/* not found */
				if (*str == '%')
					var = "%";
			}

			if (var != NULL) {
				for (i = 0; i < modifier_count; i++)
					var = modifier[i](var, &ctx);

				if (ctx.offset < 0) {
					/* if offset is < 0 then we want to
					   start at the end */
					size_t len = strlen(var);

					if (len > (size_t)-ctx.offset)
						var += len + ctx.offset;
				} else {
					while (*var != '\0' && ctx.offset > 0) {
						ctx.offset--;
						var++;
					}
				}
				if (ctx.width == 0)
					str_append(dest, var);
				else if (!ctx.zero_padding) {
					if (ctx.width < 0)
						ctx.width = strlen(var) - (-ctx.width);
					str_append_n(dest, var, ctx.width);
				} else {
					/* %05d -like padding. no truncation. */
					int len = strlen(var);
					while (len < ctx.width) {
						str_append_c(dest, '0');
						ctx.width--;
					}
					str_append(dest, var);
				}
			}
		}
	}
}

void var_expand(string_t *dest, const char *str,
		const struct var_expand_table *table)
{
	var_expand_with_funcs(dest, str, table, NULL, NULL);
}

char var_get_key(const char *str)
{
	unsigned int idx, size;

	var_get_key_range(str, &idx, &size);
	return str[idx];
}

void var_get_key_range(const char *str, unsigned int *idx_r,
		       unsigned int *size_r)
{
	const struct var_expand_modifier *m;
	unsigned int i = 0;

	/* [<offset>.]<width>[<modifiers>]<variable> */
	while ((str[i] >= '0' && str[i] <= '9') || str[i] == '-')
		i++;

	if (str[i] == '.') {
		i++;
		while ((str[i] >= '0' && str[i] <= '9') || str[i] == '-')
			i++;
	}

	do {
		for (m = modifiers; m->key != '\0'; m++) {
			if (m->key == str[i]) {
				i++;
				break;
			}
		}
	} while (m->key != '\0');

	if (str[i] != '{') {
		/* short key */
		*idx_r = i;
		*size_r = str[i] == '\0' ? 0 : 1;
	} else {
		/* long key */
		*idx_r = ++i;
		for (; str[i] != '\0'; i++) {
			if (str[i] == '}')
				break;
		}
		*size_r = i - *idx_r;
	}
}

static bool var_has_long_key(const char **str, const char *long_key)
{
	const char *start, *end;

	start = strchr(*str, '{');
	i_assert(start != NULL);

	end = strchr(++start, '}');
	if (end == NULL)
		return FALSE;

	if (strncmp(start, long_key, end-start) == 0 &&
	    long_key[end-start] == '\0')
		return TRUE;

	*str = end;
	return FALSE;
}

bool var_has_key(const char *str, char key, const char *long_key)
{
	char c;

	for (; *str != '\0'; str++) {
		if (*str == '%' && str[1] != '\0') {
			str++;
			c = var_get_key(str);
			if (c == key)
				return TRUE;

			if (c == '{' && long_key != NULL) {
				if (var_has_long_key(&str, long_key))
					return TRUE;
			}
		}
	}
	return FALSE;
}

const struct var_expand_table *
var_expand_table_build(char key, const char *value, char key2, ...)
{
	ARRAY(struct var_expand_table) variables;
	struct var_expand_table *var;
	va_list args;

	i_assert(key != '\0');

	t_array_init(&variables, 16);
	var = array_append_space(&variables);
	var->key = key;
	var->value = value;

	va_start(args, key2);
	for (key = key2; key != '\0'; key = va_arg(args, int)) {
		var = array_append_space(&variables);
		var->key = key;
		var->value = va_arg(args, const char *);
	}
	va_end(args);

	/* 0, NULL entry */
	array_append_zero(&variables);
	return array_idx(&variables, 0);
}