src/lib/var-expand.c

	var-expand.c revision e48f289d2e5b2546a2c5dcc90f7ab624cc58cca2
/* Copyright (c) 2003-2015 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 <stdlib.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);
    }
    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);
                if (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);
}