files_read_raw_ref: avoid infinite loop on broken symlinks

[git] / urlmatch.c

#include "cache.h"
#include "urlmatch.h"

#define URL_ALPHA "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
#define URL_DIGIT "0123456789"
#define URL_ALPHADIGIT URL_ALPHA URL_DIGIT
#define URL_SCHEME_CHARS URL_ALPHADIGIT "+.-"
#define URL_HOST_CHARS URL_ALPHADIGIT ".-[:]" /* IPv6 literals need [:] */
#define URL_UNSAFE_CHARS " <>\"%{}|\\^`" /* plus 0x00-0x1F,0x7F-0xFF */
#define URL_GEN_RESERVED ":/?#[]@"
#define URL_SUB_RESERVED "!$&'()*+,;="
#define URL_RESERVED URL_GEN_RESERVED URL_SUB_RESERVED /* only allowed delims */

static int append_normalized_escapes(struct strbuf *buf,
                                     const char *from,
                                     size_t from_len,
                                     const char *esc_extra,
                                     const char *esc_ok)
{
        /*
         * Append to strbuf 'buf' characters from string 'from' with length
         * 'from_len' while unescaping characters that do not need to be escaped
         * and escaping characters that do.  The set of characters to escape
         * (the complement of which is unescaped) starts out as the RFC 3986
         * unsafe characters (0x00-0x1F,0x7F-0xFF," <>\"#%{}|\\^`").  If
         * 'esc_extra' is not NULL, those additional characters will also always
         * be escaped.  If 'esc_ok' is not NULL, those characters will be left
         * escaped if found that way, but will not be unescaped otherwise (used
         * for delimiters).  If a %-escape sequence is encountered that is not
         * followed by 2 hexadecimal digits, the sequence is invalid and
         * false (0) will be returned.  Otherwise true (1) will be returned for
         * success.
         *
         * Note that all %-escape sequences will be normalized to UPPERCASE
         * as indicated in RFC 3986.  Unless included in esc_extra or esc_ok
         * alphanumerics and "-._~" will always be unescaped as per RFC 3986.
         */

        while (from_len) {
                int ch = *from++;
                int was_esc = 0;

                from_len--;
                if (ch == '%') {
                        if (from_len < 2 ||
                            !isxdigit(from[0]) ||
                            !isxdigit(from[1]))
                                return 0;
                        ch = hexval(*from++) << 4;
                        ch |= hexval(*from++);
                        from_len -= 2;
                        was_esc = 1;
                }
                if ((unsigned char)ch <= 0x1F || (unsigned char)ch >= 0x7F ||
                    strchr(URL_UNSAFE_CHARS, ch) ||
                    (esc_extra && strchr(esc_extra, ch)) ||
                    (was_esc && strchr(esc_ok, ch)))
                        strbuf_addf(buf, "%%%02X", (unsigned char)ch);
                else
                        strbuf_addch(buf, ch);
        }

        return 1;
}

char *url_normalize(const char *url, struct url_info *out_info)
{
        /*
         * Normalize NUL-terminated url using the following rules:
         *
         * 1. Case-insensitive parts of url will be converted to lower case
         * 2. %-encoded characters that do not need to be will be unencoded
         * 3. Characters that are not %-encoded and must be will be encoded
         * 4. All %-encodings will be converted to upper case hexadecimal
         * 5. Leading 0s are removed from port numbers
         * 6. If the default port for the scheme is given it will be removed
         * 7. A path part (including empty) not starting with '/' has one added
         * 8. Any dot segments (. or ..) in the path are resolved and removed
         * 9. IPv6 host literals are allowed (but not normalized or validated)
         *
         * The rules are based on information in RFC 3986.
         *
         * Please note this function requires a full URL including a scheme
         * and host part (except for file: URLs which may have an empty host).
         *
         * The return value is a newly allocated string that must be freed
         * or NULL if the url is not valid.
         *
         * If out_info is non-NULL, the url and err fields therein will always
         * be set.  If a non-NULL value is returned, it will be stored in
         * out_info->url as well, out_info->err will be set to NULL and the
         * other fields of *out_info will also be filled in.  If a NULL value
         * is returned, NULL will be stored in out_info->url and out_info->err
         * will be set to a brief, translated, error message, but no other
         * fields will be filled in.
         *
         * This is NOT a URL validation function.  Full URL validation is NOT
         * performed.  Some invalid host names are passed through this function
         * undetected.  However, most all other problems that make a URL invalid
         * will be detected (including a missing host for non file: URLs).
         */

        size_t url_len = strlen(url);
        struct strbuf norm;
        size_t spanned;
        size_t scheme_len, user_off=0, user_len=0, passwd_off=0, passwd_len=0;
        size_t host_off=0, host_len=0, port_len=0, path_off, path_len, result_len;
        const char *slash_ptr, *at_ptr, *colon_ptr, *path_start;
        char *result;

        /*
         * Copy lowercased scheme and :// suffix, %-escapes are not allowed
         * First character of scheme must be URL_ALPHA
         */
        spanned = strspn(url, URL_SCHEME_CHARS);
        if (!spanned || !isalpha(url[0]) || spanned + 3 > url_len ||
            url[spanned] != ':' || url[spanned+1] != '/' || url[spanned+2] != '/') {
                if (out_info) {
                        out_info->url = NULL;
                        out_info->err = _("invalid URL scheme name or missing '://' suffix");
                }
                return NULL; /* Bad scheme and/or missing "://" part */
        }
        strbuf_init(&norm, url_len);
        scheme_len = spanned;
        spanned += 3;
        url_len -= spanned;
        while (spanned--)
                strbuf_addch(&norm, tolower(*url++));


        /*
         * Copy any username:password if present normalizing %-escapes
         */
        at_ptr = strchr(url, '@');
        slash_ptr = url + strcspn(url, "/?#");
        if (at_ptr && at_ptr < slash_ptr) {
                user_off = norm.len;
                if (at_ptr > url) {
                        if (!append_normalized_escapes(&norm, url, at_ptr - url,
                                                       "", URL_RESERVED)) {
                                if (out_info) {
                                        out_info->url = NULL;
                                        out_info->err = _("invalid %XX escape sequence");
                                }
                                strbuf_release(&norm);
                                return NULL;
                        }
                        colon_ptr = strchr(norm.buf + scheme_len + 3, ':');
                        if (colon_ptr) {
                                passwd_off = (colon_ptr + 1) - norm.buf;
                                passwd_len = norm.len - passwd_off;
                                user_len = (passwd_off - 1) - (scheme_len + 3);
                        } else {
                                user_len = norm.len - (scheme_len + 3);
                        }
                }
                strbuf_addch(&norm, '@');
                url_len -= (++at_ptr - url);
                url = at_ptr;
        }


        /*
         * Copy the host part excluding any port part, no %-escapes allowed
         */
        if (!url_len || strchr(":/?#", *url)) {
                /* Missing host invalid for all URL schemes except file */
                if (strncmp(norm.buf, "file:", 5)) {
                        if (out_info) {
                                out_info->url = NULL;
                                out_info->err = _("missing host and scheme is not 'file:'");
                        }
                        strbuf_release(&norm);
                        return NULL;
                }
        } else {
                host_off = norm.len;
        }
        colon_ptr = slash_ptr - 1;
        while (colon_ptr > url && *colon_ptr != ':' && *colon_ptr != ']')
                colon_ptr--;
        if (*colon_ptr != ':') {
                colon_ptr = slash_ptr;
        } else if (!host_off && colon_ptr < slash_ptr && colon_ptr + 1 != slash_ptr) {
                /* file: URLs may not have a port number */
                if (out_info) {
                        out_info->url = NULL;
                        out_info->err = _("a 'file:' URL may not have a port number");
                }
                strbuf_release(&norm);
                return NULL;
        }
        spanned = strspn(url, URL_HOST_CHARS);
        if (spanned < colon_ptr - url) {
                /* Host name has invalid characters */
                if (out_info) {
                        out_info->url = NULL;
                        out_info->err = _("invalid characters in host name");
                }
                strbuf_release(&norm);
                return NULL;
        }
        while (url < colon_ptr) {
                strbuf_addch(&norm, tolower(*url++));
                url_len--;
        }


        /*
         * Check the port part and copy if not the default (after removing any
         * leading 0s); no %-escapes allowed
         */
        if (colon_ptr < slash_ptr) {
                /* skip the ':' and leading 0s but not the last one if all 0s */
                url++;
                url += strspn(url, "0");
                if (url == slash_ptr && url[-1] == '0')
                        url--;
                if (url == slash_ptr) {
                        /* Skip ":" port with no number, it's same as default */
                } else if (slash_ptr - url == 2 &&
                           !strncmp(norm.buf, "http:", 5) &&
                           !strncmp(url, "80", 2)) {
                        /* Skip http :80 as it's the default */
                } else if (slash_ptr - url == 3 &&
                           !strncmp(norm.buf, "https:", 6) &&
                           !strncmp(url, "443", 3)) {
                        /* Skip https :443 as it's the default */
                } else {
                        /*
                         * Port number must be all digits with leading 0s removed
                         * and since all the protocols we deal with have a 16-bit
                         * port number it must also be in the range 1..65535
                         * 0 is not allowed because that means "next available"
                         * on just about every system and therefore cannot be used
                         */
                        unsigned long pnum = 0;
                        spanned = strspn(url, URL_DIGIT);
                        if (spanned < slash_ptr - url) {
                                /* port number has invalid characters */
                                if (out_info) {
                                        out_info->url = NULL;
                                        out_info->err = _("invalid port number");
                                }
                                strbuf_release(&norm);
                                return NULL;
                        }
                        if (slash_ptr - url <= 5)
                                pnum = strtoul(url, NULL, 10);
                        if (pnum == 0 || pnum > 65535) {
                                /* port number not in range 1..65535 */
                                if (out_info) {
                                        out_info->url = NULL;
                                        out_info->err = _("invalid port number");
                                }
                                strbuf_release(&norm);
                                return NULL;
                        }
                        strbuf_addch(&norm, ':');
                        strbuf_add(&norm, url, slash_ptr - url);
                        port_len = slash_ptr - url;
                }
                url_len -= slash_ptr - colon_ptr;
                url = slash_ptr;
        }
        if (host_off)
                host_len = norm.len - host_off;


        /*
         * Now copy the path resolving any . and .. segments being careful not
         * to corrupt the URL by unescaping any delimiters, but do add an
         * initial '/' if it's missing and do normalize any %-escape sequences.
         */
        path_off = norm.len;
        path_start = norm.buf + path_off;
        strbuf_addch(&norm, '/');
        if (*url == '/') {
                url++;
                url_len--;
        }
        for (;;) {
                const char *seg_start;
                size_t seg_start_off = norm.len;
                const char *next_slash = url + strcspn(url, "/?#");
                int skip_add_slash = 0;

                /*
                 * RFC 3689 indicates that any . or .. segments should be
                 * unescaped before being checked for.
                 */
                if (!append_normalized_escapes(&norm, url, next_slash - url, "",
                                               URL_RESERVED)) {
                        if (out_info) {
                                out_info->url = NULL;
                                out_info->err = _("invalid %XX escape sequence");
                        }
                        strbuf_release(&norm);
                        return NULL;
                }

                seg_start = norm.buf + seg_start_off;
                if (!strcmp(seg_start, ".")) {
                        /* ignore a . segment; be careful not to remove initial '/' */
                        if (seg_start == path_start + 1) {
                                strbuf_setlen(&norm, norm.len - 1);
                                skip_add_slash = 1;
                        } else {
                                strbuf_setlen(&norm, norm.len - 2);
                        }
                } else if (!strcmp(seg_start, "..")) {
                        /*
                         * ignore a .. segment and remove the previous segment;
                         * be careful not to remove initial '/' from path
                         */
                        const char *prev_slash = norm.buf + norm.len - 3;
                        if (prev_slash == path_start) {
                                /* invalid .. because no previous segment to remove */
                                if (out_info) {
                                        out_info->url = NULL;
                                        out_info->err = _("invalid '..' path segment");
                                }
                                strbuf_release(&norm);
                                return NULL;
                        }
                        while (*--prev_slash != '/') {}
                        if (prev_slash == path_start) {
                                strbuf_setlen(&norm, prev_slash - norm.buf + 1);
                                skip_add_slash = 1;
                        } else {
                                strbuf_setlen(&norm, prev_slash - norm.buf);
                        }
                }
                url_len -= next_slash - url;
                url = next_slash;
                /* if the next char is not '/' done with the path */
                if (*url != '/')
                        break;
                url++;
                url_len--;
                if (!skip_add_slash)
                        strbuf_addch(&norm, '/');
        }
        path_len = norm.len - path_off;


        /*
         * Now simply copy the rest, if any, only normalizing %-escapes and
         * being careful not to corrupt the URL by unescaping any delimiters.
         */
        if (*url) {
                if (!append_normalized_escapes(&norm, url, url_len, "", URL_RESERVED)) {
                        if (out_info) {
                                out_info->url = NULL;
                                out_info->err = _("invalid %XX escape sequence");
                        }
                        strbuf_release(&norm);
                        return NULL;
                }
        }


        result = strbuf_detach(&norm, &result_len);
        if (out_info) {
                out_info->url = result;
                out_info->err = NULL;
                out_info->url_len = result_len;
                out_info->scheme_len = scheme_len;
                out_info->user_off = user_off;
                out_info->user_len = user_len;
                out_info->passwd_off = passwd_off;
                out_info->passwd_len = passwd_len;
                out_info->host_off = host_off;
                out_info->host_len = host_len;
                out_info->port_len = port_len;
                out_info->path_off = path_off;
                out_info->path_len = path_len;
        }
        return result;
}

static size_t url_match_prefix(const char *url,
                               const char *url_prefix,
                               size_t url_prefix_len)
{
        /*
         * url_prefix matches url if url_prefix is an exact match for url or it
         * is a prefix of url and the match ends on a path component boundary.
         * Both url and url_prefix are considered to have an implicit '/' on the
         * end for matching purposes if they do not already.
         *
         * url must be NUL terminated.  url_prefix_len is the length of
         * url_prefix which need not be NUL terminated.
         *
         * The return value is the length of the match in characters (including
         * the final '/' even if it's implicit) or 0 for no match.
         *
         * Passing NULL as url and/or url_prefix will always cause 0 to be
         * returned without causing any faults.
         */
        if (!url || !url_prefix)
                return 0;
        if (!url_prefix_len || (url_prefix_len == 1 && *url_prefix == '/'))
                return (!*url || *url == '/') ? 1 : 0;
        if (url_prefix[url_prefix_len - 1] == '/')
                url_prefix_len--;
        if (strncmp(url, url_prefix, url_prefix_len))
                return 0;
        if ((strlen(url) == url_prefix_len) || (url[url_prefix_len] == '/'))
                return url_prefix_len + 1;
        return 0;
}

static int match_urls(const struct url_info *url,
                      const struct url_info *url_prefix,
                      int *exactusermatch)
{
        /*
         * url_prefix matches url if the scheme, host and port of url_prefix
         * are the same as those of url and the path portion of url_prefix
         * is the same as the path portion of url or it is a prefix that
         * matches at a '/' boundary.  If url_prefix contains a user name,
         * that must also exactly match the user name in url.
         *
         * If the user, host, port and path match in this fashion, the returned
         * value is the length of the path match including any implicit
         * final '/'.  For example, "http://me@example.com/path" is matched by
         * "http://example.com" with a path length of 1.
         *
         * If there is a match and exactusermatch is not NULL, then
         * *exactusermatch will be set to true if both url and url_prefix
         * contained a user name or false if url_prefix did not have a
         * user name.  If there is no match *exactusermatch is left untouched.
         */
        int usermatched = 0;
        int pathmatchlen;

        if (!url || !url_prefix || !url->url || !url_prefix->url)
                return 0;

        /* check the scheme */
        if (url_prefix->scheme_len != url->scheme_len ||
            strncmp(url->url, url_prefix->url, url->scheme_len))
                return 0; /* schemes do not match */

        /* check the user name if url_prefix has one */
        if (url_prefix->user_off) {
                if (!url->user_off || url->user_len != url_prefix->user_len ||
                    strncmp(url->url + url->user_off,
                            url_prefix->url + url_prefix->user_off,
                            url->user_len))
                        return 0; /* url_prefix has a user but it's not a match */
                usermatched = 1;
        }

        /* check the host and port */
        if (url_prefix->host_len != url->host_len ||
            strncmp(url->url + url->host_off,
                    url_prefix->url + url_prefix->host_off, url->host_len))
                return 0; /* host names and/or ports do not match */

        /* check the path */
        pathmatchlen = url_match_prefix(
                url->url + url->path_off,
                url_prefix->url + url_prefix->path_off,
                url_prefix->url_len - url_prefix->path_off);

        if (pathmatchlen && exactusermatch)
                *exactusermatch = usermatched;
        return pathmatchlen;
}

int urlmatch_config_entry(const char *var, const char *value, void *cb)
{
        struct string_list_item *item;
        struct urlmatch_config *collect = cb;
        struct urlmatch_item *matched;
        struct url_info *url = &collect->url;
        const char *key, *dot;
        struct strbuf synthkey = STRBUF_INIT;
        size_t matched_len = 0;
        int user_matched = 0;
        int retval;

        if (!skip_prefix(var, collect->section, &key) || *(key++) != '.') {
                if (collect->cascade_fn)
                        return collect->cascade_fn(var, value, cb);
                return 0; /* not interested */
        }
        dot = strrchr(key, '.');
        if (dot) {
                char *config_url, *norm_url;
                struct url_info norm_info;

                config_url = xmemdupz(key, dot - key);
                norm_url = url_normalize(config_url, &norm_info);
                free(config_url);
                if (!norm_url)
                        return 0;
                matched_len = match_urls(url, &norm_info, &user_matched);
                free(norm_url);
                if (!matched_len)
                        return 0;
                key = dot + 1;
        }

        if (collect->key && strcmp(key, collect->key))
                return 0;

        item = string_list_insert(&collect->vars, key);
        if (!item->util) {
                matched = xcalloc(1, sizeof(*matched));
                item->util = matched;
        } else {
                matched = item->util;
                /*
                 * Is our match shorter?  Is our match the same
                 * length, and without user while the current
                 * candidate is with user?  Then we cannot use it.
                 */
                if (matched_len < matched->matched_len ||
                    ((matched_len == matched->matched_len) &&
                     (!user_matched && matched->user_matched)))
                        return 0;
                /* Otherwise, replace it with this one. */
        }

        matched->matched_len = matched_len;
        matched->user_matched = user_matched;
        strbuf_addstr(&synthkey, collect->section);
        strbuf_addch(&synthkey, '.');
        strbuf_addstr(&synthkey, key);
        retval = collect->collect_fn(synthkey.buf, value, collect->cb);

        strbuf_release(&synthkey);
        return retval;
}