uri.c

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/*
 * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

FILE_LICENCE ( GPL2_OR_LATER );

/** @file
 *
 * Uniform Resource Identifiers
 *
 */

#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <libgen.h>
#include <ctype.h>
#include <gpxe/vsprintf.h>
#include <gpxe/uri.h>

/**
 * Dump URI for debugging
 *
 * @v uri               URI
 */
static void dump_uri ( struct uri *uri ) {
        if ( ! uri )
                return;
        if ( uri->scheme )
                DBG ( " scheme \"%s\"", uri->scheme );
        if ( uri->opaque )
                DBG ( " opaque \"%s\"", uri->opaque );
        if ( uri->user )
                DBG ( " user \"%s\"", uri->user );
        if ( uri->password )
                DBG ( " password \"%s\"", uri->password );
        if ( uri->host )
                DBG ( " host \"%s\"", uri->host );
        if ( uri->port )
                DBG ( " port \"%s\"", uri->port );
        if ( uri->path )
                DBG ( " path \"%s\"", uri->path );
        if ( uri->query )
                DBG ( " query \"%s\"", uri->query );
        if ( uri->fragment )
                DBG ( " fragment \"%s\"", uri->fragment );
}

/**
 * Parse URI
 *
 * @v uri_string        URI as a string
 * @ret uri             URI
 *
 * Splits a URI into its component parts.  The return URI structure is
 * dynamically allocated and must eventually be freed by calling
 * uri_put().
 */
struct uri * parse_uri ( const char *uri_string ) {
        struct uri *uri;
        char *raw;
        char *tmp;
        char *path = NULL;
        char *authority = NULL;
        int i;
        size_t raw_len;

        /* Allocate space for URI struct and a copy of the string */
        raw_len = ( strlen ( uri_string ) + 1 /* NUL */ );
        uri = zalloc ( sizeof ( *uri ) + raw_len );
        if ( ! uri )
                return NULL;
        raw = ( ( ( char * ) uri ) + sizeof ( *uri ) );

        /* Copy in the raw string */
        memcpy ( raw, uri_string, raw_len );

        /* Start by chopping off the fragment, if it exists */
        if ( ( tmp = strchr ( raw, '#' ) ) ) {
                *(tmp++) = '\0';
                uri->fragment = tmp;
        }

        /* Identify absolute/relative URI.  We ignore schemes that are
         * apparently only a single character long, since otherwise we
         * misinterpret a DOS-style path name ("C:\path\to\file") as a
         * URI with scheme="C",opaque="\path\to\file".
         */
        if ( ( tmp = strchr ( raw, ':' ) ) && ( tmp > ( raw + 1 ) ) ) {
                /* Absolute URI: identify hierarchical/opaque */
                uri->scheme = raw;
                *(tmp++) = '\0';
                if ( *tmp == '/' ) {
                        /* Absolute URI with hierarchical part */
                        path = tmp;
                } else {
                        /* Absolute URI with opaque part */
                        uri->opaque = tmp;
                }
        } else {
                /* Relative URI */
                path = raw;
        }

        /* If we don't have a path (i.e. we have an absolute URI with
         * an opaque portion, we're already finished processing
         */
        if ( ! path )
                goto done;

        /* Chop off the query, if it exists */
        if ( ( tmp = strchr ( path, '?' ) ) ) {
                *(tmp++) = '\0';
                uri->query = tmp;
        }

        /* Identify net/absolute/relative path */
        if ( strncmp ( path, "//", 2 ) == 0 ) {
                /* Net path.  If this is terminated by the first '/'
                 * of an absolute path, then we have no space for a
                 * terminator after the authority field, so shuffle
                 * the authority down by one byte, overwriting one of
                 * the two slashes.
                 */
                authority = ( path + 2 );
                if ( ( tmp = strchr ( authority, '/' ) ) ) {
                        /* Shuffle down */
                        uri->path = tmp;
                        memmove ( ( authority - 1 ), authority,
                                  ( tmp - authority ) );
                        authority--;
                        *(--tmp) = '\0';
                }
        } else {
                /* Absolute/relative path */
                uri->path = path;
        }

        /* Split authority into user[:password] and host[:port] portions */
        if ( ( tmp = strchr ( authority, '@' ) ) ) {
                /* Has user[:password] */
                *(tmp++) = '\0';
                uri->host = tmp;
                uri->user = authority;
                if ( ( tmp = strchr ( authority, ':' ) ) ) {
                        /* Has password */
                        *(tmp++) = '\0';
                        uri->password = tmp;
                }
        } else {
                /* No user:password */
                uri->host = authority;
        }

        /* Split host into host[:port] */
        if ( ( tmp = strchr ( uri->host, ':' ) ) ) {
                *(tmp++) = '\0';
                uri->port = tmp;
        }

        /* Decode fields that should be decoded */
        for ( i = URI_FIRST_FIELD; i <= URI_LAST_FIELD; i++ ) {
                const char *field = uri_get_field ( uri, i );
                if ( field && ( URI_ENCODED & ( 1 << i ) ) )
                        uri_decode ( field, ( char * ) field,
                                     strlen ( field ) + 1 /* NUL */ );
        }

 done:
        DBG ( "URI \"%s\" split into", uri_string );
        dump_uri ( uri );
        DBG ( "\n" );

        return uri;
}

/**
 * Get port from URI
 *
 * @v uri               URI, or NULL
 * @v default_port      Default port to use if none specified in URI
 * @ret port            Port
 */
unsigned int uri_port ( struct uri *uri, unsigned int default_port ) {
        if ( ( ! uri ) || ( ! uri->port ) )
                return default_port;
        return ( strtoul ( uri->port, NULL, 0 ) );
}

/**
 * Unparse URI
 *
 * @v buf               Buffer to fill with URI string
 * @v size              Size of buffer
 * @v uri               URI to write into buffer, or NULL
 * @v fields            Bitmask of fields to include in URI string, or URI_ALL
 * @ret len             Length of URI string
 */
int unparse_uri ( char *buf, size_t size, struct uri *uri,
                  unsigned int fields ) {
        /* List of characters that typically go before certain fields */
        static char separators[] = { /* scheme */ 0, /* opaque */ ':',
                                     /* user */ 0, /* password */ ':',
                                     /* host */ '@', /* port */ ':',
                                     /* path */ 0, /* query */ '?',
                                     /* fragment */ '#' };
        int used = 0;
        int i;

        DBG ( "URI unparsing" );
        dump_uri ( uri );
        DBG ( "\n" );

        /* Ensure buffer is NUL-terminated */
        if ( size )
                buf[0] = '\0';

        /* Special-case NULL URI */
        if ( ! uri )
                return 0;

        /* Iterate through requested fields */
        for ( i = URI_FIRST_FIELD; i <= URI_LAST_FIELD; i++ ) {
                const char *field = uri_get_field ( uri, i );
                char sep = separators[i];

                /* Ensure `fields' only contains bits for fields that exist */
                if ( ! field )
                        fields &= ~( 1 << i );

                /* Store this field if we were asked to */
                if ( fields & ( 1 << i ) ) {
                        /* Print :// if we're non-opaque and had a scheme */
                        if ( ( fields & URI_SCHEME_BIT ) &&
                             ( i > URI_OPAQUE ) ) {
                                used += ssnprintf ( buf + used, size - used,
                                                    "://" );
                                /* Only print :// once */
                                fields &= ~URI_SCHEME_BIT;
                        }

                        /* Only print separator if an earlier field exists */
                        if ( sep && ( fields & ( ( 1 << i ) - 1 ) ) )
                                used += ssnprintf ( buf + used, size - used,
                                                    "%c", sep );

                        /* Print contents of field, possibly encoded */
                        if ( URI_ENCODED & ( 1 << i ) )
                                used += uri_encode ( field, buf + used,
                                                     size - used, i );
                        else
                                used += ssnprintf ( buf + used, size - used,
                                                    "%s", field );
                }
        }

        return used;
}

/**
 * Duplicate URI
 *
 * @v uri               URI
 * @ret uri             Duplicate URI
 *
 * Creates a modifiable copy of a URI.
 */
struct uri * uri_dup ( struct uri *uri ) {
        size_t len = ( unparse_uri ( NULL, 0, uri, URI_ALL ) + 1 );
        char buf[len];

        unparse_uri ( buf, len, uri, URI_ALL );
        return parse_uri ( buf );
}

/**
 * Resolve base+relative path
 *
 * @v base_uri          Base path
 * @v relative_uri      Relative path
 * @ret resolved_uri    Resolved path
 *
 * Takes a base path (e.g. "/var/lib/tftpboot/vmlinuz" and a relative
 * path (e.g. "initrd.gz") and produces a new path
 * (e.g. "/var/lib/tftpboot/initrd.gz").  Note that any non-directory
 * portion of the base path will automatically be stripped; this
 * matches the semantics used when resolving the path component of
 * URIs.
 */
char * resolve_path ( const char *base_path,
                      const char *relative_path ) {
        size_t base_len = ( strlen ( base_path ) + 1 );
        char base_path_copy[base_len];
        char *base_tmp = base_path_copy;
        char *resolved;

        /* If relative path is absolute, just re-use it */
        if ( relative_path[0] == '/' )
                return strdup ( relative_path );

        /* Create modifiable copy of path for dirname() */
        memcpy ( base_tmp, base_path, base_len );
        base_tmp = dirname ( base_tmp );

        /* Process "./" and "../" elements */
        while ( *relative_path == '.' ) {
                relative_path++;
                if ( *relative_path == 0 ) {
                        /* Do nothing */
                } else if ( *relative_path == '/' ) {
                        relative_path++;
                } else if ( *relative_path == '.' ) {
                        relative_path++;
                        if ( *relative_path == 0 ) {
                                base_tmp = dirname ( base_tmp );
                        } else if ( *relative_path == '/' ) {
                                base_tmp = dirname ( base_tmp );
                                relative_path++;
                        } else {
                                relative_path -= 2;
                                break;
                        }
                } else {
                        relative_path--;
                        break;
                }
        }

        /* Create and return new path */
        if ( asprintf ( &resolved, "%s%s%s", base_tmp,
                        ( ( base_tmp[ strlen ( base_tmp ) - 1 ] == '/' ) ?
                          "" : "/" ), relative_path ) < 0 )
                return NULL;

        return resolved;
}

/**
 * Resolve base+relative URI
 *
 * @v base_uri          Base URI, or NULL
 * @v relative_uri      Relative URI
 * @ret resolved_uri    Resolved URI
 *
 * Takes a base URI (e.g. "http://etherboot.org/kernels/vmlinuz" and a
 * relative URI (e.g. "../initrds/initrd.gz") and produces a new URI
 * (e.g. "http://etherboot.org/initrds/initrd.gz").
 */
struct uri * resolve_uri ( struct uri *base_uri,
                           struct uri *relative_uri ) {
        struct uri tmp_uri;
        char *tmp_path = NULL;
        struct uri *new_uri;

        /* If relative URI is absolute, just re-use it */
        if ( uri_is_absolute ( relative_uri ) || ( ! base_uri ) )
                return uri_get ( relative_uri );

        /* Mangle URI */
        memcpy ( &tmp_uri, base_uri, sizeof ( tmp_uri ) );
        if ( relative_uri->path ) {
                tmp_path = resolve_path ( ( base_uri->path ?
                                            base_uri->path : "/" ),
                                          relative_uri->path );
                tmp_uri.path = tmp_path;
                tmp_uri.query = relative_uri->query;
                tmp_uri.fragment = relative_uri->fragment;
        } else if ( relative_uri->query ) {
                tmp_uri.query = relative_uri->query;
                tmp_uri.fragment = relative_uri->fragment;
        } else if ( relative_uri->fragment ) {
                tmp_uri.fragment = relative_uri->fragment;
        }

        /* Create demangled URI */
        new_uri = uri_dup ( &tmp_uri );
        free ( tmp_path );
        return new_uri;
}

/**
 * Test for unreserved URI characters
 *
 * @v c                 Character to test
 * @v field             Field of URI in which character lies
 * @ret is_unreserved   Character is an unreserved character
 */
static int is_unreserved_uri_char ( int c, int field ) {
        /* According to RFC3986, the unreserved character set is
         *
         * A-Z a-z 0-9 - _ . ~
         *
         * but we also pass & ; = in queries, / in paths,
         * and everything in opaques
         */
        int ok = ( isupper ( c ) || islower ( c ) || isdigit ( c ) ||
                    ( c == '-' ) || ( c == '_' ) ||
                    ( c == '.' ) || ( c == '~' ) );

        if ( field == URI_QUERY )
                ok = ok || ( c == ';' ) || ( c == '&' ) || ( c == '=' );

        if ( field == URI_PATH )
                ok = ok || ( c == '/' );

        if ( field == URI_OPAQUE )
                ok = 1;

        return ok;
}

/**
 * URI-encode string
 *
 * @v raw_string        String to be URI-encoded
 * @v buf               Buffer to contain encoded string
 * @v len               Length of buffer
 * @v field             Field of URI in which string lies
 * @ret len             Length of encoded string (excluding NUL)
 */
size_t uri_encode ( const char *raw_string, char *buf, ssize_t len,
                    int field ) {
        ssize_t remaining = len;
        size_t used;
        unsigned char c;

        if ( len > 0 )
                buf[0] = '\0';

        while ( ( c = *(raw_string++) ) ) {
                if ( is_unreserved_uri_char ( c, field ) ) {
                        used = ssnprintf ( buf, remaining, "%c", c );
                } else {
                        used = ssnprintf ( buf, remaining, "%%%02X", c );
                }
                buf += used;
                remaining -= used;
        }

        return ( len - remaining );
}

/**
 * Decode URI-encoded string
 *
 * @v encoded_string    URI-encoded string
 * @v buf               Buffer to contain decoded string
 * @v len               Length of buffer
 * @ret len             Length of decoded string (excluding NUL)
 *
 * This function may be used in-place, with @a buf the same as
 * @a encoded_string.
 */
size_t uri_decode ( const char *encoded_string, char *buf, ssize_t len ) {
        ssize_t remaining;
        char hexbuf[3];
        char *hexbuf_end;
        unsigned char c;

        for ( remaining = len; *encoded_string; remaining-- ) {
                if ( *encoded_string == '%' ) {
                        encoded_string++;
                        snprintf ( hexbuf, sizeof ( hexbuf ), "%s",
                                   encoded_string );
                        c = strtoul ( hexbuf, &hexbuf_end, 16 );
                        encoded_string += ( hexbuf_end - hexbuf );
                } else {
                        c = *(encoded_string++);
                }
                if ( remaining > 1 )
                        *buf++ = c;
        }

        if ( len )
                *buf = 0;

        return ( len - remaining );
}