openwrtv4/package/uhttpd/src/uhttpd-utils.c

/*
 * uhttpd - Tiny single-threaded httpd - Utility functions
 *
 *   Copyright (C) 2010 Jo-Philipp Wich <xm@subsignal.org>
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

#define _XOPEN_SOURCE 500	/* crypt() */
#define _BSD_SOURCE			/* strcasecmp(), strncasecmp() */

#include "uhttpd.h"
#include "uhttpd-utils.h"

#ifdef HAVE_TLS
#include "uhttpd-tls.h"
#endif


static char *uh_index_files[] = {
	"index.html",
	"index.htm",
	"default.html",
	"default.htm"
};


const char * sa_straddr(void *sa)
{
	static char str[INET6_ADDRSTRLEN];
	struct sockaddr_in *v4 = (struct sockaddr_in *)sa;
	struct sockaddr_in6 *v6 = (struct sockaddr_in6 *)sa;

	if (v4->sin_family == AF_INET)
		return inet_ntop(AF_INET, &(v4->sin_addr), str, sizeof(str));
	else
		return inet_ntop(AF_INET6, &(v6->sin6_addr), str, sizeof(str));
}

const char * sa_strport(void *sa)
{
	static char str[6];
	snprintf(str, sizeof(str), "%i", sa_port(sa));
	return str;
}

int sa_port(void *sa)
{
	return ntohs(((struct sockaddr_in6 *)sa)->sin6_port);
}

int sa_rfc1918(void *sa)
{
	struct sockaddr_in *v4 = (struct sockaddr_in *)sa;
	unsigned long a = htonl(v4->sin_addr.s_addr);

	if (v4->sin_family == AF_INET)
	{
		return ((a >= 0x0A000000) && (a <= 0x0AFFFFFF)) ||
		       ((a >= 0xAC100000) && (a <= 0xAC1FFFFF)) ||
		       ((a >= 0xC0A80000) && (a <= 0xC0A8FFFF));
	}

	return 0;
}

/* Simple strstr() like function that takes len arguments for both haystack and needle. */
char *strfind(char *haystack, int hslen, const char *needle, int ndlen)
{
	int match = 0;
	int i, j;

	for (i = 0; i < hslen; i++)
	{
		if (haystack[i] == needle[0])
		{
			match = ((ndlen == 1) || ((i + ndlen) <= hslen));

			for (j = 1; (j < ndlen) && ((i + j) < hslen); j++)
			{
				if (haystack[i+j] != needle[j])
				{
					match = 0;
					break;
				}
			}

			if (match)
				return &haystack[i];
		}
	}

	return NULL;
}

/* interruptable select() */
int select_intr(int n, fd_set *r, fd_set *w, fd_set *e, struct timeval *t)
{
	int rv;
	sigset_t ssn, sso;

	/* unblock SIGCHLD */
	sigemptyset(&ssn);
	sigaddset(&ssn, SIGCHLD);
	sigaddset(&ssn, SIGPIPE);
	sigprocmask(SIG_UNBLOCK, &ssn, &sso);

	rv = select(n, r, w, e, t);

	/* restore signal mask */
	sigprocmask(SIG_SETMASK, &sso, NULL);

	return rv;
}


int uh_tcp_send_lowlevel(struct client *cl, const char *buf, int len)
{
	fd_set writer;
	struct timeval timeout;

	FD_ZERO(&writer);
	FD_SET(cl->socket, &writer);

	timeout.tv_sec = cl->server->conf->network_timeout;
	timeout.tv_usec = 0;

	if (select(cl->socket + 1, NULL, &writer, NULL, &timeout) > 0)
		return send(cl->socket, buf, len, 0);

	return -1;
}

int uh_tcp_send(struct client *cl, const char *buf, int len)
{
#ifdef HAVE_TLS
	if (cl->tls)
		return cl->server->conf->tls_send(cl, (void *)buf, len);
	else
#endif
		return uh_tcp_send_lowlevel(cl, buf, len);
}

int uh_tcp_peek(struct client *cl, char *buf, int len)
{
	/* sanity check, prevent overflowing peek buffer */
	if (len > sizeof(cl->peekbuf))
		return -1;

	int sz = uh_tcp_recv(cl, buf, len);

	/* store received data in peek buffer */
	if (sz > 0)
	{
		cl->peeklen = sz;
		memcpy(cl->peekbuf, buf, sz);
	}

	return sz;
}

int uh_tcp_recv_lowlevel(struct client *cl, char *buf, int len)
{
	fd_set reader;
	struct timeval timeout;

	FD_ZERO(&reader);
	FD_SET(cl->socket, &reader);

	timeout.tv_sec  = cl->server->conf->network_timeout;
	timeout.tv_usec = 0;

	if (select(cl->socket + 1, &reader, NULL, NULL, &timeout) > 0)
		return recv(cl->socket, buf, len, 0);

	return -1;
}

int uh_tcp_recv(struct client *cl, char *buf, int len)
{
	int sz = 0;
	int rsz = 0;

	/* first serve data from peek buffer */
	if (cl->peeklen > 0)
	{
		sz = min(cl->peeklen, len);
		len -= sz; cl->peeklen -= sz;
		memcpy(buf, cl->peekbuf, sz);
		memmove(cl->peekbuf, &cl->peekbuf[sz], cl->peeklen);
	}

	/* caller wants more */
	if (len > 0)
	{
#ifdef HAVE_TLS
		if (cl->tls)
			rsz = cl->server->conf->tls_recv(cl, (void *)&buf[sz], len);
		else
#endif
			rsz = uh_tcp_recv_lowlevel(cl, (void *)&buf[sz], len);

		if (rsz < 0)
			return rsz;

		sz += rsz;
	}

	return sz;
}


int uh_http_sendhf(struct client *cl, int code, const char *summary,
				   const char *fmt, ...)
{
	va_list ap;

	char buffer[UH_LIMIT_MSGHEAD];
	int len;

	len = snprintf(buffer, sizeof(buffer),
		"HTTP/1.1 %03i %s\r\n"
		"Connection: close\r\n"
		"Content-Type: text/plain\r\n"
		"Transfer-Encoding: chunked\r\n\r\n",
			code, summary
	);

	ensure_ret(uh_tcp_send(cl, buffer, len));

	va_start(ap, fmt);
	len = vsnprintf(buffer, sizeof(buffer), fmt, ap);
	va_end(ap);

	ensure_ret(uh_http_sendc(cl, buffer, len));
	ensure_ret(uh_http_sendc(cl, NULL, 0));

	return 0;
}


int uh_http_sendc(struct client *cl, const char *data, int len)
{
	char chunk[8];
	int clen;

	if (len == -1)
		len = strlen(data);

	if (len > 0)
	{
		clen = snprintf(chunk, sizeof(chunk), "%X\r\n", len);
		ensure_ret(uh_tcp_send(cl, chunk, clen));
		ensure_ret(uh_tcp_send(cl, data, len));
		ensure_ret(uh_tcp_send(cl, "\r\n", 2));
	}
	else
	{
		ensure_ret(uh_tcp_send(cl, "0\r\n\r\n", 5));
	}

	return 0;
}

int uh_http_sendf(struct client *cl, struct http_request *req,
				  const char *fmt, ...)
{
	va_list ap;
	char buffer[UH_LIMIT_MSGHEAD];
	int len;

	va_start(ap, fmt);
	len = vsnprintf(buffer, sizeof(buffer), fmt, ap);
	va_end(ap);

	if ((req != NULL) && (req->version > 1.0))
		ensure_ret(uh_http_sendc(cl, buffer, len));
	else if (len > 0)
		ensure_ret(uh_tcp_send(cl, buffer, len));

	return 0;
}

int uh_http_send(struct client *cl, struct http_request *req,
				 const char *buf, int len)
{
	if (len < 0)
		len = strlen(buf);

	if ((req != NULL) && (req->version > 1.0))
		ensure_ret(uh_http_sendc(cl, buf, len));
	else if (len > 0)
		ensure_ret(uh_tcp_send(cl, buf, len));

	return 0;
}


/* blen is the size of buf; slen is the length of src.  The input-string need
** not be, and the output string will not be, null-terminated.  Returns the
** length of the decoded string, -1 on buffer overflow, -2 on malformed string. */
int uh_urldecode(char *buf, int blen, const char *src, int slen)
{
	int i;
	int len = 0;

#define hex(x) \
	(((x) <= '9') ? ((x) - '0') : \
		(((x) <= 'F') ? ((x) - 'A' + 10) : \
			((x) - 'a' + 10)))

	for (i = 0; (i < slen) && (len < blen); i++)
	{
		if (src[i] == '%')
		{
			if (((i+2) < slen) && isxdigit(src[i+1]) && isxdigit(src[i+2]))
			{
				buf[len++] = (char)(16 * hex(src[i+1]) + hex(src[i+2]));
				i += 2;
			}
			else
			{
				/* Encoding error: it's hard to think of a
				** scenario in which returning an incorrect
				** 'decoding' of the malformed string is
				** preferable to signaling an error condition. */
				#if 0 /* WORSE_IS_BETTER */
				    buf[len++] = '%';
				#else
				    return -2;
				#endif
			}
		}
		else
		{
			buf[len++] = src[i];
		}
	}

	return (i == slen) ? len : -1;
}

/* blen is the size of buf; slen is the length of src.  The input-string need
** not be, and the output string will not be, null-terminated.  Returns the
** length of the encoded string, or -1 on error (buffer overflow) */
int uh_urlencode(char *buf, int blen, const char *src, int slen)
{
	int i;
	int len = 0;
	const char hex[] = "0123456789abcdef";

	for (i = 0; (i < slen) && (len < blen); i++)
	{
		if( isalnum(src[i]) || (src[i] == '-') || (src[i] == '_') ||
		    (src[i] == '.') || (src[i] == '~') )
		{
			buf[len++] = src[i];
		}
		else if ((len+3) <= blen)
		{
			buf[len++] = '%';
			buf[len++] = hex[(src[i] >> 4) & 15];
			buf[len++] = hex[ src[i]       & 15];
		}
		else
		{
			len = -1;
			break;
		}
	}

	return (i == slen) ? len : -1;
}

int uh_b64decode(char *buf, int blen, const unsigned char *src, int slen)
{
	int i = 0;
	int len = 0;

	unsigned int cin  = 0;
	unsigned int cout = 0;


	for (i = 0; (i <= slen) && (src[i] != 0); i++)
	{
		cin = src[i];

		if ((cin >= '0') && (cin <= '9'))
			cin = cin - '0' + 52;
		else if ((cin >= 'A') && (cin <= 'Z'))
			cin = cin - 'A';
		else if ((cin >= 'a') && (cin <= 'z'))
			cin = cin - 'a' + 26;
		else if (cin == '+')
			cin = 62;
		else if (cin == '/')
			cin = 63;
		else if (cin == '=')
			cin = 0;
		else
			continue;

		cout = (cout << 6) | cin;

		if ((i % 4) == 3)
		{
			if ((len + 3) < blen)
			{
				buf[len++] = (char)(cout >> 16);
				buf[len++] = (char)(cout >> 8);
				buf[len++] = (char)(cout);
			}
			else
			{
				break;
			}
		}
	}

	buf[len++] = 0;
	return len;
}

static char * canonpath(const char *path, char *path_resolved)
{
	char path_copy[PATH_MAX];
	char *path_cpy = path_copy;
	char *path_res = path_resolved;

	struct stat s;


	/* relative -> absolute */
	if (*path != '/')
	{
		getcwd(path_copy, PATH_MAX);
		strncat(path_copy, "/", PATH_MAX - strlen(path_copy));
		strncat(path_copy, path, PATH_MAX - strlen(path_copy));
	}
	else
	{
		strncpy(path_copy, path, PATH_MAX);
	}

	/* normalize */
	while ((*path_cpy != '\0') && (path_cpy < (path_copy + PATH_MAX - 2)))
	{
		if (*path_cpy == '/')
		{
			/* skip repeating / */
			if (path_cpy[1] == '/')
			{
				path_cpy++;
				continue;
			}

			/* /./ or /../ */
			else if (path_cpy[1] == '.')
			{
				/* skip /./ */
				if ((path_cpy[2] == '/') || (path_cpy[2] == '\0'))
				{
					path_cpy += 2;
					continue;
				}

				/* collapse /x/../ */
				else if ((path_cpy[2] == '.') &&
						 ((path_cpy[3] == '/') || (path_cpy[3] == '\0')))
				{
					while ((path_res > path_resolved) && (*--path_res != '/'))
						;

					path_cpy += 3;
					continue;
				}
			}
		}

		*path_res++ = *path_cpy++;
	}

	/* remove trailing slash if not root / */
	if ((path_res > (path_resolved+1)) && (path_res[-1] == '/'))
		path_res--;
	else if (path_res == path_resolved)
		*path_res++ = '/';

	*path_res = '\0';

	/* test access */
	if (!stat(path_resolved, &s) && (s.st_mode & S_IROTH))
		return path_resolved;

	return NULL;
}

/* Returns NULL on error.
** NB: improperly encoded URL should give client 400 [Bad Syntax]; returning
** NULL here causes 404 [Not Found], but that's not too unreasonable. */
struct path_info * uh_path_lookup(struct client *cl, const char *url)
{
	static char path_phys[PATH_MAX];
	static char path_info[PATH_MAX];
	static struct path_info p;

	char buffer[UH_LIMIT_MSGHEAD];
	char *docroot = cl->server->conf->docroot;
	char *pathptr = NULL;

	int slash = 0;
	int no_sym = cl->server->conf->no_symlinks;
	int i = 0;
	struct stat s;

	/* back out early if url is undefined */
	if (url == NULL)
		return NULL;

	memset(path_phys, 0, sizeof(path_phys));
	memset(path_info, 0, sizeof(path_info));
	memset(buffer, 0, sizeof(buffer));
	memset(&p, 0, sizeof(p));

	/* copy docroot */
	memcpy(buffer, docroot,
		   min(strlen(docroot), sizeof(buffer) - 1));

	/* separate query string from url */
	if ((pathptr = strchr(url, '?')) != NULL)
	{
		p.query = pathptr[1] ? pathptr + 1 : NULL;

		/* urldecode component w/o query */
		if (pathptr > url)
		{
			if (uh_urldecode(&buffer[strlen(docroot)],
							 sizeof(buffer) - strlen(docroot) - 1,
							 url, pathptr - url ) < 0)
			{
				return NULL; /* bad URL */
			}
		}
	}

	/* no query string, decode all of url */
	else
	{
		if (uh_urldecode(&buffer[strlen(docroot)],
						 sizeof(buffer) - strlen(docroot) - 1,
						 url, strlen(url) ) < 0)
		{
			return NULL; /* bad URL */
		}
	}

	/* create canon path */
	for (i = strlen(buffer), slash = (buffer[max(0, i-1)] == '/'); i >= 0; i--)
	{
		if ((buffer[i] == 0) || (buffer[i] == '/'))
		{
			memset(path_info, 0, sizeof(path_info));
			memcpy(path_info, buffer, min(i + 1, sizeof(path_info) - 1));

			if (no_sym ? realpath(path_info, path_phys)
			           : canonpath(path_info, path_phys))
			{
				memset(path_info, 0, sizeof(path_info));
				memcpy(path_info, &buffer[i],
					   min(strlen(buffer) - i, sizeof(path_info) - 1));

				break;
			}
		}
	}

	/* check whether found path is within docroot */
	if (strncmp(path_phys, docroot, strlen(docroot)) ||
		((path_phys[strlen(docroot)] != 0) &&
		 (path_phys[strlen(docroot)] != '/')))
	{
		return NULL;
	}

	/* test current path */
	if (!stat(path_phys, &p.stat))
	{
		/* is a regular file */
		if (p.stat.st_mode & S_IFREG)
		{
			p.root = docroot;
			p.phys = path_phys;
			p.name = &path_phys[strlen(docroot)];
			p.info = path_info[0] ? path_info : NULL;
		}

		/* is a directory */
		else if ((p.stat.st_mode & S_IFDIR) && !strlen(path_info))
		{
			/* ensure trailing slash */
			if (path_phys[strlen(path_phys)-1] != '/')
				path_phys[strlen(path_phys)] = '/';

			/* try to locate index file */
			memset(buffer, 0, sizeof(buffer));
			memcpy(buffer, path_phys, sizeof(buffer));
			pathptr = &buffer[strlen(buffer)];

			/* if requested url resolves to a directory and a trailing slash
			   is missing in the request url, redirect the client to the same
			   url with trailing slash appended */
			if (!slash)
			{
				uh_http_sendf(cl, NULL,
					"HTTP/1.1 302 Found\r\n"
					"Location: %s%s%s\r\n"
					"Connection: close\r\n\r\n",
						&path_phys[strlen(docroot)],
						p.query ? "?" : "",
						p.query ? p.query : ""
				);

				p.redirected = 1;
			}
			else if (cl->server->conf->index_file)
			{
				strncat(buffer, cl->server->conf->index_file, sizeof(buffer));

				if (!stat(buffer, &s) && (s.st_mode & S_IFREG))
				{
					memcpy(path_phys, buffer, sizeof(path_phys));
					memcpy(&p.stat, &s, sizeof(p.stat));
				}
			}
			else
			{
				for (i = 0; i < array_size(uh_index_files); i++)
				{
					strncat(buffer, uh_index_files[i], sizeof(buffer));

					if (!stat(buffer, &s) && (s.st_mode & S_IFREG))
					{
						memcpy(path_phys, buffer, sizeof(path_phys));
						memcpy(&p.stat, &s, sizeof(p.stat));
						break;
					}

					*pathptr = 0;
				}
			}

			p.root = docroot;
			p.phys = path_phys;
			p.name = &path_phys[strlen(docroot)];
		}
	}

	return p.phys ? &p : NULL;
}


static struct auth_realm *uh_realms = NULL;

struct auth_realm * uh_auth_add(char *path, char *user, char *pass)
{
	struct auth_realm *new = NULL;
	struct passwd *pwd;

#ifdef HAVE_SHADOW
	struct spwd *spwd;
#endif

	if((new = (struct auth_realm *)malloc(sizeof(struct auth_realm))) != NULL)
	{
		memset(new, 0, sizeof(struct auth_realm));

		memcpy(new->path, path,
			   min(strlen(path), sizeof(new->path) - 1));

		memcpy(new->user, user,
			   min(strlen(user), sizeof(new->user) - 1));

		/* given password refers to a passwd entry */
		if ((strlen(pass) > 3) && !strncmp(pass, "$p$", 3))
		{
#ifdef HAVE_SHADOW
			/* try to resolve shadow entry */
			if (((spwd = getspnam(&pass[3])) != NULL) && spwd->sp_pwdp)
			{
				memcpy(new->pass, spwd->sp_pwdp,
					   min(strlen(spwd->sp_pwdp), sizeof(new->pass) - 1));
			}

			else
#endif

			/* try to resolve passwd entry */
			if (((pwd = getpwnam(&pass[3])) != NULL) && pwd->pw_passwd &&
				(pwd->pw_passwd[0] != '!') && (pwd->pw_passwd[0] != 0))
			{
				memcpy(new->pass, pwd->pw_passwd,
					   min(strlen(pwd->pw_passwd), sizeof(new->pass) - 1));
			}
		}

		/* ordinary pwd */
		else
		{
			memcpy(new->pass, pass,
				min(strlen(pass), sizeof(new->pass) - 1));
		}

		if (new->pass[0])
		{
			new->next = uh_realms;
			uh_realms = new;

			return new;
		}

		free(new);
	}

	return NULL;
}

int uh_auth_check(struct client *cl, struct http_request *req,
				  struct path_info *pi)
{
	int i, plen, rlen, protected;
	char buffer[UH_LIMIT_MSGHEAD];
	char *user = NULL;
	char *pass = NULL;

	struct auth_realm *realm = NULL;

	plen = strlen(pi->name);
	protected = 0;

	/* check whether at least one realm covers the requested url */
	for (realm = uh_realms; realm; realm = realm->next)
	{
		rlen = strlen(realm->path);

		if ((plen >= rlen) && !strncasecmp(pi->name, realm->path, rlen))
		{
			req->realm = realm;
			protected = 1;
			break;
		}
	}

	/* requested resource is covered by a realm */
	if (protected)
	{
		/* try to get client auth info */
		foreach_header(i, req->headers)
		{
			if (!strcasecmp(req->headers[i], "Authorization") &&
				(strlen(req->headers[i+1]) > 6) &&
				!strncasecmp(req->headers[i+1], "Basic ", 6))
			{
				memset(buffer, 0, sizeof(buffer));
				uh_b64decode(buffer, sizeof(buffer) - 1,
					(unsigned char *) &req->headers[i+1][6],
					strlen(req->headers[i+1]) - 6);

				if ((pass = strchr(buffer, ':')) != NULL)
				{
					user = buffer;
					*pass++ = 0;
				}

				break;
			}
		}

		/* have client auth */
		if (user && pass)
		{
			/* find matching realm */
			for (realm = uh_realms; realm; realm = realm->next)
			{
				rlen = strlen(realm->path);

				if ((plen >= rlen) &&
					!strncasecmp(pi->name, realm->path, rlen) &&
					!strcmp(user, realm->user))
				{
					req->realm = realm;
					break;
				}
			}

			/* found a realm matching the username */
			if (realm)
			{
				/* check user pass */
				if (!strcmp(pass, realm->pass) ||
				    !strcmp(crypt(pass, realm->pass), realm->pass))
					return 1;
			}
		}

		/* 401 */
		uh_http_sendf(cl, NULL,
			"HTTP/%.1f 401 Authorization Required\r\n"
			"WWW-Authenticate: Basic realm=\"%s\"\r\n"
			"Content-Type: text/plain\r\n"
			"Content-Length: 23\r\n\r\n"
			"Authorization Required\n",
				req->version, cl->server->conf->realm
		);

		return 0;
	}

	return 1;
}


static struct listener *uh_listeners = NULL;
static struct client *uh_clients = NULL;

struct listener * uh_listener_add(int sock, struct config *conf)
{
	struct listener *new = NULL;
	socklen_t sl;

	if ((new = (struct listener *)malloc(sizeof(struct listener))) != NULL)
	{
		memset(new, 0, sizeof(struct listener));

		new->socket = sock;
		new->conf   = conf;

		/* get local endpoint addr */
		sl = sizeof(struct sockaddr_in6);
		memset(&(new->addr), 0, sl);
		getsockname(sock, (struct sockaddr *) &(new->addr), &sl);

		new->next = uh_listeners;
		uh_listeners = new;

		return new;
	}

	return NULL;
}

struct listener * uh_listener_lookup(int sock)
{
	struct listener *cur = NULL;

	for (cur = uh_listeners; cur; cur = cur->next)
		if (cur->socket == sock)
			return cur;

	return NULL;
}


struct client * uh_client_add(int sock, struct listener *serv)
{
	struct client *new = NULL;
	socklen_t sl;

	if ((new = (struct client *)malloc(sizeof(struct client))) != NULL)
	{
		memset(new, 0, sizeof(struct client));

		new->socket = sock;
		new->server = serv;

		/* get remote endpoint addr */
		sl = sizeof(struct sockaddr_in6);
		memset(&(new->peeraddr), 0, sl);
		getpeername(sock, (struct sockaddr *) &(new->peeraddr), &sl);

		/* get local endpoint addr */
		sl = sizeof(struct sockaddr_in6);
		memset(&(new->servaddr), 0, sl);
		getsockname(sock, (struct sockaddr *) &(new->servaddr), &sl);

		new->next = uh_clients;
		uh_clients = new;
	}

	return new;
}

struct client * uh_client_lookup(int sock)
{
	struct client *cur = NULL;

	for (cur = uh_clients; cur; cur = cur->next)
		if (cur->socket == sock)
			return cur;

	return NULL;
}

void uh_client_remove(int sock)
{
	struct client *cur = NULL;
	struct client *prv = NULL;

	for (cur = uh_clients; cur; prv = cur, cur = cur->next)
	{
		if (cur->socket == sock)
		{
			if (prv)
				prv->next = cur->next;
			else
				uh_clients = cur->next;

			free(cur);
			break;
		}
	}
}


#ifdef HAVE_CGI
static struct interpreter *uh_interpreters = NULL;

struct interpreter * uh_interpreter_add(const char *extn, const char *path)
{
	struct interpreter *new = NULL;

	if ((new = (struct interpreter *)malloc(sizeof(struct interpreter))) != NULL)
	{
		memset(new, 0, sizeof(struct interpreter));

		memcpy(new->extn, extn, min(strlen(extn), sizeof(new->extn)-1));
		memcpy(new->path, path, min(strlen(path), sizeof(new->path)-1));

		new->next = uh_interpreters;
		uh_interpreters = new;

		return new;
	}

	return NULL;
}

struct interpreter * uh_interpreter_lookup(const char *path)
{
	struct interpreter *cur = NULL;
	const char *e;

	for (cur = uh_interpreters; cur; cur = cur->next)
	{
		e = &path[max(strlen(path) - strlen(cur->extn), 0)];

		if (!strcmp(e, cur->extn))
			return cur;
	}

	return NULL;
}
#endif