git/http-backend.c

#include "git-compat-util.h"
#include "config.h"
#include "environment.h"
#include "git-zlib.h"
#include "hex.h"
#include "path.h"
#include "repository.h"
#include "refs.h"
#include "pkt-line.h"
#include "object.h"
#include "tag.h"
#include "exec-cmd.h"
#include "run-command.h"
#include "string-list.h"
#include "url.h"
#include "strvec.h"
#include "packfile.h"
#include "object-store-ll.h"
#include "protocol.h"
#include "date.h"
#include "write-or-die.h"

static const char content_type[] = "Content-Type";
static const char content_length[] = "Content-Length";
static const char last_modified[] = "Last-Modified";
static int getanyfile = 1;
static unsigned long max_request_buffer = 10 * 1024 * 1024;

static struct string_list *query_params;

struct rpc_service {
	const char *name;
	const char *config_name;
	unsigned buffer_input : 1;
	signed enabled : 2;
};

static struct rpc_service rpc_service[] = {
	{ "upload-pack", "uploadpack", 1, 1 },
	{ "receive-pack", "receivepack", 0, -1 },
};

static struct string_list *get_parameters(void)
{
	if (!query_params) {
		const char *query = getenv("QUERY_STRING");

		CALLOC_ARRAY(query_params, 1);
		while (query && *query) {
			char *name = url_decode_parameter_name(&query);
			char *value = url_decode_parameter_value(&query);
			struct string_list_item *i;

			i = string_list_lookup(query_params, name);
			if (!i)
				i = string_list_insert(query_params, name);
			else
				free(i->util);
			i->util = value;
		}
	}
	return query_params;
}

static const char *get_parameter(const char *name)
{
	struct string_list_item *i;
	i = string_list_lookup(get_parameters(), name);
	return i ? i->util : NULL;
}

__attribute__((format (printf, 2, 3)))
static void format_write(int fd, const char *fmt, ...)
{
	static char buffer[1024];

	va_list args;
	unsigned n;

	va_start(args, fmt);
	n = vsnprintf(buffer, sizeof(buffer), fmt, args);
	va_end(args);
	if (n >= sizeof(buffer))
		die("protocol error: impossibly long line");

	write_or_die(fd, buffer, n);
}

static void http_status(struct strbuf *hdr, unsigned code, const char *msg)
{
	strbuf_addf(hdr, "Status: %u %s\r\n", code, msg);
}

static void hdr_str(struct strbuf *hdr, const char *name, const char *value)
{
	strbuf_addf(hdr, "%s: %s\r\n", name, value);
}

static void hdr_int(struct strbuf *hdr, const char *name, uintmax_t value)
{
	strbuf_addf(hdr, "%s: %" PRIuMAX "\r\n", name, value);
}

static void hdr_date(struct strbuf *hdr, const char *name, timestamp_t when)
{
	const char *value = show_date(when, 0, DATE_MODE(RFC2822));
	hdr_str(hdr, name, value);
}

static void hdr_nocache(struct strbuf *hdr)
{
	hdr_str(hdr, "Expires", "Fri, 01 Jan 1980 00:00:00 GMT");
	hdr_str(hdr, "Pragma", "no-cache");
	hdr_str(hdr, "Cache-Control", "no-cache, max-age=0, must-revalidate");
}

static void hdr_cache_forever(struct strbuf *hdr)
{
	timestamp_t now = time(NULL);
	hdr_date(hdr, "Date", now);
	hdr_date(hdr, "Expires", now + 31536000);
	hdr_str(hdr, "Cache-Control", "public, max-age=31536000");
}

static void end_headers(struct strbuf *hdr)
{
	strbuf_add(hdr, "\r\n", 2);
	write_or_die(1, hdr->buf, hdr->len);
	strbuf_release(hdr);
}

__attribute__((format (printf, 2, 3)))
static NORETURN void not_found(struct strbuf *hdr, const char *err, ...)
{
	va_list params;

	http_status(hdr, 404, "Not Found");
	hdr_nocache(hdr);
	end_headers(hdr);

	va_start(params, err);
	if (err && *err)
		vfprintf(stderr, err, params);
	va_end(params);
	exit(0);
}

__attribute__((format (printf, 2, 3)))
static NORETURN void forbidden(struct strbuf *hdr, const char *err, ...)
{
	va_list params;

	http_status(hdr, 403, "Forbidden");
	hdr_nocache(hdr);
	end_headers(hdr);

	va_start(params, err);
	if (err && *err)
		vfprintf(stderr, err, params);
	va_end(params);
	exit(0);
}

static void select_getanyfile(struct strbuf *hdr)
{
	if (!getanyfile)
		forbidden(hdr, "Unsupported service: getanyfile");
}

static void send_strbuf(struct strbuf *hdr,
			const char *type, struct strbuf *buf)
{
	hdr_int(hdr, content_length, buf->len);
	hdr_str(hdr, content_type, type);
	end_headers(hdr);
	write_or_die(1, buf->buf, buf->len);
}

static void send_local_file(struct strbuf *hdr, const char *the_type,
				const char *name)
{
	char *p = git_pathdup("%s", name);
	size_t buf_alloc = 8192;
	char *buf = xmalloc(buf_alloc);
	int fd;
	struct stat sb;

	fd = open(p, O_RDONLY);
	if (fd < 0)
		not_found(hdr, "Cannot open '%s': %s", p, strerror(errno));
	if (fstat(fd, &sb) < 0)
		die_errno("Cannot stat '%s'", p);

	hdr_int(hdr, content_length, sb.st_size);
	hdr_str(hdr, content_type, the_type);
	hdr_date(hdr, last_modified, sb.st_mtime);
	end_headers(hdr);

	for (;;) {
		ssize_t n = xread(fd, buf, buf_alloc);
		if (n < 0)
			die_errno("Cannot read '%s'", p);
		if (!n)
			break;
		write_or_die(1, buf, n);
	}
	close(fd);
	free(buf);
	free(p);
}

static void get_text_file(struct strbuf *hdr, char *name)
{
	select_getanyfile(hdr);
	hdr_nocache(hdr);
	send_local_file(hdr, "text/plain", name);
}

static void get_loose_object(struct strbuf *hdr, char *name)
{
	select_getanyfile(hdr);
	hdr_cache_forever(hdr);
	send_local_file(hdr, "application/x-git-loose-object", name);
}

static void get_pack_file(struct strbuf *hdr, char *name)
{
	select_getanyfile(hdr);
	hdr_cache_forever(hdr);
	send_local_file(hdr, "application/x-git-packed-objects", name);
}

static void get_idx_file(struct strbuf *hdr, char *name)
{
	select_getanyfile(hdr);
	hdr_cache_forever(hdr);
	send_local_file(hdr, "application/x-git-packed-objects-toc", name);
}

static void http_config(void)
{
	int i, value = 0;
	struct strbuf var = STRBUF_INIT;

	git_config_get_bool("http.getanyfile", &getanyfile);
	git_config_get_ulong("http.maxrequestbuffer", &max_request_buffer);

	for (i = 0; i < ARRAY_SIZE(rpc_service); i++) {
		struct rpc_service *svc = &rpc_service[i];
		strbuf_addf(&var, "http.%s", svc->config_name);
		if (!git_config_get_bool(var.buf, &value))
			svc->enabled = value;
		strbuf_reset(&var);
	}

	strbuf_release(&var);
}

static struct rpc_service *select_service(struct strbuf *hdr, const char *name)
{
	const char *svc_name;
	struct rpc_service *svc = NULL;
	int i;

	if (!skip_prefix(name, "git-", &svc_name))
		forbidden(hdr, "Unsupported service: '%s'", name);

	for (i = 0; i < ARRAY_SIZE(rpc_service); i++) {
		struct rpc_service *s = &rpc_service[i];
		if (!strcmp(s->name, svc_name)) {
			svc = s;
			break;
		}
	}

	if (!svc)
		forbidden(hdr, "Unsupported service: '%s'", name);

	if (svc->enabled < 0) {
		const char *user = getenv("REMOTE_USER");
		svc->enabled = (user && *user) ? 1 : 0;
	}
	if (!svc->enabled)
		forbidden(hdr, "Service not enabled: '%s'", svc->name);
	return svc;
}

static void write_to_child(int out, const unsigned char *buf, ssize_t len, const char *prog_name)
{
	if (write_in_full(out, buf, len) < 0)
		die("unable to write to '%s'", prog_name);
}

/*
 * This is basically strbuf_read(), except that if we
 * hit max_request_buffer we die (we'd rather reject a
 * maliciously large request than chew up infinite memory).
 */
static ssize_t read_request_eof(int fd, unsigned char **out)
{
	size_t len = 0, alloc = 8192;
	unsigned char *buf = xmalloc(alloc);

	if (max_request_buffer < alloc)
		max_request_buffer = alloc;

	while (1) {
		ssize_t cnt;

		cnt = read_in_full(fd, buf + len, alloc - len);
		if (cnt < 0) {
			free(buf);
			return -1;
		}

		/* partial read from read_in_full means we hit EOF */
		len += cnt;
		if (len < alloc) {
			*out = buf;
			return len;
		}

		/* otherwise, grow and try again (if we can) */
		if (alloc == max_request_buffer)
			die("request was larger than our maximum size (%lu);"
			    " try setting GIT_HTTP_MAX_REQUEST_BUFFER",
			    max_request_buffer);

		alloc = alloc_nr(alloc);
		if (alloc > max_request_buffer)
			alloc = max_request_buffer;
		REALLOC_ARRAY(buf, alloc);
	}
}

static ssize_t read_request_fixed_len(int fd, ssize_t req_len, unsigned char **out)
{
	unsigned char *buf = NULL;
	ssize_t cnt = 0;

	if (max_request_buffer < req_len) {
		die("request was larger than our maximum size (%lu): "
		    "%" PRIuMAX "; try setting GIT_HTTP_MAX_REQUEST_BUFFER",
		    max_request_buffer, (uintmax_t)req_len);
	}

	buf = xmalloc(req_len);
	cnt = read_in_full(fd, buf, req_len);
	if (cnt < 0) {
		free(buf);
		return -1;
	}
	*out = buf;
	return cnt;
}

static ssize_t get_content_length(void)
{
	ssize_t val = -1;
	const char *str = getenv("CONTENT_LENGTH");

	if (str && *str && !git_parse_ssize_t(str, &val))
		die("failed to parse CONTENT_LENGTH: %s", str);
	return val;
}

static ssize_t read_request(int fd, unsigned char **out, ssize_t req_len)
{
	if (req_len < 0)
		return read_request_eof(fd, out);
	else
		return read_request_fixed_len(fd, req_len, out);
}

static void inflate_request(const char *prog_name, int out, int buffer_input, ssize_t req_len)
{
	git_zstream stream;
	unsigned char *full_request = NULL;
	unsigned char in_buf[8192];
	unsigned char out_buf[8192];
	unsigned long cnt = 0;
	int req_len_defined = req_len >= 0;
	size_t req_remaining_len = req_len;

	memset(&stream, 0, sizeof(stream));
	git_inflate_init_gzip_only(&stream);

	while (1) {
		ssize_t n;

		if (buffer_input) {
			if (full_request)
				n = 0; /* nothing left to read */
			else
				n = read_request(0, &full_request, req_len);
			stream.next_in = full_request;
		} else {
			ssize_t buffer_len;
			if (req_len_defined && req_remaining_len <= sizeof(in_buf))
				buffer_len = req_remaining_len;
			else
				buffer_len = sizeof(in_buf);
			n = xread(0, in_buf, buffer_len);
			stream.next_in = in_buf;
			if (req_len_defined && n > 0)
				req_remaining_len -= n;
		}

		if (n <= 0)
			die("request ended in the middle of the gzip stream");
		stream.avail_in = n;

		while (0 < stream.avail_in) {
			int ret;

			stream.next_out = out_buf;
			stream.avail_out = sizeof(out_buf);

			ret = git_inflate(&stream, Z_NO_FLUSH);
			if (ret != Z_OK && ret != Z_STREAM_END)
				die("zlib error inflating request, result %d", ret);

			n = stream.total_out - cnt;
			write_to_child(out, out_buf, stream.total_out - cnt, prog_name);
			cnt = stream.total_out;

			if (ret == Z_STREAM_END)
				goto done;
		}
	}

done:
	git_inflate_end(&stream);
	close(out);
	free(full_request);
}

static void copy_request(const char *prog_name, int out, ssize_t req_len)
{
	unsigned char *buf;
	ssize_t n = read_request(0, &buf, req_len);
	if (n < 0)
		die_errno("error reading request body");
	write_to_child(out, buf, n, prog_name);
	close(out);
	free(buf);
}

static void pipe_fixed_length(const char *prog_name, int out, size_t req_len)
{
	unsigned char buf[8192];
	size_t remaining_len = req_len;

	while (remaining_len > 0) {
		size_t chunk_length = remaining_len > sizeof(buf) ? sizeof(buf) : remaining_len;
		ssize_t n = xread(0, buf, chunk_length);
		if (n < 0)
			die_errno("Reading request failed");
		write_to_child(out, buf, n, prog_name);
		remaining_len -= n;
	}

	close(out);
}

static void run_service(const char **argv, int buffer_input)
{
	const char *encoding = getenv("HTTP_CONTENT_ENCODING");
	const char *user = getenv("REMOTE_USER");
	const char *host = getenv("REMOTE_ADDR");
	int gzipped_request = 0;
	struct child_process cld = CHILD_PROCESS_INIT;
	ssize_t req_len = get_content_length();

	if (encoding && (!strcmp(encoding, "gzip") || !strcmp(encoding, "x-gzip")))
		gzipped_request = 1;

	if (!user || !*user)
		user = "anonymous";
	if (!host || !*host)
		host = "(none)";

	if (!getenv("GIT_COMMITTER_NAME"))
		strvec_pushf(&cld.env, "GIT_COMMITTER_NAME=%s", user);
	if (!getenv("GIT_COMMITTER_EMAIL"))
		strvec_pushf(&cld.env,
			     "GIT_COMMITTER_EMAIL=%s@http.%s", user, host);

	strvec_pushv(&cld.args, argv);
	if (buffer_input || gzipped_request || req_len >= 0)
		cld.in = -1;
	cld.git_cmd = 1;
	cld.clean_on_exit = 1;
	cld.wait_after_clean = 1;
	if (start_command(&cld))
		exit(1);