Add support for environment variable expansion

This patch teaches cgit to expand environment variables in certain
cgitrc option values (cache_root, scan-path, include) plus when
finding the location of cgitrc itself.

One use case for this feature is virtual hosting - e.g. by setting
$CGIT_CONFIG='/etc/cgitrc/$HTTP_HOST' in httpd.conf, all virtual
hosts automatically gets their own cgitrc.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>

1 files changed, 71 insertions, 0 deletions

diff --git a/shared.c b/shared.c
index 5f46793..76d26dd 100644
--- a/shared.c
+++ b/shared.c
@@ -298,128 +298,199 @@ void cgit_diff_tree(const unsigned char *old_sha1,
 		    const unsigned char *new_sha1,
 		    filepair_fn fn, const char *prefix)
 {
 	struct diff_options opt;
 	int ret;
 	int prefixlen;
 
 	diff_setup(&opt);
 	opt.output_format = DIFF_FORMAT_CALLBACK;
 	opt.detect_rename = 1;
 	opt.rename_limit = ctx.cfg.renamelimit;
 	DIFF_OPT_SET(&opt, RECURSIVE);
 	opt.format_callback = cgit_diff_tree_cb;
 	opt.format_callback_data = fn;
 	if (prefix) {
 		opt.nr_paths = 1;
 		opt.paths = &prefix;
 		prefixlen = strlen(prefix);
 		opt.pathlens = &prefixlen;
 	}
 	diff_setup_done(&opt);
 
 	if (old_sha1 && !is_null_sha1(old_sha1))
 		ret = diff_tree_sha1(old_sha1, new_sha1, "", &opt);
 	else
 		ret = diff_root_tree_sha1(new_sha1, "", &opt);
 	diffcore_std(&opt);
 	diff_flush(&opt);
 }
 
 void cgit_diff_commit(struct commit *commit, filepair_fn fn)
 {
 	unsigned char *old_sha1 = NULL;
 
 	if (commit->parents)
 		old_sha1 = commit->parents->item->object.sha1;
 	cgit_diff_tree(old_sha1, commit->object.sha1, fn, NULL);
 }
 
 int cgit_parse_snapshots_mask(const char *str)
 {
 	const struct cgit_snapshot_format *f;
 	static const char *delim = " \t,:/|;";
 	int tl, sl, rv = 0;
 
 	/* favor legacy setting */
 	if(atoi(str))
 		return 1;
 	for(;;) {
 		str += strspn(str,delim);
 		tl = strcspn(str,delim);
 		if (!tl)
 			break;
 		for (f = cgit_snapshot_formats; f->suffix; f++) {
 			sl = strlen(f->suffix);
 			if((tl == sl && !strncmp(f->suffix, str, tl)) ||
 			   (tl == sl-1 && !strncmp(f->suffix+1, str, tl-1))) {
 				rv |= f->bit;
 				break;
 			}
 		}
 		str += tl;
 	}
 	return rv;
 }
 
 int cgit_open_filter(struct cgit_filter *filter)
 {
 
 	filter->old_stdout = chk_positive(dup(STDOUT_FILENO),
 		"Unable to duplicate STDOUT");
 	chk_zero(pipe(filter->pipe_fh), "Unable to create pipe to subprocess");
 	filter->pid = chk_non_negative(fork(), "Unable to create subprocess");
 	if (filter->pid == 0) {
 		close(filter->pipe_fh[1]);
 		chk_non_negative(dup2(filter->pipe_fh[0], STDIN_FILENO),
 			"Unable to use pipe as STDIN");
 		execvp(filter->cmd, filter->argv);
 		die("Unable to exec subprocess %s: %s (%d)", filter->cmd,
 			strerror(errno), errno);
 	}
 	close(filter->pipe_fh[0]);
 	chk_non_negative(dup2(filter->pipe_fh[1], STDOUT_FILENO),
 		"Unable to use pipe as STDOUT");
 	close(filter->pipe_fh[1]);
 	return 0;
 }
 
 int cgit_close_filter(struct cgit_filter *filter)
 {
 	chk_non_negative(dup2(filter->old_stdout, STDOUT_FILENO),
 		"Unable to restore STDOUT");
 	close(filter->old_stdout);
 	if (filter->pid < 0)
 		return 0;
 	waitpid(filter->pid, &filter->exitstatus, 0);
 	if (WIFEXITED(filter->exitstatus) && !WEXITSTATUS(filter->exitstatus))
 		return 0;
 	die("Subprocess %s exited abnormally", filter->cmd);
 }
 
 /* Read the content of the specified file into a newly allocated buffer,
  * zeroterminate the buffer and return 0 on success, errno otherwise.
  */
 int readfile(const char *path, char **buf, size_t *size)
 {
 	int fd, e;
 	struct stat st;
 
 	fd = open(path, O_RDONLY);
 	if (fd == -1)
 		return errno;
 	if (fstat(fd, &st)) {
 		e = errno;
 		close(fd);
 		return e;
 	}
 	if (!S_ISREG(st.st_mode)) {
 		close(fd);
 		return EISDIR;
 	}
 	*buf = xmalloc(st.st_size + 1);
 	*size = read_in_full(fd, *buf, st.st_size);
 	e = errno;
 	(*buf)[*size] = '\0';
 	close(fd);
 	return (*size == st.st_size ? 0 : e);
 }
+
+int is_token_char(char c)
+{
+	return isalnum(c) || c == '_';
+}
+
+/* Replace name with getenv(name), return pointer to zero-terminating char
+ */
+char *expand_macro(char *name, int maxlength)
+{
+	char *value;
+	int len;
+
+	len = 0;
+	value = getenv(name);
+	if (value) {
+		len = strlen(value);
+		if (len > maxlength)
+			len = maxlength;
+		strncpy(name, value, len);
+	}
+	return name + len;
+}
+
+#define EXPBUFSIZE (1024 * 8)
+
+/* Replace all tokens prefixed by '$' in the specified text with the
+ * value of the named environment variable.
+ * NB: the return value is a static buffer, i.e. it must be strdup'd
+ * by the caller.
+ */
+char *expand_macros(const char *txt)
+{
+	static char result[EXPBUFSIZE];
+	char *p, *start;
+	int len;
+
+	p = result;
+	start = NULL;
+	while (p < result + EXPBUFSIZE - 1 && txt && *txt) {
+		*p = *txt;
+		if (start) {
+			if (!is_token_char(*txt)) {
+				if (p - start > 0) {
+					*p = '\0';
+					len = result + EXPBUFSIZE - start - 1;
+					p = expand_macro(start, len) - 1;
+				}
+				start = NULL;
+				txt--;
+			}
+			p++;
+			txt++;
+			continue;
+		}
+		if (*txt == '$') {
+			start = p;
+			txt++;
+			continue;
+		}
+		p++;
+		txt++;
+	}
+	*p = '\0';
+	if (start && p - start > 0) {
+		len = result + EXPBUFSIZE - start - 1;
+		p = expand_macro(start, len);
+		*p = '\0';
+	}
+	return result;
+}