libfetch: Allow special characters in http basic auth

Currently, special characters in the username or password are not
handled correctly (when set in $http_proxy and $https_proxy). They
should be percent encoded in the environment variables then decoded
by libfetch and reencoded using base64. This implementation is mainly
taken from the current FreeBSD source and adapted to the apk-tools
version of libfetch.

fixes #10775

1 files changed, 62 insertions, 14 deletions

diff --git a/libfetch/fetch.c b/libfetch/fetch.c
index 45c92aa..68d920c 100644
--- a/libfetch/fetch.c
+++ b/libfetch/fetch.c
@@ -354,7 +354,55 @@ fetchCopyURL(const struct url *src)
 }
 
 /*
- * Split an URL into components. URL syntax is:
+ * Return value of the given hex digit.
+ */
+static int
+fetch_hexval(char ch)
+{
+	if (ch >= '0' && ch <= '9')
+		return (ch - '0');
+	else if (ch >= 'a' && ch <= 'f')
+		return (ch - 'a' + 10);
+	else if (ch >= 'A' && ch <= 'F')
+		return (ch - 'A' + 10);
+	return (-1);
+}
+
+/*
+ * Decode percent-encoded URL component from src into dst, stopping at end
+ * of string or one of the characters contained in brk.  Returns a pointer
+ * to the unhandled part of the input string (null terminator, specified
+ * character).  No terminator is written to dst (it is the caller's
+ * responsibility).
+ */
+static const char *
+fetch_pctdecode(char *dst, const char *src, const char *brk, size_t dlen)
+{
+	int d1, d2;
+	char c;
+	const char *s;
+
+	for (s = src; *s != '\0' && !strchr(brk, *s); s++) {
+		if (s[0] == '%' && (d1 = fetch_hexval(s[1])) >= 0 &&
+		    (d2 = fetch_hexval(s[2])) >= 0 && (d1 > 0 || d2 > 0)) {
+			c = d1 << 4 | d2;
+			s += 2;
+		} else if (s[0] == '%') {
+			/* Invalid escape sequence. */
+			return (NULL);
+		} else {
+			c = *s;
+		}
+		if (!dlen)
+			return NULL;
+		dlen--;
+		*dst++ = c;
+	}
+	return (s);
+}
+
+/*
+ * Split a URL into components. URL syntax is:
  * [method:/][/[user[:pwd]@]host[:port]/][document]
  * This almost, but not quite, RFC1738 URL syntax.
  */
@@ -428,25 +476,25 @@ find_user:
 	p = strpbrk(URL, "/@");
 	if (p != NULL && *p == '@') {
 		/* username */
-		for (q = URL, i = 0; (*q != ':') && (*q != '@'); q++) {
-			if (i >= URL_USERLEN) {
-				url_seterr(URL_BAD_AUTH);
-				goto ouch;
-			}
-			u->user[i++] = *q;
+		q = URL;
+		q = fetch_pctdecode(u->user, q, ":@", URL_USERLEN);
+		if (q == NULL) {
+			url_seterr(URL_BAD_AUTH);
+			goto ouch;
 		}
 
 		/* password */
 		if (*q == ':') {
-			for (q++, i = 0; (*q != '@'); q++) {
-				if (i >= URL_PWDLEN) {
-					url_seterr(URL_BAD_AUTH);
-					goto ouch;
-				}
-				u->pwd[i++] = *q;
+			q = fetch_pctdecode(u->pwd, q + 1, "@", URL_PWDLEN);
+			if (q == NULL) {
+				url_seterr(URL_BAD_AUTH);
+				goto ouch;
 			}
 		}
-
+		if (*q != '@') {
+			url_seterr(URL_BAD_AUTH);
+			goto ouch;
+		}
 		p++;
 	} else {
 		p = URL;