bug#49085: Handle more unicode characters in uri-decode

[Vivien Kraus via "Bug reports for GUILE, GNU's Ubiquitous Extension Language" <bug-guile@gnu.org>]

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Dear guilers,

uri-decode should accept unicode characters. This is difficult to
implement so that different encodings can be used, but here is my
solution.

Best regards,

Vivien

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From 7adb0e333624c617f7c95796053df60d0a504ec9 Fri Jun 18 11:57:13 2021
From: Vivien Kraus <vivien@planete-kraus.eu>
Date: Fri, 18 Jun 2021 11:57:13 +0200
Subject: [PATCH] Let uri-decode handle more cases with unicode input.

Unicode characters are allowed in URIs. However, since Guile URIs are
not automatically UTF-8, it is possible that the decoding fails in two
different ways:

1. a character in the URI cannot be part of the specified encoding, for
   instance a non-trivial unicode character with ISO-8859-1;
2. the percent-encoding sequence cannot be decoded, for instance %FF
   alone in a UTF-8 URI.
---
 module/web/uri.scm            | 17 ++++++++++++++---
 test-suite/tests/web-uri.test | 11 +++++++++++
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/module/web/uri.scm b/module/web/uri.scm
index 8e0b9bee7..bb3573fab 100644
--- a/module/web/uri.scm
+++ b/module/web/uri.scm
@@ -424,10 +424,21 @@ ENCODING was ‘#f’."
                        (put-u8 port (char->integer ch))
                        (lp (1+ i)))
                       (else
-                       (uri-error "Invalid character in encoded URI ~a: ~s"
-                                  str ch))))))))))
+                       (let ((encoded
+                              (catch 'encoding-error
+                                (lambda ()
+                                  (string->bytevector (string ch) encoding))
+                                (lambda error
+                                  (uri-error "Invalid character in encoded URI ~a: ~s"
+                                             str ch)))))
+                         (put-bytevector port encoded)
+                         (lp (1+ i))))))))))))
     (if encoding
-        (bytevector->string bv encoding)
+        (catch 'decoding-error
+          (lambda ()
+            (bytevector->string bv encoding))
+          (lambda error
+            (uri-error "Invalid character in encoded URI ~a" str)))
         ;; Otherwise return raw bytevector
         bv)))
 
diff --git a/test-suite/tests/web-uri.test b/test-suite/tests/web-uri.test
index 95fd82f16..dc1da79e6 100644
--- a/test-suite/tests/web-uri.test
+++ b/test-suite/tests/web-uri.test
@@ -686,6 +686,17 @@
   (pass-if "foo+bar"
     (equal? "foo bar" (uri-decode "foo+bar")))
 
+  (pass-if "foo✫bar"
+    (equal? "foo✫bar" (uri-decode "foo✫bar")))
+
+  (pass-if-uri-exception "foo✫bar in non-utf8 encoding"
+                         "Invalid character in encoded URI ~a: ~s"
+                         (uri-decode "foo✫bar" #:encoding "ISO-8859-1"))
+
+  (pass-if-uri-exception "foo%FFbar in utf-8"
+                         "Invalid character in encoded URI ~a"
+                         (uri-decode "foo%FFbar in utf-8"))
+
   (pass-if "foo+bar"
     (equal? '("foo+bar") (split-and-decode-uri-path "foo+bar"))))
 
-- 
2.32.0