Subject: Re: bug#26948: gnutls errors on multiple guix commands

From: [email-masked] (Ludovic Courtès)
Date: Mon, 29 May 2017 11:31:37 +0200

Hi Mark,

Mark H Weaver <[email-masked]> skribis:

> This reminds me of a bug that I found in the Guile binding in GnuTLS a
> while ago, but forgot to report.  Maybe it's related:
>
> In 'set_certificate_file' in gnutls-3.5.9/guile/src/core.c:
>
>   static unsigned int
>   set_certificate_file (certificate_set_file_function_t set_file,
>                         SCM cred, SCM file, SCM format, const char *func_name)
>   #define FUNC_NAME func_name
>   {
>     int err;
>     char *c_file;
>     size_t c_file_len;
>   
>     gnutls_certificate_credentials_t c_cred;
>     gnutls_x509_crt_fmt_t c_format;
>   
>     c_cred = scm_to_gnutls_certificate_credentials (cred, 1, FUNC_NAME);
>     SCM_VALIDATE_STRING (2, file);
>     c_format = scm_to_gnutls_x509_certificate_format (format, 3, FUNC_NAME);
>   
>     c_file_len = scm_c_string_length (file);
>     c_file = alloca (c_file_len + 1);
>   
>     (void) scm_to_locale_stringbuf (file, c_file, c_file_len + 1);
>     c_file[c_file_len] = '\0';
>   
>     err = set_file (c_cred, c_file, c_format);
>     if (EXPECT_FALSE (err < 0))
>       scm_gnutls_error (err, FUNC_NAME);
>   
>     /* Return the number of certificates processed.  */
>     return ((unsigned int) err);
>   }
>
> 'scm_c_string_length' is inappropriately assumed to return the length
> of the encoded C string in bytes, whereas it actually returns the
> number of characters (code points).

This is terrible!  WDYT of this:

diff --git a/guile/src/core.c b/guile/src/core.c
index 605c91f7a..38d573fa9 100644
--- a/guile/src/core.c
+++ b/guile/src/core.c
@@ -1,5 +1,5 @@
 /* GnuTLS --- Guile bindings for GnuTLS.
-   Copyright (C) 2007-2014, 2016 Free Software Foundation, Inc.
+   Copyright (C) 2007-2014, 2016-2017 Free Software Foundation, Inc.
 
    GnuTLS is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
@@ -1428,22 +1428,19 @@ set_certificate_file (certificate_set_file_function_t set_file,
 {
   int err;
   char *c_file;
-  size_t c_file_len;
 
   gnutls_certificate_credentials_t c_cred;
   gnutls_x509_crt_fmt_t c_format;
 
   c_cred = scm_to_gnutls_certificate_credentials (cred, 1, FUNC_NAME);
   SCM_VALIDATE_STRING (2, file);
-  c_format = scm_to_gnutls_x509_certificate_format (format, 3, FUNC_NAME);
-
-  c_file_len = scm_c_string_length (file);
-  c_file = alloca (c_file_len + 1);
 
-  (void) scm_to_locale_stringbuf (file, c_file, c_file_len + 1);
-  c_file[c_file_len] = '\0';
+  c_format = scm_to_gnutls_x509_certificate_format (format, 3, FUNC_NAME);
+  c_file = scm_to_locale_string (file);
 
   err = set_file (c_cred, c_file, c_format);
+  free (c_file);
+
   if (EXPECT_FALSE (err < 0))
     scm_gnutls_error (err, FUNC_NAME);

Unfortunately there’s a dozen of places in core.c that use this idiom
and would need to be fixed (it’s pre-2.0 code I think).

In the meantime we can work around it this way:

diff --git a/guix/build/download.scm b/guix/build/download.scm
index ce4708a87..6ef623334 100644
--- a/guix/build/download.scm
+++ b/guix/build/download.scm
@@ -296,6 +296,13 @@ session record port using PORT as its underlying communication port."
   (make-parameter (or (getenv "GUIX_TLS_CERTIFICATE_DIRECTORY")
                       (getenv "SSL_CERT_DIR"))))  ;like OpenSSL
 
+(define (set-certificate-credentials-x509-trust-file!* cred file format)
+  "Like 'set-certificate-credentials-x509-trust-file!', but without the file
+name decoding bug described at
+<https://debbugs.gnu.org/cgi/bugreport.cgi?bug=26948#17>."
+  (let ((data (call-with-input-file file get-bytevector-all)))
+    (set-certificate-credentials-x509-trust-data! cred data format)))
+
 (define (make-credendials-with-ca-trust-files directory)
   "Return certificate credentials with X.509 authority certificates read from
 DIRECTORY.  Those authority certificates are checked when
@@ -309,7 +316,7 @@ DIRECTORY.  Those authority certificates are checked when
                 (let ((file (string-append directory "/" file)))
                   ;; Protect against dangling symlinks.
                   (when (file-exists? file)
-                    (set-certificate-credentials-x509-trust-file!
+                    (set-certificate-credentials-x509-trust-file!*
                      cred file
                      x509-certificate-format/pem))))
               (or files '()))

WDYT?  I’ll commit it if that’s fine with you.

Thanks for the report!

Ludo’.