Fix a text canonicalisation bug in CMS

CHANGES

@@ -290,7 +290,27 @@
      issues, has been replaced to always returns NULL.
      [Rich Salz]
 
- Changes between 1.1.0g and 1.1.0h [xx XXX xxxx]
+
+ Changes between 1.1.0h and 1.1.0i [xx XXX xxxx]
+
+  *) Fixed a text canonicalisation bug in CMS
+
+     Where a CMS detatched signature is used with text content the text goes
+     through a canonicalisation process first prior to signing or verifying a
+     signature. This process strips trailing space at the end of lines, converts
+     line terminators to CRLF and removes additional trailing line terminators
+     at the end of a file. A bug in the canonicalisation process meant that
+     some characters, such as form-feed, were incorrectly treated as whitespace
+     and removed. This is contrary to the specification (RFC5485). This fix
+     could mean that detatched text data signed with an earlier version of
+     OpenSSL 1.1.0 may fail to verify using the fixed version, or text data
+     signed with a fixed OpenSSL may fail to verify with an earlier version of
+     OpenSSL 1.1.0. A workaround is to only verify the canonicalised text data
+     and use the "-binary" flag (for the "cms" command line application) or set
+     the SMIME_BINARY/PKCS7_BINARY/CMS_BINARY flags (if using CMS_verify()).
+     [Matt Caswell]
+
+ Changes between 1.1.0g and 1.1.0h [27 Mar 2018]
 
   *) Constructed ASN.1 types with a recursive definition could exceed the stack
 

crypto/asn1/asn_mime.c

@@ -953,12 +953,14 @@ static int strip_eol(char *linebuf, int *plen, int flags)
 
     for (p = linebuf + len - 1; len > 0; len--, p--) {
         c = *p;
-        if (c == '\n')
+        if (c == '\n') {
             is_eol = 1;
-        else if (is_eol && flags & SMIME_ASCIICRLF && c < 33)
+        } else if (is_eol && flags & SMIME_ASCIICRLF && c == 32) {
+            /* Strip trailing space on a line; 32 == ASCII for ' ' */
             continue;
-        else if (c != '\r')
+        } else if (c != '\r') {
             break;
+        }
     }
     *plen = len;
     return is_eol;