bad attempt to read a stream using bash read byte by byte

ocdec.sh

@@ -124,31 +124,38 @@ function decryptFile() {
 
   decFileKeyContent="$( openssl rc4 -d -in "$encFileKeyPath" -iv 0 -K $decUserFileShareKeyHEX )"
   decFileKeyContentHEX="$( echo -n $decFileKeyContent |od -An -tx1 |tr -dc '[:xdigit:]' )"
-  decFileKeyContentHEX=${decFileKeyContentHEX:0:64}
   # --- Get the FileKey ---
 
   # --- Decrypt the file ---
-  # OC writes the encrypted file in 8K chunks, each containing it's own iv in the end
-  chunkSize=8192
-  while read -d '' -n $chunkSize CHUNK || [ ! -z "$CHUNK" ]; do
-    #split chunk into payload an iv string (strip padding from iv)          
-    read payload iv <<<`echo $CHUNK | sed -r 's/(.*)00iv00(.{16})xx/\1 \2/'`
-    CHUNK=
-    #if [ -z $CHUNK ]; then break; fi
-    # convert base64 iv into hex
-    iv=$(echo -n "$iv" | od -An -tx1 | tr -dc '[:xdigit:]' )
-    # decode chunk
-    openssl enc -AES-256-CFB -d -nosalt -base64 -A -K $decFileKeyContentHEX -iv $iv -in <(echo "$payload")
-    #done <<<`sed -r 's/^HBEGIN:.+:HEND-*//' <"${USER}/$encFilePath"` # pipe the encrypted file without head into the loop
-    done < <(dd bs=$chunkSize skip=1 if="${USER}/$encFilePath")
+  encFileContentsALL="$(cat "${USER}/$encFilePath")"
+  encFileContentsNOHEAD=$(echo -n "$encFileContentsALL" | sed -r 's/^HBEGIN:.+:HEND-*//')
+
+  pos=0; posc=0; encStream="";
+  # bottleneck: bash read by character is super slow
+  while IFS= read -r -n1 char; do
+    (( posc++ ))
+    if $(echo ${encStream: -24} |grep -Eq "^00iv00.{16}xx$"); then
+      plainIV=$(echo ${encStream: -24} |sed -r 's/^00iv00//;s/xx$//')
+      encStreamReady=${encStream:((posc - pos - 1)):((pos - 24))}
+      (( pos=0 ))
+
+      #echo "[::] DEBUG: " $encStreamReady with $plainIV
+      # can decrypt now
+      plainFileIVHEX=$(echo -n "$plainIV" |od -An -tx1 |tr -dc '[:xdigit:]')
+      openssl enc -AES-256-CFB -d -nosalt -base64 -A -K $decFileKeyContentHEX -iv $plainFileIVHEX -in <(echo "$encStreamReady")
+      #php -r "echo openssl_decrypt('$encStreamReady', 'AES-256-CFB', '$decFileKeyContent', false, '$plainIV');"
+    fi
+    (( pos++ ))
+    encStream="$encStream$char"
+  done <<< $encFileContentsNOHEAD
   # --- Decrypt the file ---
 }
 
 # Get a username from the path (arg1)
-USER="$(echo "$1" |cut -sd / -f 1)"
+USER="$(echo $1 |cut -sd / -f 1)"
 
 # Strip off the username from the path (arg1)
-FILETD="$(echo "$1" |cut -sd / -f 2-)"
+FILETD="$(echo $1 |cut -sd / -f 2-)"
 
 if [ ! -r "$USER" ]; then
   echo "User directory cannot be found! Are you sure you are in ownCloud's data directory?"