rpcauth: Make it possible to provide a custom password

This adds the functionality to specify a custom password to
`rpcauth.py`, as well as makes the code (IMO) easier to understand.

2 files changed, 14 insertions, 7 deletions

diff --git a/share/rpcauth/README.md b/share/rpcauth/README.md
index 389278a125..20d16f0a97 100644
--- a/share/rpcauth/README.md
+++ b/share/rpcauth/README.md
@@ -8,3 +8,7 @@ Create login credentials for a JSON-RPC user.
 Usage:
 
     ./rpcauth.py <username>
+
+in which case the script will generate a password. To specify a custom password do:
+
+    ./rpcauth.py <username> <password>
diff --git a/share/rpcauth/rpcauth.py b/share/rpcauth/rpcauth.py
index da84deb5e2..566c55aba9 100755
--- a/share/rpcauth/rpcauth.py
+++ b/share/rpcauth/rpcauth.py
@@ -17,24 +17,27 @@ def generate_salt():
     salt_sequence = [cryptogen.randrange(256) for _ in range(16)]
     return ''.join([format(r, 'x') for r in salt_sequence])
 
-def generate_password(salt):
+def generate_password():
     """Create 32 byte b64 password"""
-    password = base64.urlsafe_b64encode(os.urandom(32)).decode('utf-8')
+    return base64.urlsafe_b64encode(os.urandom(32)).decode('utf-8')
 
+def password_to_hmac(salt, password):
     m = hmac.new(bytearray(salt, 'utf-8'), bytearray(password, 'utf-8'), 'SHA256')
-    password_hmac = m.hexdigest()
-
-    return password, password_hmac
+    return m.hexdigest()
 
 def main():
     if len(sys.argv) < 2:
-        sys.stderr.write('Please include username as an argument.\n')
+        sys.stderr.write('Please include username (and an optional password, will generate one if not provided) as an argument.\n')
         sys.exit(0)
 
     username = sys.argv[1]
 
     salt = generate_salt()
-    password, password_hmac = generate_password(salt)
+    if len(sys.argv) > 2:
+        password = sys.argv[2]
+    else:
+        password = generate_password()
+    password_hmac = password_to_hmac(salt, password)
 
     print('String to be appended to bitcoin.conf:')
     print('rpcauth={0}:{1}${2}'.format(username, salt, password_hmac))