netrc: don't ignore the login name specified with "--user"

- for "--netrc", don't ignore the login/password specified with "--user",
  only ignore the login/password in the URL.
  This restores the netrc behaviour of curl 7.61.1 and earlier.
- fix the documentation of CURL_NETRC_REQUIRED
- improve the detection of login/password changes when reading .netrc
- don't read .netrc if both login and password are already set

Fixes #3213
Closes #3224

3 files changed, 35 insertions, 33 deletions

diff --git a/lib/netrc.c b/lib/netrc.c
index 1724b35b0..aba355b76 100644
--- a/lib/netrc.c
+++ b/lib/netrc.c
@@ -53,6 +53,8 @@ enum host_lookup_state {
 int Curl_parsenetrc(const char *host,
                     char **loginp,
                     char **passwordp,
+                    bool *login_changed,
+                    bool *password_changed,
                     char *netrcfile)
 {
   FILE *file;
@@ -164,7 +166,7 @@ int Curl_parsenetrc(const char *host,
             if(specific_login) {
               state_our_login = strcasecompare(login, tok);
             }
-            else {
+            else if(!login || strcmp(login, tok)) {
               if(login_alloc) {
                 free(login);
                 login_alloc = FALSE;
@@ -179,7 +181,8 @@ int Curl_parsenetrc(const char *host,
             state_login = 0;
           }
           else if(state_password) {
-            if(state_our_login || !specific_login) {
+            if((state_our_login || !specific_login)
+                && (!password || strcmp(password, tok))) {
               if(password_alloc) {
                 free(password);
                 password_alloc = FALSE;
@@ -211,15 +214,19 @@ int Curl_parsenetrc(const char *host,
 
     out:
     if(!retcode) {
+      *login_changed = FALSE;
+      *password_changed = FALSE;
       if(login_alloc) {
         if(*loginp)
           free(*loginp);
         *loginp = login;
+        *login_changed = TRUE;
       }
       if(password_alloc) {
         if(*passwordp)
           free(*passwordp);
         *passwordp = password;
+        *password_changed = TRUE;
       }
     }
     else {
diff --git a/lib/netrc.h b/lib/netrc.h
index d980166e6..fe3dc357e 100644
--- a/lib/netrc.h
+++ b/lib/netrc.h
@@ -26,6 +26,8 @@
 int Curl_parsenetrc(const char *host,
                     char **loginp,
                     char **passwordp,
+                    bool *login_changed,
+                    bool *password_changed,
                     char *filename);
   /* Assume: (*passwordp)[0]=0, host[0] != 0.
    * If (*loginp)[0] = 0, search for login and password within a machine
diff --git a/lib/url.c b/lib/url.c
index 0d5a13f99..121920c76 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -2999,6 +2999,20 @@ static CURLcode override_login(struct Curl_easy *data,
   bool user_changed = FALSE;
   bool passwd_changed = FALSE;
   CURLUcode uc;
+
+  if(data->set.use_netrc == CURL_NETRC_REQUIRED && conn->bits.user_passwd) {
+    /* ignore user+password in the URL */
+    if(*userp) {
+      Curl_safefree(*userp);
+      user_changed = TRUE;
+    }
+    if(*passwdp) {
+      Curl_safefree(*passwdp);
+      passwd_changed = TRUE;
+    }
+    conn->bits.user_passwd = FALSE; /* disable user+password */
+  }
+
   if(data->set.str[STRING_USERNAME]) {
     free(*userp);
     *userp = strdup(data->set.str[STRING_USERNAME]);
@@ -3025,16 +3039,15 @@ static CURLcode override_login(struct Curl_easy *data,
   }
 
   conn->bits.netrc = FALSE;
-  if(data->set.use_netrc != CURL_NETRC_IGNORED) {
-    char *nuser = NULL;
-    char *npasswd = NULL;
+  if(data->set.use_netrc != CURL_NETRC_IGNORED &&
+      (!*userp || !**userp || !*passwdp || !**passwdp)) {
+    bool netrc_user_changed = FALSE;
+    bool netrc_passwd_changed = FALSE;
     int ret;
 
-    if(data->set.use_netrc == CURL_NETRC_OPTIONAL)
-      nuser = *userp; /* to separate otherwise identical machines */
-
     ret = Curl_parsenetrc(conn->host.name,
-                          &nuser, &npasswd,
+                          userp, passwdp,
+                          &netrc_user_changed, &netrc_passwd_changed,
                           data->set.str[STRING_NETRC_FILE]);
     if(ret > 0) {
       infof(data, "Couldn't find host %s in the "
@@ -3051,31 +3064,11 @@ static CURLcode override_login(struct Curl_easy *data,
       conn->bits.netrc = TRUE;
       conn->bits.user_passwd = TRUE; /* enable user+password */
 
-      if(data->set.use_netrc == CURL_NETRC_OPTIONAL) {
-        /* prefer credentials outside netrc */
-        if(nuser && !*userp) {
-          free(*userp);
-          *userp = nuser;
-          user_changed = TRUE;
-        }
-        if(npasswd && !*passwdp) {
-          free(*passwdp);
-          *passwdp = npasswd;
-          passwd_changed = TRUE;
-        }
+      if(netrc_user_changed) {
+        user_changed = TRUE;
       }
-      else {
-        /* prefer netrc credentials */
-        if(nuser) {
-          free(*userp);
-          *userp = nuser;
-          user_changed = TRUE;
-        }
-        if(npasswd) {
-          free(*passwdp);
-          *passwdp = npasswd;
-          passwd_changed = TRUE;
-        }
+      if(netrc_passwd_changed) {
+        passwd_changed = TRUE;
       }
     }
   }