sasl: Centralised the authentication mechanism strings

Moved the standard SASL mechanism strings into curl_sasl.h rather than
hard coding the same values over and over again in the protocols that
use SASL authentication.

For more information about the mechanism strings see:

http://www.iana.org/assignments/sasl-mechanisms

4 files changed, 88 insertions, 73 deletions

diff --git a/lib/curl_sasl.h b/lib/curl_sasl.h
index 1cac8fd63..2b6a5a26a 100644
--- a/lib/curl_sasl.h
+++ b/lib/curl_sasl.h
@@ -24,20 +24,35 @@
 
 #include "pingpong.h"
 
-/* Authentication mechanism flags */
-#define SASL_MECH_LOGIN         (1 << 0)
-#define SASL_MECH_PLAIN         (1 << 1)
-#define SASL_MECH_CRAM_MD5      (1 << 2)
-#define SASL_MECH_DIGEST_MD5    (1 << 3)
-#define SASL_MECH_GSSAPI        (1 << 4)
-#define SASL_MECH_EXTERNAL      (1 << 5)
-#define SASL_MECH_NTLM          (1 << 6)
-#define SASL_MECH_XOAUTH2       (1 << 7)
-
 /* Authentication mechanism values */
 #define SASL_AUTH_NONE          0
 #define SASL_AUTH_ANY           ~0U
 
+/* Authentication mechanism flags */
+#define SASL_MECH_LOGIN             (1 << 0)
+#define SASL_MECH_PLAIN             (1 << 1)
+#define SASL_MECH_CRAM_MD5          (1 << 2)
+#define SASL_MECH_DIGEST_MD5        (1 << 3)
+#define SASL_MECH_GSSAPI            (1 << 4)
+#define SASL_MECH_EXTERNAL          (1 << 5)
+#define SASL_MECH_NTLM              (1 << 6)
+#define SASL_MECH_XOAUTH2           (1 << 7)
+
+/* Authentication mechanism strings */
+#define SASL_MECH_STRING_LOGIN      "LOGIN"
+#define SASL_MECH_STRING_PLAIN      "PLAIN"
+#define SASL_MECH_STRING_CRAM_MD5   "CRAM-MD5"
+#define SASL_MECH_STRING_DIGEST_MD5 "DIGEST-MD5"
+#define SASL_MECH_STRING_GSSAPI     "GSSAPI"
+#define SASL_MECH_STRING_EXTERNAL   "EXTERNAL"
+#define SASL_MECH_STRING_NTLM       "NTLM"
+#define SASL_MECH_STRING_XOAUTH2    "XOAUTH2"
+
+/* This is used to test whether the line starts with the given mechanism */
+#define sasl_mech_equal(line, wordlen, mech) \
+  (wordlen == (sizeof(mech) - 1) / sizeof(char) && \
+   !memcmp(line, mech, wordlen))
+
 /* This is used to generate a base64 encoded PLAIN authentication message */
 CURLcode Curl_sasl_create_plain_message(struct SessionHandle *data,
                                         const char *userp,
diff --git a/lib/imap.c b/lib/imap.c
index 7c0bf5c0e..5d3a1a17e 100644
--- a/lib/imap.c
+++ b/lib/imap.c
@@ -555,13 +555,13 @@ static CURLcode imap_perform_authenticate(struct connectdata *conn)
 #ifndef CURL_DISABLE_CRYPTO_AUTH
   if((imapc->authmechs & SASL_MECH_DIGEST_MD5) &&
      (imapc->prefmech & SASL_MECH_DIGEST_MD5)) {
-    mech = "DIGEST-MD5";
+    mech = SASL_MECH_STRING_DIGEST_MD5;
     state1 = IMAP_AUTHENTICATE_DIGESTMD5;
     imapc->authused = SASL_MECH_DIGEST_MD5;
   }
   else if((imapc->authmechs & SASL_MECH_CRAM_MD5) &&
           (imapc->prefmech & SASL_MECH_CRAM_MD5)) {
-    mech = "CRAM-MD5";
+    mech = SASL_MECH_STRING_CRAM_MD5;
     state1 = IMAP_AUTHENTICATE_CRAMMD5;
     imapc->authused = SASL_MECH_CRAM_MD5;
   }
@@ -570,7 +570,7 @@ static CURLcode imap_perform_authenticate(struct connectdata *conn)
 #ifdef USE_NTLM
     if((imapc->authmechs & SASL_MECH_NTLM) &&
        (imapc->prefmech & SASL_MECH_NTLM)) {
-    mech = "NTLM";
+    mech = SASL_MECH_STRING_NTLM;
     state1 = IMAP_AUTHENTICATE_NTLM;
     state2 = IMAP_AUTHENTICATE_NTLM_TYPE2MSG;
     imapc->authused = SASL_MECH_NTLM;
@@ -585,7 +585,7 @@ static CURLcode imap_perform_authenticate(struct connectdata *conn)
   if(((imapc->authmechs & SASL_MECH_XOAUTH2) &&
       (imapc->prefmech & SASL_MECH_XOAUTH2) &&
       (imapc->prefmech != SASL_AUTH_ANY)) || conn->xoauth2_bearer) {
-    mech = "XOAUTH2";
+    mech = SASL_MECH_STRING_XOAUTH2;
     state1 = IMAP_AUTHENTICATE_XOAUTH2;
     state2 = IMAP_AUTHENTICATE_FINAL;
     imapc->authused = SASL_MECH_XOAUTH2;
@@ -597,7 +597,7 @@ static CURLcode imap_perform_authenticate(struct connectdata *conn)
   }
   else if((imapc->authmechs & SASL_MECH_LOGIN) &&
      (imapc->prefmech & SASL_MECH_LOGIN)) {
-    mech = "LOGIN";
+    mech = SASL_MECH_STRING_LOGIN;
     state1 = IMAP_AUTHENTICATE_LOGIN;
     state2 = IMAP_AUTHENTICATE_LOGIN_PASSWD;
     imapc->authused = SASL_MECH_LOGIN;
@@ -608,7 +608,7 @@ static CURLcode imap_perform_authenticate(struct connectdata *conn)
   }
   else if((imapc->authmechs & SASL_MECH_PLAIN) &&
           (imapc->prefmech & SASL_MECH_PLAIN)) {
-    mech = "PLAIN";
+    mech = SASL_MECH_STRING_PLAIN;
     state1 = IMAP_AUTHENTICATE_PLAIN;
     state2 = IMAP_AUTHENTICATE_FINAL;
     imapc->authused = SASL_MECH_PLAIN;
@@ -885,21 +885,21 @@ static CURLcode imap_state_capability_resp(struct connectdata *conn,
         wordlen -= 5;
 
         /* Test the word for a matching authentication mechanism */
-        if(wordlen == 5 && !memcmp(line, "LOGIN", 5))
+        if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_LOGIN))
           imapc->authmechs |= SASL_MECH_LOGIN;
-        if(wordlen == 5 && !memcmp(line, "PLAIN", 5))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_PLAIN))
           imapc->authmechs |= SASL_MECH_PLAIN;
-        else if(wordlen == 8 && !memcmp(line, "CRAM-MD5", 8))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_CRAM_MD5))
           imapc->authmechs |= SASL_MECH_CRAM_MD5;
-        else if(wordlen == 10 && !memcmp(line, "DIGEST-MD5", 10))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_DIGEST_MD5))
           imapc->authmechs |= SASL_MECH_DIGEST_MD5;
-        else if(wordlen == 6 && !memcmp(line, "GSSAPI", 6))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_GSSAPI))
           imapc->authmechs |= SASL_MECH_GSSAPI;
-        else if(wordlen == 8 && !memcmp(line, "EXTERNAL", 8))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_EXTERNAL))
           imapc->authmechs |= SASL_MECH_EXTERNAL;
-        else if(wordlen == 4 && !memcmp(line, "NTLM", 4))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_NTLM))
           imapc->authmechs |= SASL_MECH_NTLM;
-        else if(wordlen == 7 && !memcmp(line, "XOAUTH2", 7))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_XOAUTH2))
           imapc->authmechs |= SASL_MECH_XOAUTH2;
       }
 
@@ -2275,19 +2275,19 @@ static CURLcode imap_parse_url_options(struct connectdata *conn)
 
       if(strequal(value, "*"))
         imapc->prefmech = SASL_AUTH_ANY;
-      else if(strequal(value, "LOGIN"))
+      else if(strequal(value, SASL_MECH_STRING_LOGIN))
         imapc->prefmech = SASL_MECH_LOGIN;
-      else if(strequal(value, "PLAIN"))
+      else if(strequal(value, SASL_MECH_STRING_PLAIN))
         imapc->prefmech = SASL_MECH_PLAIN;
-      else if(strequal(value, "CRAM-MD5"))
+      else if(strequal(value, SASL_MECH_STRING_CRAM_MD5))
         imapc->prefmech = SASL_MECH_CRAM_MD5;
-      else if(strequal(value, "DIGEST-MD5"))
+      else if(strequal(value, SASL_MECH_STRING_DIGEST_MD5))
         imapc->prefmech = SASL_MECH_DIGEST_MD5;
-      else if(strequal(value, "GSSAPI"))
+      else if(strequal(value, SASL_MECH_STRING_GSSAPI))
         imapc->prefmech = SASL_MECH_GSSAPI;
-      else if(strequal(value, "NTLM"))
+      else if(strequal(value, SASL_MECH_STRING_NTLM))
         imapc->prefmech = SASL_MECH_NTLM;
-      else if(strequal(value, "XOAUTH2"))
+      else if(strequal(value, SASL_MECH_STRING_XOAUTH2))
         imapc->prefmech = SASL_MECH_XOAUTH2;
       else
         imapc->prefmech = SASL_AUTH_NONE;
diff --git a/lib/pop3.c b/lib/pop3.c
index bb3ed31cc..a77193384 100644
--- a/lib/pop3.c
+++ b/lib/pop3.c
@@ -313,21 +313,21 @@ static bool pop3_endofresp(struct connectdata *conn, char *line, size_t len,
           wordlen++;
 
         /* Test the word for a matching authentication mechanism */
-        if(wordlen == 5 && !memcmp(line, "LOGIN", 5))
+        if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_LOGIN))
           pop3c->authmechs |= SASL_MECH_LOGIN;
-        else if(wordlen == 5 && !memcmp(line, "PLAIN", 5))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_PLAIN))
           pop3c->authmechs |= SASL_MECH_PLAIN;
-        else if(wordlen == 8 && !memcmp(line, "CRAM-MD5", 8))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_CRAM_MD5))
           pop3c->authmechs |= SASL_MECH_CRAM_MD5;
-        else if(wordlen == 10 && !memcmp(line, "DIGEST-MD5", 10))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_DIGEST_MD5))
           pop3c->authmechs |= SASL_MECH_DIGEST_MD5;
-        else if(wordlen == 6 && !memcmp(line, "GSSAPI", 6))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_GSSAPI))
           pop3c->authmechs |= SASL_MECH_GSSAPI;
-        else if(wordlen == 8 && !memcmp(line, "EXTERNAL", 8))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_EXTERNAL))
           pop3c->authmechs |= SASL_MECH_EXTERNAL;
-        else if(wordlen == 4 && !memcmp(line, "NTLM", 4))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_NTLM))
           pop3c->authmechs |= SASL_MECH_NTLM;
-        else if(wordlen == 7 && !memcmp(line, "XOAUTH2", 7))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_XOAUTH2))
           pop3c->authmechs |= SASL_MECH_XOAUTH2;
 
         line += wordlen;
@@ -576,13 +576,13 @@ static CURLcode pop3_perform_authenticate(struct connectdata *conn)
 #ifndef CURL_DISABLE_CRYPTO_AUTH
     if((pop3c->authmechs & SASL_MECH_DIGEST_MD5) &&
        (pop3c->prefmech & SASL_MECH_DIGEST_MD5)) {
-      mech = "DIGEST-MD5";
+      mech = SASL_MECH_STRING_DIGEST_MD5;
       state1 = POP3_AUTH_DIGESTMD5;
       pop3c->authused = SASL_MECH_DIGEST_MD5;
     }
     else if((pop3c->authmechs & SASL_MECH_CRAM_MD5) &&
             (pop3c->prefmech & SASL_MECH_CRAM_MD5)) {
-      mech = "CRAM-MD5";
+      mech = SASL_MECH_STRING_CRAM_MD5;
       state1 = POP3_AUTH_CRAMMD5;
       pop3c->authused = SASL_MECH_CRAM_MD5;
     }
@@ -591,7 +591,7 @@ static CURLcode pop3_perform_authenticate(struct connectdata *conn)
 #ifdef USE_NTLM
     if((pop3c->authmechs & SASL_MECH_NTLM) &&
        (pop3c->prefmech & SASL_MECH_NTLM)) {
-      mech = "NTLM";
+      mech = SASL_MECH_STRING_NTLM;
       state1 = POP3_AUTH_NTLM;
       state2 = POP3_AUTH_NTLM_TYPE2MSG;
       pop3c->authused = SASL_MECH_NTLM;
@@ -606,7 +606,7 @@ static CURLcode pop3_perform_authenticate(struct connectdata *conn)
     if(((pop3c->authmechs & SASL_MECH_XOAUTH2) &&
         (pop3c->prefmech & SASL_MECH_XOAUTH2) &&
         (pop3c->prefmech != SASL_AUTH_ANY)) || conn->xoauth2_bearer) {
-      mech = "XOAUTH2";
+      mech = SASL_MECH_STRING_XOAUTH2;
       state1 = POP3_AUTH_XOAUTH2;
       state2 = POP3_AUTH_FINAL;
       pop3c->authused = SASL_MECH_XOAUTH2;
@@ -618,7 +618,7 @@ static CURLcode pop3_perform_authenticate(struct connectdata *conn)
     }
     else if((pop3c->authmechs & SASL_MECH_LOGIN) &&
        (pop3c->prefmech & SASL_MECH_LOGIN)) {
-      mech = "LOGIN";
+      mech = SASL_MECH_STRING_LOGIN;
       state1 = POP3_AUTH_LOGIN;
       state2 = POP3_AUTH_LOGIN_PASSWD;
       pop3c->authused = SASL_MECH_LOGIN;
@@ -629,7 +629,7 @@ static CURLcode pop3_perform_authenticate(struct connectdata *conn)
     }
     else if((pop3c->authmechs & SASL_MECH_PLAIN) &&
             (pop3c->prefmech & SASL_MECH_PLAIN)) {
-      mech = "PLAIN";
+      mech = SASL_MECH_STRING_PLAIN;
       state1 = POP3_AUTH_PLAIN;
       state2 = POP3_AUTH_FINAL;
       pop3c->authused = SASL_MECH_PLAIN;
@@ -1788,31 +1788,31 @@ static CURLcode pop3_parse_url_options(struct connectdata *conn)
         pop3c->preftype = POP3_TYPE_APOP;
         pop3c->prefmech = SASL_AUTH_NONE;
       }
-      else if(strequal(value, "LOGIN")) {
+      else if(strequal(value, SASL_MECH_STRING_LOGIN)) {
         pop3c->preftype = POP3_TYPE_SASL;
         pop3c->prefmech = SASL_MECH_LOGIN;
       }
-      else if(strequal(value, "PLAIN")) {
+      else if(strequal(value, SASL_MECH_STRING_PLAIN)) {
         pop3c->preftype = POP3_TYPE_SASL;
         pop3c->prefmech = SASL_MECH_PLAIN;
       }
-      else if(strequal(value, "CRAM-MD5")) {
+      else if(strequal(value, SASL_MECH_STRING_CRAM_MD5)) {
         pop3c->preftype = POP3_TYPE_SASL;
         pop3c->prefmech = SASL_MECH_CRAM_MD5;
       }
-      else if(strequal(value, "DIGEST-MD5")) {
+      else if(strequal(value, SASL_MECH_STRING_DIGEST_MD5)) {
         pop3c->preftype = POP3_TYPE_SASL;
         pop3c->prefmech = SASL_MECH_DIGEST_MD5;
       }
-      else if(strequal(value, "GSSAPI")) {
+      else if(strequal(value, SASL_MECH_STRING_GSSAPI)) {
         pop3c->preftype = POP3_TYPE_SASL;
         pop3c->prefmech = SASL_MECH_GSSAPI;
       }
-      else if(strequal(value, "NTLM")) {
+      else if(strequal(value, SASL_MECH_STRING_NTLM)) {
         pop3c->preftype = POP3_TYPE_SASL;
         pop3c->prefmech = SASL_MECH_NTLM;
       }
-      else if(strequal(value, "XOAUTH2")) {
+      else if(strequal(value, SASL_MECH_STRING_XOAUTH2)) {
         pop3c->preftype = POP3_TYPE_SASL;
         pop3c->prefmech = SASL_MECH_XOAUTH2;
       }
diff --git a/lib/smtp.c b/lib/smtp.c
index 2d4055c24..9626a30d8 100644
--- a/lib/smtp.c
+++ b/lib/smtp.c
@@ -277,21 +277,21 @@ static bool smtp_endofresp(struct connectdata *conn, char *line, size_t len,
           wordlen++;
 
         /* Test the word for a matching authentication mechanism */
-        if(wordlen == 5 && !memcmp(line, "LOGIN", 5))
+        if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_LOGIN))
           smtpc->authmechs |= SASL_MECH_LOGIN;
-        else if(wordlen == 5 && !memcmp(line, "PLAIN", 5))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_PLAIN))
           smtpc->authmechs |= SASL_MECH_PLAIN;
-        else if(wordlen == 8 && !memcmp(line, "CRAM-MD5", 8))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_CRAM_MD5))
           smtpc->authmechs |= SASL_MECH_CRAM_MD5;
-        else if(wordlen == 10 && !memcmp(line, "DIGEST-MD5", 10))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_DIGEST_MD5))
           smtpc->authmechs |= SASL_MECH_DIGEST_MD5;
-        else if(wordlen == 6 && !memcmp(line, "GSSAPI", 6))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_GSSAPI))
           smtpc->authmechs |= SASL_MECH_GSSAPI;
-        else if(wordlen == 8 && !memcmp(line, "EXTERNAL", 8))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_EXTERNAL))
           smtpc->authmechs |= SASL_MECH_EXTERNAL;
-        else if(wordlen == 4 && !memcmp(line, "NTLM", 4))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_NTLM))
           smtpc->authmechs |= SASL_MECH_NTLM;
-        else if(wordlen == 7 && !memcmp(line, "XOAUTH2", 7))
+        else if(sasl_mech_equal(line, wordlen, SASL_MECH_STRING_XOAUTH2))
           smtpc->authmechs |= SASL_MECH_XOAUTH2;
 
         line += wordlen;
@@ -473,13 +473,13 @@ static CURLcode smtp_perform_authenticate(struct connectdata *conn)
 #ifndef CURL_DISABLE_CRYPTO_AUTH
   if((smtpc->authmechs & SASL_MECH_DIGEST_MD5) &&
      (smtpc->prefmech & SASL_MECH_DIGEST_MD5)) {
-    mech = "DIGEST-MD5";
+    mech = SASL_MECH_STRING_DIGEST_MD5;
     state1 = SMTP_AUTH_DIGESTMD5;
     smtpc->authused = SASL_MECH_DIGEST_MD5;
   }
   else if((smtpc->authmechs & SASL_MECH_CRAM_MD5) &&
           (smtpc->prefmech & SASL_MECH_CRAM_MD5)) {
-    mech = "CRAM-MD5";
+    mech = SASL_MECH_STRING_CRAM_MD5;
     state1 = SMTP_AUTH_CRAMMD5;
     smtpc->authused = SASL_MECH_CRAM_MD5;
   }
@@ -488,7 +488,7 @@ static CURLcode smtp_perform_authenticate(struct connectdata *conn)
 #ifdef USE_NTLM
   if((smtpc->authmechs & SASL_MECH_NTLM) &&
      (smtpc->prefmech & SASL_MECH_NTLM)) {
-    mech = "NTLM";
+    mech = SASL_MECH_STRING_NTLM;
     state1 = SMTP_AUTH_NTLM;
     state2 = SMTP_AUTH_NTLM_TYPE2MSG;
     smtpc->authused = SASL_MECH_NTLM;
@@ -503,7 +503,7 @@ static CURLcode smtp_perform_authenticate(struct connectdata *conn)
   if(((smtpc->authmechs & SASL_MECH_XOAUTH2) &&
       (smtpc->prefmech & SASL_MECH_XOAUTH2) &&
       (smtpc->prefmech != SASL_AUTH_ANY)) || conn->xoauth2_bearer) {
-    mech = "XOAUTH2";
+    mech = SASL_MECH_STRING_XOAUTH2;
     state1 = SMTP_AUTH_XOAUTH2;
     state2 = SMTP_AUTH_FINAL;
     smtpc->authused = SASL_MECH_XOAUTH2;
@@ -515,7 +515,7 @@ static CURLcode smtp_perform_authenticate(struct connectdata *conn)
   }
   else if((smtpc->authmechs & SASL_MECH_LOGIN) &&
      (smtpc->prefmech & SASL_MECH_LOGIN)) {
-    mech = "LOGIN";
+    mech = SASL_MECH_STRING_LOGIN;
     state1 = SMTP_AUTH_LOGIN;
     state2 = SMTP_AUTH_LOGIN_PASSWD;
     smtpc->authused = SASL_MECH_LOGIN;
@@ -526,7 +526,7 @@ static CURLcode smtp_perform_authenticate(struct connectdata *conn)
   }
   else if((smtpc->authmechs & SASL_MECH_PLAIN) &&
           (smtpc->prefmech & SASL_MECH_PLAIN)) {
-    mech = "PLAIN";
+    mech = SASL_MECH_STRING_PLAIN;
     state1 = SMTP_AUTH_PLAIN;
     state2 = SMTP_AUTH_FINAL;
     smtpc->authused = SASL_MECH_PLAIN;
@@ -1786,19 +1786,19 @@ static CURLcode smtp_parse_url_options(struct connectdata *conn)
 
       if(strequal(value, "*"))
         smtpc->prefmech = SASL_AUTH_ANY;
-      else if(strequal(value, "LOGIN"))
+      else if(strequal(value, SASL_MECH_STRING_LOGIN))
         smtpc->prefmech = SASL_MECH_LOGIN;
-      else if(strequal(value, "PLAIN"))
+      else if(strequal(value, SASL_MECH_STRING_PLAIN))
         smtpc->prefmech = SASL_MECH_PLAIN;
-      else if(strequal(value, "CRAM-MD5"))
+      else if(strequal(value, SASL_MECH_STRING_CRAM_MD5))
         smtpc->prefmech = SASL_MECH_CRAM_MD5;
-      else if(strequal(value, "DIGEST-MD5"))
+      else if(strequal(value, SASL_MECH_STRING_DIGEST_MD5))
         smtpc->prefmech = SASL_MECH_DIGEST_MD5;
-      else if(strequal(value, "GSSAPI"))
+      else if(strequal(value, SASL_MECH_STRING_GSSAPI))
         smtpc->prefmech = SASL_MECH_GSSAPI;
-      else if(strequal(value, "NTLM"))
+      else if(strequal(value, SASL_MECH_STRING_NTLM))
         smtpc->prefmech = SASL_MECH_NTLM;
-      else if(strequal(value, "XOAUTH2"))
+      else if(strequal(value, SASL_MECH_STRING_XOAUTH2))
         smtpc->prefmech = SASL_MECH_XOAUTH2;
       else
         smtpc->prefmech = SASL_AUTH_NONE;