From: Andrew G. Morgan <morgan@kernel.org>
Date: Tue, 9 Jul 2002 04:44:18 +0000 (+0000)
Subject: Relevant BUGIDs: 521314
X-Git-Tag: Linux-PAM-0-76
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=067affee9267fa0d1c21835182ba639ba33e820f;p=linux-pam

Relevant BUGIDs: 521314

Purpose of commit: bugfix

Commit summary:
---------------
bigcrypt does not match crypt when password length is too long.
This led to a pam_unix problem when the module had not set the
password in bigcrypt mode, but was trying to compare with bigcrypt
output. The fix is to use the stored password as a guide to how much
of the encrypted password to compare against.
---

diff --git a/CHANGELOG b/CHANGELOG
index 085abc87..03d6045a 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -55,6 +55,8 @@ bug report - outstanding bugs are listed here:
 0.76: please submit patches for this section with actual code/doc
       patches!
 
+* pam_unix: fix for legacy crypt() support when the password entered
+  was long. (Bug 521314 - agmorgan).
 * pam_access no longer include gethostname() prototype complained from
   David Lee (Bug 415423 - agmorgan).
 * make pam_nologin more secure by default, added two new module
diff --git a/modules/pam_unix/pam_unix_passwd.c b/modules/pam_unix/pam_unix_passwd.c
index fcfe187e..6b51a6b2 100644
--- a/modules/pam_unix/pam_unix_passwd.c
+++ b/modules/pam_unix/pam_unix_passwd.c
@@ -965,6 +965,8 @@ PAM_EXTERN int pam_sm_chauthtok(pam_handle_t * pamh, int flags,
 				/* 
 				 * to avoid using the _extensions_ of the bigcrypt()
 				 * function we truncate the newly entered password
+				 * [Problems that followed from this are fixed as per
+				 *  Bug 521314.]
 				 */
 				char *temp = malloc(9);
 
diff --git a/modules/pam_unix/support.c b/modules/pam_unix/support.c
index 9b6b19a2..5998c7db 100644
--- a/modules/pam_unix/support.c
+++ b/modules/pam_unix/support.c
@@ -617,7 +617,16 @@ int _unix_verify_password(pam_handle_t * pamh, const char *name
 			/* the moment of truth -- do we agree with the password? */
 			D(("comparing state of pp[%s] and salt[%s]", pp, salt));
 
-			if (strcmp(pp, salt) == 0) {
+			/*
+			 * Note, we are comparing the bigcrypt of the password with
+			 * the contents of the password field. If the latter was
+			 * encrypted with regular crypt (and not bigcrypt) it will
+			 * have been truncated for storage relative to the output
+			 * of bigcrypt here. As such we need to compare only the
+			 * stored string with the subset of bigcrypt's result.
+			 * Bug 521314: The strncmp comparison is for legacy support.
+			 */
+			if (strncmp(pp, salt, strlen(salt)) == 0) {
 				retval = PAM_SUCCESS;
 			} else {
 				retval = PAM_AUTH_ERR;
diff --git a/modules/pam_unix/unix_chkpwd.c b/modules/pam_unix/unix_chkpwd.c
index 9581d046..9ba11041 100644
--- a/modules/pam_unix/unix_chkpwd.c
+++ b/modules/pam_unix/unix_chkpwd.c
@@ -149,7 +149,16 @@ static int _unix_verify_password(const char *name, const char *p, int opt)
 		}
 	} else {
 		pp = bigcrypt(p, salt);
-		if (strcmp(pp, salt) == 0) {
+		/*
+		 * Note, we are comparing the bigcrypt of the password with
+		 * the contents of the password field. If the latter was
+		 * encrypted with regular crypt (and not bigcrypt) it will
+		 * have been truncated for storage relative to the output
+		 * of bigcrypt here. As such we need to compare only the
+		 * stored string with the subset of bigcrypt's result.
+		 * Bug 521314: the strncmp comparison is for legacy support.
+		 */
+		if (strncmp(pp, salt, strlen(salt)) == 0) {
 			retval = UNIX_PASSED;
 		}
 	}