RT4337: Crash in DES

Salt must be two ASCII characters.  Add tests to check for that,
and a test to test the checks.

Reviewed-by: Matt Caswell <matt@openssl.org>

crypto/des/fcrypt.c

@@ -66,26 +66,22 @@ char *DES_crypt(const char *buf, const char *salt)
     char e_buf[32 + 1];         /* replace 32 by 8 ? */
     char *ret;
 
-    /* Copy at most 2 chars of salt */
-    if ((e_salt[0] = salt[0]) != '\0')
+    if (salt[0] == '\0' || salt[1] == '\0')
+        return NULL;
+
+    /* Copy salt, convert to ASCII. */
+    e_salt[0] = salt[0];
     e_salt[1] = salt[1];
+    e_salt[2] = '\0';
+    ebcdic2ascii(e_salt, e_salt, sizeof(e_salt));
 
-    /* Copy at most 32 chars of password */
-    strncpy(e_buf, buf, sizeof(e_buf));
-
-    /* Make sure we have a delimiter */
-    e_salt[sizeof(e_salt) - 1] = e_buf[sizeof(e_buf) - 1] = '\0';
-
-    /* Convert the e_salt to ASCII, as that's what DES_fcrypt works on */
-    ebcdic2ascii(e_salt, e_salt, sizeof e_salt);
-
-    /* Convert the cleartext password to ASCII */
+    /* Convert password to ASCII. */
+    OPENSSL_strlcpy(e_buf, buf, sizeof(e_buf));
     ebcdic2ascii(e_buf, e_buf, sizeof e_buf);
 
-    /* Encrypt it (from/to ASCII) */
+    /* Encrypt it (from/to ASCII); if it worked, convert back. */
     ret = DES_fcrypt(e_buf, e_salt, buff);
-
-    /* Convert the result back to EBCDIC */
+    if (ret != NULL)
         ascii2ebcdic(ret, ret, strlen(ret));
 
     return ret;
@@ -103,25 +99,14 @@ char *DES_fcrypt(const char *buf, const char *salt, char *ret)
     unsigned char *b = bb;
     unsigned char c, u;
 
-    /*
-     * eay 25/08/92 If you call crypt("pwd","*") as often happens when you
-     * have * as the pwd field in /etc/passwd, the function returns
-     * *\0XXXXXXXXX The \0 makes the string look like * so the pwd "*" would
-     * crypt to "*".  This was found when replacing the crypt in our shared
-     * libraries.  People found that the disabled accounts effectively had no
-     * passwd :-(.
-     */
-#ifndef CHARSET_EBCDIC
-    x = ret[0] = ((salt[0] == '\0') ? 'A' : salt[0]);
+    x = ret[0] = salt[0];
+    if (x == 0 || x >= sizeof(con_salt))
+        return NULL;
     Eswap0 = con_salt[x] << 2;
-    x = ret[1] = ((salt[1] == '\0') ? 'A' : salt[1]);
+    x = ret[1] = salt[1];
+    if (x == 0 || x >= sizeof(con_salt))
+        return NULL;
     Eswap1 = con_salt[x] << 6;
-#else
-    x = ret[0] = ((salt[0] == '\0') ? os_toascii['A'] : salt[0]);
-    Eswap0 = con_salt[x] << 2;
-    x = ret[1] = ((salt[1] == '\0') ? os_toascii['A'] : salt[1]);
-    Eswap1 = con_salt[x] << 6;
-#endif
 
     /*
      * EAY r=strlen(buf); r=(r+7)/8;

doc/crypto/des.pod

@@ -240,8 +240,9 @@ is thread safe, unlike the normal crypt.
 
 DES_crypt() is a faster replacement for the normal system crypt().
 This function calls DES_fcrypt() with a static array passed as the
-third parameter.  This emulates the normal non-thread safe semantics
+third parameter.  This mostly emulates the normal non-thread-safe semantics
 of crypt(3).
+The B<salt> must be two ASCII characters.
 
 DES_enc_write() writes I<len> bytes to file descriptor I<fd> from
 buffer I<buf>. The data is encrypted via I<pcbc_encrypt> (default)
@@ -272,15 +273,11 @@ DES_string_to_key() is available for backward compatibility with the
 MIT library.  New applications should use a cryptographic hash function.
 The same applies for DES_string_to_2key().
 
-=head1 CONFORMING TO
-
-ANSI X3.106
+=head1 NOTES
 
 The B<des> library was written to be source code compatible with
 the MIT Kerberos library.
 
-=head1 NOTES
-
 Applications should use the higher level functions
 L<EVP_EncryptInit(3)> etc. instead of calling these
 functions directly.
@@ -288,6 +285,14 @@ functions directly.
 Single-key DES is insecure due to its short key size.  ECB mode is
 not suitable for most applications; see L<des_modes(7)>.
 
+=head1 HISTORY
+
+The requirement that the B<salt> parameter to DES_crypt() and DES_fcrypt()
+be two ASCII characters was first enforced in
+OpenSSL 1.1.0.  Previous versions tried to use the letter uppercase B<A>
+if both character were not present, and could crash when given non-ASCII
+on some platforms.
+
 =head1 SEE ALSO
 
 L<des_modes(7)>,

test/destest.c

@@ -35,8 +35,6 @@ int main(int argc, char *argv[])
 #else
 # include <openssl/des.h>
 
-# define crypt(c,s) (DES_crypt((c),(s)))
-
 /* tisk tisk - the test keys don't all have odd parity :-( */
 /* test data */
 # define NUM_TESTS 34
@@ -660,16 +658,31 @@ int main(int argc, char *argv[])
     }
     printf("\n");
     printf("fast crypt test ");
-    str = crypt("testing", "ef");
+    str = DES_crypt("testing", "ef");
     if (strcmp("efGnQx2725bI2", str) != 0) {
         printf("fast crypt error, %s should be efGnQx2725bI2\n", str);
         err = 1;
     }
-    str = crypt("bca76;23", "yA");
+    str = DES_crypt("bca76;23", "yA");
     if (strcmp("yA1Rp/1hZXIJk", str) != 0) {
         printf("fast crypt error, %s should be yA1Rp/1hZXIJk\n", str);
         err = 1;
     }
+    str = DES_crypt("testing", "y\202");
+    if (str != NULL) {
+        printf("salt error only usascii are accepted\n");
+        err = 1;
+    }
+    str = DES_crypt("testing", "\0A");
+    if (str != NULL) {
+        printf("salt error cannot contain null terminator\n");
+        err = 1;
+    }
+    str = DES_crypt("testing", "A");
+    if (str != NULL) {
+        printf("salt error must be at least 2\n");
+        err = 1;
+    }
     printf("\n");
     return (err);
 }