Extend --enable-weak-hashes configure option

Extend --enable-weak-hashes configure option to accept optional "glibc"
parameter.  When specified, it enables only those of weak hashes that
are supported by historic versions of the GNU libc.

Closes: besser82#7

Makefile.am

@@ -114,9 +114,13 @@ check_PROGRAMS = \
 
 if ENABLE_WEAK_HASHES
 libcrypt_la_SOURCES += \
-	crypt-md5.c crypt-des.c crypt-nthash.c crypt-pbkdf1-sha1.c \
-	crypt-sunmd5.c \
-	alg-des.c alg-hmac-sha1.c alg-md4.c alg-md5.c alg-sha1.c
+	crypt-des.c crypt-md5.c alg-des.c alg-md5.c
+
+if ENABLE_WEAK_NON_GLIBC_HASHES
+libcrypt_la_SOURCES += \
+	crypt-nthash.c crypt-pbkdf1-sha1.c crypt-sunmd5.c \
+	alg-hmac-sha1.c alg-md4.c alg-sha1.c
+endif
 
 nodist_libcrypt_la_SOURCES = \
 	alg-des-tables.c
@@ -143,11 +147,15 @@ alg-des-tables.c: gen-des-tables
 	$(AM_V_at)mv -f alg-des-tables.c.T alg-des-tables.c
 
 check_PROGRAMS += \
-	test-alg-des test-alg-hmac-sha1 test-alg-md4 \
-        test-alg-md5 test-alg-sha1 \
-	test-crypt-badsalt test-crypt-des test-crypt-md5 \
+	test-alg-des test-alg-md5 test-crypt-des test-crypt-md5 \
+	test-crypt-badsalt
+
+if ENABLE_WEAK_NON_GLIBC_HASHES
+check_PROGRAMS += \
+	test-alg-hmac-sha1 test-alg-md4 test-alg-sha1 \
 	test-crypt-nthash test-crypt-sunmd5 test-crypt-pbkdf1-sha1
 endif
+endif
 
 if ENABLE_OBSOLETE_API
 libcrypt_la_SOURCES += crypt-des-obsolete.c

configure.ac

@@ -204,17 +204,28 @@ AC_ARG_ENABLE([obsolete-api],
 
 AC_ARG_ENABLE([weak-hashes],
     AS_HELP_STRING(
-        [--disable-weak-hashes],
-        [do not include any support for weak hashes (DES, MD5).
-         Implies --disable-obsolete-api, and breaks binary compatibility
-         with glibc's libcrypt.]
+        [--enable-weak-hashes[=ARG]],
+        [When set to "yes", all of the hashing methods documented in crypt(5)
+         are supported for authenticating existing password hashes, including
+         several that are too weak to use for new passwords.
+
+         When set to "glibc", only the weak hashes supported by historic
+         versions of GNU libc are supported: traditional DES and FreeBSD-style
+         MD5, but not bigcrypt-DES, BSDi extended DES, SHA1, SUNMD5, or NTHASH.
+
+         When set to "no", only bcrypt, SHA512, and SHA256 are supported.
+         This mode implies --disable-obsolete-api and breaks binary
+         compatibility with glibc's libcrypt.
+
+         [default=yes]]
     ),
     [case "${enableval}" in
-        yes) enable_weak_hashes=1 ;;
-         no) enable_weak_hashes=0 ;;
+        yes) enable_weak_hashes=1; enable_weak_non_glibc_hashes=1 ;;
+      glibc) enable_weak_hashes=1; enable_weak_non_glibc_hashes=0 ;;
+         no) enable_weak_hashes=0; enable_weak_non_glibc_hashes=0 ;;
           *) AC_MSG_ERROR([bad value ${enableval} for --enable-weak-hashes]) ;;
      esac],
-     [enable_weak_hashes=1]
+     [enable_weak_hashes=1; enable_weak_non_glibc_hashes=1]
 )
 
 # If weak hashes are disabled, then the obsolete APIs won't work anyway
@@ -293,6 +304,10 @@ AC_DEFINE_UNQUOTED([ENABLE_WEAK_HASHES], [$enable_weak_hashes],
   If this is 0, ENABLE_OBSOLETE_API must also be 0.])
 AM_CONDITIONAL([ENABLE_WEAK_HASHES], [test $enable_weak_hashes = 1])
 
+AC_DEFINE_UNQUOTED([ENABLE_WEAK_NON_GLIBC_HASHES], [$enable_weak_non_glibc_hashes],
+ [Define as 1 if weak hashes not supported by glibc should be included, 0 otherwise.])
+AM_CONDITIONAL([ENABLE_WEAK_NON_GLIBC_HASHES], [test $enable_weak_non_glibc_hashes = 1])
+
 # The Makefile needs to know which versions of the library we are building.
 AM_CONDITIONAL([ENABLE_STATIC], [test $enable_static = yes])
 AM_CONDITIONAL([ENABLE_SHARED], [test $enable_shared = yes])

crypt-des.c

@@ -144,7 +144,10 @@ des_gen_hash (struct des_ctx *ctx, uint32_t count, uint8_t *output,
 }
 
 /* The original UNIX DES-based password hash, no extensions.  */
-static void
+#if ENABLE_WEAK_NON_GLIBC_HASHES
+static
+#endif
+void
 crypt_des_trd_rn (const char *phrase, const char *setting,
                   uint8_t *output, size_t o_size,
                   void *scratch, size_t s_size)
@@ -192,6 +195,7 @@ crypt_des_trd_rn (const char *phrase, const char *setting,
   des_gen_hash (ctx, 25, cp, pkbuf);
 }
 
+#if ENABLE_WEAK_NON_GLIBC_HASHES
 /* This algorithm is algorithm 0 (default) shipped with the C2 secure
    implementation of Digital UNIX.
 
@@ -342,6 +346,7 @@ crypt_des_xbsd_rn (const char *phrase, const char *setting,
   des_set_salt (ctx, salt);
   des_gen_hash (ctx, count, cp, pkbuf);
 }
+#endif /* ENABLE_WEAK_NON_GLIBC_HASHES */
 
 void
 gensalt_des_trd_rn (unsigned long count,
@@ -365,6 +370,7 @@ gensalt_des_trd_rn (unsigned long count,
   output[2] = '\0';
 }
 
+#if ENABLE_WEAK_NON_GLIBC_HASHES
 void
 gensalt_des_xbsd_rn (unsigned long count,
                      const uint8_t *rbytes, size_t nrbytes,
@@ -406,3 +412,4 @@ gensalt_des_xbsd_rn (unsigned long count,
 
   output[9] = '\0';
 }
+#endif /* ENABLE_WEAK_NON_GLIBC_HASHES */

crypt-port.h

@@ -217,7 +217,11 @@ void _xcrypt_secure_memset (void *s, size_t len)
 #if ENABLE_WEAK_HASHES
 #define comp_maskl               _crypt_comp_maskl
 #define comp_maskr               _crypt_comp_maskr
+#if ENABLE_WEAK_NON_GLIBC_HASHES
 #define crypt_des_trd_or_big_rn  _crypt_crypt_des_trd_or_big_rn
+#else
+#define crypt_des_trd_rn         _crypt_crypt_des_trd_rn
+#endif
 #define crypt_des_xbsd_rn        _crypt_crypt_des_xbsd_rn
 #define crypt_md5_rn             _crypt_crypt_md5_rn
 #define crypt_nthash_rn          _crypt_crypt_nthash_rn

crypt-private.h

@@ -39,15 +39,16 @@ extern void gensalt_sha_rn (char tag, size_t maxsalt, unsigned long defcount,
 /* Individual hash functions */
 
 #if ENABLE_WEAK_HASHES
+extern void crypt_md5_rn (const char *phrase, const char *setting,
+                          uint8_t *output, size_t o_size,
+                          void *scratch, size_t s_size);
+#if ENABLE_WEAK_NON_GLIBC_HASHES
 extern void crypt_des_trd_or_big_rn (const char *phrase, const char *setting,
                                      uint8_t *output, size_t o_size,
                                      void *scratch, size_t s_size);
 extern void crypt_des_xbsd_rn (const char *phrase, const char *setting,
                                uint8_t *output, size_t o_size,
                                void *scratch, size_t s_size);
-extern void crypt_md5_rn (const char *phrase, const char *setting,
-                          uint8_t *output, size_t o_size,
-                          void *scratch, size_t s_size);
 extern void crypt_nthash_rn (const char *phrase, const char *setting,
                              uint8_t *output, size_t o_size,
                              void *scratch, size_t s_size);
@@ -57,6 +58,11 @@ extern void crypt_sha1_rn (const char *phrase, const char *setting,
 extern void crypt_sunmd5_rn (const char *phrase, const char *setting,
                              uint8_t *output, size_t o_size,
                              void *scratch, size_t s_size);
+#else
+extern void crypt_des_trd_rn (const char *phrase, const char *setting,
+                              uint8_t *output, size_t o_size,
+                              void *scratch, size_t s_size);
+#endif
 #endif
 
 extern void crypt_sha256_rn (const char *phrase, const char *setting,
@@ -73,12 +79,13 @@ extern void crypt_bcrypt_rn (const char *phrase, const char *setting,
 extern void gensalt_des_trd_rn (unsigned long count,
                                 const uint8_t *rbytes, size_t nrbytes,
                                 uint8_t *output, size_t o_size);
-extern void gensalt_des_xbsd_rn (unsigned long count,
-                                 const uint8_t *rbytes, size_t nrbytes,
-                                 uint8_t *output, size_t o_size);
 extern void gensalt_md5_rn (unsigned long count,
                             const uint8_t *rbytes, size_t nrbytes,
                             uint8_t *output, size_t o_size);
+#if ENABLE_WEAK_NON_GLIBC_HASHES
+extern void gensalt_des_xbsd_rn (unsigned long count,
+                                 const uint8_t *rbytes, size_t nrbytes,
+                                 uint8_t *output, size_t o_size);
 extern void gensalt_nthash_rn (unsigned long count,
                                const uint8_t *rbytes, size_t nrbytes,
                                uint8_t *output, size_t o_size);
@@ -89,6 +96,7 @@ extern void gensalt_sunmd5_rn (unsigned long count,
                                const uint8_t *rbytes, size_t nrbytes,
                                uint8_t *output, size_t o_size);
 #endif
+#endif
 
 extern void gensalt_sha256_rn (unsigned long count,
                                const uint8_t *rbytes, size_t nrbytes,

crypt.c

@@ -87,16 +87,19 @@ static const struct hashfn tagged_hashes[] =
   /* legacy hashes */
 #if ENABLE_WEAK_HASHES
   { "$1$",    crypt_md5_rn,    gensalt_md5_rn      },
+#if ENABLE_WEAK_NON_GLIBC_HASHES
   { "$3$",    crypt_nthash_rn, gensalt_nthash_rn   },
   { "$md5",   crypt_sunmd5_rn, gensalt_sunmd5_rn   },
   { "$sha1",  crypt_sha1_rn,   gensalt_sha1_rn     },
+#endif
 #endif
   { "$5$",    crypt_sha256_rn, gensalt_sha256_rn   },
   { "$6$",    crypt_sha512_rn, gensalt_sha512_rn   },
   { 0, 0, 0 }
 };
 
 #if ENABLE_WEAK_HASHES
+#if ENABLE_WEAK_NON_GLIBC_HASHES
 /* BSD-style extended DES */
 static const struct hashfn bsdi_extended_hash =
 {
@@ -109,6 +112,16 @@ static const struct hashfn traditional_hash =
   "", crypt_des_trd_or_big_rn, gensalt_des_trd_rn
 };
 
+#else
+
+/* Traditional DES */
+static const struct hashfn traditional_hash =
+{
+  "", crypt_des_trd_rn, gensalt_des_trd_rn
+};
+
+#endif
+
 static int
 is_des_salt_char (char c)
 {
@@ -131,8 +144,10 @@ get_hashfn (const char *setting)
       return 0;
     }
 #if ENABLE_WEAK_HASHES
+#if ENABLE_WEAK_NON_GLIBC_HASHES
   else if (setting[0] == '_')
     return &bsdi_extended_hash;
+#endif
   else if (setting[0] == '\0' ||
            (is_des_salt_char (setting[0]) && is_des_salt_char (setting[1])))
     return &traditional_hash;

test-crypt-des.c

@@ -20,6 +20,7 @@ static const struct
   { "XX", "XXxzOu6maQKqQ", "*U*U*U*U" },
   { "SD", "SDbsugeBiC58A", "" },
 
+#if ENABLE_WEAK_NON_GLIBC_HASHES
   /* BSDI-extended-DES, ditto */
   { "_J9..CCCC", "_J9..CCCCXBrJUJV154M", "U*U*U*U*" },
   { "_J9..CCCC", "_J9..CCCCXUhOBTXzaiE", "U*U***U" },
@@ -63,6 +64,7 @@ static const struct
     "6M..............", "6MvZdspyAL4QEId8ugLUEeDs",
     "\xf3\xf4\xe5\xf0\xe8\xe1\xee\xe9\xe5" /* stephanie */
   },
+#endif
 };
 
 #define ntests ARRAY_SIZE (tests)

test-gensalt.c

@@ -24,11 +24,13 @@ static const struct testcase testcases[] =
 {
 #if ENABLE_WEAK_HASHES
   { "",       2 }, // DES
-  { "_",      9 }, // BSDi extended DES
   { "$1$",   11 }, // MD5
+#if ENABLE_WEAK_NON_GLIBC_HASHES
+  { "_",      9 }, // BSDi extended DES
   { "$3$",   29 }, // NTHASH
   { "$md5",  27 }, // SUNMD5
   { "$sha1", 34 }, // PBKDF with SHA1
+#endif
 #endif
   { "$5$",   19 }, // SHA-2-256
   { "$6$",   19 }, // SHA-2-512