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+/* One way encryption based on the SHA512-based Unix crypt implementation.
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+ *
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+ * Written by Ulrich Drepper <drepper at redhat.com> in 2007 [1].
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+ * Modified by Zack Weinberg <zackw at panix.com> in 2017, 2018.
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+ * Composed by Björn Esser <besser82 at fedoraproject.org> in 2018.
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+ * Modified by Björn Esser <besser82 at fedoraproject.org> in 2020.
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+ * Modified by Steffen Jaeckel <jaeckel-floss at eyet-services.de> in 2020.
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+ * To the extent possible under law, the named authors have waived all
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+ * copyright and related or neighboring rights to this work.
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+ *
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+ * See https://creativecommons.org/publicdomain/zero/1.0/ for further
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+ * details.
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+ *
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+ * This file is a modified except from [2], lines 1403 up to 1676.
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+ *
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+ * [1] https://www.akkadia.org/drepper/sha-crypt.html
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+ * [2] https://www.akkadia.org/drepper/SHA-crypt.txt
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+ */
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+
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+#include "crypt-port.h"
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+#include "alg-sha512.h"
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+
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+#include <errno.h>
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+#include <stdio.h>
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+#include <stdlib.h>
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+
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+#if INCLUDE_sha512crypt
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+
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+/* Define our magic string to mark salt for SHA512 "encryption"
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+ replacement. */
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+static const char sha512_salt_prefix[] = "$6$";
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+
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+/* Prefix for optional rounds specification. */
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+static const char sha512_rounds_prefix[] = "rounds=";
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+
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+/* Maximum salt string length. */
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+#define SALT_LEN_MAX 16
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+/* Default number of rounds if not explicitly specified. */
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+#define ROUNDS_DEFAULT 5000
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+/* Minimum number of rounds. */
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+#define ROUNDS_MIN 1000
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+/* Maximum number of rounds. */
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+#define ROUNDS_MAX 999999999
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+
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+/* The maximum possible length of a SHA512-hashed password string,
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+ including the terminating NUL character. Prefix (including its NUL)
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+ + rounds tag ("rounds=$" = "rounds=\0") + strlen(ROUNDS_MAX)
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+ + salt (up to SALT_LEN_MAX chars) + '$' + hash (86 chars). */
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+
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+#define LENGTH_OF_NUMBER(n) (sizeof #n - 1)
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+
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+#define SHA512_HASH_LENGTH \
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+ (sizeof (sha512_salt_prefix) + sizeof (sha512_rounds_prefix) + \
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+ LENGTH_OF_NUMBER (ROUNDS_MAX) + SALT_LEN_MAX + 1 + 86)
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+
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+static_assert (SHA512_HASH_LENGTH <= CRYPT_OUTPUT_SIZE,
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+ "CRYPT_OUTPUT_SIZE is too small for SHA512");
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+
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+/* A sha512_buffer holds all of the sensitive intermediate data. */
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+struct sha512_buffer
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+{
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+ SHA512_CTX ctx;
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+ uint8_t result[64];
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+ uint8_t p_bytes[64];
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+ uint8_t s_bytes[64];
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+};
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+
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+static_assert (sizeof (struct sha512_buffer) <= ALG_SPECIFIC_SIZE,
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+ "ALG_SPECIFIC_SIZE is too small for SHA512");
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+
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+
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+/* Subroutine of _xcrypt_crypt_sha512crypt_rn: Feed CTX with LEN bytes of a
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+ virtual byte sequence consisting of BLOCK repeated over and over
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+ indefinitely. */
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+static void
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+sha512_process_recycled_bytes (unsigned char block[64], size_t len,
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+ SHA512_CTX *ctx)
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+{
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+ size_t cnt;
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+ for (cnt = len; cnt >= 64; cnt -= 64)
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+ SHA512_Update (ctx, block, 64);
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+ SHA512_Update (ctx, block, cnt);
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+}
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+
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+void
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+crypt_sha512crypt_rn (const char *phrase, size_t phr_size,
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+ const char *setting, size_t ARG_UNUSED (set_size),
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+ uint8_t *output, size_t out_size,
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+ void *scratch, size_t scr_size)
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+{
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+ /* This shouldn't ever happen, but... */
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+ if (out_size < SHA512_HASH_LENGTH
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+ || scr_size < sizeof (struct sha512_buffer))
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+ {
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+ errno = ERANGE;
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+ return;
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+ }
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+
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+ struct sha512_buffer *buf = scratch;
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+ SHA512_CTX *ctx = &buf->ctx;
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+ uint8_t *result = buf->result;
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+ uint8_t *p_bytes = buf->p_bytes;
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+ uint8_t *s_bytes = buf->s_bytes;
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+ char *cp = (char *)output;
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+ const char *salt = setting;
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+
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+ size_t salt_size;
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+ size_t cnt;
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+ /* Default number of rounds. */
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+ size_t rounds = ROUNDS_DEFAULT;
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+ bool rounds_custom = false;
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+
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+ /* Find beginning of salt string. The prefix should normally always
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+ be present. Just in case it is not. */
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+ if (strncmp (sha512_salt_prefix, salt, sizeof (sha512_salt_prefix) - 1) == 0)
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+ /* Skip salt prefix. */
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+ salt += sizeof (sha512_salt_prefix) - 1;
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+
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+ if (strncmp (salt, sha512_rounds_prefix, sizeof (sha512_rounds_prefix) - 1)
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+ == 0)
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+ {
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+ const char *num = salt + sizeof (sha512_rounds_prefix) - 1;
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+ /* Do not allow an explicit setting of zero rounds, nor of the
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+ default number of rounds, nor leading zeroes on the rounds. */
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+ if (!(*num >= '1' && *num <= '9'))
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+ {
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+ errno = EINVAL;
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+ return;
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+ }
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+
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+ errno = 0;
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+ char *endp;
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+ rounds = strtoul (num, &endp, 10);
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+ if (endp == num || *endp != '$'
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+ || rounds < ROUNDS_MIN
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+ || rounds > ROUNDS_MAX
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+ || errno)
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+ {
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+ errno = EINVAL;
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+ return;
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+ }
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+ salt = endp + 1;
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+ rounds_custom = true;
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+ }
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+
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+ /* The salt ends at the next '$' or the end of the string.
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+ Ensure ':' does not appear in the salt (it is used as a separator in /etc/passwd).
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+ Also check for '\n', as in /etc/passwd the whole parameters of the user data must
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+ be on a single line. */
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+ salt_size = strcspn (salt, "$:\n");
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+ if (!(salt[salt_size] == '$' || !salt[salt_size]))
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+ {
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+ errno = EINVAL;
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+ return;
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+ }
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+
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+ /* Ensure we do not use more salt than SALT_LEN_MAX. */
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+ if (salt_size > SALT_LEN_MAX)
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+ salt_size = SALT_LEN_MAX;
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+
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+ /* Compute alternate SHA512 sum with input PHRASE, SALT, and PHRASE. The
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+ final result will be added to the first context. */
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+ SHA512_Init (ctx);
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+
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+ /* Add phrase. */
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+ SHA512_Update (ctx, phrase, phr_size);
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+
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+ /* Add salt. */
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+ SHA512_Update (ctx, salt, salt_size);
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+
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+ /* Add phrase again. */
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+ SHA512_Update (ctx, phrase, phr_size);
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+
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+ /* Now get result of this (64 bytes) and add it to the other
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+ context. */
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+ SHA512_Final (result, ctx);
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+
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+ /* Prepare for the real work. */
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+ SHA512_Init (ctx);
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+
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+ /* Add the phrase string. */
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+ SHA512_Update (ctx, phrase, phr_size);
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+
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+ /* The last part is the salt string. This must be at most 8
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+ characters and it ends at the first `$' character (for
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+ compatibility with existing implementations). */
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+ SHA512_Update (ctx, salt, salt_size);
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+
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+ /* Add for any character in the phrase one byte of the alternate sum. */
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+ for (cnt = phr_size; cnt > 64; cnt -= 64)
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+ SHA512_Update (ctx, result, 64);
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+ SHA512_Update (ctx, result, cnt);
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+
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+ /* Take the binary representation of the length of the phrase and for every
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+ 1 add the alternate sum, for every 0 the phrase. */
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+ for (cnt = phr_size; cnt > 0; cnt >>= 1)
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+ if ((cnt & 1) != 0)
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+ SHA512_Update (ctx, result, 64);
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+ else
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+ SHA512_Update (ctx, phrase, phr_size);
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+
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+ /* Create intermediate result. */
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+ SHA512_Final (result, ctx);
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+
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+ /* Start computation of P byte sequence. */
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+ SHA512_Init (ctx);
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+
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+ /* For every character in the password add the entire password. */
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+ for (cnt = 0; cnt < phr_size; ++cnt)
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+ SHA512_Update (ctx, phrase, phr_size);
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+
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+ /* Finish the digest. */
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+ SHA512_Final (p_bytes, ctx);
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+
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+ /* Start computation of S byte sequence. */
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+ SHA512_Init (ctx);
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+
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+ /* For every character in the password add the entire password. */
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+ for (cnt = 0; cnt < (size_t) 16 + (size_t) result[0]; ++cnt)
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+ SHA512_Update (ctx, salt, salt_size);
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+
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+ /* Finish the digest. */
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+ SHA512_Final (s_bytes, ctx);
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+
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+ /* Repeatedly run the collected hash value through SHA512 to burn
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+ CPU cycles. */
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+ for (cnt = 0; cnt < rounds; ++cnt)
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+ {
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+ /* New context. */
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+ SHA512_Init (ctx);
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+
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+ /* Add phrase or last result. */
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+ if ((cnt & 1) != 0)
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+ sha512_process_recycled_bytes (p_bytes, phr_size, ctx);
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+ else
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+ SHA512_Update (ctx, result, 64);
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+
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+ /* Add salt for numbers not divisible by 3. */
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+ if (cnt % 3 != 0)
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+ sha512_process_recycled_bytes (s_bytes, salt_size, ctx);
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+
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+ /* Add phrase for numbers not divisible by 7. */
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+ if (cnt % 7 != 0)
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+ sha512_process_recycled_bytes (p_bytes, phr_size, ctx);
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+
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+ /* Add phrase or last result. */
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+ if ((cnt & 1) != 0)
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+ SHA512_Update (ctx, result, 64);
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+ else
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+ sha512_process_recycled_bytes (p_bytes, phr_size, ctx);
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+
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+ /* Create intermediate result. */
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+ SHA512_Final (result, ctx);
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+ }
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+
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+ /* Now we can construct the result string. It consists of four
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+ parts, one of which is optional. We already know that buflen is
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+ at least sha512_hash_length, therefore none of the string bashing
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+ below can overflow the buffer. */
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+
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+ memcpy (cp, sha512_salt_prefix, sizeof (sha512_salt_prefix) - 1);
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+ cp += sizeof (sha512_salt_prefix) - 1;
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+
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+ if (rounds_custom)
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+ {
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+ int n = snprintf (cp,
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+ SHA512_HASH_LENGTH - (sizeof (sha512_salt_prefix) - 1),
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+ "%s%zu$", sha512_rounds_prefix, rounds);
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+ cp += n;
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+ }
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+
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+ memcpy (cp, salt, salt_size);
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+ cp += salt_size;
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+ *cp++ = '$';
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+
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+#define b64_from_24bit(B2, B1, B0, N) \
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+ do { \
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+ unsigned int w = ((((unsigned int)(B2)) << 16) | \
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+ (((unsigned int)(B1)) << 8) | \
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+ ((unsigned int)(B0))); \
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+ int n = (N); \
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+ while (n-- > 0) \
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+ { \
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+ *cp++ = b64t[w & 0x3f]; \
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+ w >>= 6; \
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+ } \
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+ } while (0)
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+
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+ b64_from_24bit (result[0], result[21], result[42], 4);
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+ b64_from_24bit (result[22], result[43], result[1], 4);
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+ b64_from_24bit (result[44], result[2], result[23], 4);
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+ b64_from_24bit (result[3], result[24], result[45], 4);
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+ b64_from_24bit (result[25], result[46], result[4], 4);
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+ b64_from_24bit (result[47], result[5], result[26], 4);
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+ b64_from_24bit (result[6], result[27], result[48], 4);
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+ b64_from_24bit (result[28], result[49], result[7], 4);
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+ b64_from_24bit (result[50], result[8], result[29], 4);
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+ b64_from_24bit (result[9], result[30], result[51], 4);
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+ b64_from_24bit (result[31], result[52], result[10], 4);
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+ b64_from_24bit (result[53], result[11], result[32], 4);
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+ b64_from_24bit (result[12], result[33], result[54], 4);
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+ b64_from_24bit (result[34], result[55], result[13], 4);
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+ b64_from_24bit (result[56], result[14], result[35], 4);
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+ b64_from_24bit (result[15], result[36], result[57], 4);
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+ b64_from_24bit (result[37], result[58], result[16], 4);
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+ b64_from_24bit (result[59], result[17], result[38], 4);
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+ b64_from_24bit (result[18], result[39], result[60], 4);
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+ b64_from_24bit (result[40], result[61], result[19], 4);
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+ b64_from_24bit (result[62], result[20], result[41], 4);
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+ b64_from_24bit (0, 0, result[63], 2);
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+
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+ *cp = '\0';
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+}
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+
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+#ifndef NO_GENSALT
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+
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+void
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+gensalt_sha512crypt_rn (unsigned long count,
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+ const uint8_t *rbytes, size_t nrbytes,
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+ uint8_t *output, size_t output_size)
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+{
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+ gensalt_sha_rn ('6', SALT_LEN_MAX, ROUNDS_DEFAULT, ROUNDS_MIN, ROUNDS_MAX,
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+ count, rbytes, nrbytes, output, output_size);
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+}
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+
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+#endif
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+
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+#endif
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