From d12726b2d42ace2f31944e14769890f272d594c6 Mon Sep 17 00:00:00 2001
From: Falk Werner <falk.werner@gmx.net>
Date: Sun, 17 Mar 2019 21:12:11 +0100
Subject: [PATCH] adds example to compute password hash

---
 CMakeLists.txt        | 24 +++++++++++
 example/passwd/main.c | 98 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 122 insertions(+)
 create mode 100644 example/passwd/main.c

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f19c3f3..d801f23 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -181,6 +181,30 @@ target_link_libraries(wsfs-provider-app PUBLIC wsfs-provider ${EXTRA_LIBS})
 target_include_directories(wsfs-provider-app PUBLIC ${EXTRA_INCLUDE_DIRS})
 target_compile_options(wsfs-provider-app PUBLIC ${EXTRA_CFLAGS})
 
+# wsfs-passwd
+
+pkg_check_modules(OPENSSL REQUIRED openssl)
+
+
+add_executable(wsfs-passwd
+	example/passwd/main.c
+)
+
+target_link_libraries(wsfs-passwd PUBLIC 
+	${OPENSSL_LIBRARIES}
+)
+
+target_include_directories(wsfs-passwd PUBLIC 
+	example/passwd
+	${OPENSSL_INCLUDE_DIRS}
+)
+
+target_compile_options(wsfs-passwd PUBLIC
+	${C_WARNINGS}
+	${OPENSSL_CFLAGS_OTHER}
+)
+
+
 endif(NOT WITHOUT_EXAMPLE)
 
 # tests
diff --git a/example/passwd/main.c b/example/passwd/main.c
new file mode 100644
index 0000000..0f8f971
--- /dev/null
+++ b/example/passwd/main.c
@@ -0,0 +1,98 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <openssl/opensslv.h>
+#include <openssl/evp.h>
+
+#define HASH_ALGORITHM "sha512"
+
+static char hex_char(unsigned char value)
+{
+    switch (value)
+    {
+        case  0x00: return '0';
+        case  0x01: return '1';
+        case  0x02: return '2';
+        case  0x03: return '3';
+        case  0x04: return '4';
+        case  0x05: return '5';
+        case  0x06: return '6';
+        case  0x07: return '7';
+        case  0x08: return '8';
+        case  0x09: return '9';
+        case  0x0a: return 'a';
+        case  0x0b: return 'b';
+        case  0x0c: return 'c';
+        case  0x0d: return 'd';
+        case  0x0e: return 'e';
+        case  0x0f: return 'f';
+        default: return '?';
+    }
+}
+
+static char * to_hex(unsigned char const * value, size_t length)
+{
+    char * result = malloc((2 * length) + 1);
+    if (NULL != result)
+    {
+        for (size_t i = 0, j = 0; i < length; i++, j+=2)
+        {
+            unsigned char high = (value[i] >> 4) & 0x0f;
+            unsigned char low =   value[i]       & 0x0f;
+
+            result[j    ] = hex_char(high);
+            result[j + 1] = hex_char(low);
+        }
+
+        result[2 * length] = '\0';
+    }
+
+    return result;
+}
+
+static char * get_password_hash(
+    char const * password,
+    char const * salt,
+    char * pepper)
+{
+    EVP_MD const * digest = EVP_get_digestbyname(HASH_ALGORITHM);
+    if (NULL == digest)
+    {
+        fprintf(stderr, "error: hash algorithm %s not supported\n", HASH_ALGORITHM);
+        exit(EXIT_FAILURE);
+    }
+
+    char * result = NULL;
+    unsigned int hash_size = digest->md_size;
+    unsigned char * hash = malloc(hash_size);
+
+    if (NULL != hash)
+    {
+        EVP_MD_CTX context;        
+        EVP_MD_CTX_init(&context);
+        EVP_DigestInit_ex(&context, digest, NULL);        
+        EVP_DigestUpdate(&context, password, strlen(password));
+        EVP_DigestUpdate(&context, salt, strlen(salt));
+        EVP_DigestUpdate(&context, pepper, strlen(pepper));
+        EVP_DigestFinal_ex(&context, hash, &hash_size);
+        EVP_MD_CTX_cleanup(&context);
+
+        result = to_hex(hash, hash_size);
+        free(hash);
+    }
+
+    return result;
+}
+
+int main(int argc, char * argv[])
+{
+    OPENSSL_init();
+    OPENSSL_add_all_algorithms_conf();
+
+    char * test = get_password_hash("secret", "123\n", "");
+    puts(test);
+    free(test);
+
+    return EXIT_SUCCESS;
+}
\ No newline at end of file