Move actual password derivation to separate class

LegacyPasswordGenerator.h

@@ -0,0 +1,18 @@
+#import <ObjFW/ObjFW.h>
+
+@interface LegacyPasswordGenerator: OFObject
+{
+	size_t _length;
+	OFString *_site;
+	const char *_passphrase;
+	unsigned char *_output;
+}
+
+@property size_t length;
+@property (copy) OFString *site;
+@property const char *passphrase;
+@property (readonly) unsigned char *output;
+
++ (instancetype)generator;
+- (void)derivePassword;
+@end

LegacyPasswordGenerator.m

@@ -0,0 +1,51 @@
+#import "LegacyPasswordGenerator.h"
+
+@implementation LegacyPasswordGenerator
+@synthesize length = _length, site = _site, passphrase = _passphrase;
+@synthesize output = _output;
+
++ (instancetype)generator
+{
+	return [[[self alloc] init] autorelease];
+}
+
+- init
+{
+	self = [super init];
+
+	_length = 16;
+
+	return self;
+}
+
+- (void)derivePassword
+{
+	OFSHA256Hash *siteHash = [OFSHA256Hash cryptoHash];
+	[siteHash updateWithBuffer: [_site UTF8String]
+			    length: [_site UTF8StringLength]];
+
+	if (_output != NULL) {
+		of_explicit_memset(_output, 0, _length);
+		[self freeMemory: _output];
+	}
+
+	_output = [self allocMemoryWithSize: _length + 1];
+
+	of_scrypt(8, 524288, 2, [siteHash digest],
+	    [[siteHash class] digestSize], _passphrase, strlen(_passphrase),
+	    _output, _length);
+
+	/*
+	 * This has a bias, however, this is what scrypt-genpass does and the
+	 * legacy mode wants to be compatible to scrypt-genpass.
+	 */
+	_output[0] = "abcdefghijklmnopqrstuvwxyz"[_output[0] % 26];
+	_output[1] = "0123456789"[_output[1] % 10];
+	_output[2] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"[_output[2] % 26];
+
+	for (size_t i = 3; i < _length; i++)
+		_output[i] = "abcdefghijklmnopqrstuvwxyz"
+		    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+		    "0123456789"[_output[i] % (26 + 26 + 10)];
+}
+@end

ScryptPWGen.m

@@ -3,6 +3,7 @@
 #include <unistd.h>
 
 #import "ScryptPWGen.h"
+#import "LegacyPasswordGenerator.h"
 
 OF_APPLICATION_DELEGATE(ScryptPWGen)
 
@@ -34,10 +35,9 @@ showHelp(OFStream *output, bool verbose)
 	OFOptionsParser *optionsParser =
 	    [OFOptionsParser parserWithOptions: options];
 	of_unichar_t option;
-	OFString *site, *prompt;
+	size_t length;
 	char *passphrase;
-	OFSHA256Hash *siteHash;
-	unsigned char *output;
+	OFString *site, *prompt;
 
 	while ((option = [optionsParser nextOption]) != '\0') {
 		switch (option) {
@@ -80,9 +80,9 @@ showHelp(OFStream *output, bool verbose)
 
 	if (lengthStr != nil) {
 		@try {
-			_length = (size_t)[lengthStr decimalValue];
+			length = (size_t)[lengthStr decimalValue];
 
-			if (_length < 3)
+			if (length < 3)
 				@throw [OFInvalidFormatException exception];
 		} @catch (OFInvalidFormatException *e) {
 			[of_stderr writeFormat:
@@ -91,8 +91,7 @@ showHelp(OFStream *output, bool verbose)
 
 			[OFApplication terminateWithStatus: 1];
 		}
-	} else
-		_length = 16;
+	}
 
 	if ([[optionsParser remainingArguments] count] != 1) {
 		showHelp(of_stderr, false);
@@ -100,48 +99,32 @@ showHelp(OFStream *output, bool verbose)
 		[OFApplication terminateWithStatus: 1];
 	}
 
-	site = [[optionsParser remainingArguments] firstObject];
-	siteHash = [OFSHA256Hash cryptoHash];
-	[siteHash updateWithBuffer: [site UTF8String]
-			    length: [site UTF8StringLength]];
-
 	prompt = [OFString stringWithFormat: @"Passphrase for site \"%@\": ",
 					     site];
-	passphrase = getpass([prompt cStringWithEncoding:
-	    [OFSystemInfo native8BitEncoding]]);
 
-	output = [self allocMemoryWithSize: _length + 1];
+	LegacyPasswordGenerator *generator =
+	    [LegacyPasswordGenerator generator];
+	generator.length = length;
+	generator.site = [[optionsParser remainingArguments] firstObject];
 
-	of_scrypt(8, 524288, 2, [siteHash digest],
-	    [[siteHash class] digestSize], passphrase, strlen(passphrase),
-	    output, _length);
+	passphrase = getpass(
+	    [prompt cStringWithEncoding: [OFSystemInfo native8BitEncoding]]);
+	@try {
+		generator.passphrase = passphrase;
 
+		[generator derivePassword];
+		@try {
+			[of_stdout writeBuffer: generator.output
+					length: generator.length];
+			[of_stdout writeBuffer: "\n"
+					length: 1];
+		} @finally {
+			of_explicit_memset(generator.output, 0,
+			    generator.length);
+		}
+	} @finally {
 		of_explicit_memset(passphrase, 0, strlen(passphrase));
-
-	/*
-	 * This has a bias, but is what scrypt-genpass does. This should be
-	 * compatible to passwords generated by scrypt-genpass for now to allow
-	 * an easy migration.
-	 *
-	 * This will be replaced with something better later on and the current
-	 * code only available in legacy mode (which can be enabled using a
-	 * flag).
-	 */
-	output[0] = "abcdefghijklmnopqrstuvwxyz"[output[0] % 26];
-	output[1] = "0123456789"[output[1] % 10];
-	output[2] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"[output[2] % 26];
-
-	for (size_t i = 3; i < _length; i++)
-		output[i] = "abcdefghijklmnopqrstuvwxyz"
-		    "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
-		    "0123456789"[output[i] % (26 + 26 + 10)];
-
-	output[_length] = '\n';
-
-	[of_stdout writeBuffer: output
-			length: _length + 1];
-
-	of_explicit_memset(output, 0, _length + 1);
+	}
 
 	[OFApplication terminate];
 }