SASL-plain.c
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	dereckson
	May 14 2023, 12:37

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SASL-plain.c
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	/* -------------------------------------------------------------
	Test SASL PLAIN authentication
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	Project: Nasqueron
	Description: Test SASL plain authentication to solve T1739
	License: BSD-2-Clause
	------------------------------------------------------------- */

	#include <stdio.h>
	#include <string.h>
	#include <stdlib.h>

	#include <openssl/bio.h>
	#include <openssl/evp.h>
	#include <openssl/buffer.h>

	/* -------------------------------------------------------------
	SASL plain authentication
	- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

	/**
	* Build a SASL PLAIN string, encoded in Base64
	* @identity: The identity you want to authenticate as
	* @username: The username
	* @password: The password, in plain
	* @out_len: Pointer to output length variable, or %NULL if not used
	* Returns: Allocated buffer of out_len bytes of encoded data,
	* or %NULL on failure
	*
	* If the specification isn't clear what to use as identity, generally
	* you can pass again the username. If not, pass an empty string.
	*
	* Caller is responsible for freeing the returned buffer. Returned buffer is
	* nul terminated to make it easier to use as a C string.
	*/
	char* build_sasl_plain_string(char* identity, char* username, char* password) {
	// Authentication string: concatenate the fields, with 2 NUL separator
	// A lot of string.h functions stop at NUL character, so memcpy is safer.
	// For example, with sprintf, only identity is copied to sasl_plain_string.
	int identity_len = strlen(identity);
	int username_len = strlen(username);
	int password_len = strlen(password);

	int sasl_plain_string_len = identity_len + username_len + password_len + 2;
	char* sasl_plain_string = (char*) malloc(sasl_plain_string_len);

	char* buffer = sasl_plain_string;

	memcpy(buffer, identity, identity_len);
	buffer += identity_len;
	*buffer++ = '\0';

	memcpy(buffer, username, username_len);
	buffer += username_len;
	*buffer++ = '\0';

	memcpy(buffer, password, password_len);
	buffer += password_len;
	*buffer++ = '\0';

	// Base64 encode
	int base64_len = 0;
	int sasl_plain_string_len_with_padding = sasl_plain_string_len + 2; // Add 2 for padding bytes
	char* base64_string = (char*)malloc(EVP_ENCODE_LENGTH(sasl_plain_string_len_with_padding));
	EVP_EncodeBlock((unsigned char)base64_string, (const unsigned char)sasl_plain_string, sasl_plain_string_len_with_padding);
	base64_len = strlen(base64_string);

	char* result = (char*)malloc(base64_len + 1);
	memcpy(result, base64_string, base64_len);
	result[base64_len] = '\0';

	free(base64_string);
	free(sasl_plain_string);

	return result;
	}

	/* -------------------------------------------------------------
	Program entry point
	- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

	int main(int argc, char **argv) {
	char *username;
	char *password;

	if (argc != 3) {
	fprintf(stderr, "Usage: %s <username> <password>\n", argv[0]);
	return 1;
	}

	username = argv[1];
	password = argv[2];

	char* payload = build_sasl_plain_string(username, username, password);
	printf("%s\n", payload);

	free(payload);

	return 0;
	}

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