wg: improve error reporting and detection

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

src/config.c

@@ -93,12 +93,8 @@ static inline uint16_t parse_port(const char *value)
 static inline bool parse_key(uint8_t key[WG_KEY_LEN], const char *value)
 {
 	uint8_t tmp[WG_KEY_LEN + 1];
-	if (strlen(value) != b64_len(WG_KEY_LEN) - 1) {
-		fprintf(stderr, "Key is not the correct length: `%s`\n", value);
-		return false;
-	}
-	if (b64_pton(value, tmp, WG_KEY_LEN + 1) < 0) {
-		fprintf(stderr, "Could not parse base64 key: `%s`\n", value);
+	if (strlen(value) != b64_len(WG_KEY_LEN) - 1 || b64_pton(value, tmp, WG_KEY_LEN + 1) != WG_KEY_LEN) {
+		fprintf(stderr, "Key is not the correct length or format: `%s`\n", value);
 		return false;
 	}
 	memcpy(key, tmp, WG_KEY_LEN);

src/genkey.c

@@ -11,6 +11,7 @@
 
 #include "curve25519.h"
 #include "base64.h"
+#include "subcommands.h"
 
 #ifdef __NR_getrandom
 static inline ssize_t get_random_bytes(uint8_t *out, size_t len)
@@ -37,6 +38,11 @@ int genkey_main(int argc, char *argv[])
 	char private_key_base64[b64_len(CURVE25519_POINT_SIZE)];
 	struct stat stat;
 
+	if (argc != 1) {
+		fprintf(stderr, "Usage: %s %s\n", PROG_NAME, argv[0]);
+		return 1;
+	}
+
 	if (!fstat(STDOUT_FILENO, &stat) && S_ISREG(stat.st_mode) && stat.st_mode & S_IRWXO)
 		fputs("Warning: writing to world accessible file.\nConsider setting the umask to 077 and trying again.\n", stderr);
 
@@ -47,9 +53,8 @@ int genkey_main(int argc, char *argv[])
 	if (argc && !strcmp(argv[0], "genkey"))
 		curve25519_normalize_secret(private_key);
 
-	if (b64_ntop(private_key, sizeof(private_key), private_key_base64, sizeof(private_key_base64)) < 0) {
-		errno = EINVAL;
-		perror("b64");
+	if (b64_ntop(private_key, sizeof(private_key), private_key_base64, sizeof(private_key_base64)) != sizeof(private_key_base64) - 1) {
+		fprintf(stderr, "%s: Could not convert key to base64\n", PROG_NAME);
 		return 1;
 	}
 

src/pubkey.c

@@ -3,29 +3,46 @@
 #include <errno.h>
 #include <resolv.h>
 #include <stdio.h>
+#include <ctype.h>
 
 #include "curve25519.h"
 #include "base64.h"
+#include "subcommands.h"
 
-int pubkey_main(__attribute__((unused)) int argc, __attribute__((unused)) char *argv[])
+int pubkey_main(int argc, char *argv[])
 {
 	unsigned char private_key[CURVE25519_POINT_SIZE + 1] = { 0 }, public_key[CURVE25519_POINT_SIZE] = { 0 };
 	char private_key_base64[b64_len(CURVE25519_POINT_SIZE)] = { 0 }, public_key_base64[b64_len(CURVE25519_POINT_SIZE)] = { 0 };
+	int trailing_char;
+
+	if (argc != 1) {
+		fprintf(stderr, "Usage: %s %s\n", PROG_NAME, argv[0]);
+		return 1;
+	}
 
 	if (fread(private_key_base64, 1, sizeof(private_key_base64) - 1, stdin) != sizeof(private_key_base64) - 1) {
 		errno = EINVAL;
-		perror("fread(private key)");
+		fprintf(stderr, "%s: Key is not the correct length or format\n", PROG_NAME);
 		return 1;
 	}
-	if (b64_pton(private_key_base64, private_key, sizeof(private_key)) < 0) {
-		errno = EINVAL;
-		perror("b64");
+
+	for (;;) {
+		trailing_char = getc(stdin);
+		if (!trailing_char || isspace(trailing_char) || isblank(trailing_char))
+			continue;
+		if (trailing_char == EOF)
+			break;
+		fprintf(stderr, "%s: Trailing characters found after key\n", PROG_NAME);
+		return 1;
+	}
+
+	if (b64_pton(private_key_base64, private_key, sizeof(private_key)) != sizeof(private_key) - 1) {
+		fprintf(stderr, "%s: Key is not the correct length or format\n", PROG_NAME);
 		return 1;
 	}
 	curve25519_generate_public(public_key, private_key);
-	if (b64_ntop(public_key, sizeof(public_key), public_key_base64, sizeof(public_key_base64)) < 0) {
-		errno = EINVAL;
-		perror("b64");
+	if (b64_ntop(public_key, sizeof(public_key), public_key_base64, sizeof(public_key_base64)) != sizeof(public_key_base64) - 1) {
+		fprintf(stderr, "%s: Could not convert key to base64\n", PROG_NAME);
 		return 1;
 	}
 	puts(public_key_base64);

src/wg.c

@@ -23,12 +23,13 @@ static const struct {
 	{ "pubkey", pubkey_main, "Reads a private key from stdin and writes a public key to stdout" }
 };
 
-static void show_usage(void)
+static void show_usage(FILE *file)
 {
-	fprintf(stderr, "Usage: %s <cmd> [<args>]\n\n", PROG_NAME);
-	fprintf(stderr, "Available subcommands:\n");
+	fprintf(file, "Usage: %s <cmd> [<args>]\n\n", PROG_NAME);
+	fprintf(file, "Available subcommands:\n");
 	for (size_t i = 0; i < sizeof(subcommands) / sizeof(subcommands[0]); ++i)
-		fprintf(stderr, "  %s: %s\n", subcommands[i].subcommand, subcommands[i].description);
+		fprintf(file, "  %s: %s\n", subcommands[i].subcommand, subcommands[i].description);
+	fprintf(file, "You may pass `--help' to any of these subcommands to view usage.\n");
 }
 
 int main(int argc, char *argv[])
@@ -37,8 +38,8 @@ int main(int argc, char *argv[])
 	PROG_NAME = argv[0];
 
 	if (argc == 2 && (!strcmp(argv[1], "-h") || !strcmp(argv[1], "--help") || !strcmp(argv[1], "help"))) {
-		show_usage();
-		return 1;
+		show_usage(stdout);
+		return 0;
 	}
 
 	if (argc == 1) {
@@ -61,6 +62,6 @@ findsubcommand:
 	}
 
 	fprintf(stderr, "Invalid subcommand: `%s`\n", argv[1]);
-	show_usage();
+	show_usage(stderr);
 	return 1;
 }