X-Git-Url: http://git.tuebingen.mpg.de/?a=blobdiff_plain;f=crypt_common.c;h=ff24e356ab8d837f8d59d67a3c983d5264376db1;hb=62c0894fbb589dd45e69b7d9ef1fd152a9960d62;hp=1308af4148851246fbf328c2d4037a44dc43ac39;hpb=6a7393e2abdcf30dd4201b84a417d08f6136e8d6;p=paraslash.git

diff --git a/crypt_common.c b/crypt_common.c
index 1308af41..ff24e356 100644
--- a/crypt_common.c
+++ b/crypt_common.c
@@ -1,32 +1,28 @@
-/*
- * Copyright (C) 2005-2011 Andre Noll <maan@systemlinux.org>
- *
- * Licensed under the GPL v2. For licencing details see COPYING.
- */
+/* Copyright (C) 2005 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
 
-/** \file crypt_common.c Crypto functions independent of the implementation. */
+/** \file crypt_common.c Crypto functions independent of openssl/libgcrypt. */
 
 #include <regex.h>
-#include <stdbool.h>
 
 #include "para.h"
 #include "error.h"
 #include "string.h"
-#include "crypt_backend.h"
 #include "crypt.h"
+#include "crypt_backend.h"
+#include "portable_io.h"
+#include "fd.h"
+#include "base64.h"
 
+/** If the key begins with this text, we treat it as an ssh key. */
 #define KEY_TYPE_TXT "ssh-rsa"
 
-/**
- * Check if given buffer starts with a ssh rsa key signature.
- *
- * \param data The buffer.
- * \param size Number of data bytes.
+/*
+ * Check if the given buffer starts with an ssh rsa key signature.
  *
- * \return Number of header bytes to be skipped on success, zero if
- * ssh rsa signature was not found.
+ * Returns number of header bytes to be skipped on success, zero if no ssh rsa
+ * signature was found.
  */
-size_t is_ssh_rsa_key(char *data, size_t size)
+static size_t is_ssh_rsa_key(char *data, size_t size)
 {
 	char *cp;
 
@@ -46,181 +42,19 @@ size_t is_ssh_rsa_key(char *data, size_t size)
 }
 
 /*
- * This base64/uudecode stuff below is taken from openssh-5.2p1, Copyright (c)
- * 1996 by Internet Software Consortium.  Portions Copyright (c) 1995 by
- * International Business Machines, Inc.
- */
-
-static const char Base64[] =
-	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
-static const char Pad64 = '=';
-/*
- * Skips all whitespace anywhere. Converts characters, four at a time, starting
- * at (or after) src from base - 64 numbers into three 8 bit bytes in the
- * target area. it returns the number of data bytes stored at the target, or -1
- * on error.
- */
-static int base64_decode(char const *src, unsigned char *target, size_t targsize)
-{
-	unsigned int tarindex, state;
-	int ch;
-	char *pos;
-
-	state = 0;
-	tarindex = 0;
-
-	while ((ch = *src++) != '\0') {
-		if (para_isspace(ch)) /* Skip whitespace anywhere. */
-			continue;
-
-		if (ch == Pad64)
-			break;
-
-		pos = strchr(Base64, ch);
-		if (pos == 0) /* A non-base64 character. */
-			return -1;
-
-		switch (state) {
-		case 0:
-			if (target) {
-				if (tarindex >= targsize)
-					return (-1);
-				target[tarindex] = (pos - Base64) << 2;
-			}
-			state = 1;
-			break;
-		case 1:
-			if (target) {
-				if (tarindex + 1 >= targsize)
-					return (-1);
-				target[tarindex]   |=  (pos - Base64) >> 4;
-				target[tarindex+1]  = ((pos - Base64) & 0x0f)
-							<< 4 ;
-			}
-			tarindex++;
-			state = 2;
-			break;
-		case 2:
-			if (target) {
-				if (tarindex + 1 >= targsize)
-					return (-1);
-				target[tarindex]   |=  (pos - Base64) >> 2;
-				target[tarindex+1]  = ((pos - Base64) & 0x03)
-							<< 6;
-			}
-			tarindex++;
-			state = 3;
-			break;
-		case 3:
-			if (target) {
-				if (tarindex >= targsize)
-					return (-1);
-				target[tarindex] |= (pos - Base64);
-			}
-			tarindex++;
-			state = 0;
-			break;
-		}
-	}
-
-	/*
-	 * We are done decoding Base-64 chars.  Let's see if we ended
-	 * on a byte boundary, and/or with erroneous trailing characters.
-	 */
-
-	if (ch == Pad64) {		/* We got a pad char. */
-		ch = *src++;		/* Skip it, get next. */
-		switch (state) {
-		case 0:		/* Invalid = in first position */
-		case 1:		/* Invalid = in second position */
-			return (-1);
-
-		case 2:		/* Valid, means one byte of info */
-			/* Skip any number of spaces. */
-			for (; ch != '\0'; ch = *src++)
-				if (!isspace(ch))
-					break;
-			/* Make sure there is another trailing = sign. */
-			if (ch != Pad64)
-				return (-1);
-			ch = *src++;		/* Skip the = */
-			/* Fall through to "single trailing =" case. */
-			/* FALLTHROUGH */
-
-		case 3:		/* Valid, means two bytes of info */
-			/*
-			 * We know this char is an =.  Is there anything but
-			 * whitespace after it?
-			 */
-			for (; ch != '\0'; ch = *src++)
-				if (!isspace(ch))
-					return (-1);
-
-			/*
-			 * Now make sure for cases 2 and 3 that the "extra"
-			 * bits that slopped past the last full byte were
-			 * zeros.  If we don't check them, they become a
-			 * subliminal channel.
-			 */
-			if (target && target[tarindex] != 0)
-				return (-1);
-		}
-	} else {
-		/*
-		 * We ended by seeing the end of the string.  Make sure we
-		 * have no partial bytes lying around.
-		 */
-		if (state != 0)
-			return (-1);
-	}
-
-	return (tarindex);
-}
-
-int uudecode(const char *src, unsigned char *target, size_t targsize)
-{
-	int len;
-	char *encoded, *p;
-
-	/* copy the 'readonly' source */
-	encoded = para_strdup(src);
-	/* skip whitespace and data */
-	for (p = encoded; *p == ' ' || *p == '\t'; p++)
-		;
-	for (; *p != '\0' && *p != ' ' && *p != '\t'; p++)
-		;
-	/* and remove trailing whitespace because base64_decode needs this */
-	*p = '\0';
-	len = base64_decode(encoded, target, targsize);
-	free(encoded);
-	return len >= 0? len : -E_BASE64;
-}
-
-/*
- * Can not use the inline functions of portable_io.h here because the byte
- * order is different.
+ * Perform some sanity checks on the decoded ssh key.
+ *
+ * This function returns the size of the header. Usually, the header is 11
+ * bytes long: four bytes for the length field, and the string "ssh-rsa".
  */
-uint32_t read_ssh_u32(const void *vp)
-{
-	const unsigned char *p = (const unsigned char *)vp;
-	uint32_t v;
-
-	v  = (uint32_t)p[0] << 24;
-	v |= (uint32_t)p[1] << 16;
-	v |= (uint32_t)p[2] << 8;
-	v |= (uint32_t)p[3];
-
-	return v;
-}
-
-int check_ssh_key_header(const unsigned char *blob, int blen)
+static int check_ssh_key_header(const unsigned char *blob, int blen)
 {
 	const unsigned char *p = blob, *end = blob + blen;
 	uint32_t rlen;
 
 	if (p + 4 > end)
 		return -E_SSH_KEY_HEADER;
-	rlen = read_ssh_u32(p);
+	rlen = read_u32_be(p);
 	p += 4;
 	if (p + rlen < p)
 		return -E_SSH_KEY_HEADER;
@@ -228,36 +62,80 @@ int check_ssh_key_header(const unsigned char *blob, int blen)
 		return -E_SSH_KEY_HEADER;
 	if (rlen < strlen(KEY_TYPE_TXT))
 		return -E_SSH_KEY_HEADER;
-	PARA_DEBUG_LOG("type: %s, rlen: %d\n", p, rlen);
+	PARA_DEBUG_LOG("type: %s, rlen: %u\n", p, rlen);
 	if (strncmp((char *)p, KEY_TYPE_TXT, strlen(KEY_TYPE_TXT)))
 		return -E_SSH_KEY_HEADER;
 	return 4 + rlen;
 }
 
-int check_key_file(const char *file, bool private_key)
+/**
+ * Perform sanity checks and base64-decode an ssh-rsa key.
+ *
+ * \param filename The public key file (usually id_rsa.pub).
+ * \param blob Pointer to base64-decoded blob is returned here.
+ * \param decoded_size The size of the decoded blob.
+ *
+ * The memory pointed at by the returned blob pointer has to be freed by the
+ * caller.
+ *
+ * \return On success, the offset in bytes of the start of the key values
+ * (modulus, exponent..). This is the number of bytes to skip from the blob
+ * until the start of the first encoded number. On failure, a negative error
+ * code is returned.
+ *
+ * \sa \ref uudecode().
+ */
+int decode_public_key(const char *filename, unsigned char **blob,
+		size_t *decoded_size)
+{
+	int ret, ret2;
+	void *map;
+	size_t map_size;
+
+	ret = mmap_full_file(filename, O_RDONLY, &map, &map_size, NULL);
+	if (ret < 0)
+		return ret;
+	ret = is_ssh_rsa_key(map, map_size);
+	if (ret == 0) {
+		ret = -E_SSH_PARSE;
+		goto unmap;
+	}
+	ret = uudecode(map + ret, map_size - ret, (char **)blob, decoded_size);
+	if (ret < 0)
+		goto unmap;
+	ret = check_ssh_key_header(*blob, *decoded_size);
+	if (ret < 0)
+		goto unmap;
+unmap:
+	ret2 = para_munmap(map, map_size);
+	if (ret >= 0 && ret2 < 0)
+		ret = ret2;
+	return ret;
+}
+
+/**
+ * Check existence and permissions of a private key file.
+ *
+ * \param file The path of the key file.
+ *
+ * This checks whether the file exists and its permissions are restrictive
+ * enough. It is considered an error if we own the file and it is readable for
+ * others.
+ *
+ * \return Standard.
+ */
+int check_private_key_file(const char *file)
 {
 	struct stat st;
 
 	if (stat(file, &st) != 0)
 		return -ERRNO_TO_PARA_ERROR(errno);
-	if (!private_key)
-		return 0;
 	if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0)
 		return -E_KEY_PERM;
 	return 1;
 }
 
-/**
- * Convert a hash value to ascii format.
- *
- * \param hash the hash value.
- * \param asc Result pointer.
- *
- * \a asc must point to an area of at least 2 * \p HASH_SIZE + 1 bytes which
- * will be filled by the function with the ascii representation of the hash
- * value given by \a hash, and a terminating \p NULL byte.
- */
-void hash_to_asc(unsigned char *hash, char *asc)
+void hash_to_asc(const unsigned char *hash, char *asc)
 {
 	int i;
 	const char hexchar[] = "0123456789abcdef";
@@ -269,16 +147,7 @@ void hash_to_asc(unsigned char *hash, char *asc)
 	asc[2 * HASH_SIZE] = '\0';
 }
 
-/**
- * Compare two hashes.
- *
- * \param h1 Pointer to the first hash value.
- * \param h2 Pointer to the second hash value.
- *
- * \return 1, -1, or zero, depending on whether \a h1 is greater than,
- * less than or equal to h2, respectively.
- */
-int hash_compare(unsigned char *h1, unsigned char *h2)
+int hash_compare(const unsigned char *h1, const unsigned char *h2)
 {
 	int i;
 
@@ -292,60 +161,159 @@ int hash_compare(unsigned char *h1, unsigned char *h2)
 }
 
 /**
- * Receive a buffer, decrypt it and write terminating NULL byte.
+ * Check header of an openssh private key and compute bignum offset.
  *
- * \param scc The context.
- * \param buf The buffer to write the decrypted data to.
- * \param size The size of \a buf.
+ * \param data The base64-decoded key.
+ * \param len The size of the decoded key.
  *
- * Read at most \a size - 1 bytes from file descriptor given by \a scc, decrypt
- * the received data and write a NULL byte at the end of the decrypted data.
+ * Several assumptions are made about the key. Most notably, we only support
+ * single unencrypted keys without comments.
  *
- * \return The return value of the underlying call to \ref
- * sc_recv_bin_buffer().
+ * \return The offset at which the first bignum of the private key (the public
+ * exponent n) starts. Negative error code on failure.
  */
-int sc_recv_buffer(struct stream_cipher_context *scc, char *buf, size_t size)
+int find_openssh_bignum_offset(const unsigned char *data, int len)
 {
-	int n;
-
-	assert(size);
-	n = sc_recv_bin_buffer(scc, buf, size - 1);
-	if (n >= 0)
-		buf[n] = '\0';
-	else
-		*buf = '\0';
-	return n;
+	/*
+	 * Unencrypted keys without comments always start with the below byte
+	 * sequence. See PROTOCOL.key of the openssh package.
+	 */
+	static const unsigned char valid_openssh_header[] = {
+		/* string "openssh-key-v1" */
+		0x6f, 0x70, 0x65, 0x6e, 0x73, 0x73, 0x68, 0x2d, 0x6b, 0x65,
+			0x79, 0x2d, 0x76, 0x31,
+		/* length of the cipher name */
+		0x00, 0x00, 0x00, 0x00, 0x04,
+		/* cipher name: "none" */
+		0x6e, 0x6f, 0x6e, 0x65,
+		/* length of the kdfname (only used for encrypted keys) */
+		0x00, 0x00, 0x00, 0x04,
+		/* kdfname: "none" */
+		0x6e, 0x6f, 0x6e, 0x65,
+		/* length of kdfoptions */
+		0x00, 0x00, 0x00, 0x00,
+		/* number of keys */
+		0x00, 0x00, 0x00, 0x01,
+	};
+	uint32_t val;
+	const unsigned char *p, *end = data + len;
+
+	if (len <= sizeof(valid_openssh_header) + 4)
+		return -E_OPENSSH_PARSE;
+	if (memcmp(data, valid_openssh_header, sizeof(valid_openssh_header)))
+		return -E_OPENSSH_PARSE;
+	p = data + sizeof(valid_openssh_header);
+	/* length of public key */
+	val = read_u32_be(p);
+	if (val > end - p - 4)
+		return -E_OPENSSH_PARSE;
+	p += val + 4;
+	/* length of private key */
+	val = read_u32_be(p);
+	if (val > end - p - 4)
+		return -E_OPENSSH_PARSE;
+	p += 4;
+	/* two equal random integers ("checkint") */
+	if (p + 8 > end)
+		return -E_OPENSSH_PARSE;
+	if (read_u32_be(p) != read_u32_be(p + 4))
+		return -E_OPENSSH_PARSE;
+	p += 8;
+	/* length of name of key type "ssh-rsa" */
+	if (p + 11 > end)
+		return -E_OPENSSH_PARSE;
+	if (read_u32_be(p) != 7)
+		return -E_OPENSSH_PARSE;
+	if (memcmp(p + 4, "ssh-rsa", 7))
+		return -E_OPENSSH_PARSE;
+	p += 11;
+	return p - data;
 }
 
-/**
- * Encrypt and send a \p NULL-terminated buffer.
- *
- * \param scc The context.
- * \param buf The buffer to send.
- *
- * \return The return value of the underyling call to sc_send_bin_buffer().
- */
-int sc_send_buffer(struct stream_cipher_context *scc, const char *buf)
-{
-	return sc_send_bin_buffer(scc, buf, strlen(buf));
-}
+/** Private PEM keys (legacy format) start with this header. */
+#define PRIVATE_PEM_KEY_HEADER "-----BEGIN RSA PRIVATE KEY-----"
+/** Private OPENSSH keys (RFC4716) start with this header. */
+#define PRIVATE_OPENSSH_KEY_HEADER "-----BEGIN OPENSSH PRIVATE KEY-----"
+/** Private PEM keys (legacy format) end with this footer. */
+#define PRIVATE_PEM_KEY_FOOTER "-----END RSA PRIVATE KEY-----"
+/** Private OPENSSH keys (RFC4716) end with this footer. */
+#define PRIVATE_OPENSSH_KEY_FOOTER "-----END OPENSSH PRIVATE KEY-----"
 
 /**
- * Format, encrypt and send a buffer.
+ * Decode an openssh-v1 (aka RFC4716) or PEM (aka ASN.1) private key.
+ *
+ * \param key_file The private key file (usually id_rsa).
+ * \param result Pointer to base64-decoded blob is returned here.
+ * \param blob_size The size of the decoded blob.
  *
- * \param scc The context.
- * \param fmt A format string.
+ * This only checks header and footer and base64-decodes the part in between.
+ * No attempt to read the decoded part is made.
  *
- * \return The return value of the underyling call to sc_send_buffer().
+ * \return Negative on errors, PKT_PEM or PKT_OPENSSH on success, indicating
+ * the type of key.
  */
-__printf_2_3 int sc_send_va_buffer(struct stream_cipher_context *scc,
-		const char *fmt, ...)
+int decode_private_key(const char *key_file, unsigned char **result,
+		size_t *blob_size)
 {
-	char *msg;
-	int ret;
-
-	PARA_VSPRINTF(fmt, msg);
-	ret = sc_send_buffer(scc, msg);
-	free(msg);
+	int ret, ret2, i, j, key_type;
+	void *map;
+	size_t map_size, key_size;
+	unsigned char *blob = NULL;
+	char *begin, *footer, *key;
+
+	ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
+	if (ret < 0)
+		goto out;
+	ret = -E_KEY_MARKER;
+	if (strncmp(map, PRIVATE_PEM_KEY_HEADER,
+			strlen(PRIVATE_PEM_KEY_HEADER)) == 0) {
+		key_type = PKT_PEM;
+		begin = map + strlen(PRIVATE_PEM_KEY_HEADER);
+		footer = strstr(map, PRIVATE_PEM_KEY_FOOTER);
+		PARA_INFO_LOG("detected legacy PEM key %s\n", key_file);
+	} else if (strncmp(map, PRIVATE_OPENSSH_KEY_HEADER,
+			strlen(PRIVATE_OPENSSH_KEY_HEADER)) == 0) {
+		key_type = PKT_OPENSSH;
+		begin = map + strlen(PRIVATE_OPENSSH_KEY_HEADER);
+		footer = strstr(map, PRIVATE_OPENSSH_KEY_FOOTER);
+		PARA_INFO_LOG("detected openssh key %s\n", key_file);
+	} else
+		goto unmap;
+	if (!footer)
+		goto unmap;
+	/* skip whitespace at the beginning */
+	for (; begin < footer; begin++) {
+		if (para_isspace(*begin))
+			continue;
+		break;
+	}
+	ret = -E_KEY_MARKER;
+	if (begin >= footer)
+		goto unmap;
+
+	key_size = footer - begin;
+	key = para_malloc(key_size + 1);
+	for (i = 0, j = 0; begin + i < footer; i++) {
+		if (para_isspace(begin[i]))
+			continue;
+		key[j++] = begin[i];
+	}
+	key[j] = '\0';
+	ret = base64_decode(key, j, (char **)&blob, blob_size);
+	free(key);
+	if (ret < 0)
+		goto unmap;
+	ret = key_type;
+unmap:
+	ret2 = para_munmap(map, map_size);
+	if (ret >= 0 && ret2 < 0)
+		ret = ret2;
+	if (ret < 0) {
+		free(blob);
+		blob = NULL;
+	}
+out:
+	*result = blob;
 	return ret;
 }
+