+/*
+ * Copyright (C) 2005-2011 Andre Noll <maan@systemlinux.org>
+ *
+ * Licensed under the GPL v2. For licencing details see COPYING.
+ */
+
+/** \file crypt_common.c Crypto functions independent of the implementation. */
+
+#include <regex.h>
+#include <stdbool.h>
+
+#include "para.h"
+#include "error.h"
+#include "string.h"
+#include "crypt_backend.h"
+#include "crypt.h"
+
+#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.
+ *
+ * \return Number of header bytes to be skipped on success, zero if
+ * ssh rsa signature was not found.
+ */
+size_t is_ssh_rsa_key(char *data, size_t size)
+{
+ char *cp;
+
+ if (size < strlen(KEY_TYPE_TXT) + 2)
+ return 0;
+ cp = memchr(data, ' ', size);
+ if (cp == NULL)
+ return 0;
+ if (strncmp(KEY_TYPE_TXT, data, strlen(KEY_TYPE_TXT)))
+ return 0;
+ cp++;
+ if (cp >= data + size)
+ return 0;
+ if (*cp == '\0')
+ return 0;
+ return cp - data;
+}
+
+/*
+ * 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.
+ */
+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)
+{
+ 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);
+ p += 4;
+ if (p + rlen < p)
+ return -E_SSH_KEY_HEADER;
+ if (p + rlen > end)
+ 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);
+ 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)
+{
+ 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)
+{
+ int i;
+ const char hexchar[] = "0123456789abcdef";
+
+ for (i = 0; i < HASH_SIZE; i++) {
+ asc[2 * i] = hexchar[hash[i] >> 4];
+ asc[2 * i + 1] = hexchar[hash[i] & 0xf];
+ }
+ 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 i;
+
+ for (i = 0; i < HASH_SIZE; i++) {
+ if (h1[i] < h2[i])
+ return -1;
+ if (h1[i] > h2[i])
+ return 1;
+ }
+ return 0;
+}
+
+/**
+ * Receive a buffer, decrypt it and write terminating NULL byte.
+ *
+ * \param scc The context.
+ * \param buf The buffer to write the decrypted data to.
+ * \param size The size of \a buf.
+ *
+ * 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.
+ *
+ * \return The return value of the underlying call to \ref
+ * sc_recv_bin_buffer().
+ */
+int sc_recv_buffer(struct stream_cipher_context *scc, char *buf, size_t size)
+{
+ int n;
+
+ assert(size);
+ n = sc_recv_bin_buffer(scc, buf, size - 1);
+ if (n >= 0)
+ buf[n] = '\0';
+ else
+ *buf = '\0';
+ return n;
+}
+
+/**
+ * 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));
+}
+
+/**
+ * Format, encrypt and send a buffer.
+ *
+ * \param scc The context.
+ * \param fmt A format string.
+ *
+ * \return The return value of the underyling call to sc_send_buffer().
+ */
+__printf_2_3 int sc_send_va_buffer(struct stream_cipher_context *scc,
+ const char *fmt, ...)
+{
+ char *msg;
+ int ret;
+
+ PARA_VSPRINTF(fmt, msg);
+ ret = sc_send_buffer(scc, msg);
+ free(msg);
+ return ret;
+}