X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=crypt_common.c;h=235b8b8d3e398551fc28bfbc746349c5dc8f6f1c;hp=71aabf53f944eea64d4214fccff354787b7e6f9b;hb=bab99bab677988723afe14a7d680e6d5cc7ddda4;hpb=56df9bb38aa4725f9244a7898d765608d8a1fffa diff --git a/crypt_common.c b/crypt_common.c index 71aabf53..235b8b8d 100644 --- a/crypt_common.c +++ b/crypt_common.c @@ -1,8 +1,4 @@ -/* - * Copyright (C) 2005-2014 Andre Noll - * - * Licensed under the GPL v2. For licencing details see COPYING. - */ +/* Copyright (C) 2005 Andre Noll , see file COPYING. */ /** \file crypt_common.c Crypto functions independent of openssl/libgcrypt. */ @@ -13,20 +9,20 @@ #include "string.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; @@ -46,219 +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 = '='; - -/** - * base64-decode a buffer. - * - * \param src The buffer to decode. - * \param target Result is stored here. - * \param targsize Number of bytes of \a target. - * - * 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. + * Perform some sanity checks on the decoded ssh key. * - * \return The number of data bytes stored at the target, -E_BASE64 on errors. + * 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". */ -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 == NULL) /* A non-base64 character. */ - return -E_BASE64; - - switch (state) { - case 0: - if (target) { - if (tarindex >= targsize) - return -E_BASE64; - target[tarindex] = (pos - Base64) << 2; - } - state = 1; - break; - case 1: - if (target) { - if (tarindex + 1 >= targsize) - return -E_BASE64; - 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 -E_BASE64; - target[tarindex] |= (pos - Base64) >> 2; - target[tarindex+1] = ((pos - Base64) & 0x03) - << 6; - } - tarindex++; - state = 3; - break; - case 3: - if (target) { - if (tarindex >= targsize) - return -E_BASE64; - 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 -E_BASE64; - - 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 -E_BASE64; - 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 -E_BASE64; - - /* - * 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 -E_BASE64; - } - } else { - /* - * We ended by seeing the end of the string. Make sure we - * have no partial bytes lying around. - */ - if (state != 0) - return -E_BASE64; - } - - return tarindex; -} - -/** - * uudecode a buffer. - * - * \param src The buffer to decode. - * \param target Result buffer. - * \param targsize The length of \a target in bytes. - * - * This is just a simple wrapper for base64_decode() which strips whitespace. - * - * \return The return value of the underlying call to base64_decode(). - */ -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; -} - -/** - * Read a 4-byte number from a buffer in big-endian format. - * - * \param vp The buffer. - * - * The byte-order of the buffer is expected to be big-endian, unlike read_u32() - * of portable_io.h which expects little endian. - * - * \return The 32 bit number given by \a vp. - */ -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; -} - -/** - * Sanity checks for the header of an ssh key. - * - * \param blob The buffer. - * \param blen The number of bytes of \a blob. - * - * This performs some checks to make sure we really have an ssh key. It also - * computes the offset in bytes of the start of the key values (modulus, - * exponent..). - * - * \return The number of bytes to skip until the start of the first encoded - * number (usually 11). - */ -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; @@ -266,32 +62,74 @@ 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; } /** - * Check existence and permissions of a key file. + * 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_ssh_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. - * \param private_key Whether this is a private key. * - * This checks whether the file exists. If it is a private key, we additionally - * check that the permissions are restrictive enough. It is considered an error - * if we own the file and it is readable for others. + * 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_key_file(const char *file, bool private_key) +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;