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Diffstat (limited to '')
| -rw-r--r-- | lib/af_alg.c | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/lib/af_alg.c b/lib/af_alg.c new file mode 100644 index 0000000..9f022ce --- /dev/null +++ b/lib/af_alg.c @@ -0,0 +1,213 @@ +/* af_alg.c - Compute message digests from file streams and buffers. + Copyright (C) 2018-2023 Free Software Foundation, Inc. + + This file is free software: you can redistribute it and/or modify + it under the terms of the GNU Lesser General Public License as + published by the Free Software Foundation; either version 2.1 of the + License, or (at your option) any later version. + + This file is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. */ + +/* Written by Matteo Croce <mcroce@redhat.com>, 2018. */ + +#include <config.h> + +#include "af_alg.h" + +#if USE_LINUX_CRYPTO_API + +#include <unistd.h> +#include <string.h> +#include <stdio.h> +#include <errno.h> +#include <linux/if_alg.h> +#include <sys/stat.h> +#include <sys/sendfile.h> +#include <sys/socket.h> + +#include "sys-limits.h" + +#define BLOCKSIZE 32768 + +/* Return a newly created socket for ALG. + On error, return a negative error number. */ +static int +alg_socket (char const *alg) +{ + struct sockaddr_alg salg = { + .salg_family = AF_ALG, + .salg_type = "hash", + }; + /* Copy alg into salg.salg_name, without calling strcpy nor strlen. */ + for (size_t i = 0; (salg.salg_name[i] = alg[i]) != '\0'; i++) + if (i == sizeof salg.salg_name - 1) + /* alg is too long. */ + return -EINVAL; + + int cfd = socket (AF_ALG, SOCK_SEQPACKET | SOCK_CLOEXEC, 0); + if (cfd < 0) + return -EAFNOSUPPORT; + int ofd = (bind (cfd, (struct sockaddr *) &salg, sizeof salg) == 0 + ? accept4 (cfd, NULL, 0, SOCK_CLOEXEC) + : -1); + close (cfd); + return ofd < 0 ? -EAFNOSUPPORT : ofd; +} + +int +afalg_buffer (const char *buffer, size_t len, const char *alg, + void *resblock, ssize_t hashlen) +{ + /* On Linux < 4.9, the value for an empty stream is wrong (all zeroes). + See <https://patchwork.kernel.org/patch/9308641/>. + This was not fixed properly until November 2016, + see <https://patchwork.kernel.org/patch/9434741/>. */ + if (len == 0) + return -EAFNOSUPPORT; + + int ofd = alg_socket (alg); + if (ofd < 0) + return ofd; + + int result; + + for (;;) + { + ssize_t size = (len > BLOCKSIZE ? BLOCKSIZE : len); + if (send (ofd, buffer, size, MSG_MORE) != size) + { + result = -EAFNOSUPPORT; + break; + } + buffer += size; + len -= size; + if (len == 0) + { + result = read (ofd, resblock, hashlen) == hashlen ? 0 : -EAFNOSUPPORT; + break; + } + } + + close (ofd); + return result; +} + +int +afalg_stream (FILE *stream, const char *alg, + void *resblock, ssize_t hashlen) +{ + int ofd = alg_socket (alg); + if (ofd < 0) + return ofd; + + /* If STREAM's size is known and nonzero and not too large, attempt + sendfile to pipe the data. The nonzero restriction avoids issues + with /proc files that pretend to be empty, and lets the classic + read-write loop work around an empty-input bug noted below. */ + int fd = fileno (stream); + int result; + struct stat st; + off_t off = ftello (stream); + if (0 <= off && fstat (fd, &st) == 0 + && (S_ISREG (st.st_mode) || S_TYPEISSHM (&st) || S_TYPEISTMO (&st)) + && off < st.st_size && st.st_size - off < SYS_BUFSIZE_MAX) + { + /* Make sure the offset of fileno (stream) reflects how many bytes + have been read from stream before this function got invoked. + Note: fflush on an input stream after ungetc does not work as expected + on some platforms. Therefore this situation is not supported here. */ + if (fflush (stream)) + result = -EIO; + else + { + off_t nbytes = st.st_size - off; + if (sendfile (ofd, fd, &off, nbytes) == nbytes) + { + if (read (ofd, resblock, hashlen) == hashlen) + { + /* The input buffers of stream are no longer valid. */ + if (lseek (fd, off, SEEK_SET) != (off_t)-1) + result = 0; + else + /* The file position of fd has not changed. */ + result = -EAFNOSUPPORT; + } + else + /* The file position of fd has not changed. */ + result = -EAFNOSUPPORT; + } + else + /* The file position of fd has not changed. */ + result = -EAFNOSUPPORT; + } + } + else + { + /* sendfile not possible, do a classic read-write loop. */ + + /* Number of bytes to seek (backwards) in case of error. */ + off_t nseek = 0; + + for (;;) + { + char buf[BLOCKSIZE]; + /* When the stream is not seekable, start with a single-byte block, + so that we can use ungetc() in the case that send() fails. */ + size_t blocksize = (nseek == 0 && off < 0 ? 1 : BLOCKSIZE); + ssize_t size = fread (buf, 1, blocksize, stream); + if (size == 0) + { + /* On Linux < 4.9, the value for an empty stream is wrong (all 0). + See <https://patchwork.kernel.org/patch/9308641/>. + This was not fixed properly until November 2016, + see <https://patchwork.kernel.org/patch/9434741/>. */ + result = ferror (stream) ? -EIO : nseek == 0 ? -EAFNOSUPPORT : 0; + break; + } + nseek -= size; + if (send (ofd, buf, size, MSG_MORE) != size) + { + if (nseek == -1) + { + /* 1 byte of pushback buffer is guaranteed on stream, even + if stream is not seekable. */ + ungetc ((unsigned char) buf[0], stream); + result = -EAFNOSUPPORT; + } + else if (fseeko (stream, nseek, SEEK_CUR) == 0) + /* The position of stream has been restored. */ + result = -EAFNOSUPPORT; + else + result = -EIO; + break; + } + + /* Don't assume that EOF is sticky. See: + <https://sourceware.org/bugzilla/show_bug.cgi?id=19476>. */ + if (feof (stream)) + { + result = 0; + break; + } + } + + if (result == 0 && read (ofd, resblock, hashlen) != hashlen) + { + if (nseek == 0 || fseeko (stream, nseek, SEEK_CUR) == 0) + /* The position of stream has been restored. */ + result = -EAFNOSUPPORT; + else + result = -EIO; + } + } + close (ofd); + return result; +} + +#endif |