b83dcf7928
With its current design, a careless use of pg_cryptohash_final() could would result in an out-of-bound write in memory as the size of the destination buffer to store the result digest is not known to the cryptohash internals, without the caller knowing about that. This commit adds a new argument to pg_cryptohash_final() to allow such sanity checks, and implements such defenses. The internals of SCRAM for HMAC could be tightened a bit more, but as everything is based on SCRAM_KEY_LEN with uses particular to this code there is no need to complicate its interface more than necessary, and this comes back to the refactoring of HMAC in core. Except that, this minimizes the uses of the existing DIGEST_LENGTH variables, relying instead on sizeof() for the result sizes. In ossp-uuid, this also makes the code more defensive, as it already relied on dce_uuid_t being at least the size of a MD5 digest. This is in philosophy similar to cfc40d3 for base64.c and aef8948 for hex.c. Reported-by: Ranier Vilela Author: Michael Paquier, Ranier Vilela Reviewed-by: Kyotaro Horiguchi Discussion: https://postgr.es/m/CAEudQAoqEGmcff3J4sTSV-R_16Monuz-UpJFbf_dnVH=APr02Q@mail.gmail.com
150 lines
3.4 KiB
C
150 lines
3.4 KiB
C
/*-------------------------------------------------------------------------
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*
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* md5_common.c
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* Routines shared between all MD5 implementations used for encrypted
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* passwords.
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*
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* Sverre H. Huseby <sverrehu@online.no>
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*
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* Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* IDENTIFICATION
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* src/common/md5_common.c
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef FRONTEND
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#include "postgres.h"
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#else
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#include "postgres_fe.h"
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#endif
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#include "common/cryptohash.h"
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#include "common/md5.h"
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static void
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bytesToHex(uint8 b[16], char *s)
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{
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static const char *hex = "0123456789abcdef";
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int q,
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w;
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for (q = 0, w = 0; q < 16; q++)
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{
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s[w++] = hex[(b[q] >> 4) & 0x0F];
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s[w++] = hex[b[q] & 0x0F];
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}
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s[w] = '\0';
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}
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/*
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* pg_md5_hash
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*
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* Calculates the MD5 sum of the bytes in a buffer.
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*
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* SYNOPSIS #include "md5.h"
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* int pg_md5_hash(const void *buff, size_t len, char *hexsum)
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*
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* INPUT buff the buffer containing the bytes that you want
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* the MD5 sum of.
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* len number of bytes in the buffer.
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*
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* OUTPUT hexsum the MD5 sum as a '\0'-terminated string of
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* hexadecimal digits. an MD5 sum is 16 bytes long.
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* each byte is represented by two hexadecimal
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* characters. you thus need to provide an array
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* of 33 characters, including the trailing '\0'.
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*
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* RETURNS false on failure (out of memory for internal buffers
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* or MD5 computation failure) or true on success.
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*
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* STANDARDS MD5 is described in RFC 1321.
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*
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* AUTHOR Sverre H. Huseby <sverrehu@online.no>
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*
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*/
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bool
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pg_md5_hash(const void *buff, size_t len, char *hexsum)
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{
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uint8 sum[MD5_DIGEST_LENGTH];
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pg_cryptohash_ctx *ctx;
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ctx = pg_cryptohash_create(PG_MD5);
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if (ctx == NULL)
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return false;
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if (pg_cryptohash_init(ctx) < 0 ||
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pg_cryptohash_update(ctx, buff, len) < 0 ||
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pg_cryptohash_final(ctx, sum, sizeof(sum)) < 0)
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{
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pg_cryptohash_free(ctx);
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return false;
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}
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bytesToHex(sum, hexsum);
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pg_cryptohash_free(ctx);
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return true;
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}
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bool
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pg_md5_binary(const void *buff, size_t len, void *outbuf)
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{
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pg_cryptohash_ctx *ctx;
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ctx = pg_cryptohash_create(PG_MD5);
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if (ctx == NULL)
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return false;
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if (pg_cryptohash_init(ctx) < 0 ||
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pg_cryptohash_update(ctx, buff, len) < 0 ||
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pg_cryptohash_final(ctx, outbuf, MD5_DIGEST_LENGTH) < 0)
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{
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pg_cryptohash_free(ctx);
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return false;
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}
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pg_cryptohash_free(ctx);
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return true;
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}
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/*
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* Computes MD5 checksum of "passwd" (a null-terminated string) followed
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* by "salt" (which need not be null-terminated).
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*
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* Output format is "md5" followed by a 32-hex-digit MD5 checksum.
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* Hence, the output buffer "buf" must be at least 36 bytes long.
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*
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* Returns true if okay, false on error (out of memory).
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*/
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bool
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pg_md5_encrypt(const char *passwd, const char *salt, size_t salt_len,
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char *buf)
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{
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size_t passwd_len = strlen(passwd);
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/* +1 here is just to avoid risk of unportable malloc(0) */
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char *crypt_buf = malloc(passwd_len + salt_len + 1);
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bool ret;
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if (!crypt_buf)
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return false;
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/*
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* Place salt at the end because it may be known by users trying to crack
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* the MD5 output.
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*/
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memcpy(crypt_buf, passwd, passwd_len);
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memcpy(crypt_buf + passwd_len, salt, salt_len);
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strcpy(buf, "md5");
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ret = pg_md5_hash(crypt_buf, passwd_len + salt_len, buf + 3);
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free(crypt_buf);
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return ret;
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}
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